General Description
Following is a more complete general description of the
important features of the UB 88:
German submarines were divided into several classes,
depending upon the work they were to perform. One type was
wholly used for torpedo work, another was a combined type
which carried both torpedoes and mines, and a third
consisted of the mine-layers, which carried mines only.
These vessels were again divided into classes according to
their sizes and dates of construction.
The UB 88 was a small straight torpedo type of submarine
(UB-III class), carrying ten torpedoes, one 8.8 cm. gun,
and bombs which were used for destroying surrendered
merchant vessels. She was propelled by two six-cylinder,
four cycle, 450 revolution, 550 H.P. reversing Diesel
engines. Connected to the engine shaft by means of friction
clutches are four electric motors, (two on each shaft)
which are used to propel the vessel in confined waters and
when submerged. They are of about 325 H.P. apiece. The
power for these motors is obtained from a 124 cell storage
battery, divided into two groups of 62 cells each.
Torpedo Tubes
The vessel has five torpedo tubes, four of which are
located in the bow and one in the stern. These are
constructed of bronze. Length from door to door 24' 8".
Length from door to No. 6 ballast tank bulkhead 9' 1".
Diameter 20". The bottom of the tubes are fitted with
pockets to receive zincs. There are three of these pockets
holding two zincs each. There are two drains in each tube,
one forward and one aft about 2-1/2" in diameter. The upper
tube bow doors work on the same principal as do the doors
on our Holland "L" and "N" class. The lower tubes have only
a bow door, there are no outer shutters. The rear door
seats on a knife edge against a leather gasket and is
operated by a lever with a worm that engaged a rack on the
locking ring. There are three safety devices, one locking
inner door while outer door is open, one locking outer door
while inner door is open, and one to prevent stop bolt from
lifting while impulse valve is lifted. The tube is so
fitted that the torpedo can be boosted while in the tube,
and depth and curve fire can be changed while torpedo is in
the tube. The rear door is fitted with a small plug that
can be removed to insert impulse gauge.
Impulse Tanks
Located in torpedo rooms, eight forward, two aft. There are
two impulse tanks to each tube. Each set having its own
reducer from a high pressure line and can be fired
electrically or by hand. There are two valves, one between
the impulse tanks separating the high from the low pressure
tanks and the other forward of the firing or impulse valve,
preventing same from functioning until stop is lifted. The
capacity of these tanks is about 6 cubic feet per set.
These tanks were used also as volume tanks to supply air
for blowing tubes. The blow line has its own reducer
leading to the tanks.
Periscopes
There were two periscopes of the walk-around type, of zero
and six power. They were fitted with two small shifting
levers, one to shift high and low power, and one to shift
the objective prisms to elevate or depress. Both are
housing periscopes. The after periscope well contained an
elevator. This periscope could be raised and lowered by
motor or hand.
Air Flasks
There are ten air flasks located between inner and outer
hull, above the water line, with exception of Nos. 1 and 2
groups, which are located in central control room and pump
room. These flasks can be charged from the engine air
compressor or from the auxiliary compressor, also in engine
room, and were usually charged to 160 atmospheres. Each
flask group has a separate line to the high pressure
manifold.
Oxygen
There are ten oxygen flasks, seven forward and three aft.
These can be charged from ashore while in the boat. They
are connected to manifolds fitted with charging caps used
for charging small bottles on escape helmets.
Bunking Arrangement
The boat has bunking facilities for a crew of twenty-seven
men and three officers. There are four bunks for chief
petty officers in a separate compartment, and a cook's bunk
near the galley. Due to very poor ventilation the latter
bunk was considered unfit for use at sea. The crew's bunks
are located partly in the torpedo compartment and partly in
the after battery compartment.
Radio Set
The 1/2 K.W. Radio set as installed at present is almost
completely of American make. The Motor Generator is German.
The other apparatus was found to be broken or stolen when
the boats were taken over and a new set (received from the
U.S.S. BUSHNELL) was installed.
The antenna is T-type. The rat-tail enters the boat through
a porcelain tube. This tube is heated with an electrical
coil which keeps the outside dry, so that the set can be
used immediately upon coming to surface.
