U-boat Archive - Type VII C Manual

U-Boat Type VIIC	U-boat Information	Page III

	Amendments

Note the section, page and paragraph No., to which changes or additions are registered:			Certified to be Correct

Page	Contents	Paragraph No.		Place	Date	Signed

Page IV	U-boat Information	U-Boat Type VIIC

	Amendments

Note the section, page and paragraph No., to which changes or additions are registered:			Certified to be Correct

Page	Contents	Paragraph No.		Place	Date	Signed

U-Boat Type VIIC	U-boat Information	Page V

	Table of Contents

Contents of U-boat Information

=====================

			Page
Title Page			I
Excerpt from the regulations for the establishment, examination and conduct of General Navy Regulations and Damage Control Procedures			II
Amendments to U-boat Information			III
Table of Contents Ship Information			V
Table of Contents Machinery Installations			X
Introduction: Development of the Type VII C U-boat			XIII
A. Ship Information
I. General.
1.	Shipyard information		1
2.	Overview of ship construction		2
	a)	Dimensions	2
	b)	Measured displacement	3
	c)	Volume and distance from center of mass	3
	d)	Test and operating pressures	7
	e)	Materials	8
	f)	Weights	9
	g)	Stability	9
3.	Weapons overview		11
	a)	Torpedoes and mines	11
	b)	Artillery	12
	c)	Small arms	12
4.	Safety and rescue equipment overview		12
	a)	Structural safety installations	12
	b)	Safety equipment	13
	c)	Rescue equipment	13
5.	Test data		14
	a)	Speed [surfaced] and [submerged]	14
	b)	Diving time	14
	c)	Diving depth	14
	d)	Depth differences for bow and stern	15

Page VI	U-boat Information	U-Boat Type VIIC

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			Page
6.	Practical values		15
	a)	Speeds for various operating conditions	15
	b)	Behavior of the boat under different rudder angle and wind conditions	17
	c)	Turning radius	17
	d)	Behavior in a seaway	20
	e)	Diving characteristics	20
	f)	Depth control	21
	g)	Vibrations	23
	h)	Sound levels	24
II. Boat and Pressure Hull - including openings.
1.	General construction of the boat		26
2.	Construction of the pressure hull		26
3.	Partitioning of the pressure hull		27
4.	Conning tower structure		28
5.	Openings in the pressure hull		29
6.	Construction of the outer shell		34
7.	Partitioning of the outer shell		36
III. Diving Installations.
1.	Tanks and fuel oil tanks		37
	a)	Main ballast tanks	37
	b)	Main ballast and reserve fuel oil tanks	37
	c)	Bow and stern buoyancy tanks	38
	d)	Regulating tanks	38
	e)	Regulating and reserve fuel oil tanks	39
	f)	Trim tanks	39
	g)	Negative buoyancy tanks	39
	h)	Torpedo compensating tanks	40
2.	Blowing and exhaust gas blowing installation		40
	a)	Compressed air blowing	40
	b)	Exhaust gas blowing	40
3.	Venting and vent valves		40
4.	Compressed air systems		41
	a)	Electric air compressor	41
	b)	Diesel air compressor	42
	c)	High pressure compressed air flasks	43
	d)	Compressed air equipment	43
5.	Pumps		46
6.	Dive planes		47

U-Boat Type VIIC	U-boat Information	Page VII

	Table of Contents

			Page
IV. Armament.
1.	Torpedoes and mines		48
	a)	Torpedo tubes	48
	b)	Installation for mine ejection	49
	c)	Stowage	49
	d)	Torpedo loading equipment	51
	e)	Torpedo fire control system	51
	f)	Weight compensation during torpedo firing and mine ejecting	53
2.	Gunnery		56
	a)	Weapons	56
	b)	Ammunition	56
3.	Mine and demolition equipment		56
4.	Small arms		57
V. Communications
1.	Visual and acoustic equipment		58
	a)	Visual equipment	58
	b)	Acoustic equipment	58
2.	Electronic communication equipment		59
	a)	Radio installation	59
	b)	Broadcast and announcement system	61
	c)	Ultra short wave portable transmitter and receiver	61
	d)	Aerial installations	62
	e)	Radio converter installation	63
	f)	UT Installation (sound)	63
	g)	G.H.G. installation	63
	h)	K.D.B. equipment	64
3.	Power supply for electronic communications equipment		64
4.	Aerials		66
VI. Steering System and Anchor Installation.
1.	Steering system		67
	a)	General	67
	b)	Main rudder installation	68
	c)	Dive planes installation	69
2.	Anchor installation		69
VII. Equipment and Installations for Ship Control.
1.	Ship Control		71
2.	Periscopes		71

Page VIII	U-boat Information	U-Boat Type VIIC

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	a)	Attack periscope	71
	b)	Air search periscope	72
	c)	Periscope drive	72
3.	Compass installation		73
	a)	Gyro compass installation	73
	b)	Projector compass installation	74
4.	Signal equipment		74
5.	Depth sounding equipment		75
	a)	Echolot	75
	b)	Elektrolot	76
	c)	Hand lead	76
6.	Log installation		76
7.	Alarm installation		77
8.	Ordering and reporting installations		78
VIII. Safety and Rescue Installations.
1.	Installations for submerged and surfaced boat		79
	a)	Emergency lighting	79
	b)	Hand lamps	80
	c)	Fire extinguishers	80
	d)	Flooding installation	80
	e)	Drainage installation	80
	f)	UT and G.H.G. installation	80
	g)	Emergency steering gear	81
	h)	Diving suit	81
	i)	Emergency escape gear	81
	k)	Life rafts	81
	l)	Damage control materials	81
2.	Installations for surfaced boat		81
	a)	Battery ventilation	81
	b)	Emergency vent valves	81
	c)	Coaming	82
	d)	Life buoy, night signal buoy and dinghy	83
	e)	Life jackets	83
	f)	Railing and tethers	83
	g)	Recognition marks for aircraft	84
3.	Installations for submerged boat		84
	a)	Compartmentation	84
	b)	Air purification system	84

U-Boat Type VIIC	U-boat Information	Page IX

	Table of Contents

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	c)	Compressed air and emergency blowing manifold	86
	d)	Emergency air supply system	86
	e)	Life rafts	87
	f)	Air trap	87
	g)	Emergency escape gear	87
	h)	Net deflector	88
	i)	Net cutter	88
	k)	Compartment ready indicating system	88
	l)	Hull closure indicating system	88
	m)	Vent valve indicating system	88
IX. Damage Control.
1.	General		89
	a)	Damage control parties	89
	b)	Balancing the boat	90
	c)	Reserve buoyancy	91
2.	Weights and trim adjustment with water flooding		91
	a)	Leakage into external tanks with the boat surfaced	92
	b)	Leakage into pressure hull with the boat surfaced	93
	c)	Leakage into external tanks and into pressure hull with the boat surfaced	97
	d)	Leakage with the boat submerged and with the boat lying on the bottom	102
3.	Leakage counter measures		103
	a)	Blowing	103
	b)	Sealing the compartments	104
	c)	Sealing leaks	104
	d)	Pumping	105
	e)	Weight relief	106
4.	Escape from a sunken boat		106
	a)	Escape procedures	106
	b)	Influence of chlorine gas, nitrogen and oxygen	107
	c)	The practical use of the emergency escape gear	111
	d)	Flooding options and flooding time	112
5.	Gas hazard		117
6.	Fire hazard		117
7.	Fire extinguishing equipment and flooding installation		117
8.	Drainage and compressed air systems		117

Page X	U-boat Information	U-Boat Type VIIC

	Table of Contents

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B. Machinery Installation.
I. Propulsion Plant			118
1.	M.A.N. diesel engine installation		118
	a)	M.A.N. general and performance figures	118
	b)	Construction of the M.A.N. propulsion plant	119
	c)	Auxiliary machinery associated with M.A.N. engines	120
1.	G.W. diesel engine installation		123
	a)	G.W. general and performance figures	124
	b)	Construction of the G.W. propulsion plant	124
	c)	Auxiliary machinery associated with G.W. engines	125
1-1	Comparison between M.A.N. - G.W. engines		129
2.	Batteries		131
	a)	Technical and performance data	131
	b)	Construction and maintenance	131
	c)	Capacity, discharging, final voltage	133
	d)	Charging	133
3.	The main switchboards and battery connections		134
4.	E motor installation		134
	a)	Design and performance data	134
	b)	Motor construction and connections	135
5.	Shaft lines		136
	a)	Propellers	136
	b)	Drive shafts, bearings and shaft brakes	136
	c)	Main thrust bearing	137
	d)	Clutches	138
6.	Interaction of the engines and motors		140
	a)	General	140
	b)	Diesel engine only drive	140
	c)	E motors only	140
	d)	Support and buffer mode	140
	e)	Diesel-electric drive	141
	f)	Charging operation	141
II. Auxiliary Machinery for Propulsion.			142
1.	Ship's auxiliary machinery		142
	a)	Main rudder and dive planes	142
	b)	Anchor and warping capstan installation	143
	c)	Air compressor	144

U-Boat Type VIIC	U-boat Information	Page XI

	Table of Contents

			Page
	d)	Auxiliary drain and trim pump	145
	e)	Main drain pump	145
	f)	Intake and exhaust air fan	145
	g)	Periscope drive	146
	h)	Refrigeration plant	148
	i)	Distilling unit	149
	k)	Hand pumps etc	150
	l)	W.C. installation	151
	m)	Gyro compass installation	151
2.	Auxiliary machinery for the diesel engine installation		151
	a)	Auxiliary lubricating oil pump	151
	b)	Auxiliary cooling water pump	152
3.	Auxiliary machinery for the E installation		153
	a)	E motor fan blower	153
	b)	Cooling pump	153
III. Draining and Flooding.
1.	Main drainage installation		155
2.	Auxiliary drainage installation		155
3.	Hand drainage installation		156
4.	Artificial flooding installation		156
5.	Natural flooding installation		156
IV. Sea, Wash, and Fresh Water Installations.
1.	Sea water installation		158
2.	Wash water installation		158
3.	Fresh water installation		158
V. Ventilating Systems.			160
VI. Heating Installations.			161
VII. Lubricating Oil Installations.			163
VIII. Fuel oil Installations.			165
IX. E Installations.
1.	E motors		167
2.	Batteries		167
3.	Main switchboards		168
	a)	Main switchboards with lever switches	168
	b)	Main switchboards with rotary switches	170

Page XII	U-boat Information	U-Boat Type VIIC

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4.	Auxiliary switchboards and power distribution		173
5.	Electric equipment		174
	a)	E drive motors and their current draw	174
	b)	Rotary converters and associated equipment	175
	c)	Ordering and reporting installations	179
		General information and power supply	179
		Engine order telegraph system	180
		Shaft revolution indicator system	180
		Rudder order telegraph and rudder angle indicator system	181
		Dive planes angle indicator system	182
		Alarm bell and flashing light system	182
		Compartment ready indicating system	183
		Hull closure indicating system	183
		Vent valve indicating system	183
		Torpedo orders indicator system	184
	d)	Signal equipment	184
		General information and power supply	184
		Running lights	185
		Searchlight equipment	185
	e)	Power load for ships purposes	185
		Boat lighting	185
		Hot plates	186
		Boats heating	186
C. Annex: Drawings

- . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . -

U-Boat Type VIIC	U-boat Information	Page XIII

	Introduction

Development of the Type VII C U-boat

===========================

The first medium size U-boats of the German Navy were the Type VII U-boats (displacement 500 tons) of U-Flotilla "Saltzwedel" (1936). Their main distinguishing characteristic was the aft torpedo tube on the upper deck.

This boat was developed into the Type VII B (displacement 517 tons). These boats which together formed U-Flotilla "Wegener" (1938) had the aft torpedo tube inside the pressure hull and also some diving and operational improvements and greater propulsion plant performance as a result of installed superchargers.

The Type VII B U-boats came into service during peace time, but after war broke-out in 1939, they proved their outstanding utility as a prefect front-line submarine. They fulfilled all requirements completely.

Nevertheless, even before war time there were attempts to make some other improvements, which eventually led to the Type VII C U-boat:

1. New electronic and communication equipment required more space to install. This space was obtained by lengthening the control room by the distance of one half frame forward of, and one half frame aft of the search periscope. The type VII C boat was lengthened by one frame.

2. Related to above changes, the quite constricted type VII B conning tower dimensions were increased in width by 60 mm and length by 300 mm.

3. Diving characteristics, especially in heavy seas, were improved by adding pressure-proof negative buoyancy tanks forward of the port and starboard regulating tanks.

4. Surface range was improved by increasing the fuel oil capacity of fuel oil tank 1 (internal). This was achieved by moving the aft bulkhead of main ballast tank 3 one frame forward. The volume of fuel oil tank 1(internal) was increased from 32.5 m³ in the type VII B to 37.9 m³ in the type VII C.

Page XIV	U-boat Information	U-Boat Type VIIC

	Introduction

5. One of the two electrically driven compressors (Krupp design) was replaced by a diesel engine driven compressor (Junkers design) in order to reduce electric power consumption.

6. To achieve required reliability the lubricating oil purifying installation was provided.

U-Boat Type VIIC	A. Ship Information	Page 1

U-boat Information	I. General	1

A. Ship Information.

I. General.

1. Shipyard information.

Shipyards.

Primary Yard:

Friedrich Krupp Germaniawerft A.-G., Kiel-Gaarden

North Sea Area

Follow-on Yards:

Nordseewerke Emden

Kriegsmarinewerft Wilhelmshaven

Vegesacker Werft

Blohm and Voß Hamburg

Howaldtwerke Hamburg

H.C. Stülken Hamburg

Baltic Area

Flensburger Shipbuilding Company

Deutsche Werke Kiel

Lübecker Flenderwerke

Danzinger Werft

Schichauwerft Danzig

Construction data for U-____


Construction yard	Keel laying	Launching	1. Commissioning	Decommissioning	2. Commissioning

U-boat Commands must enter valid data on page 1 under "Construction data for U-____" and on page 3 under "Measured displacement" for their boats in their U-boat Manuals. [Pasted note]

Page 2	A. Ship Information	U-Boat Type VIIC

2	I. General	U-boat Information

2. Overview (ship construction).
	a)	Dimensions.
		Length:
		Length over all		m
		Length at the waterline		m
		Length of the pressure hull with end caps		m
		Length of pressure hull without end caps		m

		Width:
		Maximum width		mm
		Maximum width at the waterline		mm
		Maximum width of the pressure hull		mm
		Diameter of the forward end of the pressure hull		mm
		Diameter of the aft end of the pressure hull		mm

		Draft:
		Draft aft		m
		Draft amidships		m
		Draft forward		m
		Note: Length, width, and draft are classified.

		Height:
		Upper deck above keel	6000	mm
		Top of conning tower above keel	9397	mm
		Top of attack periscope above conning tower fairing	5266	mm
		Top of search periscope above conning tower fairing	2602	mm
		Extended attack periscope above keel	14663	mm
		Extended air search periscope above keel	11999	mm

		Conning tower and keel:
		Height of conning tower above pressure hull	2630	mm
		Length of the conning tower	2950	mm
		Width of the conning tower	1760	mm
		Height of the keel	550	mm
		Width of the keel	1100	mm
		Length of straight keel	32355	mm

U-Boat Type VIIC	A. Ship Information	Page 3

U-boat Information	I. General	3

b) Measured displacement.

U-boat Commands must enter valid data on page 1 under "Construction data for U-____" and on page 3 under "Measured displacement" for their boats in their U-boat Manuals. [Pasted note]

Surfaced displacement

m³

Submerged displacement

m³

Official displacement

m³

c) Volume and distance from center of mass.

