German WW2 U-Boat Decoy "Water-Donkey".

[klem]

Among decoys devices seems to be used by the Germans during WW2.The water donkey consisted in attracting allied planes and ships during submarine attacks near the coast. The Decoy had the shape of a slightly short submarine shell just under the surface of the Sea. On this shell is mounted the exact reproduction of the structure of a real submarine, connected by an electrical cable, the decoy is towed by the submarine about a kilometer. The maneuver was done as follows: when the Commander of the submarine identifies an allied plane, he switches on the sound machine in the decoy. A plane or a warship would be likely to detect this sound. If the plane, for example, attacked the decoy thinking that it is a submarine, cylinders of oils and compressed air evacuate their content at the same time on the surface of the sea and if bombs were dropped On the Decoy, other wreckages were ejected for a more realistic attack result by the flooding of its tanks, which gives an opportunity for the submarine to escape. However,I would have more sources convincing than an article without references published in a review.

 

[dan_inbox]

It looks like the decoy doesn't fit in the sub, hence has to be towed all the way.
Must really hamper range and speed.

 

[Jemiba]

The same device is mentioned in one of the old Heyne Bildpapaperback issues (German counterpart of the
Phoebus "History of the World Wars" series, I think).The description says, that it is not known, if it was ever used
in combat, and that an U-Boot commander would hardly have been happy to carry such an amount of explosives
tied to the deck of his ship to the operational area ...
And against any other attack, than ramming, it wouldn't have been effective anyway !

 

[klem]

The description says, that it is not known, if it was ever used in combat,

Thanks for the additional information, it proves that the history of this project has been reported (by which document) elsewhere but always without real pictures, sketches or plans of realization, except by artists' representations.

 

[Hood]

I'd be tempted to classify this as myth unless more concrete information comes out. The original article (presumably 1940s, 50s judging by the illustration) could easily just be hearsay converted into a plausible looking cutaway drawing. We've seen plenty of these illustrations in things like Popular Mechanics and British Illustrated News that look semi-convincing but are actually page filler eye candy that on closer inspection aren't realistically engineered.