There are places for two masts, one forward and one aft,
but these were never installed. Arrangements were made to
raise and lower these masts by compressed air from the
Radio room.
Signals
No methods of signaling (except recognition) were found on
the boat. Forward of the gun on deck, there is a sheet iron
semi-circle. When in one position it shows only the iron
surface, when turned over it makes a complete white circle.
This is thought to have been used for aeroplane
recognition.
Ground Tackle
There is a patent anchor housed in the superstructure,
starboard side, weighing about 100 lbs. It is fitted with
120 fathoms of 3/4" stud link chain and it can be
controlled from the deck or torpedo room. This anchor gear
is similar in construction to that of our Holland boats of
the "L" type with the exception of the housing. A capstan
connected to the anchor control shaft can be operated
independent of the anchor by disengaging a clutch fitted to
the shaft. The anchor is fitted with a compressor and a
controller that can be operated from the deck or from
below. There is a small compartment built in No. 6 ballast
tank to receive the chain.
Deck Arrangement
The deck is fitted with lockers, that serve as stowage
space for lines, and ready ammunition for deck gun. Forward
of the torpedo hatch there is a large locker that served
for boat stowage. The ammunition lockers are constructed of
very light material and were intended to be water-tight.
The mooring arrangements consist of cleats and bits that
can be housed in the superstructure while underway. There
is a tripod fitted on the forecastle to which is fitted a
saw tooth net cutter. This tripod also serves as a guide
and brace for the clearing lines. These clearing lines run
from the bow up and over the tripod, over the braces on the
wings of the bridge, to the stern and are there fitted with
turnbuckles. They also serve as an antenna support for the
radio. There are two cradles or beds, one forward and one
aft, on deck that served as housing for large Radio Masts
that could be raised and lowered. These were not installed.
There are four hatches, the forward or torpedo hatch, the
conning tower hatch, the engine room hatch (which is on an
angle to receive torpedoes), and the galley hatch.
Bridge
The bridge is of the open chariot type, constructed of a
light bronze extending 3/4 way around, the after end being
enclosed by a rail. A small periscope cut-water comes up
through the center, standing about two and one-half feet in
height. On the after end of the bridge there is an
insulator for the radio and a telescopic flagstaff. In the
center, forward and on either wing of chariot there are
fitted permanent pelorus dials with a portable sight for
same. The running lights are permanent fixtures on either
wing of the bridge.
Holds
There are three holds in the forward torpedo room and two
in the central control room. The one on the starboard side
of torpedo room is for fresh stores, one on the port-side
for dry stores and one for miscellaneous stores. One
vegetable locker and one reserve ammunition locker are
located in central control room. The torpedo room bilge is
fitted with brackets to carry spare torpedoes.
Main Ballast Tanks and
Vents
These are six in number. No. 1 is located in extreme after
end of ship, capacity about 5 tons; Nos. 2 and 3 located in
engine room, capacity about 15 tons each; No. 4 located in
central control room, and extends into cabin; No. 5 in
torpedo room, and No. 6 forward. Nos. 1 and 6 have one
flood valve or Kingston, while Nos. 2, 3, 4 and 5, are
fitted with two. There are two blow lines to each tank, one
from high and low pressure and one from the turbo blower.
Vents are installed at four parts of superstructure. Nos. 1
and 6 ballast tanks have single pipe to the vent dome.
Tanks Nos. 2 and 3 (main ballast) vent to one dome aft of
conning tower fairwater. Tanks Nos. 4 and 5 (main ballast)
vent to a single forward of the torpedo hatch. Tanks Nos.
2, 3, 4 and 5 can be vented independently or in tandem by
master vent controlling shafts in the central control room.
There are no inboard vents on these tanks. The only way of
determining whether or not these tanks are full is by
trying the pet-cocks in vent lines.
Batteries
There are two batteries, No. 1 (after) and No. 2 (forward)
composed of sixty-two (62) lead, acid cells each. The cells
are about the same size and dimensions as American Gould
and Exide inclosed type cell. Gravity has been brought up
to 1.230 or 1.235 on full charge. None of the cells have
been disassembled or cell covers taken off and exact number
of plates is unknown. Capacity of battery according to
ampere hour meter is 8,000 A.H.S. It is not known whether
there is a lead lining around sides of battery tank as none
can be seen.