Interior Rooms:


Room	Volume m³	Distance meters

Aft torpedo room and E motor room	62	-18.75
Diesel engine room	88	-10.95
Petty officer quarters without/with battery compartment 1	33/47	-4.55
Control room	45	+2.3
Officers, chief petty officers, radio, listening, switch rooms without/with battery compartment 2	63/77	+9.65
Forward torpedo room	72	+18.85
Conning tower without/with periscope shaft	10/14	+2.3
Total volume:	405

Exterior Spaces:


Room	Volume m³	Distance meters

Stern buoyancy tank	4.28	-31.15
Bow buoyancy tank	8.0	+29.05

Ballast tanks, Fuel oil tanks, Tanks and Reservoirs:

Measured volume (liters)


U-boat	Regulating tanks		Trim tanks		Regulating and reserve fuel oil tanks		Torpedo compensating tanks
No.	Stb.	Port	Aft	Forward	Stb.	Port	1	2	3

F 93	(7850)	(7850)	(3550)	(3600)	(4700)	(4700)	(2350)	(5750)	(5750)
(Type boat)
. . .	7800	7660	3640	3680	4640	4580	2450	5680	5790
	Figures in parentheses are calculated

Page 4	A. Ship Information	U-Boat Type VIIC

4	I. General	U-boat Information

Tanks: (Calculated values)


Tank	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Main ballast tank 1	30.700	6	-26.00
Main ballast tank 3 (with vent duct 1 m³)	47.750	30	+2.10
Main ballast tank 5	25.150	6	+26.47
Regulating tank 2 stb. (total 7.850 m³)	7.600	140	-0.10
Regulating tank 2 port (total 7.850 m³)	7.600	140	-0.10
Aft trim tank	3.550	30	-23.05
Forward trim tank	3.600	30	+18.55
Torpedo compensating tank 1	2.350	30	-21.15
Torpedo compensating tank 2	5.750	30	+15.25
Torpedo compensating tank 3	5.750	30	+15.25
Fresh water tank 1 (Galley)	2.625	3	-7.05
Fresh water tank 2 (Control room)	0.465	3	+1.25
Fresh water tank 3 (Officers room)	0.785	3	+9.90
Wash water tank (Listening room)	0.485	3	+7.75
Waste water tank 1	0.760	1	-6.05
Waste water tank 2	0.485	1	+7.75
Negative buoyancy tank stb. (total 2.15 m³)	2.070	30	+2.45
Negative buoyancy tank port (total 2.15 m³)	2.070	30	+2.45

Fuel Oil Tanks: (Calculated values)


Bunker	Volume m³	Test Pressure meters H₂O	Distance meters

Main ballast and reserve fuel oil tank 2 starboard	11.300	6	-7.9
Main ballast and reserve fuel oil tank 2 port	11.300	6	-7.9
Main ballast and reserve fuel oil tank 4 starboard.	13.300	6	+7.0
Main ballast and reserve fuel oil tank 4 port	13.300	6	+7.0
Regulating and reserve fuel oil tank 1 starboard	4.700	140	-3.2
Regulating and reserve fuel oil tank port	4.700	140	-3.2
Fuel oil tank 1 (internal)	37.900	8	-3.2
Fuel oil tank 2 (internal)	32.800	8	+8.3
Fuel oil collecting tank	0.425	6	-9.5

U-Boat Type VIIC	A. Ship Information	Page 5

U-boat Information	I. General	5

Tanks:


Tank	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Lubricating oil supply tank 1	3.270	6	-11.45
Lubricating oil supply tank 2	3.230	6	-11.45
Lubricating oil collecting tank starboard	0.800	6	-11.65
Lubricating oil collecting tank port	0.800	6	-10.45
Dirty lubricating oil tank	0.790	6	-12.85

Storage and Weight:


Storage	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Fuel oil gravity feed tank	0.730		-11.50
Lubrication oil daily service tank	0.026		-7.55
Water distillate tanks 1-3			-18.50
149 liters + 199 liters + 153 liters	0.501		-16.70
			-16.25
Storage for flare shells	0.033		+5.45
Storage for demolition charges	0.500		+9.90
Ammunition magazine	7.350		+6.85
Provisions storage aft	2.000		-6.65
Provisions storage forward	1.600		+13.15
Wash water daily supply tank	0.030		-5.90
Brine tank	0.030		+3.05

Torpedo stowage:


Tubes	Volume liters	Remarks	Distance meters

Torpedo tubes I - V		Piston 70 kg	fwd: +25.25
with piston inserted	1680		aft: -26,15
without piston	1740		fwd: +25.10
			aft: -26.00
Upper deck container forward, aft	2500		fwd: +19.18
with/without G 7 A		0.5 atm	aft: -20.23
		test pressure	fwd: +18.75
			aft: -19.80

Page 6	A. Ship Information	U-Boat Type VIIC

6	I. General	U-boat Information

Torpedo stowage:


Tubes	Volume liters	Remarks	Distance meters

Torpedo in the tube	-	G 7 E =	fwd: +25.63
G 7 E / G 7 A		G 7 E =	aft: -26.53
		G 7 A =	fwd: +25.56
		G 7 A =	aft: -26.46

Reserve stowage forward, aft	-	G 7 E =	fwd: +17.75
		G 7 A =	fwd: +17.66
		G 7 A =	aft: -18.30

Residual Water in tanks and bunkers:


Designation	Volume m³	Remarks

Main ballast tank 1	2.550)
Main ballast tank 3	0.800)	100 mm above
Main ballast tank 5	1.980)	upper edge
Main ballast and reserve fuel oil tank 2 port/stb.	0.950)	of flood opening
Main ballast and reserve fuel oil tank 4 port/stb.	1.050)
Regulating and reserve fuel oil tank 1 port/stb.	~ 0
Regulating tank 2 port/stb.	0.500	Not pumpable
Negative buoyancy tank port/stb.	0.160	Not blowable

Total capacity:

Ballast tanks	103.600 m³
Ballast tanks and ballast and reserve fuel oil tanks	152.800 m³
Fuel oil tank 1 and 2 (internal)	70.700 m³
Fuel oil tanks (internal), main ballast and reserve fuel oil tanks, and regulating and reserve fuel oil tanks	129.700 m³
Lubricating oil supply tanks 1 and 2	6.500 m³
Lubricating oil collecting tanks port and stb.	1.600 m³
Fresh water tanks	3.875 m³
High pressure air flasks at 205 kg/cm²	3900 liters
Oxygen flasks at 150 kg/cm²	500 liters

U-Boat Type VIIC	A. Ship Information	Page 7

U-boat Information	I. General	7

d)	Test and operating pressures.
	Spaces, vents/valves.
	Pressure test in pressure dock under external pressure	10.5 atm
	Watertight bow and watertight stern under air pressure	0.02 atm
	Pressure hull and conning tower including periscope shafts with internal pressure equivalent to water pressure at the bottom of the pressure hull	30 meters Pressure head
	Pressure-proof curved watertight bulkheads from the cupped side with internal pressure equivalent to water pressure at the top of the pressure hull	30 meters Pressure head
	Watertight bulkheads with internal pressure equivalent to water pressure at the top of the pressure hull	1 meter Pressure head
	Testing the bulkhead tightness of the ammunition magazine for gas tightness	1 meter Pressure head
	Hull plating tested to	15 atm
	Flood valves of main ballast and reserve fuel oil tanks and main ballast tank 3 at the valve	1 meter Pressure head
	Vent valves with pressure equivalent to water pressure at the top of main ballast tanks or main ballast and reserve fuel oil tanks to	6 meters Pressure head
	Emergency vent valves for main ballast tank 3	1 meter Pressure head
	Emergency vent valves for main ballast and reserve fuel oil tanks 2 and 4 port and stb.	6 meters Pressure head
	Deck of the battery compartment by filling the battery compartment with air under pressure	100 mm Pressure head

Tanks, Fuel Oil Tanks, Bunkers, Gravity Tanks see paragraph I 2 c

High pressure air, oxygen and pressure oil flasks.
	High pressure air flasks:	Operating pressure	205 kg/cm²
		Test pressure	280 kg/cm²
	Starting air flasks MAN:	Operating pressure	75 kg/cm²
		Test pressure	120kg/cm²
	Starting air flasks GW:	Operating pressure	30 kg/cm²
		Test pressure	50 kg/cm²
	Oxygen flasks:	Operating pressure	150 kg/cm²
		Test pressure	225 kg/cm²
	Hydraulic oil flasks	Operating pressure	70 kg/cm²
		Test pressure	120 kg/cm²

Page 8	A. Ship Information	U-Boat Type VIIC

8	I. General	U-boat Information

Auxiliary Machinery.
Air compressor:	Operating pressure	LP stage	1.2-1.4 kg/cm²
		MP stage 1	7-9 kg/cm²
		MP stage 2	19.5 - 45 kg/cm²
		HP stage	205 kg/cm²
	Test pressure = 1.5 x operating pressure
	Test pressure radiator casing 15 kg/cm²
Capstan motor:	Operating pressure		3.5 kg/cm²
Hydraulic oil pump for periscope drive: Operating pressure			70 kg/cm²
Compartment ventilating fan:	Operating pressure	424 mm H₂O
	Test pressure of fan enclosure		0.25 kg/cm²

Safety valves:
	HP air manifold		220 kg/cm²
	Ballast tank blowing manifold		30 kg/cm²
	Low pressure air manifold		18 kg/cm²
	Trim air pressure distributor		2.5 kg/cm²
	Regulating tank pressure discharge distributor		12 kg/cm²
	Anchor capstan		6 kg/cm²

e)	Materials.
	Pressure hull	St 52 K M
	Conning tower casing	Wh - n/A Special type
	Conning tower deck	Chromium Nickel-Molybdenum-Steel
	Upper deck canisters for torpedoes	Aluminium
	Casting	Hy 51
	Sheet	Hy 5 W
	Flood valves	Steel casting
	Flood valve frames	Steel casting
	Vent valves, casing	Steel casting
	Vent valves, seat	Steel casting with bronze
	Emergency vent valves	Steel casting

U-Boat Type VIIC	A. Ship Information	Page 9

U-boat Information	I. General	9

	HP air flasks	Chromium Nickel-Molybdenum steel

	Armatures	Steel casing with bronze
	Piping	Mild steel inside and galvanized outside
	Piping in fuel oil bunkers, battery room and fresh water tanks	Galvanized mild steel
All gear rods and linkages with their bearings installed outside the pressure hull are galvanized or made from sea water-proof material.

f)	Weights.
	I.	Ship's hull including ballast	= %
	II.	Auxiliary machinery for propulsion	= %
	III.	Armour	= %
	IV.	Propulsion plant including associated auxiliary machinery	= %
	V.	Gunnery	= %
	VI.	Torpedo weaponry	= %
	VII.	Equipment	= %
	VIII.	Fuel and lubricating oil	= %
	IX.	Weight reserve	= %
	Sum of I – IX = Construction displacement = 100%
	Note: Above data is not filled because it is secret.

g)	Stability.
	General.
	The stability of the boat can be expressed as the lever arm MG (so called "meta centric height"), i.e. the distance between the center of gravity G and transverse meta centre M (intersection of the upward force of buoyancy and ship vertical centre-line).
	The heeling of the boat by the force P by angle φ creates the righting arm (stabilizing arm):

	The position of the M over the buoyancy center F during -cruise depends on the position of the floating line (transverse water line gives the height of the M).

Page 10	A. Ship Information	U-Boat Type VIIC

10	I. General	U-boat Information

	When heeling angles are small (0-2°) the position of M can be considered as constant, so stabilizing arm * sin φ is also constant (starting stability).
	At large heeling angles the position of M is changing. In U-boats, however, the stability at large declinations is not calculated - as you know, U-boats with sufficient starting stability are stable at large heeling angles. The "starting stability" will be called "stability".
	During -cruise M overlaps with buoyancy center F:

	The stabilizing arm * sin φ is equal for longitudinal and lateral declinations. Longitudinal stability during -cruise is also as large as transverse stability, whereof it reacts to trim changes.
	During -cruise the longitudinal stability is very large (MG approximately = ship length).

Note: Free surfaces are not accounted for in stability considerations.

U-Boat Type VIIC	A. Ship Information	Page 11

U-boat Information	I. General	11

	Inclining test.
	The inclining test verifies previously calculated ship stability and is carried out by applying a well known heeling moment , which is equal to the righting moment .
	The deflection from the plumb-line gives the heel angle and then from

	the righting arm can be calculated.

	Stability Values for Type VII C U-boats
	For the following trim conditions the corresponding approximate stability values ratio apply:
	a:b:c:d: = 5:4:3:2

	a)	-cruise, trim condition A
	b)	-cruise, trim condition B
	c)	-cruise
	d)	The least stability is during diving, when the upper edge of the main ballast reserve fuel oil tanks comes under the surface.
	The stability of boats with G.W. engines is about 30 mm lower than in boats with M.A.N. engines.
	Note: For the absolute values of the meta centric height of the boats with M.A.N. and G.W. engines see secret documents.

3)	Weapons overview.
	a) Torpedo and mine armament.
	14 53-cm torpedoes may be carried
	4 in the bow torpedo tubes
	1 in the stern torpedo tube
	9 in reserve storage

Page 12	A. Ship Information	U-Boat Type VIIC

12	I. General	U-boat Information

In some torpedo stowage 2 TMA or 3 TMB mines can be stored in place of torpedoes.

The following examples of maximum load are provided:


	G 7a	G 7e	TMA	TMB

1	5	9	-	-
2	3	2	-	21
3	3	2	14	-
4	3	1	-	21
5	3	1	16	-

For storage see paragraph IV 1 c.

Artillery

1 cannon SK C/35, caliber 8.8 cm

1 machine gun C/30, caliber 2 cm

For munitions see paragraph IV 2 b.

Small arms

1 LMG C/34

2 Machine guns

3 Mauser pistols, calibre 7.65 cm

3 bayonets

2 signal pistols

For munitions see paragraph IV 4.

Safety and rescue equipment overview.

Structural safety installations.

Spherical bulkheads for pressure-tight partition	2
Watertight bulkheads	3
Hatch with retractable latches	1
Net cutter	2
Net deflector	3
Recognition marks for aircraft	1

U-Boat Type VIIC	A. Ship Information	Page 13

U-boat Information	I. General	13

Safety equipment.

High pressure air system, air volume at 205 atm: 3900 liters

Oxygen renewal system, oxygen volume at 1 atm: 75000 liters

Air purification system, sodium hydrate cartridges: 212 units

Emergency vent valves for the main ballast tank 3 and main ballast and reserve fuel oil tanks 2 and 4

Emergency blowing manifold (1) for all main ballast and main ballast and reserve fuel oil tanks

Emergency air supply connection (3 x 2) in each pressure-tight compartment

Automatically switched on emergency lamps: 8

Battery ventilation

Compartment ready indicating system

Hull closure indicating system

GHG installation

KDB installation

UT installation

Dry fire extinguisher 3

Foam fire extinguisher 1

Flooding installation

Drainage installation

Damage control materials

Rescue equipment.

Rescue buoys with night signal light	2
Battery powered hand lamps	8
Life buoys	3
Emergency escape gear	55
Life jackets	40
Diving suit	1
Diving suit without weighting systems	1
Watertight suit for the emergency escape set	1
Raft with buoy	2
Dinghy	1

For further information about safety and rescue equipment see section VIII.

Page 14	A. Ship Information	U-Boat Type VIIC

14	I. General	U-boat Information

Test data.

Speed

and


	Diesel engines			E motors

	Turns	Speed		Turns	Speed
		Condition A	Condition B
	R.P.M.	knots	knots	R.P.M.	knots	knots

	Ahead

2 x KF
KF	180	7.2	7.0	55	2.3	1.5
LF	275	10.2	10.0	110	4.5	3
HF	340	12.4	12.0	160	6.3	4.5
2 x HF	396	14.6	14.0	215	8.2	6
GF	435	16.3	16.0	250	9.3	7
AK	471	17.7	17.5	285	10.5	8
3 x AK	480	18.1	17.9	300	11

	Astern

KF	180			55
LF	210			110
HF	250			160
2 x HF	310			215
AK	400			250

Diving time.

While staying still	seconds
At HF forward	seconds
Fast diving	seconds

Diving depth.

Construction depth	100 meters
Tested in pressure dock	105 meters
Deepest allowable depth

U-Boat Type VIIC	A. Ship Information	Page 15

U-boat Information	I. General	15

	d)	Depth differences for bow and stern.
		As per the chart on page 16.

6)	Practical values.
	a)	Speeds for various operating conditions.

Page 16	A. Ship Information	U-Boat Type VIIC

16	I. General	U-boat Information

Tauchungeunterschiede von Bug und Heck gegenüber der Druckmessertiefe

Diving differences for bow and stern opposed to the depth gage

Achterlastig Down by the stern

Bock für Netzabweiser Support for net deflector

Bug Bow

Bug (untere) Netzsäge Bow (bottom of) Net saw/cutter

Bug höher Bow higher

Bug tiefer Bow deeper

Grad Degrees

Heck Stern

Höhertauchung Shallower immersion

Kiel Keel

Netzsäge (oben) Net saw/cutter (top of)

Rudderhacke Rudder heel (bottom of the rudder)

Tiefertauchung Deeper immersion

Turm Conning tower

Vorlastig Down by the bow

U-Boat Type VIIC
A. Ship Information
Page 17

U-boat Information
I. General
17

b) Behavior of the boat under different rudder angle and wind conditions.

c) Turning circles.

Turning circle diameter

Depending on main rudder angle and speed.

Surfaced:

Trim Condition

Rudder angle

Turning circle diameter in meters

AK RPM=471

GF RPM=435

HF RPM=340

LF RPM=275

KF RPM=180

32°

270

265

253

245

230

30°

295

260

250

A

25°

350

310

290

20°

418

370

345

15°

530

475

440

32°

286

280

270

265

253

30°

B

25°

20°

15°

Page 18	A. Ship Information	U-Boat Type VIIC

18	I. General	U-boat Information

Submerged:


Circle to:	Rudder angle	Turning circle diameter in meters
Circle to:	Rudder angle	AK RPM=285	GF RPM=215	HF RPM=160	LF RPM=110	KF RPM=55

	32°	280	260	225	205	180
	30°		270
Port	25°		315
	20°		370
	15°		440
	10°		525

	32°		250
	30°		260
Starboard	25°		305
	20°		350
	15°		405
	10°		480

Note: RPM are valid at the moment of running into the turning circle and during the steady turning condition of the boat are accordingly lower.

