Bold (decoys)
The Bold was a device that was developed to deceive the enemy ASDIC location for German submarines . It should the submarine hunters a decoy pretending under water, in the "shadow", the submarine of the opponent's prosecution should withdraw.
The first development was called "Lügenbold". But the device did not get out of the experimental stage. The development was stopped when tests with S-systems showed that air bubbles in the water produced an echo. The message center trial command then (NPC) developed another device, the "Tarnbold" that air bubbles could generate in the water. Later the device was only called "Bold".
A bold consisted of a cylindrical wire cage about 10 cm in diameter with a swimming cap, filled with a mixture of coarsely ground calcium hydride , which was coated with water-soluble paint. This could generate hydrogen gas bubbles for half an hour in shallow water, which reflected the sound waves emitted by the enemy like a submarine. Three to five Bolde were enough to generate a stronger echo in shallow water than a submarine in the bow or stern position to the tracking transmitter.
After attempts in the Bay of Biscay and on a patrol in 1941, during which an opposing submarine hunter was successfully deceived, it was decided to equip the submarines with it. An ejection device was designed for this purpose and installed on all front submarines from 1942 onwards.
This enabled six cages to be ejected underwater. More could be reloaded.
This Boldschleuse was casually called “pill thrower” by the crews. Since the effectiveness decreased at greater depths, in addition to the Bold 4 used in 1944, work was also carried out on a more effective Bold 5 which could also be ejected at depths of 200 m.
The Bold had proven itself very well by the end of the war.
literature
- Eberhard Rössler : History of the German submarine building. Volume 1: Development, construction and properties of the German submarines from the beginning until 1943. Licensed edition. Bechtermünz, Augsburg 1996, ISBN 3-86047-153-8 .
- Fritz Köhl: From the original to the model: Uboottyp XXI. A picture and plan documentation. 3. Edition. Bernard and Graefe, Koblenz 2003, ISBN 3-7637-6031-8 .
Web links
- Description and drawing on Battle of the Atlantic: Technical Intelligence From Allied Communications Intelligence
- Bold at uboat.net