These batteries have no advantage over ours unless it is in
locating, which is such as will not allow entry of salt
water, as there are no hatches over battery. The batteries
are difficult of access for instead of the whole battery
deck being removed, there are installed steel doors in a
steel deck. Through the center line of the boat these steel
doors are about 2' by 4' in size, the outboard doors are
about 18". For example, if an outboard cell had to be
pulled, the center cells would have to be pulled first;
then by moving the outboard cell to the center line it
could be lifted. This arrangement is very poor.
The outboard rows on port and starboard sides of each
battery set about a foot higher than the rest of the
battery and the only way to see inside cells in outside
rows in by means of a mirror, which is very awkward and
slow when watering. It is not known whether there is lead
lining in bottom of battery tank to prevent acid from leaky
cells from eating holes in the hull.
Main Motors
Seimens Schuckert made. There are four (4) motors, ten
pole, interpole, shunt, two inside same case on each shaft,
controlled by same switches, so one motor can be cut out
only by pulling fuses for same. Horse power about 225 each.
Reversing or rotation is done by reversing field. Speed
variation is obtained by using batteries is series or
parallel or by switching the two motors on same shaft in
either series or parallel. Starboard and port motors cannot
be put in series. They also have control by field rheostat
in shunt field.
There are no advances over American motors except that they
have greater speed variation in that the batteries can be
hooked up to the motors on either shaft and may operate off
batteries in series while the other side uses batteries in
parallel or vice versa, and the two motors on the same side
can be operated in series or parallel regardless of the
other side.
The motors are located low in the boat, near bilges and
under switchboards and the other gear is installed so close
to them that they cannot be gotten at to repair without
removing all parts abaft the engines. The motor case and
brush rigging of the two after motors must be removed in
order to reach after motor bearing.
There is one ventilating blower to starboard motors and one
to port motors, operated by an intermittent duty motor at
each end, one or both motors may run at the same time.
Blower Motors and Ventilating System
There are two (2) two pole, interpole, shunt, blower
motors, 3 to 4.6 H.P. run on 24 amperes, 110 to 170 volts.
They are situated one on the port and one on the starboard
side of the forward end of engine room.
The ventilating system is so installed that one or both
motors may take suction from battery or compartments, or
both at the same time. The system is also arranged so that
starboard motor may take suction from outside of boat and
discharge fresh air inside boat and battery, while port
motor takes from boat and battery and discharges overboard,
this method gives best results.
The only advantage over American systems are that one
blower may take foul air out of the boat while the other
feeds fresh air in, and both blowers may take suction from
battery while charging.
These motors have only one speed which is so high that they
will not stand continuous running. The ventilating system
is fitted with numerous valves located in places that are
hard to get at to overhaul when froze from action of acid
from batteries.
Lighting System
There are two distribution boards for lighting, one in
motor space and one near central control room. One board
feeds lights on starboard side and the other feeds port
side. One or both distribution boards may feed from either
battery. Branch distribution boxes are located in each
compartment protected by plug fuses. Lamp bases are about
the same as American and fit standard screw base lamp.
If one board or one battery is out of commission half the
lights in each compartment remain in commission. (This is a
decided advantage over our system). All fuses are enclosed
in a porcelain cap and cannot be shorted when working near
a fuse box.
Connections in junction boxes are easy to work on as the
wires do not have to be bent around the securing screws.
Rotary snapswitches are installed but contain too many
parts. These get out of order very easily. Fuses are hard
to reload, everything being enclosed, making repair work
slow. The system takes an excessive amount of wire cable.
Heating System
Each compartment is fitted with a receptacle to plug in a
portable electric heater. These heaters are about the same
as American, except in shape, these being about 12" x 12" x
16". Current is obtained from power circuit.
A steam radiator is fitted in each compartment hooked up to
a pipe leading to outside of boat, supposedly for getting
steam heat from Tender. This has never been tried out.