Time to reciprocal heading

Rudder Hard Over

and


Speed setting	Time to Reciprocal heading
Speed setting	Trim Condition A	Trim Condition B	Submerged

AK	1 min 10 sec	1 min 13 sec	min sec
GF	1 min 11 sec	1 min 15 sec	min sec
HF	1 min 17 sec	1 min 23 sec	min sec
LF	1 min 33 sec	1 min 36 sec	min sec
KF	2 min 23 sec	2 min 35 sec	min sec

U-Boat Type VIIC	A. Ship Information	Page 19

U-boat Information	I. General	19

Time to put in and to take effect

with main rudders in astern cruise


Rudder angle	Time to put in		Time to result
Rudder angle	RPM=100	RPM=360	RPM=100	RPM=360

32°	7.3 sec	sec	8.8 sec	sec
30°	6.8 sec	sec	8.2 sec	sec
25°	5.8 sec	sec	7.0 sec	sec
20°	4.8 sec	sec	5.6 sec	sec
15°	3.8 sec	sec	4.3 sec	sec
10°	2.8 sec	3 sec	3.0 sec	3.5 sec

Main Rudder Limits

astern cruise


AK	GF	HF	LF	KF

10°	15°	32°	32°	32°

Page 20	A. Ship Information	U-Boat Type VIIC

20	I. General	U-boat Information

	d)	Behavior in a seaway.










	e)	Diving characteristics, crash dives.

U-Boat Type VIIC	A. Ship Information	Page 21

U-boat Information	I. General	21

	f)	Depth control characteristics.
		Normal









		In a seaway

Page 22	A. Ship Information	U-Boat Type VIIC

22	I. General	U-boat Information


		During torpedo firing









		During mine firing

U-Boat Type VIIC	A. Ship Information	Page 23

U-boat Information	I. General	23

	g)	Vibration:
		By engines at different RPM






		by torpedo firing




		by periscope with drag at speed
		Attack periscope (aft periscope):






		Air search periscope (forward periscope):

Page 24	A. Ship Information	U-Boat Type VIIC

24	I. General	U-boat Information

	h)	Sound levels (from testing with "U-45 and "U-51")
		(updated for VII C boats after testing)

		Boat lying on the bottom
		Sound from auxiliary machinery at 250 meters distance
		Operating: Underwater telegraphy converter and gyro compass


Not heard	Quiet	Moderately loud	Loud	Very loud

Gyro compass-circulation pump	Radio converter	UT converter	Main drain pump	Auxiliary drain and trim pump
Gyro compass- converter	Hydraulic oil pump	Auxiliary LO pump		Air compressor
Extending attack periscope	W.C. pump	Retracting attack periscope		Drive motor for turning attack periscope
Extending air search periscope	Echolot (shallow depth device)	Retracting air search periscope
Tracking motor in torpedo data computer	Control valves for the periscope drive	Compartment ventilation fan	Walking in the boat	Speaking in the boat
Dive planes electric drive	Engine order telegraph without buzzer	Engine order telegraph with buzzer
Dive planes (hand drive)				Working in the boat
Main rudder electric drive	Main rudder (hand drive)			Echolot (deep depth device)

Boat hanging on the periscope

Sound from auxiliary machinery at 250 meters distance. Motors stopped. No auxiliary machinery

except for UT converter and gyro compass.


Not heard	Quiet	Moderately loud	Loud	Very loud

Extending air search periscope		Retracting air search periscope
Extending attack periscope		Retracting attack periscope

U-Boat Type VIIC	A. Ship Information	Page 25

U-boat Information	I. General	25

Boat at attack depth

Boat driven

at attack depth in a circle of 500 meters radius


Not heard	Quiet	Moderately loud	Loud	Very loud

One motor KF = 50 RPM
Attack periscope	Draining and trimming with air		Draining and trimming with auxiliary drain and trim pump
Dive plane driving motor	Operating both dive planes by hand

Both motors KF = 50 RPM	Compartment ventilating fan

Compartment ventilating fan				Both motors LF 100 RPM

Both dive plane driving motors		Both motors 80 RPM	Both motors 140 RPM	Both motors 250 RPM
Attack periscope		Both motors 50 RPM	Both motors 120 RPM	Both motors 200 RPM
Compartment ventilating fan			Both motors LF 100 RPM	Both motors 180 RPM
				Both motors 160 RPM

At starboard 110 and port 90 RPM the noise is weaker than with both motors at 100 RPM

Draining and trimming by means of air at 80 RPM or less: slight noise is audible.

Detection range with different RPM rates (submerged)


At	80 RPM:	4500 meters	(Detection range particularly large because of howling sound)
At	160 RPM:	5000 meters	(Detection range lowered.)

Page 26	A. Ship Information	U-Boat Type VIIC

1	II. Boat and Pressure Hull	U-boat Information

II. Boat and Pressure Hull - including thru-hull openings.

1.	General construction of U-boats.
	Type VIIC U-boats are medium sized mixed construction boats.
	The boat is built from following parts:
	pressure hull with conning tower
	outer shell
	upper deck and bridge deck.
	The conning tower, which is located above the control room at half of the pressure hull length is connected to it by means of the control room hatch.
	The outer shell encloses the stern, both sides and the bow of the pressure hull. The substructure of the upper deck extends over the full length of the boat and is welded to the pressure hull by means of knee-plates. To reduce the drag while submerged, the conning tower is enclosed by the conning tower casing.
	In the bottom of the pressure hull there is a 0.5 meter high and 1.1 meter wide keel box.

2)	Construction of the pressure hull.
	The pressure hull has a circular cross-section over its full length. The hull consists of one cylindrical and seven cone-shaped parts. These parts are joined together by arc welding, and strengthened from inside by 82 frames - which are made from bulb tee girders – and pressure-proof and watertight bulkheads. The quality of the arc welds are tested by the shipyard with radiographics. At first 25% of all welded joints on type VII boats were faulty, due to strict testing this number reached 15%. This ensures greater resistance to water pressure at deep depths. The thickness of the pressure hull plates decreases towards the ends.

U-Boat Type VIIC	A. Ship Information	Page 27

U-boat Information	II. Boat and Pressure Hull	2

	Especially stressed areas (i.e. under the conning tower and around the aft torpedo hatch, exhaust valves and diesel engine room patch) are further strengthened with thicker plates. Both ends of the pressure hull are enclosed by two outside cambered dished plates. The forward end of the pressure hull is adequately strengthened to account for the weakening due to the openings for the four torpedo tubes. The thickness of plating in the cylindrical part of the hull is 18.5 mm and decreases towards the forward and aft ends and in conical parts is 16 mm. The thickness of plating at both hull endings is 35 mm.

3)	Partitioning of the pressure hull.
	The pressure hull is divided into three compartments by two pressure-proof bulkheads and subdivided into six rooms by the following watertight bulkheads, which from aft are as follows: (see Chapter C: Tanks and installations plan)
	Compartment I (Frame 0-39).
	Room 1: Aft torpedo- and E motor room Frame 0 - 16-1/2.
	1 stern torpedo tube, E motors, converters, switchboards, air compressors, driving motors for main rudders and after dive planes, torpedo compensating tank and after trim tank, 1 oxygen flask, 1 emergency fresh water tank.
	Under floor: stowage for 1 reserve torpedo, stowage for 3 distilled water containers.
	Room 2: Diesel engine room Frame 16-1/2 - 29.
	Diesel engines and auxiliary machinery, 2 starting air flasks, 2 oxygen flasks.
	Under floor: lubricating oil supply tanks, lubricating oil collecting tanks, dirty oil tank, fuel oil collecting tanks.
	Room 3: Petty officers room Frame 29 - 39.
	W.C., galley, stowage for provisions, automatic battery switch 1, refrigeration plant, HP air bank 3.
	Under floor: fresh water tank 1, waste water tank 1, fuel oil tank 1, battery room 1.

Page 28	A. Ship Information	U-Boat Type VIIC

3	II. Boat and Pressure Hull	U-boat Information

	Compartment II (Frame 39 - 50-1/2).
	Room 4: Control room.
	Main drain pump, auxiliary drain and trim pump, drive for aft (attack) periscope, control station for main rudder and dive planes, gyro compass, refrigeration plant, distilling unit, trimming station, fresh water tank 2, 4 oxygen flasks.
	Under floor: main ballast tank 3 (Frame 41 - 48).

	Compartment III (Frame 50-1/2 - 80).
	Room 5: Officers- and chief petty officers quarters Frame 50-1/2 - 60, radio- and underwater telegraphy room, listening room, automatic battery switch 2, stowage for provisions, W.C., fresh water tank 3.
	Under floor: fuel oil tank 2 (Frame 48 – 63), storage for explosive charges, munitions magazine, active sonar room, wash water tank, waste water tank 2, battery room 2.
	Room 6: Forward torpedo room Frame 63 - 80.
	4 bow torpedo tubes, auxiliary stowage for 2 reserve torpedoes, HP air pressure bank 4 and 5, 3 oxygen flasks.
	Under floor: stowage for 4 reserve torpedoes or mines, torpedo compensation tanks 2 and 3, forward trim tank.

4)	Conning tower structure.
	The shape of the conning tower in horizontal cross-section is an ellipse in the aft section and the arc of a circle in the lateral and forward sections. These parts are joined together without flat spots. The radius of the forward arc is 575 mm, and that of the side arcs 2260 mm. To decrease the drag of the conning tower during submerged cruise, the tower is enclosed with a casing.
	The conning tower is enclosed at the top by the bridge deck fabricated from 30 mm thick steel plate, which is welded to the conning tower walls. The thickness of the conning tower wall plates is 32 mm.

U-Boat Type VIIC	A. Ship Information	Page 29

U-boat Information	II. Boat and Pressure Hull	4

In conning tower are installed: aft (attack) periscope with hydraulic driving motor, main rudder steering station, torpedo fire control installation.

Openings in the pressure hull.

The opening in the pressure hull are necessary for:

Linkage and shafts

Lines

Hull fittings

Communication equipment

Measuring equipment.

All installations passing through the hull are tested at 15 atm.

In each room there are the following openings:

Aft torpedo and E motor room.

Openings for linkage and/or shafts:
	For	Vent valve for main ballast tank 1	1
	"	Main rudder drive	1
	"	Aft dive planes	1
	"	Propeller shafts	2
	"	Outer torpedo tube door opening	1
	"	Vent valve for the stern buoyancy tank	1
	"	Torpedo loading hatch (clearance 660 mm)	1
Openings for lines:
	For	Emergency air supply and exhaust	2
	"	Mine ejection	2
	"	Blowing line for main ballast tank 1	1
	"	Lubrication for main ballast tank 1	1
	"	Hull valve in blowing line for stern buoyancy tank	1
	"	Flooding line for torpedo tube	1
	"	Vent line for torpedo tube	1
	"	Hull valve for HP air bank 1	1

Page 30	A. Ship Information	U-Boat Type VIIC

5	II. Boat and Pressure Hull	U-boat Information

Openings for hull fittings:
	For	Hull valve for cooling water discharge	1
	"	Hull valve for cooling water pump intake and flooding torpedo compensating tank	1

Diesel engine room.

Openings for linkage and/or shafts:
	For	Vent valve for main ballast and reserve fuel oil tank 2 stb. and port	1
	"	Main blowing valve for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Grinding mechanism for the exhaust gas valves stb. and port	4
	"	Ventilation exhaust foot valve	1
	"	Ventilation supply foot valve	1
	"	Diesel engine air induction trunk foot valve	1
	"	Selector valve for lubricating points	2
Openings for lines:
	For	Hull valve in fuel oil delivery line from main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for air evacuation for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for fuel oil intake	1
	"	Hull valve for lubricating oil intake	1
	"	Hull valve for the compensating water line	1
	"	Ships steam heating connection	2
	"	Hull valve for HP air bank 2	1
Openings for hull fittings:
	For	Hull valve for cooling water pump stb. and port	2
	"	Assembly patch 4940 x 1890 mm and in this an assembly hatch 860 x 1890 mm	1

Petty officer room (with galley).

Openings for linkage and/or shafts:
	For	Flood valves for main ballast and reserve fuel oil tank 2 stb. and port	4
	"	Emergency vent valves for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Marker buoy flooding and drainage operation shafting	2
Openings for lines:
	For	Blowing lines for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for fuel delivery line from main ballast and reserve fuel oil tank 2 stb. and port	2

U-Boat Type VIIC	A. Ship Information	Page 31

U-boat Information	II. Boat and Pressure Hull	6

	For	Cooling water gravity tank (warm sea water)	1
	"	Hull valve for filling fresh water and wash water tanks	1
	"	Lubricating, flood valves main ballast and reserve fuel oil tank 2 stb. and port	4
Openings for hull fittings:
		Assembly patch (battery hatch) 550 x 420 mm	1
		Aft W.C.	2
		Galley hatch (600 mm diameter)	1

Control room.

Openings for linkage and/or shafts:
	For	Flood valves for main ballast and reserve fuel oil tank 4 stb. and port	4
	"	Emergency vent valves main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Vent valve for main ballast and reserve fuel oil tank 2 and 4 stb. and port	2
	"	Vent valve for main ballast tank 3	2
	"	Flood valve for main ballast tank 3	4
	"	Diesel engine air induction trunk head valve	1
	"	Ventilation supply and exhaust head valve	2
	"	Emergency vent valves for main ballast tank 3	2
	"	Exhaust gas blowing valves	8
	"	Aft (air search) periscope (through the deck, main ballast tank 3, pressure hull and conning tower)	3
	"	DF antenna	1
Openings for lines:
	For	Lubrication of flood valves main ballast tank 3	8
	"	Lubrication of emergency vent valves main ballast tank 3	2
	"	Port and stb. blowing lines for main ballast tank 3	2
	"	Blowing lines for main ballast and reserve fuel oil tank 4 stb. and port	2
		Hull valve for emergency air supply and exhaust	2
		Hull valve for emergency blowing of main ballast tanks 1 and 5	2
		Compressed air measuring lines	8
		Hull valve for compressed air filling intake	1
		Tyfon air whistle	3

Page 32	A. Ship Information	U-Boat Type VIIC

7	II. Boat and Pressure Hull	U-boat Information

	For	Regulating tanks water level indicators	4
	"	Depth gauges	4
	"	Log installation	2
	"	Vent line for regulating tank 2 port and stb.	2
	"	Vent line for regulating reserve fuel oil tank 1 port and stb.	2
	"	Viewing port for magnetic compass	1
	"	Vent gate valve for main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Hull valve for oxygen intake	1
	"	Cooling water for gyro compass intake and discharge	2
	"	Drainage for compartment ventilation supply and exhaust and diesel engine air induction trunk head valves	3
	"	Hull valve deck washing water	1
	"	Hull valve in fuel oil delivery line from main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Echo depth sounder (deep depth device)	3
	"	Intake for fine control of flooding regulating tanks and/or regulating reserve fuel oil tanks	1
	"	Telephone connection for pressure dock	1
	"	Lubrication for flood valves of main ballast and reserve fuel oil tank 4 stb. and port	4
Openings for hull fittings:
	For	Flood valves of main ballast tank 3	6
	"	Intake hull valve for fine flooding of regulating tanks	1
	"	Hull valve for flooding munitions magazine	1
	"	Hull valve from the sea	1
	"	Hull valve discharge drain pump	1

Officers and chief petty officer's room.

Openings for linkage and/or shafts:
	For	Antenna trunk	1
	"	Active sonar	1
	"	Echo depth sounder (shallow depth device)	2
	"	Echo depth sounder (deep depth device)	3
	"	Underwater telegraphy	2
	"	Active sonar transducer/projector	2
	"	Marker buoy flooding drainage and operation shafting	3
	"	Cooling water gravity tank	1

U-Boat Type VIIC	A. Ship Information	Page 33

U-boat Information	II. Boat and Pressure Hull	8

Openings for hull fittings:
	"	Forward W.C.	2
	"	Assembly patch (battery hatch) 700 x 445 mm	1

Forward torpedo room.

Openings for linkage and/or shafts:
	For	Control valve for anchor capstan	1
	"	Clutch and brake for anchor capstan	1
	"	Anchor release mechanism	1
	"	Chain stopper	1
	"	Shifter for raising and lowering anchor	1
	"	Forward dive planes	1
	"	Annunciator mechanism for length of extended chain	1
	"	Vent valve for main ballast tank 5	1
	"	Vent valve for bow buoyancy tank	1
	"	Outer torpedo tube door opening	4
Openings for lines:
	For	Passive sonar array	4
	"	Transmitter for underwater telegraphy	4
	"	Rotating passive hydrophone	1
	"	Hull valve for emergency air supply	1
	"	Hull valve for emergency air exhaust	1
	"	Hull valve for HP air bank 6	1
	"	Mine ejection	4
	"	Blowing line for main ballast tank 5	1
	"	Blowing line for bow buoyancy tank	1
	"	Flooding line for torpedo tubes	4
	"	Vent line for torpedo tubes	4
	"	Lubrication for vent valve for main ballast tank 5	1
Openings for hull fittings:
	For	Forward torpedo loading hatch (clearance 660 mm)	1
	"	Hull valve from the sea for flooding torpedo compensating tanks 2 and 3	1
	"	Forward torpedo tubes	4

Page 34	A. Ship Information	U-Boat Type VIIC

9	II. Boat and Pressure Hull	U-boat Information

Conning tower.

Openings for linkage and/or shafts:
	For	Forward (attack) periscope	1
Openings for lines:
	For	Targeting and gyro compass repeater	2
	"	Torpedo fire control installation	2
	"	Bridge main rudder angle indicator	1
	"	Air whistle	3
	"	Voice tube	1
	"	Emergency air supply	1
Openings for hull fittings:
	For	Air connection to the bridge	1
	"	Conning tower hatch	1
Openings for lines in floor of conning tower:
	For	Emergency air supply	1
	"	Emergency air exhaust	1
	"	Voice tube	2
	"	Hydraulic oil for periscope (pressure and return)	2
	"	Dive planes angle indicator	1
	"	Drainage	2
	"	Air supply to conning tower	1
	"	Air exhaust from conning tower	1

Construction of the outer shell.

