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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.