Cooking System
The galley is fitted with an electric cooking system.
Current is obtained from after distribution board, fused
for 60 amperes. Current may be taken from either battery by
turning a four-way rotary switch on the line to each
receptacle. Large portable pots varying in size from about
one to twenty gallons are used. Each contains its own
heating coil between the inside and outside shell of the
pot. Each pot heating coil is divided into two or three
parts. Different degrees of of heat may be obtained by
changing hook-up of the coils, this is done by shifting
position of the plug on pot, which may be plugged in four
positions.
Battery Charging Data
No German charging data is available. Charging is done
similar to charging American submarine batteries, starting
at not exceeding 1200 amperes in series, charging until
voltage reaches about 295 or 300 volts, then cutting down
load gradually, keeping voltage constant at 295 or 300 till
gravity reaches 1.225 or 1.230 or until temperature of
pilot cell reaches 105 degrees F.
A chemical ampere hour meter is installed, but does not
give a good indication of charge as gravity, so ampere hour
meter is only used to get a rough estimate.
Gyro Compass
The gyro compass consists of three A.C. 90 volt induction
motors 120 degrees apart, suspended on an inner gimble
ring, which floats in a mercury bowl. The main voltage, 125
D.C. comes from ship's mains to motor generator set, which
converts and steps it down to 90 volts A.C. The rotors are
about four inches in diameter and weigh about ten pounds
each. They spin in the air as there is no vacuum chamber on
the compass. The repeater system is operated by a
three-phase motor, turning a shaft with a row of contacts,
which cut in simultaneously the field poles in the step by
step motors in the repeaters. The three-phase motor is
operated back and forth by having one phase split with each
side connected to contacts on the inner compass standard.
When the compass finds its course the hunting motor on
bottom of compass moves the two contacts so that the motor
contact will be between them and keep the repeater in stop.
All the repeaters are D.C. The lights are dimmed in the
repeaters by cutting in resistance.
Arrangement
The interior arrangement is very poor. Repairs at sea are
almost out of the question. This is due to the
inaccessibility of the parts which are most likely to get
out of running order; for example; the main motors and
fields are directly below the switchboards in heavy
casings. In order to remove a motor or field coil it is
necessary to remove a section of the hull. The pumps are
located behind or under a network of piping and cables.
The UB-88, although of only about 750 tons displacement, is
an excellent sea boat. This may be accounted for by the
fact that the boat is of the saddle tank type, which gives
larger beam dimensions for small tonnage.
Engines
Engine Builder: Vulcan Works, Hamburg & Stettin,
Germany Number of engines installed: Two (2) R.P.M.: 450
Horsepower: 550 Number of cylinders: Six (6) Cycle: Four
(4) Bore: 13-3/4" Stroke: 13-3/4"
There are two sets of cams shifted by hand from forward end
of engine, by means of hand lever and worm gears.
The engines may be started by air or electric motors.
The pistons are of high grade cast iron, and the top of
pistons are concave. The pistons are oil cooled.
Wrist pin is keyed into piston by taper pins.
Wrist pin bearings are of white metal keyed into connecting
rod.
Engine base and bed plates are of cast iron.
Crank shaft is of high grade carbon steel and disc friction
clutch acts as fly wheel to engine.
The rocker arms are of cast iron, located on the upper
inboard side of the engine above and outboard of camshaft
on a sectional eccentric rocker arm shaft. A two peice
collar holds each arm in place so that in renewing or
overhauling any valve the rocker arm can be easily shifted
so as not to interfere with the lifting out of the valve.
If necessary to remove cylinder head, the section of rocker
arm shaft can be removed by lifting off boxing on each side
of the cylinder.
The rocker arms are operated on the forward end of engine
by means of two levers; each lever controlling three
sections of shaft by three cylinders.
The fuel pump, lubricating pump, and circulating water pump
of each engine are also at forward end of engine, forward
of air compressor. The fuel pump and circulating water
pumps are driven by a horizontal crank driven off the main
crank by worm gears.
The fuel pumps are similar to the Nelseco.
The circulating water pumps are plunger type.
The lubricating and circulating pumps may be cross
connected for either engine.