Stern.

In the stern part of the outer shell are located main ballast tank 1 and the stern buoyancy tank, both with flood openings. The main top beams are: 1 longitudinal main girder in the middle and 2 shorter, lateral girders, all welded to the aft top part of pressure hull.

The main bottom beams: 2 heavy stringers.

The stringers with transversal frames and top middle girder are assembled into a truss. The truss is strengthened in the transverse direction by means of the torpedo tube bulkhead.

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U-boat Information	II. Boat and Pressure Hull	10

	The aft torpedo tube is used as horizontal bracing for the stern buoyancy tank.
	In the bow part of outer shell is located the main ballast tank 5 and the bow buoyancy tank, both with flood openings.
	The main top beams: 2 I-girders reaching the forward torpedo tubes bulkhead and one main girder in the middle reaching the bow.
	The main bottom beams: 1 heavy I-girder.
	The bow part of outer shell in the area of the torpedo tubes shutters is not braced by girders. An additional middle girder is located above the bow buoyancy tank at the deck.
	All girders and decks are joined by transversal frames, supporting and uniting the torpedo tube bulkhead and the buoyancy tank bulkhead into one strong structure.

	Saddle tanks.
	The main ballast and reserve fuel oil tanks, regulating and reserve fuel oil tanks, regulating tanks and negative buoyancy tanks are built as lateral saddle tanks, with frames welded to the pressure hull by means of knee-plates. The regulating and reserve fuel oil tanks, regulating tanks, and negative buoyancy tanks are made pressure-proof.

	Upper deck.
	The upper deck spreads over the full length of the boat. The frames of the upper deck are connected with pressure hull by means of knee and support plates. Two support girders made from Z-shaped iron brace the upper deck. The wooden deck, side plates and all free-flooding spaces have flooding holes to prevent the formation of air pockets when diving.

	Conning tower.
	The conning tower casing is made from light plates.
	This casing encloses:
	Air trunks, aerials trunks, DF antenna, rod antenna, forward (air search) periscope, pressure-proof container for MG C/30 gun barrels, cooling water gravity tank. The top part of the conning tower casing is a bridge, used as command station when surfaced and as a platform for the MG C/30 gun.

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11	II. Boat and Pressure Hull	U-boat Information

Special stiffeners.

The parts of the torpedo tubes extending beyond the pressure hull are supported by torpedo tube bulkheads located in stern and bow parts of the outer shell. Places especially exposed to loads (area of dive planes, torpedo guiding plates, the widest part of the hull, shaft support, anchor capstan etc.) are braced with stringers, girders and beams.

Partitioning of the outer shell.

After end: from aft to Frame 12.
	Stern buoyancy tank	Sternpost		to		Fr. 10
	Flooded space		Fr. -10	to		Fr -9
	Main ballast tank 1		Fr. -9	to		Fr. +4/6
	Free flooded space		Fr. +4/6	to		Fr. +12
Amidships: from Frame 19 to Frame 79.
	Free flooded space		Fr. +19	to		Fr. +24
	Main ballast and reserve fuel oil tank 2 stb.		Fr. +24	to	PH.	Fr. +34
	Main ballast and reserve fuel oil tank 2 port		Fr. +24	to	PH.	Fr. +34
	Regulating and reserve fuel oil tank 1 stb.	PH.	Fr. +34	to	PH.	Fr. +38
	Regulating and reserve fuel oil tank 1 port	PH.	Fr. +34	to	PH.	Fr. +38
	Regulating tank 2 stb.	PH.	Fr. +38	to	PH.	Fr. +44
	Regulating tank 2 port	PH.	Fr. +38	to	PH.	Fr. +44
	Negative buoyancy tank stb.	PH.	Fr. +44	to	PH.	Fr. +46
	Negative buoyancy tank port	PH.	Fr. +44	to	PH.	Fr. +46
	Main ballast and reserve fuel oil tank 4 stb.	PH.	Fr. +46	to		Fr. +75
	Main ballast and reserve fuel oil tank 4 port	PH.	Fr. +46	to		Fr. +75
	Free flooded space		Fr. +75	to		Fr. +79
Fore ship: from Frame 92 to bow
	Main ballast tank 5		Fr. +92	to		Fr. +106
	Free flooded space		Fr. +106	to		Bow
	Bow buoyancy tank		Fr. +102	to		Fr. +113
The chain locker is located in main ballast tank 5			Fr. +101	to		Fr. +103

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U-boat Information	III. Diving Installations	1

III. Diving Installations.

1)	Tanks and fuel oil tanks.
	a)	Main ballast tanks.
		Three main ballast tanks are provided, which give the boat the buoyancy necessary for surfaced cruise: main ballast tanks 1 and 5 are located respectively at the aft and forward end of the outer shell, main ballast tank 3 is located inside the pressure hull under the floor of control room. Main ballast tanks 1 and 5 have flooding slits and one vent valve each. The vent valve of main ballast tank 5 opens to the outside - in the opposite direction from all the other vent valves. Main ballast tank 3 is sickle shaped, and is strengthened with perforated bulkheads. On the port and stb. sides there are three rectangular, outward opening, flood valves, which are operated by means of four linkage rods from the control room. Venting of main ballast tank 3 takes place through two separate port and stb. pressure-proof trunks near the aft part of control room, which are then led through the port and stb. regulating fuel oil tanks respectively. These trunks are provided with vent valves, which are independently operated. In the area of passing through the pressure hull, the vent trunks are provided with two emergency vent valves, which are operated manually from the control room. The emergency vent valves are opened in normal conditions and are shut only in case of damage to the vent trunks.

	b)	Main ballast and reserve fuel oil tanks.
		Main ballast and reserve fuel oil tanks 2 and 4 port and stb. are located in the outer shell. The flood valves of these tanks are operated from inside the boat and open inwards. Venting of tanks takes place through venting trunks. Trunks from stb. tank 2 and stb. tank 4 are led to a common vent valve at the stb. side. The same arrangement is made for the port tanks.

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2	III. Diving Installations	U-boat Information

		Vent valves are operated from the control room. Each vent trunk also has an emergency vent valve installed directly at the joint with the tank operated from inside. The emergency vent valves are closed in case of damage to the vent trunks. After each emergency vent valve a gate valve installed, which should be closed, when the tanks are filled with fuel oil.
		Main ballast and reserve fuel oil tanks 2 port and stb. are also fitted at their after ends with a residual air vent installation. There are two cut-off valves installed at the joints with the tanks and two vent valves port and stb. Both vent valves are operated manually from control room by means of linkage rods.

	c)	Stern and bow buoyancy tanks.
		The aft and forward parts of outer shell are constructed as stern and bow buoyancy tanks and are used to dampen longitudinal pitching of the boat. Both tanks have flood slits and one vent valve each.

	d)	Regulating tanks.
		To compensate for changes of weight caused by consumption of provisions, fuel oil, munitions, different number of crew and buoyancy changes due to leakage, regulating tanks 2 port and stb. are provided. They are located on both sides of pressure hull near the control room and are pressure-tight. The amount of water inside the tanks is readable by means of water level indicators or measurable by means of an air pressure gauge. The regulating tanks are connected to the drainage installation in control room and can be drained by main drain pump, auxiliary drain and trim pump as well as by means of compressed air.

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U-boat Information	III. Diving Installations	3

	e)	Regulating reserve fuel oil tanks.
		The regulating reserve fuel oil tanks 1 port and stb. are also located outside the pressure hull between main ballast and reserve fuel oil tanks 2 and the regulating tanks. They are pressure-tight and have the same flood and drain ability as regulating tanks except for blowing with compressed air. The amount of the water inside the tanks is measured by means of air pressure gauge. The tanks can be used as regulating tanks or fuel oil tanks. When used as fuel oil tanks, they are connected with low pressure air installation (through pressure reducing valve to 0.5 atm) and with fuel oil delivery lines. The tanks are also fitted with their own venting and sounding lines.

	f)	Trim tanks.
		The previous consideration of submerged stability (the longitudinal stability during -cruise is as great as transverse stability) that said, even relatively small changes in weight displacement in the longitudinal axis cause trim changes. To compensate for changes of trim during torpedo and mine launching, provision consumption and so on, the trimming installation is provided. In the forward and aft torpedo rooms there are two trim tanks, located 41.6 meters apart. They are connected by a pipeline with a water meter, trim line valve and trim controller. Trimming takes place by means of compressed air or the auxiliary drain and trim pump.

	g)	Negative buoyancy tanks.
		The negative buoyancy tanks stb. and port are located outside the pressure hull, forward of the regulating tanks. They are provided to reduce diving time. The tanks are constructed as pressure-proof. Each tank is flooded by a flood valve operated from control room. Tanks are vented inside the boat and blown by means of compressed air.

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4	III. Diving Installations	U-boat Information

	h)	Torpedo compensating tanks.
		The torpedo compensating tanks are flooded to compensate for the weight of a launched torpedo or mine. Two tanks are located in forward torpedo room and one tank is located in E motor room.
		Each torpedo compensating tank has its own sounding pipe, can be flooded with sea water through a water meter and is connected to the drainage installation. Torpedo compensating tank 2 in the forward torpedo room is also connected with hand wash water pump in the forward W.C.

2) Blowing installation.
	a)	Compressed air blowing.
		The main ballast tanks are blown with compressed air controlled from the blowing distributor, which is located on the stb. side of the control room. Blowing takes place until the boat has sufficient buoyancy to safely open the conning tower hatch.
		All blowing lines are led inside the pressure hull and at places where they pass through hull to tanks they are fitted with cut-off valves. The highest pressure in the installation is 25 atm.

	b)	Exhaust gas blowing.
		Exhaust gas from the diesel engines is used to blow residual water from the ballast tanks. The exhaust gases are fed through the main blowing valves port and stb. to the exhaust gas blowing manifold. The manifold is located outside the pressure hull, over the control room, on the stb. side. Linkage rods pass through the hull to control room.
		The exhaust gas pressure measured in control room should be 0.5 atm.

3) Venting and vent valves.
		All ballast tanks and reserve fuel oil ballast tanks as well as stern and bow buoyancy tanks are fitted with vents that are operated from inside the hull by means of linkage.

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U-boat Information	III. Diving Installations	5

		For protection against foreign bodies the tank vents are cased with steel plates and wired mesh. The vent valves of bow and stern buoyancy tanks are operated from the forward and aft torpedo room respectively. The vents of main ballast tanks and reserve fuel oil ballast tanks are operated from control room. Main ballast tank 1 has a vent valve which is operated by means of a linkage rod and hand wheel located at the aft bulkhead of the control room. Main ballast tank 3 is vented through pressured trunks port and stb., which pass through regulating tank 2 port and stb. and lead to vent valve chambers located above pressure hull. The valves are operated from control room by means of hand levers.
		Main ballast and reserve fuel oil tanks 2 and 4 port as well as main ballast and reserve fuel oil tanks 2 and 4 stb. have on both sides vent ducts installed outside the pressure hull, which lead to common vent valve chambers port and stb. respectively. The common vent valves port and stb. are operated from the control room by means of hand levers.
		Main ballast and reserve fuel oil tanks 2 port and stb. are also provided with a residual air vent installation. Both residual air vent valves are operated by one common hand wheel.
		Main ballast tank 3, main ballast and reserve fuel oil tanks 2 port and stb. and main ballast and reserve fuel oil tanks 4 port and stb. also have emergency vent valves installed, operated from control room and petty officers room respectively.
		After filling the reserve fuel oil ballast tanks with fuel oil, the vents can be secured by closing the gate valves installed in the vent and residual air vent trunks.
		Main ballast tank 5 has a vent valve, which is operated by means of a linkage rod and hand wheel located at the forward bulkhead of the control room.

4) Compressed air systems.
	a)	Electric air compressor.
		The compressed air required for blowing ballast tanks, starting diesel engines, for torpedo launching installation, anchor installation and so on, is produced by two electric, 4-stage air compressors, located in the aft torpedo room.

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6	III. Diving Installations	U-boat Information

		Their performance is 6.1 liters/minute at 205 kg/cm².
		Compressed air from each stage is cooled down in a cooler. The air cooler and lubricating oil cooler are located in one case outside the compressor. The compressor is cooled by sea water. The two-stage cooling water pump is located on the coupling side of compressor and is driven by means of helical gears from the crankshaft. The gear type lubricating oil pump is located on the front side of compressor at its base plate and is driven from the crankshaft by means of gear wheels.
		The compressor is driven by a direct current, shunt electric motor, with starting compound winding on commutating poles. The motor is splash-proof and self-cooled with air.

	b)	Diesel air compressor.
		Type VIIC U-boats since Boat No. ____ are provided with one electric air compressor and one diesel air compressor.
		The diesel air compressor is a horizontal, double piston, two-stroke diesel engine with free pistons which are directly coupled with a four-stage compressor. Its performance is 8.5 liters/minute at 205 kg/cm².
		After compression the air from each stage passes through a condenser for cooling. The cooler for all four stages is located beneath the compressor in individual cases. The air is cooled by means of sea water. The cooling water pump, rotary vane type, driven by a gear shaft, forces the water in the following order: cooler IV, combustion chamber cooling jacket, compressor stage I, compressor stage IV, cooler III, compressor stage III, compressor stage II, cooler I, cooler II.
		The lubricating oil pump, driven by means of an eccentric from the gear shaft, lubricates all sliding parts.
		The compressor is driven by two-stroke diesel engine made by Junkers, with two opposed pistons,

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U-boat Information	III. Diving Installations	7

which are coupled together by means of two sets of traverses, two gear racks with a geared wheel located between them. Engine pistons control intake of air, which is compressed and exhausted. The stage I compressor piston is connected with left engine piston, the stage II compressor piston is connected with right engine piston. The stage IV compressor piston is coupled with the left piston rack and the stage III compressor piston is coupled with the right piston rack. The compressor is started by means of compressed air admitted to particular compressor stage chambers.

The compressor casing is splash-proof.

High pressure compressed air flasks.

Compressed air is stored in 12 high pressure air flasks with total capacity of 3.900 m³. Each flask has capacity of 325 liters and is tested at pressure of 280 atm. The flasks are grouped in 6 banks (2 flasks each), which are located as follows.

Bank 1	Upper deck aft, on both sides of the aft external torpedo container
Bank 2	Upper deck, above the diesel engine assembly patch
Bank 3	Petty officer's room port and stb.
Bank 4	Forward torpedo room to port
Bank 5	Forward torpedo room to stb.
Bank 6	One flask in the bow buoyancy tank, one flask on the stb. side forward of the external torpedo container.

The flasks are smooth shaped and are lined with lead. On both ends they narrow into the neck, capped by means of flange and cover. To drain the flask a drainage pipe is provided in the deepest point of flask. Furthermore, the flasks are inclined 4 degrees from the horizontal.

Compressed air equipment.

The following compressed air equipment is installed:

1. High pressure equipment

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8	III. Diving Installations	U-boat Information

		2. Medium pressure equipment
		3. Low pressure equipment
		Particular devices are supplied with pressure air from high air pressure distributor, low air pressure distributor and blowing distributor. For blowing regulating tanks, regulating reserve fuel oil tanks and negative buoyancy tanks one or more manifolds are provided in the control room.

High Pressure Air Distributor.

		1.		To blowing distributor
		2.		From HP air bank 2
		3.		" " " 6
		4.		" " " 1
		5.		" " " 5
		6.		" " " 3
		7.		" " " 4
		8.		From HP air filling connection on upper deck
		9.		To Blowing manifold for regulating tanks and negative buoyancy tanks
		10.		To torpedo HP air manifold aft
		11.		To torpedo HP air manifold fwd.
		12.		From HP air compressors
		13.		To pressure reducing valve LP air manifold
		14.		To LP air manifold
		15.		Drain valve
		Valves 2-7 are provided as adjustable cone stop-check valves with pressure gauges.

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U-boat Information	III. Diving Installations	9

Blowing Distributor for Ballast Tanks

		1.		Master blowing valve for ballast tanks
		2.		Individual blow valve for MBT 1
		3.		" " " " MBT 5
		4.		" " " " MBT 3 stb.
		5.		" " " " MBT 3 port
		6.		" " " " MB/RFOT 2 stb.
		7.		" " " " MB/RFOT 2 port
		8.		" " " " MB/RFOT 4 stb.
		9.		" " " " MB/RFOT 4 port
		10.		Drain valve
		11.		To blowing distributor for regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks
		The master blowing valve and the valves for main ballast tanks 1 and 5 are provided with sharply tapered seats for fine control.

Low Pressure Air Distributor

		1.		Regulating valve LP air distributor
		2.		To pressure reducing valve
		3.		To Tyfon air whistles
		4.		To torpedo LP air manifold aft
		5.		To torpedo LP air manifold forward
		6.		To pneumatic tool connection
		7.		To compressed air clutch for forward and aft dive planes
		8.		To blow trim tanks
		9.		To compressed air gauge
		10.		To blow sea connection for flooding regulating tanks and distilling unit intakes
		11.		Regulating valve for raising direction finding antenna
		12.		Drain valve

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10	III. Diving Installations	U-boat Information

Blowing distributors for regulating tanks, regulating and reserve fuel oil tanks and negative buoyancy tanks

For blowing regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks a blowing manifold is provided in the control room. The safety valves for regulating tanks and regulating and reserve fuel oil tanks are set at 13 atm and for negative buoyancy tanks at 10 atm. Each regulating tank has a pressure differential gauge installed.

