PETER WIHTOL has written an article on the ‘Seehund’ which appeared in the SubCommittee Report, has an article on the ‘Biber’ as well as one on ‘accessories’, coming out in that publication. Photos sent by PETER out of Kriegsmarine and OSS Photos

U-boats in the Bay of Biscay started to get clobbered by the Allies in 1943. The Kriegsmarine had to do things differently and this is what they developed to increase U-boat survivability. This article lists what US Navy had discovered.

U-5075 restored by PETER’s group

This article is based upon Office of Naval Intelligence publications. Rules-of-thumb for understanding intelligence reports:

• The more original and closer to an event, the generally more accurate the information
• To determine what concerned the US most, look at: The number of reports on a topic. Their lengths. And the level of detail covered.
• In reading US and Allied reports contrast what the Allies thought Germany was doing versus what Germany was actually doing. In brackets I’ve added my own edits and 20/20 (year 2003) hindsight commentaries.

WHAT US NAVAL INTELLIGENCE KNEW DECEPTION DEVICES

UNDERWATER BUBBLE TARGETS (Bold or Kobold = deceiving spirit)

These are chemical “pills,” which create bubbles to produce a false Sonar target. They are ejected from six inch tubes (“pillenwerfer” = pill thrower) through the pressure hull. They begin to dissolve within two minutes of being in contact with the seawater. Then for six minutes they create an echo-reflecting target approximately the size of a U-boat. This is capable of fooling inexperienced Sonar operators. This was a 15cm diameter cylinder containing chemicals which would react with water. There was an adjustable valve that controlled the flow of seawater into the canister and thus it controlled the duration and volume of the bubbles. This device reportedly could work up to 25 minutes. And additionally, from a U-595 POW interrogation report: “six pills are inserted in the tube” and “a metal cloth bag which is very limp”]

EDITOR NOTE – to be more precise, the BOLD was a slug of iron filings that would disperse in the sea, giving a sonar reflection like a submarine. Pillenwerfer was a chemical mix which when mixed with seawater, would produce fizzing and bubbling sounds like a submarine’s propellers. BOLD and Pillenwerfer were two very different ECM devices.

OIL PATCH OR OIL LEAK DEVICE

No further information was given about this device. It was simply a 6 inch cylinder that contained oil. This oil rose to the surface.

SUBMARINE MOTOR SOUND SIMULATOR

This is a miniature torpedo 18 inches long by six to seven inches in diameter. It is propelled by a battery-powered motor that drives a three-bladed, high-speed propeller. This simulator is effective in heavy seas but is otherwise easily detected [correctly identified as a simulator?]. [It would be set to circle at a given depth.]

RADAR DECOY BALLOONS

Are used to allow a U-boat either to escape or to attack while the attention of surface ships or aircraft are focused on these devices. These are hydrogen-filled balloons tied by 100 foot long cords to sea anchors and having three-to-ten, long, aluminum foil strips tied to the bottom of the balloons. The aluminum strips reflect radar impulses that is equivalent to a surfaced U-boat at higher radar frequencies. However, at lower frequencies of radar waves the returned signal is stronger than that of a surfaced U-boat. The aluminum foils [balloons?] are effective from 2-8 hours, depending upon the atmospheric conditions. The balloons will blow down in winds over 25 knots. Approximately 90 balloons are known to have been stowed in containers on deck along with hydrogen bottles for their inflation. [Apparently the German name for these decoy balloons was Aphrodite. Also during this time German scientists developed a series of progressively better radar sensing or detecting devices which were then used by the Kriegsmarine and by U-boats.]

IR AND UV RELATED TECHNOLOGIES

U-boats are painted with “a special gray absorbing paint.” They removed all bright markings and provided their crews with optical devices [viewing equipment] that can detect infra-red or UV rays. Crews have abbreviated codes and viewers for receiving messages. But reportedly only surface ships carry the signaling equipment [high power spotlight with a filter]. [Incidentally, infra-red penetrates much better through haze and fog. Thus it would be a better choice for marine signaling.]

RUBBER COVERING

Reports indicate the external use of cellulose rubber coating to deaden the sound reception of enemy listening devices. Such insulation consists of two thin layers of rubber, a few millimeters in thickness, which are laid over the entire hull and superstructure in 36 inch widths. This experiment is said to have proved unsatisfactory outside of the Baltic, since insulation tends to carry away. EDITOR NOTE – it was called “Alberich” and named after a character in the German legend of the Niebellung. He had a magic cap that made him invisible when he put it on.

[Additionally I remember one TV program where they said that the Germans believed that the high mortality rate of their U-boats was due to the Allies doing something new with radar that they did not understand – and it was improving a lot! Coatings were being tried on the U-boats, to reduce their radar signatures. One major reason for the high losses of U-boats was the breaking of the German codes and the fact that the German high command and Admiral Dönitz refused to consider that their codes had been broken.]

SCUTTLING CHARGES AND BOOBY TRAPS

[When you are scrambling to exit a sinking U-boat, the last thing you are thinking of is your obligation to set charges and booby traps. Words cannot express the primitive, animal feelings of terror and the intense, do-anything-necessary-to-live thoughts that click on, in your mind. Escape is your only thought and goal.]