Engine Air compressors
The engine air compressors are similar to the Nelseco,
except that they are four stage and are located at the
forward end of engine. There are two trunk type pistons
with the 1st stage in the middle, the 2nd at the bottom,
and 3rd and 4th tops of pistons. The air suction to
compressor is governed by small throttle connected to a
piston valve allowing the required amount of air to 1st
stage of compressor. The first stage compresses the air
from 2 to 3 atmospheres and discharges it through the
cooler to the 2nd stage. The 2nd stage compresses the air
from 9 to 10 atmospheres discharging through the cooler to
the 3rd stage. The third stage compresses from 32 to 44
atmospheres and discharges through the cooler to 4th stage.
The 4th stage compresses from 60 to 90 atmospheres, (relief
valve set at 160 atmospheres) and discharges through cooler
to restrictor where the air is distributed, the required
amount for the engine to the spray bottle and the amount
over can be sent to the ship's air flasks.
Pumps
1 - Auxiliary lubricating oil pump, centrifugal.
1 - Auxiliary circulating water pump, centrifugal.
1 - Fuel pump, centrifugal for loading oil to tanks.
1 - Bilge pump, centrifugal.
1 - Adjusting pump, plunger type, for pumping to or from
trims, regulating tanks, fresh water tanks and bilges.
Opinion
It is the opinion of the Commanding Officer that the German
type of submarine is superior to the American type (both
Holland and Lake) in the following particulars only:
1. Easier riding in heavy seas, with seas ahead, astern, or
on the beam. This is attributed to the fact that all German
boats are of saddle tank construction and therefore have
larger dimensions for the same tonnage than our submarines.
There is very little tendency for the boat to bury itself
in a sea way. The bridge, in any kind of weather is
comfortable. Seas have never broken over the bridge since
the trip was started, and only occasionally does spray come
over.
2. Wooden deck. This feature is far superior to our steel
decks in that it gives a firm foothold, does not require
constant attention to keep in good condition; it is easier
to repair or remove for getting in inaccessible parts of
the hull; it is lighter, and is much cheaper.
3. Gyro compass. The Aushulz type of gyro compass is an
almost perfect working instrument. During the entire trip
of 15,361 miles, mostly in rough water, this compass was
never over three degrees off the meridian. Trouble has been
experienced with the repeaters.
4. Bunking arrangements are excellent but the accessibility
of the batteries has been sacrificed to obtain this
condition. Would not recommend any change from our system.
5. Sounding machine. This machine is installed in the
central operating room and should be an indispensable
feature of our submarines.
6. Periscopes. From observations and comparisons the German
type of periscope is superior, due to greater light
transmission of the reflecting prisms and lenses.
7. Turbo blower. This blower greatly facilitates the
blowing of tanks. It saves all the high-pressure air which
is ordinarily used for that purpose and which should be
kept available for emergency or torpedo use. Only air tanks
of sufficient capacity for torpedo work or emergency use
need be installed.
8. The propellers on the UB 88 are under the fan tail and
are more deeply submerged than ours. This of course reduces
the propeller losses and ensures complete propeller
submergence in all weather.
9. Hull paint. While in dry-dock the underwater hull was
found to be absolutely free from all rust and growth. The
hull paint used by the Germans should be tried out, as it
appears to be superior to that used by our service. It is,
from a superficial examination, made from an asphalt or
coal tar base.
10. Diving rudders. The forward diving rudders are placed
about two and a half feet above the keel. This ensures full
rudder effect at any depth. The forward diving rudders on
U.S. submarines are placed so high on the bow that they
lose a great deal of their power when near the surface due
to lack of weight of water above them. I think this change
would cut down the crash dive time an appreciable amount.
The interior arrangement of the UB 88 is exceedingly poor.
This is probably accounted for by the fact that these boats
were built in a hurry and were only intended for the
duration of the war. The lack of copper and brass is
apparent and much of the piping is rapidly going to pieces.
This is especially true of the circulating water piping on
the main engines and the high pressure air lines.
Except as noted above the UB 88 presents nothing new in
submarine construction or anything which is superior to our
boats.