(Regulating/RFO tanks) (Regulating tanks) (Negative buoyancy tanks)

1.	Regulating valve - regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks
2.	Blow valves for regulating tanks, regulating and reserve fuel oil tanks, stb. and port
3.	Hull valve negative buoyancy tanks stb. and port (stop check valve)
4.	Drain valve
5.	To blowing distributor for main ballast tanks

5) Pumps.
		The following pumps are part of the diving installation:
		a) main drain pump
		b) auxiliary drain and trim pump.
		The main drain pump is a self-priming, reversible, two stage, centrifugal type. It is built from two impellers, which can be connected either in serial (high pressure – low performance) or parallel (low pressure – high performance).
		Its performance at pressure head of 15 meters H₂O in parallel mode is 1300 liters/minute and at pressure head of 105 meters H₂O in serial mode is 500 liters/minute at RPM = 2600.

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U-boat Information	III. Diving Installations	11

		The pump is driven by an electric motor and is used to drain large quantities of water from regulating tanks, regulating and reserve fuel oil tanks, torpedo compensating tanks and from rooms during flooding. When draining from the forward and aft parts of the boat, pump performance is reduced due to flow resistance in pipelines (see paragraph IX 3 d).
		The auxiliary drain and trim pump is a double-acting, two cylinder, piston type. The pump is driven by an electric motor built above by means of worm gear with a vertical worm shaft.
		Its performance is 358 liters/minute at RPM = 115. The maximum operating pressure is 10 atm. The pump is used to drain small quantities of water from regulating tanks, regulating reserve fuel oil tanks, torpedo compensating tanks, bilges and for trimming. Both the main drain pump and the auxiliary drain pump have the capability of pumping water out to main ballast tank 3.

6) Dive planes.
		For controlling depth there are two sets of dive planes, aft located directly after the propellers and forward located laterally below the torpedo tubes. Both set of dive planes are protected with frames, the aft edge of the forward planes also with guy wires. Dive planes are driven either electrically or manually. The dive planes station for electric and manual control as well as for operating the compressed air pistons of the dive plane clutches are located in the control room.

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1	IV. Armament	U-boat Information

IV. Armament.

1) Torpedoes and mines.
	a)	Torpedo tubes.
		The boat is equipped with 4 forward and one after torpedo tubes, whose diameter is 553.6 mm and whose length is 7552 mm. 2/3 of the length of these 5 tubes is located outside the pressure hull and they are supported by the ends of pressure hull and by torpedo tube bulkheads in the bow and aft parts of outer shell. Torpedo launch takes place by means of compressed air.
		The tubes consist of forward, middle and aft sections, joined together by means of flanges and bolts. The forward part is closed with an outer door, which opens on a vertical axis towards amidships. The breech door located at the inner end of tube is closed and secured by means of a locking ring. The interlock mechanism between the breech and outer door operating gears prevents simultaneous opening.
		The following installations pass through the pressure hull:
		Outer door operating shafts,
		Flood and drainage installations,
		Venting installation for the forward parts of tubes,
		Compressed air installation for the mine stop bolt actuator.
		The tubes are provided with gears for setting the desired depth, speed and gyro angle of a loaded torpedo during attack approach. The air impulse tank capacity is 220 liters and is used to provide compressed air for torpedo launch. During torpedo launch, the firing rod gear retracts the torpedo stop bolt and admits air into the tube.
		To avoid the appearance of air bubbles, which could betray the boats position, a suppressor is provided.

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U-boat Information	IV. Armament	2

Distances between tube axes.

Forward torpedo tubes Aft torpedo tube

	b)	Installation for mine ejection.
		All 5 tubes are adapted for mine ejection in addition to torpedo launching.

	c)	Stowage.
		The largest payload of torpedoes and mines can be arranged as follows:

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3	IV. Armament	U-boat Information


Payload	In torpedo tubes		In reserve stowage		In deck containers		In auxiliary stowage
Payload	fwd.	aft	fwd.	aft	fwd.	aft	fwd.

Case 1
5 G 7 a			2	1	1	1
9 G 7 e	4	1	2				2

Case 2
3 G 7 a				1	1	1	-
2 G 7 e	2						-
21 TMB	6	3	12				-

Case 3
3 G 7 a				1	1	1	-
2 G 7 e	2						-
14 TMA	4	2	8				-

Case 4
2 G 7 a				1	-	1	-
1 G 7 e	1				-		-
24 TMB	9	3	12		-		-

Case 5
3 G 7 a				1	1	1	-
1 G 7 e	1						-
16 TMA	6	2	8				-

Cases 1-5 are feasible down to sea water density (1.003) without additional changes in trim and weight of the boat.

		G7a can be stored in all places except auxiliary stowage, because there the engine chamber would be positioned at the support point.
		G7e can not be stored in both deck containers and in aft reserve stowage because access for maintenance is insufficient.
		TMA and TMB can not be stored in: both deck containers, auxiliary stowage under forward torpedo room floor and in aft reserve stowage. These locations are intended only for torpedoes, and set the minimal number of torpedoes that could be carried in the forward torpedo room. Mines cannot be stored in the aft torpedo room because of danger from electric fields, therefore TMA and TMB mines should be loaded into the aft torpedo tube only when the electric motors are disengaged. Case 3 with 14 TMA corresponds to case 2 with 21 TMB. Case 5, with 16 TMA, allows one more torpedo to be carried than case 4 with 24 TMB.

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U-boat Information	IV. Armament	4

Secured storage for torpedo munitions (9 contact pistols and 10 torpedo fuses) is provided in the forward torpedo room.

Torpedo loading equipment.

Torpedoes can be loaded from land or from ships by means of a port or ship crane, or from the water by means of a portable crane. This crane can be mounted on the forward upper deck on port side, or, on the after deck on either the port or starboard side of galley hatch.

To transport torpedoes into the boat, a chute is installed; supporting beams are used to assure proper motion of the torpedo despite rolling of the boat. Torpedoes are pulled down by means of windlasses, which are installed either on the conning tower or near the galley hatch.

Transport splints with gear racks are installed in the boat. Each splint is hung by means of two hoists and three holding lugs. The splint is equipped with two trolleys. The torpedo is attached to these trolleys by means of steel bands. The torpedo is moved longitudinally by means of the aft trolley, which is equipped with gear rack and crank arm. Two transverse splints are provided for lateral movements.

Mines are loaded using the same equipment.

Torpedo fire control system.

Torpedo Direction Computing installation

The torpedo direction computing installation is intended to calculate the gyro angle based on estimated and measured values and to transmit it to torpedo tube electrically (single or salvo shot without turning the boat).

Consists of the following parts:
On the bridge:	1	Surface sight with target bearing transmitter and pedestal

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5	IV. Armament	U-boat Information

In the conning tower	1	Torpedo data computer
	1	Target bearing transmitter 1 (for attack periscope)
	1	Terminal box (for surface sight)
	1	Fuze box
In control room	U-boat coupling and transmitting equipment
	1	Target bearing transmitter 2 (for air search periscope)
	1	Switch box
	1	Blue switch
	2	Fuze box
	1	Main switch box (with starter and regulator for rotary converter and torpedo gyro setting gears and fuses for torpedo fire control system)
In forward torpedo room	1	Torpedo gyro angle receiver
In aft torpedo room	1	55 V AC rotary amplifier for the gyro angle setting gear

Firing data from the conning tower and control room are transmitted electrically to torpedo gyro angle receivers. In the forward and aft torpedo rooms the gyro angle of the torpedo can be set electrically or manually by means of gyro setting gears.

This installation is powered with AC voltage from auxiliary switchboard 1 through rotary converter located in aft torpedo room (the servo motors are powered from auxiliary switchboard 2).

The transmitter of the torpedo order indicator system located in the conning tower provides transference of orders (“flood torpedo tubes”, “open outer doors”, “get tubes ready” and so on) from the conning tower to order receivers in the forward and aft torpedo rooms.

Torpedo firing installation.

The firing installation provides electrical firing from the bridge and from the conning tower in addition to mechanical launching at the tube.

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U-boat Information	IV. Armament	6

Consists of following parts:

On the bridge:	Pressure resistant firing switch
In the conning tower:	1	Firing switch
	1	Lamp board for the five tubes
	1	Terminal box (for firing switches)
In the control room:	Switch box with
	Selector switch for bridge or conning tower
	Selector for single shot
	Selector for salvo shot
	Salvo interval timer
	Fuze box
In the forward torpedo room:	1	Tube distributor box
	1	Ready lamp box
	4	Firing electromagnets with automatic cut-off switches
In the aft torpedo room:	2	Torpedo-charging units

The salvo interval timer launches the torpedoes when salvo is selected at predefined time intervals. In the case of failure of the electrical firing system, the flashing of corresponding lamps indicates the time delay for mechanical launch.

The firing installation is powered with 110 DC voltage from auxiliary switchboard 2.

Torpedo Order Indicating System.

In the conning tower:	Optical and acoustic order transmitter
In the control room:	Acoustic order transmitter
In the forward torpedo room:	Optical and acoustic order receiver
In the aft torpedo room:	Optical and acoustic order receiver

Weight compensation during torpedo firing and mine ejecting.

To drain water from tubes and to compensate for the weight of launched torpedoes two torpedo compensating tanks are provided in the forward torpedo room and one torpedo compensating tank in the aft torpedo room. Tanks are connected to the drain installation and are equipped with venting and sounding pipes. The forward tanks are flooded through a hull valve on the port side of hull.

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7	IV. Armament	U-boat Information

		The tank in aft torpedo room is flooded from the intake for the cooling water pump. For capacities of torpedo compensating tanks see paragraph A I 2 d.

U-Boat Type VIIC	A. Ship Information	Page 55

U-boat Information	IV. Armament	8

Weight and Balance for torpedoes


Torpedo Types		G. 7a Model	G. 7a Model Combat	G. 7a Drill 60 atm	G. 7a Drill 100 atm	G. 7a Drill 130 atm	G. 7a Drill 200 atm	G. 7a Combat 200 atm	G. 7e Model Combat	G. 7e Drill	G. 7e Combat


Torpedo weight	kg	1245.5	1540.5	1406	1438	1462	1518	1528	1573.5	1279	1606
Torpedo displacement	liters	1310.5	1310.5	1254	1254	1254	1254	1254	1310.5	1306	1306
Volume to flood tube	liters	370	370	426	426	426	426	426	370	374	374
Positive and buoyancy	kg	65	230	152	184	208	264	274	263	27	300
Trim moment - forward shot	mkg	+1661	-5879	-3885	-4703	-5316	-6748	-7003	-5741	+692	-7689
Trim moment - aft shot	mkg	-1720	+6086	+4022	+4869	+5504	+6985	+7250	+5977	-716	+7959

To calculate trim moment the distance between boat and torpedo G7 a or G7 e gravity center is taken as moment arm.

Weight and Balance for mines


Mine types		T.M.A.	T.M.B.	T.M.B.Ex.

Total weight (Case and Anchor)	kg	806	742	740
Mine displacement	liters	585	470	459
Surrounding water 1 mine	liters	1095	1210	1221
Surrounding water 2 mines	liters	510	740	762
Surrounding water 3 mines	liters		270	303
Buoyancy	kg	221	272	281
Trim moment - forward eject	mkg	-5547	-6827	-7053
Trim moment - aft eject	mkg	+5746	+7072	+7306

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9	IV. Armament	U-boat Information

2) Gunnery.
	a)	Weapons.
		8.8 cm Gun (S.K. C/35).
		The gun is installed on deck forward of the conning tower near hull frame 54. The gun mounting is pyramid shaped and is strengthened by longitudinal and transverse supporting beams.
		The upper deck is widened to about 3800 mm in the area of gun mounting.

		M.G. C 30.
		The M.G. C 30 gun is installed on the aft part of conning tower casing. The base is formed as a cylindrical column attached to pressure hull, strengthened with 4 knee sheets.

	b)	Ammunition.
		Total amount of ammunition that can be carried:
		8.8 cm munitions: 205 rounds HE shell C/35
		MG C/30 munitions: 1500 rounds
		Of these in munitions magazine in officers room between Frames 50 ½ – 53:
		177 rounds 8,8 cm HE shell C/35
		1200 rounds MG C/30
		Ready-use ammunition for the S.K. C/35 is stored in pressure-proof canisters [one shell to a canister placed in a rack] in the upper deck just aft of and outside the operating circle to both sides of the conning tower:
		28 rounds 8.8 cm HE shell C/35
		3 ammo clips with 20 rounds each are stored in the conning tower.
		The munitions magazine in officers room is connected to the flooding and drainage installation.

3) Mine and demolition equipment.
		For TMA and TMB mines stowage see paragraph IV 1 c.
		Additional demolition equipment includes:
		2 boxes with 4 demolition charges each [for self destruction]

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U-boat Information	IV. Armament	10

		2 boxes with 12 demolition slabs each [general purpose explosives in a rectangular metal case with openings to insert the slow match fuse with detonator]
		2 boxes with 12 time fuses each
		Fuse (slow match) with manual ignition and detonator.
		Explosives are stored in a floodable magazine in the control room.

4) Small arms.
		In the boat are stored:
		1 MG 34 machine gun
		2 submachine guns
		6 Mauser pistols 7.65 mm
		3 bayonets 84/98 with body belts and 2 ammunition pouches
		1 flare gun (single barreled)
		1 flare gun (double barreled)
		The ammunition allocation is as follows:
		3000 rounds for submachine guns
		860 rounds for pistols
		180 rounds for flare guns (star signals)
		200 rounds for flare guns (recognition signals)
		Ammunition for small arms is stored in a munitions magazine in the officers room.

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1	V. Communications	U-boat Information

V. Communications.

1) Visual and acoustic equipment.
	a)	Visual equipment:
		Large searchlight and small signal searchlight
		Aldis lamp
		Running lights
		Signal and semaphore flags
		Star signal pistol
		Flares.

		The 24 V searchlight is powered from the transformer located in control room from the TDC converter installed in aft torpedo room.
		Watertight switches and outlets are installed in the conning tower.
		The 24 V signal search light is powered in the same way. The watertight and pressure-resistant outlet is installed on the bridge, one more watertight outlet is installed in the conning tower. Switches for both outlets are located in the conning tower.
		The following running lights are installed: steaming, side and stern lights. These lights are controlled by means of switch located in conning tower. Both stern lights are provided with a dimming-resistor in conning tower with a control switch and indicator lamp.
		To power the steaming light a watertight and pressure-resistant outlet on the bridge and a watertight outlet in the conning tower are provided.
		The flares and flare lighter are stored in a can in the control room.

	b)	Acoustic equipment:
		Tyfone air whistle
		Ship's bell.
		The tyfone air whistle can be operated from conning tower and from the bridge.
		The ship's bell can be mounted on the bridge railing, when diving it was stored inside the boat.

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U-boat Information	V. Communications	2

2) Electronic communications equipment.
	a)	Radio installation.
		The radio installation consists of short and long wave equipment and an auxiliary direction finding receiver.
		The short wave equipment consists of a transmitter (output power 200 W, frequency range 3750-15000 kHz and wavelength 80-20 meters) and a 6-stage receiver (1500-25000 kHz, wavelength 200-12 meters).
		The transmitter consists of three-stages, with continuously variable frequency. The control stage is divided into 10 separate ranges, which are overlapping. The transmitter can be switched into toneless or sounding telegraphy mode.
		The following voltages are needed for operation:
		1500 V DC for powering vacuum tube anodes in the output stage
		400 V DC for powering vacuum tube anodes in the buffer stage and through a voltage divider:
		a) screen grids of vacuum tubes in the buffer stage and,
		b) screen grids of vacuum tubes in the output stage, by which output power control is possible in the range of 2-200 W.
		280 V 100 Hz AC
		a) after previous required transformation for heating the cathodes of tubes in all stages and,
		b) after previous rectification as a cut-off and biasing voltage in the control and output stages (from -110 to 300 V),
		c) for powering the key relay (24 V).
		The receiver is a five-tube, six-stage large ship receiver. The frequency range is divided into 8 separate ranges, which are overlapping. The receiver requires following power supplies:
		a) 200 V DC for powering vacuum tube anodes,
		b) 4 V DC for heating the cathodes of vacuum tubes and,
		c) -1.5 V DC for cut-off voltage for all tubes.
		The long wave equipment consists of a transmitter (output power 150 W, frequency range 300-600 kHz, wavelength 1000-500 meters) and a direction finding receiver used as long wave receiver.

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3	V. Communications	U-boat Information

		(for details see direction finding installation).
		The transmitter consists of two-stages, with continuously variable frequency. Unlike the short wave transmitter, the output stage with antenna circuit is separated in its own case from the main transmitter casing.
		The following voltages are needed for operation:
		1500 V DC for powering vacuum tube anodes in output stage
		400 V DC for powering vacuum tube anodes in control stage and through voltage divider screen grids of vacuum tubes in output stage, by which output power control is possible.
		280 V AC after previous required transformation for heating the cathodes of tubes in all stages and after previous transformation and rectification as a cut-off and biasing voltage in control and output stages.
		Both transmitters can be connected with common control unit by means of a selector switch on the transmitter switchboard. This unit provides a telegraph key, output power control, volume control and operation mode (toneless, sounding telegraphy) selection.