SCUTTLING CHARGES

These charges are either the cartridge or canister types with a 9-minute fuse and 5 ounces of Ecrasit [commercial trade name for an ammonium nitrate based explosive], or 4 pounds of H.E. charges. All U-boats operating in enemy waters are equipped with scuttling charges. These charges were initially kept in storage and not in a permanent position. Boarding parties should expect charges placed in the following diabolical locations:

• Bowroom, between main and bow pressure hull sections.
• Control room at the bottom of the periscope well, in the CO’s cabin, the wireless room, or near a bilge pump.
• Motor or diesel rooms next to HP air tanks, air compressors or next to the diesel exhaust pipe.
• Torpedo warheads, magazines, etc.

EDITOR NOTE – while the US Navy may have thought all these things, we have never met a U-Boatman yet who knew anything about scuttling charges or booby traps.

BOOBY TRAPS

Could be installed to detonate torpedoes by a trip wire or by a charge, acting upon the removal of torpedoes from the tubes. Could be placed so they’d explode when pumps are started.

RUBBER BOATS

In addition to life preservers being provided for each crew member, almost all U-boats carry collapsible 25 foot or 13 foot rubber boats in the forward superstructure. Three boats, six feet in length, are carried by a 1,600 tonner. These craft are used to transfer provisions and personnel between U-boats.

NETCUTTERS

Although netcutters were observed on U-boats manufactured earlier in the war, this device seems to have been removed from most current operational boats.

CLEARING LINES

These are being retained on all types of U-boats. These fore and aft cables also serve as the aerials for radio communication. Another type spans from the periscope (when extended) to the stern supports.

MISCELLANEOUS SPECIAL EQUIPMENT

HELICOPTER

Some 1,200 ton U-boats are reportedly now equipped with a one-man helicopter for observation purposes. This device is stowed in two containers on the after part of the platform. In operation it is reeled out on a cable up to an altitude of about 400 feet. The spotter carries out communication with the U-boat with a walkie-talkie or telephone. The launching and maintaining of altitude depends upon the U-boat’s speed relative to the wind velocity, since there is no motor. The operator is provided with a parachute.

[This “helicopter” was actually a motorless autogyro. Three blades, 24 feet in diameter, about 180 pounds in weight. Rotor speed 205 RPM. This was a Focke-Achgelis, Fa-330. It was flown as a kite, trailing behind the U-boat. Reportedly, the normal towing speed relative to the wind was 25 mph (28 knots) and the minimum towing speed was 17 mph (19 knots). (Top speed of a Type IX is about 18 knots.) It could hold an altitude of 400 feet and the operator could see up to 25 miles on a clear day. He used binoculars and made reports by a telephone. This autogyro was initially made in 1942. About 200 were built. The operators first trained in a wind tunnel and then while being towed behind a power boat. After this, they were ready to see duty on a U-boat. The Fa-330’s became operational in mid 1942, but due to the heavy Allied presence in the Atlantic, they were not used much there. However they were employed by Type IX D-2 U-boats in the less patrolled South Atlantic and Indian Oceans. The main problem with them was Allied aircraft in the vicinity causing the need for the U-boat to rapidly submerge. This demanded crash dives that were too rapid for the observer to be recovered. An emergency procedure was used to jettison the blades and parachute the observer down from 400 feet, at best! An Fa-330 is on display at the USAF Museum in Dayton, Ohio. Pavla Models in the Czech Republic has a 1/72 scale.

LOOKOUT MASTS

Several 740 and 1,200 tonners have 48 foot, extendible look-out masts fitted to their decks immediately abaft [to the rear] of the conning tower. Another type of extendible mast is located between the periscopes. Experiments involving lookout balloons and kites have also been reported.

DEPTH CHARGE LOCATING PLOTTER

A panel arrangement of lights is reported to be able to locate the exploding depth charges that are within a range of 500 meters. The U-boat may head directly for the explosion when its location has been determined. [A U-boat could hide in the area of a recently exploded depth charge, because nothing could be identified there for about 5-10 minutes particularly if it exploded at 250-500 feet. It took that long for the bubbles to dissipate.]

A RECENT DEVELOPMENT: THE THETIS RADAR DECOY DEVICE

[Thetis is the mythological Greek goddess of the sea. She is the mother of Achilles and protected him by providing him with armor. The Bay of Biscay is of course the area just north of Spain and west of Southern France. From 1943 on, it was called “The Valley of Death” by U-boat men.]

CAMOUFLAGE

Although a few U-boats were extensively camouflaged early in the war, very few cases of deceptive patterns have been recently been reported. Generally U-boats are painted to blend in with the light and water conditions in which they are operating.

Arctic – White or light grey;
Atlantic – Medium-dark grey, sometimes light green, brown-green, or green-blue.
Mediterranean – Light grey, sometimes in an alternate striping pattern with green.

Thanks PETER. We always look forward to your articles.

Sneak Craft: German Biber Mini-Submarines
Sneak Craft: U-5075 Hund Mini-Sub
Sneak Craft: U-Boat Accessories 1944