		The direction finding installation is used to obtain relative bearings form radio beacons and in this way to get own location. It consists of a direction finding receiver and pressure-resistant and watertight loop antenna.
		The direction finding receiver has two operational ranges: frequency: 1000-75 kHz, wavelength: 300-4000 meters and frequency: 25-15 kHz, wavelength: 12000-20000 meters. These are divided into 7 separate sub-ranges. Due to their good direction and receiving properties the longest waves (12000-20000 meters) are especially suitable for receiving while submerged.
		The dedicated power supplier supplies following voltages needed for the receiver:
		a) 4 V DC for heating the cathodes of vacuum tubes
		b) 60 V DC for powering the vacuum tube anodes.
		The loop antenna installation consists of the directional loop, rotating shaft, clutch casing, manual drive for rotating the shaft and installation for rising and lowering the antenna. Raising and lowering takes place by means of compressed air, controlled by three-way cock. Rotation of the directional loop is done with a directional wheel in the radio room.

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U-boat Information	V. Communications	4

Broadcast and announcement system:

The system consists of: 1 broadcast radio receiver, 1 record player with amplifier, 10 fixed mounted speakers and 6 microphones.

The broadcast selection switch enables connecting either the radio receiver or the record player to the broadcast system amplifier.

The arrangement of speakers and microphones is as follows:

Aft torpedo room:	Speaker	Microphone
E motor room:	"	"
Diesel engine room:	"
Petty officers room:	"
Control room:	"	"
Conning tower:	"	2 "
Officers room:	"	"
Chief petty officers room:	"
Forward torpedo room:	"	"
Radio room:	Control speaker

The speakers combined with microphones are used for passing orders.

Broadcast radio receiver, record player and amplifier are powered by 220 V AC.

Ultra short wave portable transmitter and receiver:

The device is a portable transmitter and receiver with following operating modes: toneless and sounding telegraphy, telephony and broadcast receiving. It is used for passing orders and communication within visual range.

Transmitter, receiver, accumulator, dry batteries, headphones, telegraph key and telescoping antenna are hosted in an armoured wooden case.

The device output power is 0.6 W, frequency range 41.67-45.15 MHz, wavelength 7.2-6.5 meters. This range is divided on the transmitter and receiver scale into 10 channels (9-18).

The accumulator delivers 2 V power for heating the cathodes of transmitter and receiver vacuum tubes, while the dry batteries

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5	V. Communications	U-boat Information

		connected in series deliver 120 V voltage for powering the vacuum tube anodes and about 3 V power for cut-off voltage.
		When operating on the boat, the rod aerial installed on the pennant masthead is used. When operating on land, a telescoping antenna attached to armoured wooden case is used.

		Back-up radio equipment.
		In case of damage to the short wave equipment the auxiliary radio in the listening room is provided. It consists of a transmitter (output power 40 W, frequency range 3000-16670 kHz, wavelength 100-18 meters) and an all wave receiver (15-20000 kHz, wavelength 20000-15 meters). The transmitter and receiver are connected to a common control panel.
		The transmitter is designed as two stage, long-range device. The frequency range is divided into three separate sub-ranges. It provides only toneless telegraphy operating mode.
		The dedicated power supply, powered by 220 V AC, supplies following voltages needed by the transmitter:
		390 V DC for powering the anodes of vacuum tubes in the control stage
		600 V '' '' '' '' output stage
		12.6 V AC for heating the cathodes of all vacuum tubes
		110 V and 195 V DC for powering the screen grids of vacuum tubes
		-210 V and 190 V DC as cut-off voltage
		The all wave receiver is a two stage, four vacuum tube device and is dedicated to receiving all types of modulation. The frequency range is divided into 10 sub-ranges.
		The dedicated power supplier supplies following voltages needed by receiver:
		100 V DC for powering the anodes of vacuum tubes
		4 V for heating the cathodes of all vacuum tubes
		-3 and -1.5 V as a cut-off voltage.

	d)	Aerial installation:
		The jumping wires [net deflectors] are used as transmit and receiving aerials. The wires are separated from hull by means of coconut insulators. Two aerial selector panels in the radio room allow plugging in the transmitter or receiver to the forward or aft jumping wires. The aerial feed lines are led in pressure proof and water resistant shafts.

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U-boat Information	V. Communications	6

	e)	Radio - converter installation:
		The installation consists of 1 transmitter converter and 3 receiver converters.
		The transmitter converter provides following voltages:
		1500 V DC 0.3 A, 400 V DC 0.3 A, 280 V AC 1 A.
		The following receiver converters can be used:
		1 6 kVA – converter for powering all receivers, active sonar, passive sonar or
		1 1.5 kVA – converter for powering receiver and passive sonar or
		1 0.3 kVA – converter for powering only two receivers.

	f)	UT [Underwater Telegraphy] installation (sound).
		The UT installation is used to communicate during submerged and surfaced cruise.
		The installation consists of 2 x 2 sound transmitters and 2 x 2 sound receivers, which are located on the port and stb. side, near main ballast tank 5 under the waterline, the UT converter with automatic and manual starter, the switchboard, the amplifier, headphones, and telegraphy key.
		The transmitters and receivers on each side are installed in a pressure-resistant cable box. From there, through pressure-resistant cable trunks, the connecting cables lead into the boat.
		The DC-AC, sound frequency, single phase converter supplies 120 V AC controlled by the telegraphy key, through the switchboard to power the transmitters. Incoming sound waves are passed from the receivers through the amplifier to the headphones.

	g)	G.H.G. [Grupenhorchgerät = Group Listening Apparatus - passive sonar] installation.
		The G.H.G. installation is used to obtain the bearing of surface or submerged vessels.
		The installation consists of 24 sound receivers each on the stb. and port sides, located below the waterline, near main ballast tank 5, each with a pre-amplifier, the power supply, the compensator and

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7	V. Communications	U-boat Information

		the bearing unit with bearing scale. Each set of 8 receivers is connected through pressure-resistant trunks with connection boxes, so that, 6 pressure hull pass-throughs are needed for all 48 receivers. The connecting boxes are located near the hull pass-throughs, directly under the upper deck forward torpedo container. The installation is powered by 220 V AC from the radio receiver converter.

	h)	K.D.B. [Kristalbasisgerät = Crystal Rotating Base Apparatus - passive sonar] equipment.
		The installation has the same function as the G.H.G. It consists of crystal receivers on a rotatable mount, the shaft, the amplifier and bearing scale. The installation is located between the forward torpedo tubes. The shaft passes through the pressure hull forward of the anchor capstan. The rotatable mount rises 40 cm above the upper deck. The installation is powered in the same way as the G.H.G.

3) Power supply for electronic communications equipment.
		The power supply line for the electronic equipment branches from auxiliary switchboard 1 in the E motor room and leads to auxiliary switchboard 1A (radio regulating switchboard) in the E motor room and to the radio switchboard in the radio and the listening rooms.
		From auxiliary switchboard 1 (regulated part) main bus (110 V) a line goes to the radio switchboard 110 V bus. The following installations and equipment are powered from this bus:
		Transmitter switchboard,
		Underwater telegraphy installation,
		Echo depth sounder,
		Auxiliary transmitter and receiver control panel.
		From auxiliary switchboard 1 (unregulated part) main bus a line goes through the auxiliary switchboard 1A to the top bus (110 V) of the radio switchboard. The following devices are connected to this bus:
		6 kVA rotary converter
		1.5 kVA '' ''
		0.3 kVA '' ''
		These 3 converters power the 220 V AC bus.

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U-boat Information	V. Communications	8

		Bus I, which can be powered only by the 6 kVA converter, branches to the following installations:
		Active sonar
		Auxiliary transmitter
		Underwater telegraphy installation
		All wave receiver
		Preheating of the transmitter switchboard
		Bus II, which can be powered by all three converters, branches to:
		Group Listening Apparatus (G.H.G.)
		Rotating Hydrophone Apparatus (K.D.B.)
		Depth sounder
		Short wave receiver
		Direction finder receiver
		Broadcast receiver with record player
		Sound amplifier
		Coding machine (through transformer 220/4 AC)
		Electrical outlets
		The transmitter switchboard is powered (110 V DC and 220 V AC) from the radio switchboard (see above). By means of the transmitter rotary converter (1.2 kW) the 110 V DC current is converted into 1500 V and 400 V DC and 280 V AC (double armature converter with collector rings). The following devices are powered from the transmitter switchboard:
		Short wave transmitter
		1500 V DC
		400 V DC
		280 V AC
		Long wave transmitter
		1500 V DC
		400 V DC
		280 V AC
		Control unit for short and long wave transmitters
		Output stage for long wave transmitter
		Ultra short wave portable transmitter and receiver are powered by:

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9	V. Communications	U-boat Information

		A 2 V battery is used to heating the cathodes of vacuum tubes, for powering the microphone and for temperature compensation of capacitors. Two 90 V batteries power the tubes, screen grids and for cut-off voltage.

4) Antennas.
		The ship is equipped with following aerial systems:
		Forward jumping wire [net deflector]
		Aft jumping wires.
		All three jumping wires can be used as transmitter and receiver aerials for short and long wave and broadcast radio equipment.
		Rod aerial.
		The rod aerial is used as transmitter aerial for short and long wave equipment when submerged (at periscope depth).
		Loop aerial.
		The loop aerial is used as a receiver aerial for direction finder receiver. (to obtain position of own boats other ships and aircraft)

U-Boat Type VIIC	A. Ship Information	Page 67

U-boat Information	VI. Steering Gear System and Anchor Installation	1

VI. Steering Gear System and Anchor Installation.

1) Steering System.
	a)	General.
		The rudder installation includes the following:
		Two identical main rudder planes parallel to each other,
		Forward dive planes,
		After dive planes,
		Plane drive,
		Steering stations,
		Steering lines.

		Steering plane construction:
		To keep the driving force low, all steering planes are built as displacement, balanced rudders. They are made from watertight plating on both sides, with stiffeners provided between the plates. The spaces between plates are filled with tarred wood.

		Steering plane protection:
		A skeg is provided to protect the main rudder, especially from hitting the bottom, from which two arms lead to both rudders and are attached to the rudder pins. To prevent entanglement with naval mine wires and antisubmarine nets all linkages are made smooth and all faces are rounded.
		The outer edges of dive planes are protected against naval mine wires.
		To avoid corrosion (galvanic current between bronze and steel in sea water) all steering planes are provided with zinc protection plates.

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2	VI. Steering Gear System and Anchor Installation	U-boat Information

	b)	Main rudder installation.
		The main rudder is twin type and can be either electrically or manually driven.

		The main rudder is driven by means of vertical intermediate shaft, which passes through the pressure hull between frames 1 and 2 and which is driven by worm gear. The shaft bearing is installed at the pressure hull and is retightened from inside by a stuffing box.
		To top of the intermediate shaft (in the upperdeck) is attached to a double arm, which is connected by means of two long connecting rods with two, center-facing, main rudder arms. Each main rudder has an area of 2.75 m². The rudder maximum deflection is 33° when electrically driven and 35° when manually driven.

Ruderblätter Rudder planes

Fester winkel Fixed angle

Drehpunkt des Ruderblattes Pivot point of rudder planes

Hauptruderhebel Main rudder arm

Schubstange Connecting rod

Senkrechte Zwischenwelle Vertical intermediate shaft

Doppelhebel Double arm

U-Boat Type VIIC
A. Ship Information
Page 69

U-boat Information
VI. Steering Gear System and Anchor Installation
           3

The maximum deflection of the main rudder and forward and aft dive planes is limited electrically by means of a limit switch and mechanically by means of mechanical limit stop.

c) Dive planes installation.

The forward and aft dive planes are mounted on common shafts. The maximum deflection of the forward planes is 30° up and 30° down, for the aft planes 25° up and 35° down. The spindle driven by an electric motor moves the pushing rod either in or out and through the connection with the rudder shaft lever deflects the dive planes. The aft dive planes each have an area of 2.25 m², each of the the forward dive planes area is 2.4 m².

2) Anchor installation.

The anchor installation consists of:

        Anchor, anchor chain,

        Chain stopper, chain tripping device,

        Anchor windlass and capstan.

The boat is fitted with Hall stockless type anchor and chain of length 150 meters. The anchor weight is 400 kg and chain weight is 1676 kg. The chain consists of 6 parts each 25 meters long connected by means of shackles.

Motor mit Getriebe Electric motor with gear box

Drucklager Thrust bearing

Kupplung Clutch

Führungsstange mit Gewinde Threaded guide rod

Stopfbuchsen Stuffing boxes

Kreuzkopf Limit slider

Druckkorper Pressure hull

Lenkstange Pushing rod

Ruderwelle mit Hebel Rudder shaft with lever

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A. Ship Information
U-Boat Type VIIC

4
VI. Steering Gear System and Anchor Installation
U-boat Information

To keep the anchor chain still when anchor windlass is not driven, a chain stopper is installed at the upperdeck, which is operated from inside the boat by means of linkage and a handle.

The anchor chain locker is located within main ballast tank 5.

The capstan raises the lowered anchor at a speed of 10 meters/minute and heaves the chain at a speed of 20 meters/minute. The output power of the compressed-air motor is 19 Hp at 740 RPM and 3.5 atm. The motor can be operated and reversed from the forecastle and from inside the boat. The capstan is driven by a compressed-air motor through double-cone worm gear. After double-cone worm gear and horizontal intermediate shaft the drive branches to the anchor windlass. Moreover, manual drive is possible by means of a removable capstan head.

The length of expended anchor chain is observed by means of an indicating device from inside the boat as well as from the upper deck.

U-Boat Type VIIC	A. Ship Information	Page 71

U-boat Information	VII. Equipment and Installations for Navigation	1

VII. Equipment and Installations for Navigation.

1) Ship control.
	As the ship control station are used:
		The bridge
		Conning tower
		Control room
		The following installations are available:
		Main rudder control station on the bridge, in the conning tower and in the control room,
		Dive planes control station in the control room,
		Engine order telegraph in the conning tower and in the control room,
		Gyro-compass repeater on the bridge (pressure-proof), in the conning tower and in the control room,
		Main rudder angle indicator on the bridge (pressure-proof), in the conning tower and in the control room,
		Alarm bell activating switches in the conning tower and control room,
		Periscopes in the conning tower and in the control room,
		Auxiliary main rudder control station in the E motor room (manual drive) with mechanical main rudder angle indicator.

2) Periscopes.
	The boat is equipped with two periscopes.
	a)	Attack periscope (PH. Frame 44).
		The aft periscope has its upper part tapered as much as possible (has low light transmission) and is used mainly during day attack.
		It is constructed as a fixed-eye-level periscope and so offers the advantage of fixed height of viewing during lowering and rising of the scope. The scope is operated in the conning tower. The periscope is lead out through the deck covering the conning tower by means of a guide bushing and to avoid vibrations it is supported by the periscope stand on the bridge.
		The periscope well extends from the lower part of the pressure hull to the level above the conning tower deck. Inside main ballast tank 3 the well is pressure-proof and

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2	VII. Equipment and Installations for Navigation	U-boat Information

		can be accessed for inspection purposes (removing the prism box) from the control room through the pressure-proof man hole in the control room deck.

	b)	Air search periscope (PH. Frame 47-1/2).
		The forward periscope has greater light transmission (thicker tube) and is mainly used during night attacks.
		It is operated from the control room and is lead out in front of the conning tower. The scope is guided in a bushing and at the level of conning tower covering plate by a support stand to avoid vibration. On the bridge the scope is surrounded by a light protective cover which is bolted to the conning tower casing and provided with flooding holes.
		The well of the forward periscope extends from a level 500 mm above the lower part of pressure hull in main ballast tank 3 to a level 600 mm above control room deck. The well is constructed as pressure-proof.
		For scopes details see classified periscope manuals.

	c)	Periscope drive.
		Both periscopes are driven hydraulically. Hydraulic oil is used as a pressurized hydraulic fluid. The electrically driven screw pump (main or auxiliary) pressurizes oil from the collecting tank into three steel flasks of capacity 125 liters each. A connection from high pressure air installation to each flask is used to create the required pressure and air cushion. From the flasks the oil under a working pressure of 80-45 kg/cm² is supplied to the screw motors, where the energy of pressured oil is transformed into movement. Each periscope has its own screw motor used for raising and lowering. Moreover, the attack periscope is provided with one additional motor (with smaller output power) for rotating the scope.
		The oil pumps are automatically turned on and off when the marginal pressure is reached (45 and 80 kg/cm²) by means of pressure control switches.
		The hydraulic motors are turned on and off and reversed by means of control valves.

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U-boat Information	VII. Equipment and Installations for Navigation	3

		Each periscope is provided with an automatic limit switch, which turns off the motor at the end positions.

3) Compass installation.
		The compass installation consists of:
		a) Gyro compass (Anschutz type)
		b) Projector compass (Askania type)
		In case of damage to the gyro compass the projector compass is used for navigation.

	a)	Gyro compass installation.
		The gyro compass installation consists of the gyro compass (in the control room) and seven gyro repeaters.
		The repeaters are located as follows:
		1 in the control room,
		1 in the conning tower,
		2 on the bridge (one with bearing telescope),
		1 in the radio room,
		1 wall repeater in the control room near the active sonar equipment,
		1 in the listening room.
		Both repeaters on the bridge are pressure-proof. The repeater in the control room can be moved to the auxiliary main rudder control station in the aft torpedo room.
		The currents and voltages required for driving the gyro compass are supplied by the gyro compass rotary converter (Anschütz type) located in the E motor room. This converter can be powered through the selector switch by the port or starboard auxiliary switchboard.
		Operating principle of gyro compass:
		When the ship changes its course, the outer - follow-up - sphere in its floating mounting rotates the same angle. Due to gyroscopic effect (gyro keeps always its main axis parallel to the meridian plane) the inner - gyro - sphere is always set to the north-south line.

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4	VII. Equipment and Installations for Navigation	U-boat Information

		Thus there occurs a difference in the liquid path resistance, which affects the current, which - amplified - powers the follow-up motor. This motor is coupled by means of gear drive with servo transmitter, which transmits the movement to the servo receivers (azimuth motor and repeaters) with 1/16 deg accuracy.
		The azimuth motor of the gyro compass rotates the follow-up sphere by means of a gear drive as long as the servo transmitter is rotated by follow-up motor. When the follow-up sphere is rotated to a position, in which the liquid path resistance is equal - that is at the same angle as the course change - the follow-up motor stops. The motors of the repeaters behave exactly as the azimuth motor and turn their compass roses at the same angle as the azimuth motor turns the follow-up sphere.

	b)	Projector compass installation.
		The projector compass is installed forward of the conning tower in a pressure-proof casing together with the compass rose illumination and optics system which projects the view of the rose to the control room. To eliminate the influence of electric currents to the magnetic compass, non-magnetic materials are used within a radius of 900 mm from the compass center.
		The desiccator of the periscopes can be used to dry out the optical projection system or the compass casing.

4) Signal equipment.
	Signal equipment consists of the following:
	a)	Running lights.
		Stern light (stern)
		Stern light (conning tower)
		Sidelights (port and stb.)
		Steaming light
		All around light

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U-boat Information	VII. Equipment and Installations for Navigation	5

Searchlight equipment.

24 Volt signal search light

24 Volt searchlight

For details see section V.1.

5) Depth sounding equipment.

The boat is equipped with the following depth sounding equipment.

1. Echolot [echo sounder]

2. Elektrolot [explosive echo sounder]

3. Hand lead

The Echolot device can be used also during submerged cruise.

Echolot.

The Echolot consists of a shallow and a deep depth device. Measurement of water depth performed by both devices is based on determination of the elapsed time of the sound from the ship to the sea bottom and back. The product of the elapsed time and sound velocity in sea water gives the length of the sound path. Half of this length is the water depth.

The sounding device has three measurement ranges:

1. 0-125 meters	shallow/supersonic sounding device
2. 0-1000 meters	shallow/supersonic sounding device
3. 150-3000 meters	deep/sonic sounding device

The shallow and deep depth devices work totally independently, though measured depth is displayed on the same common depth indicator located in control room. By means of an arm switch the depth indicator can be connected either with the shallow or deep depth sounding device. By means of the scale switch the shallow and deep depth devices can be connected simultaneously.

Each device consists of: transmitter, receiver and amplifier. The shallow depth sounding device works noiselessly, while the deep depth device sends sound impulses which are audible. Both devices are powered by the AC shallow and deep depth echo sounding converter located in the E-motor room.

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6	VII. Equipment and Installations for Navigation	U-boat Information

		The shallow depth sounding device has three transmitters and three receivers which are mounted in the keel. The deep depth sounding device has one transmitter and one receiver. Both are mounted on bottom of the hull, on the port side, near the munitions magazine.

	b)	Elektrolot.
		In this method, an explosive charge is thrown into the sea and when it breaks the water surface, a stopwatch is started. When the device reaches the sea bottom (the sound of explosion returns) – the timer is stopped (rate of sinking is 2 meters/second).

	c)	Hand lead.
		The hand lead consists of sounding line and plummet. The line is 50 meters long and is provided with marks spaced at 2 meters for reading the depth.

6) Log installation.
		The speed is obtained by measuring the pressure difference between static and dynamic pressure. The dynamic pressure is obtained from nozzles located on the port and starboard sides of the bow.
		The static pressure is obtained from nozzles located on port and stb. side of main ballast tank 3. Each nozzle is connected by means of pipes with the master unit installed in the control room. The speed can be read on master unit in the control room or on a repeater in the conning tower, to which the speed is electrically transmitted. In the conning tower a distance counter is also provided.
		The installation consists of:
		piping with control manifold
		master unit (transmitter)
		repeater (receiver)
		distance counter
		The control manifold and master unit are installed in the control room. Transmitting the height of the quicksilver column takes place by means of a magnetic clutch. The indicator axis is coupled by variable resistance to transmit the indicator position to the log repeater and to the integrator of the distance counter.

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U-boat Information	VII. Equipment and Installations for Navigation	7

		The repeater is installed in conning tower. The coil of the indicator is powered by 24 V current, taken from the light circuit through the voltage divider. The speed is shown by means of rotating indicator on a linear 270° arc scale.
		The distance counter is installed in the conning tower. The device has two mechanical counters, on which the upper one shows the travelled distance. The counter is resetable. The second counter can be set to a desired distance. The optical indicator signals when that distance is travelled. The distance counter is powered by 110 V current.

7) Alarm installation.
		The alarm installation is used to tell the crew to take their diving stations as quickly as possible.
		The installation is powered by 110 V DC from either starboard or port light group. The power line branches from auxiliary switchboard in the E motor room and in the control room and through fuse boxes leads to the control panel in the control room, and to alarm bells and both flashing circuits in the diesel engine room. The flashing circuits are connected with the port and starboard lights circuits of the diesel engine room and control 5 lamps in the starboard and 7 lamps in the port circuit respectively.
		Alarm bells are located as follows:
		1. in the E motor room,
		2. in the petty officers room,
		3. in the diesel engine room,
		4. in the control room,
		5. in the chief petty officers room,
		6. in the forward torpedo room.
		The alarm can be activated from the control room or from the conning tower by means of a two-pole switch. When the switch is on, the alarm circuit is energized. Alarm bells start to ring and flashing circuits switch the lamps in the diesel engine room on and off at short intervals.

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8	VII. Equipment and Installations for Navigation	U-boat Information

8) Ordering and reporting installations.
		The electric ordering and reporting installation and indicating installation consists of:
		1. Engine order telegraph system,
		2. Rudder order telegraph and rudder angle indicator system,
		3. Alarm installation,
		4. Compartment ready indicating system,
		5. Hull closure indicating system,
		6. Broadcast and announcement system (see paragraph V b).
		For details of electric ordering and reporting installation see paragraph B IX 5c.

		Voice tubes are installed for passing verbal orders between rooms.
		Connecting bridge and conning tower with:
		E motor room,
		Control room (branches to diving officer station and to main rudder control station),
		Radio and listening rooms,
		Commanding Officer's room.
		Also connecting conning tower with:
		Aft torpedo room,
		Forward torpedo room.
		By means of a bi-directional whistle system the control room and conning tower can be called from the aft and forward torpedo rooms.
		Each voice tube has several bulkhead valves installed, which enable isolating pressure-proof compartments from each other in case of water intake.

U-Boat Type VIIC	A. Ship Information	Page 79

U-boat Information	VIII. Safety and Rescue Installation	1

VIII. Safety and Rescue Installations.

1) Installations for submerged and surfaced boat.

Emergency lighting.

The emergency lighting should, in case of damage to the main lighting, point the way to emergency exits and illuminate the rooms.

For that reason there are 8 automatically switched on battery powered emergency lamps, 9 mountings for battery powered hand lamps and 8 battery powered hand lamps located as follows:


Room Plan	Battery Powered Emergency Lamp		Room Plan	Battery Powered Hand Lamp - Mounting
	No.	PH. Frame		No.	PH. Frame

E motor room	1	16-1/2	Aft torpedo room	1	At the torpedo tube
		(Bulkhead)
Diesel engine room	1	29	E motor room	1	16-1/2
		(Bulkhead)			(Bulkhead stb.)
Galley	1	29	Diesel engine room	1	29
		(Bulkhead)			(Bulkhead)
Petty officers room	1	39	Galley	1	29
		(Bulkhead)			(Bulkhead)
Control room	1	Periscope shaft port	Control room	1	Periscope shaft aft
Conning tower	1	Air shaft port	Control room	1	48
					Illumination of the depth meter
Officer and chief petty officers' room	1	50-1/2	Conning tower	1	To starboard
		(Spherical bulkhead)
Forward torpedo room	1	63	Officer and chief petty officers' room	1	50-1/2
		(Bulkhead)			(Spherical bulkhead)
			Forward torpedo room	1	69-70 port

Both types of lamps have as a power source battery type M 4/1 with output voltage of 4 V, capacity of 10.5 Ah at 0.75 A current load. The switching circuit of the battery powered emergency lamps

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2	VIII. Safety and Rescue Installations	U-boat Information

		consists of 2 relays, one connected to the starboard, the other connected to the port light circuit, so that in case of damage to both light circuits, the lamps will be automatically switched on.

	b)	Hand lamps.
		Each boat is equipped with 8 battery powered hand lamps, whose location is shown in the preceding table. To help with location, the power switch of each lamp is surrounded by a ring covered with luminous paint.
		Also, each crew member has a pocket lamp.

	c)	Fire extinguishers.
		There are 4 fire extinguishers provided as follows:
		In the E motor room 1 dry extinguisher
		In the diesel engine room 1 foam extinguisher
		In the control room (near the auxiliary switchboard) 1 dry extinguisher
		In the officers room (near radio and listening room) 1 dry extinguisher.
		The fire extinguishing installation is connected to the auxiliary drain and trim pump manifold and consists of a flexible hose connection and stop valve. There is a branch leading through a hull valve to the upper deck. At the upper deck, the piping is led in the upper deck casing parallel to the pressure hull. There are three connections for hoses with stop valves – in the aft part of the upper deck, in the middle (conning tower casing) and the forward part.

	d)	Flooding installation. See section B III.

	e)	Drainage installation. See section B III.

	f)	UT and G.H.G. installation.
		The UT installation is used for communication during submerged cruise between two boats or between the boat and a surface vessel. The transmitters and receivers are installed on the bow part of hull. The UT rotary converter and UT control unit are located in active sonar room, the G.H.G. rotary converter is located in E motor room.

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U-boat Information	VIII. Safety and Rescue Installations	3

		The G.H.G. installation is used to listen to propeller noises, torpedoes etc. during submerged and surfaced cruise. 6 sound receivers are located on each side of bow. [Note: the number 6 is apparently an error - there were actually 24 receivers on each side of the bow for the G.H.G.]

	g)	Emergency steering gear.
		Manual emergency steering gear is provided for the main rudder located in the aft torpedo room. This steering station is equipped with mechanical main rudder angle indicator, 1 rudder order telegraph receiver with ordered angle indicator and 1 call bell.

	h)	Diving suit.
		2 full diving suits, 1 simple diving suit with oxygen flask, without helmet, 1 set of weight chains, 1 pair of weighted shoes are provided.

	i)	Emergency escape gear.
		See paragraph A VIII 3 h.

	k)	Life rafts.
		2 Life rafts with buoys.
		To store the life rafts with buoys, 2 pressure-proof containers are provided on the upper deck, together with installation for flooding, venting and opening, which is operated from inside the boat.

	l)	Damage control materials.
		See paragraph A IX 3 c.

2) Installations for surfaced boat.
	a)	Battery ventilation.
		The ventilation installation of the battery rooms should prevent accumulation of explosive gases, which are formed when the batteries are charged. In all parts of the battery ventilation system there should be a rarefaction of the gases by fresh air at least 20 times by the end stage of charging with 415 A current.

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4	VIII. Safety and Rescue Installations	U-boat Information

		The extractor pipe under battery room deck is connected with main exhaust trunk by means of an extractor duct. A stop valve is installed in the extractor duct at the point of passage through the battery room deck and is bent upward just before connection with main exhaust trunk.
		Over the battery a grid of suction pipes is installed, which is connected to each battery cell by means of glass bend and rubber pipe. The single suction pipes are fastened to cell poles by means of insulated brackets and are connected to the extractor pipe, which in turn is connected with main exhaust trunk.
		At the joint with extractor pipe each suction pipe has an adjustable, ebonite orifice plate installed, which enables a balanced flow rate to be maintained.
		To check the amount of suction, pressure indicating devices connected at the blank end of each extractor pipe, which are installed over the battery room deck. They show the pressure difference between the suction pipes and battery room. Also, at the end of each extractor pipe, at the lowest point, a tank is installed, which is dedicated for acid carried away by the air flow.

	b)	Emergency vent valves.
		The following main ballast tanks and main ballast and reserve fuel oil tanks are equipped with emergency vent valves:
		Main ballast tank 3 port and stb.,
		Main ballast and reserve fuel oil tank 2 port and stb.,
		Main ballast and reserve fuel oil tank 4 port and stb.
		The emergency vent valves for main ballast tank 3 port and starboard are located at the point where the vent trunks pass through the pressure hull. The vents for main ballast and reserve fuel oil tank 2 and 4 port and starboard are located where the vent trunks pass through the outer hull plating.

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U-boat Information	VIII. Safety and Rescue Installations	5

		The emergency vent valves are operated manually from inside the pressure hull. The operating handles are sealed in the open position and are closed in case of damage to the vent trunks or vent valves or after filling main ballast and reserve fuel oil tank 2 and 4 with fuel oil.

	c)	Coaming.
		In case of flooding the boat, to keep enough air space, coamings extending downward from the hatches are provided with additional extensible downward plates. These movable extensions are pushed up during surface cruise and secured in that position. During submerged cruise, the plates are lowered.
		For the same purpose, the lower conning tower hatch coaming is extended downward to the level about 1650 mm above control room deck by means of a 3 mm thick skirt.

	d)	Life buoy, night signal buoy and dinghy.
		There are three horseshoe-shaped life buoys, two of them are kept handy during surfaced cruise on the sides of the conning tower casing. During submerged cruise they are stored together with two night signal buoys. The dinghy is stored at the forward part of upper deck, on port side, near the torpedo container and is attached by means of lashings.

	e)	Life jackets.
		There are 40 life jackets on board. They are stored in each crew accommodation room near the escape hatches.

	f)	Railing and tethers.
		The railing is installed on the upper deck on both sides and leads from the bow to the stern. The railing pennants are mounted in railing supports by means of clamping bolts. Demounted railing can be stowed in the upper deck casing.

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6	VIII. Safety and Rescue Installations	U-boat Information

		There are 10 tethers and safety belts provided for use by the crew operating the deck gun and the bridge watch while cruising in stormy seas.

	g)	Recognition marks for aircraft.
		Each boat is equipped with recognition marks for aircraft, which are unfolded on the upper deck, forward of the deck gun.

3) Installations for submerged boat.
	a)	Compartmentation.
		The pressure hull is divided by means of two spherical bulkheads into three pressure-proof compartments and by means of another three watertight bulkheads into 6 rooms.
		See paragraph A II 3.

	b)	Air purification system.
		The air purification system consists of:
		Purification system: removing CO₂ by means of sodium hydroxide cartridges
		Renewal system: bleeding O₂ from oxygen flasks.
		A man when breathing, creates 30 liters/hour of CO₂ and needs the same amount of O₂. The air purification system maintains the CO₂ content at 1.5% level and O₂ content at 17.5%.
		CO₂ content above 2% is injurious.
		The estimation of time, when 1.5% CO₂ content in 400 m³ of air in the boat will be reached:
		37 men creates per hour: 37 x 30 x 100/400000 = 0.28% CO₂ / hour
		So 1.5% CO₂ content will be reached after 5 hours 20 minutes.
		The measurement of CO₂ and O₂ concentration is made by means of Orsat devices, first time after 4 hours of submerged cruise. Moreover there are CO₂ sampling tubes to detect carbon dioxide content above 1.5%.

		Air purification
		3 air purifiers are used for air purification connected to exhaust air duct, located as follows:
		In the aft torpedo and E motor room
		In the control room
		In the forward torpedo room
		Each air purifier consists of 4 sodium hydroxide cartridges.

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U-boat Information	VIII. Safety and Rescue Installations	7

The air from the compartment is withdrawn through an air exhaust duct through the air purifier and purified air is returned by an air intake duct. The regulating valve allows adjustment of the amount of air passing through the purifier. When adjusting, the amount of passing air should be kept as low as possible to avoid warming the cartridges, because in this case, the cartridges don't reach their full efficiency. Ventilation capacity is:

In the 1st hour – 350 liters/hour

In the 2nd hour – 400 liters/hour

In the 3rd hour – 450 liters/hour

Air renewal

Air renewal takes place, when the oxygen content drops below 17.5%. 10 oxygen flasks are provided, with capacity 50 liters each at a pressure of 150 atm. These flasks are located as follows:

E motor room	1 flask
Diesel engine room	2 flasks
Control room	4 flasks
Forward torpedo room	3 flasks

The main manifold, to which all flasks are connected, has a branch from the control room to the upper deck, which is used for filling the flasks with oxygen. Oxygen can be supplied through connecting pipes to the air exhaust duct and added to circulating air or bled directly into the compartments of the boat.

Regulating valves installed in the connecting ducts and in the end of branch leading to the conning tower, which allow adjusting the oxygen feed rate depending on crew numbers.

The stored oxygen and sodium hydroxide cartridges enable the crew of 37 men, to remain continuously submerged for 72 hours.

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8	VIII. Safety and Rescue Installations	U-boat Information

	c)	Compressed air and emergency blowing manifold.
		The compressed air reserve is 3900 liters at 205 atm. For details see paragraph A III 4.
		To blow the main ballast tanks and the main ballast and reserve fuel oil tanks from a rescue vessel, there are branches from both emergency air supply lines, between the screw joint and straight-way valve, which each lead through the straight-way valve to the common line and then to the emergency blowing manifold located in the conning tower casing. Its location is marked with a red mark.


		Just before the connection with the manifold, a check-valve is installed. By means of 8 straight-way manifold valves all main ballast tanks and main ballast and reserve fuel oil tanks can be blown. From two emergency manifold valves the lines lead through the hull valves to main ballast tank 1 and main ballast tank 5 blowing lines. These hull valves can be operated from the inside the boat as well as from the upper deck. The valves are normally sealed.
		The emergency blowing lines of the other tanks lead from the emergency blowing manifold through the straight-way valves to the respective exhaust gases blowing lines.
		The emergency blowing manifold valves in the conning tower casing are located according to order of the the ballast tanks and have enlarged handles for ease of operation by divers.

	d)	Emergency air supply system.
		To ventilate the sunken boat from a rescue vessel by means of pressure-proof, armored hose, the following emergency air supply and emergency air exhaust connections are provided:
		In the aft torpedo room over the air compressor
		In the control room on the port, foreside of the periscope well
		In the forward torpedo room near rear part of torpedo tubes
		In the conning tower (air supply only) at the conning tower deck
		The emergency air supply system in the aft and forward torpedo rooms consists of screw joints and hull valves operated from inside the boat.

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U-boat Information	VIII. Safety and Rescue Installations	9

		The emergency air supply system in control room consists of screw joints and valves, which are operated from the upper deck. Inside the boat in the air supply and exhaust lines hull and three-way valves installed. By means of a three-way valve either the control room or the conning tower can be ventilated.
		The emergency air supply to the conning tower consists of external screw joint and internal valve, which is operated from inside the boat. The location of all connections at the upper deck is marked with a circle sign:


	e)	Rafts.
		See paragraph A VIII 1 k.

	f)	Air trap.
		For the watertight bulkheads between:
		E motor room and Diesel engine room,
		Diesel engine room and petty officers room,
		Officers and chief petty officers room and forward torpedo room.
		The area above the upper edge of bulkhead doors serves as an air trap. Other air traps are made by the coamings of the galley hatch, control room hatch and conning tower hatch.

	g)	Emergency escape gear.
		39 sets of emergency escape gear are provided for the crew on board, and another 20 sets as reserve - total number: 59 sets. The escape gear is so located, that during submerged cruise, in case of emergency, there is a sufficient number of sets in each compartment for each crew member at their diving stations.
		Also, two full diving suits (one with and one without weights) and 40 life jackets are provided on board.

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10	VIII. Safety and Rescue Installations	U-boat Information

	h)	Net deflector.
		Over the entire length of the boat, from bow to the stern, a jumping wire is stretched and attached to the bridge bulwark in such way, that underwater nets are moved over the wire and do not catch on the bridge bulwark. From the conning tower to the bow there is a single wire, from stern to the conning tower a double jumping wire is installed. During torpedo loading the jumping wire can be demounted by means of tensioning screws. Because the jumping wire is used as an aerial, it is isolated from the boat hull by means of a chain of three coconut porcelain insulators fitted at each end.

	i)	Net cutter.
		At the stem, under the standard waterline there is a fixed, while at stern a detachable net cutter is installed. The net cutter at stem is protected by a cover made of 4 mm thick plate. The cover at its lower part is formed in tongue shape, which slides in the pocket in the stem, while at upper part it is mounted to the stem by means of bolts. Thus the cover can be removed without placing the boat in the dry dock.

	k)	Compartment ready indicating system.
		See paragraph B IX 5 c(7).

	l)	Hull closure indicating system.
		See paragraph B IX 5 c(8).

	m)	Vent valve indicating system.
		Not installed.

U-Boat Type VIIC	A. Ship Information	Page 89

U-boat Information	IX. Damage Control	1

IX. Damage Control.

1) General.
	a)	Damage control parties.
		To increase the safety of the boat, hull, electrical and machinery parties are formed. These parties have following tasks:
		Removing leaks due to enemy action
		Removing damage to machinery and electrical installations due to enemy action
		Passing orders through the boat
		Reducing noise during approach and evasion and thereby improving depth keeping, which is especially demanding in the presence of the enemy.

		Damage control parties are formed from off duty crew members and are divided as follows:


Party	Post	Petty Officers	Ratings

Hull Party I	E motor room	1 career track II	1 career track VII T
			1 career track II

Hull Party II	Petty officers room	1 career track I	1 career track III

Hull Party III	Forward torpedo room	1 career track VII T	1 career track VII T
			1 career track II
			1 career track I

Machinery-Party	Diesel engine room		2 career track II

Electrical-Party I	Petty officers room		1 career track II

Electrical-Party II	Officers room	1 career track II	1 career track II

Career track (Laufbahn)

Specialty

Career track

Specialty

I
Seaman
VIII
Unused

II
Machinist (Engine room personnel)
IX
Administrative

III
Helmsman/Navigation
X
Clerical

IV
Radio operator
XI
Medical

V
Carpenter
XIII
Musician

VI
Ordnance
XIV
Coastal Artillery

VII
Mechanic (Artificers/Torpedomen)
XV
Motor Transport

Page 90
A. Ship Information
U-Boat Type VIIC

             2

IX. Damage Control

U-boat Information

The party leader is always the most senior ranking crew member in the party.

The hull, mechanical and electrical parties have to take action immediately after damage occurs. If necessary, the member of parties located near the damage must assist as far as possible. The damage control equipment and tools for the mechanical and electrical parties are kept at hand for immediate use.

b) Boat's compensation.

The boat is so designed, that when with standard load (main ballast and reserve fuel oil tanks filled with water) and empty regulating and reserve fuel oil tanks, regulating tanks and negative buoyancy tanks, at sea water of density = 1.003 it has 0 tons of buoyancy. [see note below]

The excess buoyancy which - when with main ballast and reserve fuel oil tanks 2 and 4 (49.6 m³ of oil + 0.223 m³ of air in pressure proof parts of vent pipes) filled with fuel oil of density = 0.87- is 6.28 tons, is compensated by loading on board additional supplies:

        2.11 tons of lubricating oil

        1.61 tons of provisions

        1.77 tons of fresh water

        1.33 tons of water in regulating tanks (or additional wash water in torpedo compensating tanks 1 and 2).

For both trim conditions the following loads are provided:

Supply

Trim Condition A

Trim Condition B

Remarks

Normal load capacity

Maximum load capacity

35 Days

56 Days

Fuel Oil (density = 0.87)

(including fuel oil gravity tank)
m³

tons

m³

tons

a) regulating/RFO tanks empty (Baltic)
71.43

62.14

121.03

105.30

at sea water density < 1.014

b) regulating/RFO tanks full (North Sea)
80.83

70.32

130.43

113.47

at sea water density > 1.014

Lubricating oil

5.00

7.11

Provisions

2.68

4.29

Fresh and wash water

2.72

4.50

     In wartime conditions maximum load capacity is always taken.

Note: The average density of seawater at the ocean surface is 1.025 grams/ml. Seawater is denser than both fresh water and pure water (density 1.0 grams/ml at 4 °C (39 °F)) because dissolved salts add mass without contributing significantly to volume. Sea water density varies with salinity and temperature from about 1.020 - 1.030 grams/ml.

The water density 1.003 cited above (at which the boat would have 0 buoyancy) is very low and would never be encountered by the boat while it was operating in sea water.

The density of sea water in the Baltic is significantly lower (as low as 1.005 at salinity 7.5%) due to fresh water from rivers than in the North sea (1.025 at salinity 35%).

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A. Ship Information
Page 91

U-boat Information
IX. Damage Control
            3

c) Reserve buoyancy.

As is written above, when surfaced , at sea water density = 1.003, with empty regulating tanks and regulating and reserve fuel oil tanks, buoyancy is created by air contained in main ballast tanks and main ballast and reserve fuel oil tanks. When sea water density is greater, it is necessary to fill regulating tanks accordingly.

The reserve buoyancy in:

Trim Condition A (main ballast tanks and main ballast and reserve fuel oil tanks empty, standard load)

Va = 154.95          ≈ 155 m³

Trim Condition B (main ballast tanks and main ballast and reserve fuel oil tanks filled with fuel oil, increased load)

Vb = 154.95 – 49.6             ≈ 105 m³

Reserve buoyancy with increased load is also maintained when the largest room, the Diesel engine room (volume 88 m³), is flooded by water. Moreover, the watertight bulkheads allow for isolation and localization of the leakage (at pressure up to 1 meter over upper edge of pressure hull) in the affected room. However the trim change when end rooms are fully flooded is so large, that if any counter ballasting action is taken, the boat slants forward or aft respectively, and total loss of the boat occurs.

For details see the next section.

Remarks: It should be noted, that when pressure inside the boat increases, the depth gauge not longer shows the real depth, but a lesser value, relative to the pressure difference between water pressure and air pressure inside the boat. That's why the depth should be also controlled by means of the Papenberg column, periscope or conning tower flood valve.

2) Weights and trim adjustment with water flooding.

Possible causes: influence of enemy weapon, ramming, explosions and spontaneous combustion on board, material defects and operating errors.

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4	IX. Damage Control	U-boat Information

	a)	Leakage into external tanks with the boat surfaced (Table 1).
		Leaks into external tanks are not dangerous for the boat. The reserve buoyancy in each case gives enough displacement, which also is not affected by trim change. In the case of flooding all external main ballast tanks, and main ballast and reserve fuel oil tanks, including regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks, the pressure-proof main ballast tank 3 gives enough displacement of 47.00 m³ with level immersion.
		The buoyancy when external tanks are flooded is (values are rounded, regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks are half full):


Leak	Capacity	Remaining buoyancy in m³
	m³	Trim Condition A	Trim Condition B

Main ballast tank 1	32	123	73
Main ballast tank 5	25	130	80
Main ballast/RFO tank 2 port and stb.	11	144	105++
Main ballast/RFO tank 4 port and stb.	13	142	105++
Regulating tank 2 port and stb.	4	151+	101+
Regulating/RFO tank 1 port and stb.	3	152+	105+
Negative buoyancy tank port and stb.	1	154+	104+

+) Calculated half full of water
++) Calculated full of fuel oil

		Limitations to diving characteristics can generally be avoided because of the spatial arrangement of venting and flooding installations. However seaworthiness, in certain circumstances, can be strongly affected by heeling and trim changes (i.e. the flooding of main ballast tank 5 lowers the bow of the boat up to 61 cm). These changes can be fixed by counter ballasting.

U-Boat Type VIIC	A. Ship Information	Page 93

U-boat Information	IX. Damage Control	5

Table 1:

Counter ballasting for leaks in external tanks.


Leak				Measure		Final State

Tank	Capacity	Trim or heel		Counter ballasting	Intake	Remaining buoyancy tons	Trim Status
	m³	Trim or heel		Counter ballasting	m³	Remaining buoyancy tons	Trim Status

MBT 5	25	Trim condition A	aft: -37 cm	MBT 1	32	97	Bow moves
			mid: +12 cm				40 cm higher
			fwd: +61 cm				21 cm//deeper

		B	aft: -56 cm	MBT 1	32	48	Bow moves
			mid: +14 cm				45 cm higher
			fwd: +84 cm				39 cm //deeper

MB/RFOT 2 stb.	11	Trim condition A	2.7° stb.	MB/RFOT 4 port	13	130	0° Boat leveled, slightly deeper

MB/RFOT 4 stb.	13	A	3° stb.	MB/RFOT 2 port	11	130	0° Boat leveled, slightly deeper

MBT/RFOT 2 and 4, R 1, R/RFOT 2 stb.	31	A	9° stb.	MB/RFOT 2 and 4 port	24	99	~ 0°
							20 cm //deeper

With a leak in MBT 1 port tanks, the measurements are analogous.

= Flood

	b)	Leakage into pressure hull with the boat surfaced (Table 2).
		Small leaks (see paragraph 3 d) can be removed by means of the main drain pump. However larger leaks in the end rooms lead, when any counter ballasting is taken, to a trim moment, which despite sufficient buoyancy, tilt the boat forward or aft. The free water surface effect also increases this danger. Without counter ballasting or draining, the boat is floatable only when:
		In trim condition A the following rooms are fully flooded:
		petty officers room,
		or the control room,
		or the officer and chief petty officers room,
		or main ballast tank 3.
		In trim condition B the following rooms are fully flooded:
		control room,
		or main ballast tank 3,
		possibly the petty officers room.

Page 94	A. Ship Information	U-Boat Type VIIC

6	IX. Damage Control	U-boat Information

		With 40 tons or less buoyancy, the boat is still floatable only when there is no load.
		The dangerous trim moment caused by flooding end rooms can be compensated by simultaneous counter ballasting or blowing and draining. Next, weight reduction by localization of the leakages and immediate applying the steps from paragraph 3 e should be accomplished. Thus, any leakage in one room at trim condition A and B can be compensated by counter ballasting or draining. In each case the following measures are to taken to maintain sufficient buoyancy (gathered in Table 2):

		= Flood; = Blow; = Drain;
		Drain the fuel oil to the main ballast and reserve fuel oil tanks by means of auxiliary lubricating oil pump through the flexible hose and fuel oil compensating lines, the remaining overboard.

U-Boat Type VIIC	A. Ship Information	Page 95

U-boat Information	IX. Damage Control	7


Leak			Measure				Final State

Room	Capacity	Arm	Measure for		Intake	Arm	Remaining buoyancy	Total moment	Trim
	m³	+/- m	Trim condition A and B		m³	+/-	tons	+/- m tons	Status

E motor room	62	-18.75	A	MBT 5	25.3	+25.8
				MB/RFOT 4 stb./port	26.8	+6.95	79	-200.3	floatable
				Fuel oil tank 1(I)	37.9	-3.25

			B	MBT 5	25.3	+25.8
				MB/RFOT 2 stb./port	22.8	-7.95	78	-207.6	As per A
				Fuel oil tank 1(I)	37.9	-3.25

Diesel engine room	88	-10.95	A	MBT 5	25.3	+25.8	25
Diesel engine room				Forward torpedo room only partly	16.5	+18.85		0	floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85
				MB/RFOT 4 stb./port	26.8	+6.95	25		As per A
				MBT 5	25.3	+25.8		0
				Forward torpedo room only partly	16.8	+18.85

Petty officers Room	47	-4.55	A	MBT 5 only partly	8.3	+25.8	100	0	floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85	80		As per A
				MBT 5 only partly	1.35	+25.8		0

Control room	45	+2.30	A	Not required			110	+103.5	floatable

			B	Not required			60	+103.5	As per A

Officer and chief petty officers room	77	+9.65	A	Fuel oil tank 2(I)	32.8	+8.30
Officer and chief petty officers room				MB/RFOT 2 stb./port	22.8	-7.85	77
				MBT 1 only partly	11.2	-26.0		0	floatable

			B	Fuel Oil Tank 2	32.8	+8.30
				MB/RFOT 4 stb./port	26.8	+6.95	77
				MBT 1 only partly	11.0	-26.0		0	floatable

Forward torpedo room	72	+18.85	A	Fuel oil tank 2(I)	32.8	+8.30
Forward torpedo room				MB/RFOT 2 stb./port	22.8	-7.85	61	+66
				MBT 1	32.3	-26.0			floatable

			B	Fuel oil tank 2(I)	32.8	+8.30
				MB/RFOT 4 stb./port	26.8	+6.95	60	+59	As per A
				MBT 1	32.3	-26.0

Tauchungeunterschiede von Bug und Heck gegenüber der Druckmessertiefe
Diving differences for bow and stern opposed to the depth gage

Achterlastig	Down by the stern
Bock für Netzabweiser	Support for net deflector
Bug	Bow
Bug (untere) Netzsäge	Bow (bottom of) Net saw/cutter
Bug höher	Bow higher
Bug tiefer	Bow deeper
Grad	Degrees
Heck	Stern
Höhertauchung	Shallower immersion
Kiel	Keel
Netzsäge (oben)	Net saw/cutter (top of)
Rudderhacke	Rudder heel (bottom of the rudder)
Tiefertauchung	Deeper immersion
Turm	Conning tower
Vorlastig	Down by the bow

Ruderblätter	Rudder planes
Fester winkel	Fixed angle
Drehpunkt des Ruderblattes	Pivot point of rudder planes
Hauptruderhebel	Main rudder arm
Schubstange	Connecting rod
Senkrechte Zwischenwelle	Vertical intermediate shaft
Doppelhebel	Double arm

Motor mit Getriebe	Electric motor with gear box
Drucklager	Thrust bearing
Kupplung	Clutch
Führungsstange mit Gewinde	Threaded guide rod
Stopfbuchsen	Stuffing boxes
Kreuzkopf	Limit slider
Druckkorper	Pressure hull
Lenkstange	Pushing rod
Ruderwelle mit Hebel	Rudder shaft with lever

Career track (Laufbahn)	Specialty	Career track	Specialty
I	Seaman	VIII	Unused
II	Machinist (Engine room personnel)	IX	Administrative
III	Helmsman/Navigation	X	Clerical
IV	Radio operator	XI	Medical
V	Carpenter	XIII	Musician
VI	Ordnance	XIV	Coastal Artillery
VII	Mechanic (Artificers/Torpedomen)	XV	Motor Transport