Why didn't the hydrophones work on the surface?
 

Just something I was wondering about. The hydrophone head is mounted on the deck of the boat. Why didn't they put it on the keel, as surface ships did?

They did... it's called GHG "Gruppenhorchgeräte".

A small whitepaper by Arthur O. Bauer on the subject: http://www.mediafire.com/?gyc60je7r88b84b


For more papers, look here... http://www.cdvandt.org/index.htm

Likewise, KDB is better than GHG. GHG hull mounted acoustics have a very annoying forward baffle. Likewise, the baffles of GHG cannot be cleared except through maneuvering. The KDB baffle can be cleared by shutting off the engines. Technically, the KDB is more vulnerable to damage because it is deck mounted. However, if a depth charge gets close enough to ruin the KDB, chances are you have bigger problems.:dead:

Yes, surface ships had the sonar array in a retractible ball under the keel, but they couldn't hear other surface ships or surfaced submarines. US subs had the same setup, but whether they could hear very well, or at all, on the surface has been the subject of much debate. What we don't have is good evidence that they could hear while surfaced.

Part of the problem is the amount of noise created by the surface wave of the ship at any speed. Surface ships at the time had a problem hearing submerged submarines if the destroyer was travelling at speeds above 12 knots or so. It's my understanding that by the end of the war this had been upped to around 18 knots, but I don't recall where that tidbit came from.

Interesting stuff guys, many thanks. That was bugging me :)

I just read a Book from a German UBoat Radiooperator on the GHG.

Its called Feindfahrt from Hirschfeld. He tells in his Book that one Day they where pulled of a Convoy and 5 Destroyers laying around them. They surfaced the Boat in the Darkness and pulled right out of the Deathtrap at Night. The Enemy Destroyers couldnt localise them on Surface with their Asdic! ;)

Absolutely true. Sonar/Asdic, whether passive or active, has a hard time detecting anything on the surface. I've put this picture up before, but one more time never hurts. It explains how different British Asdic types worked, including the blind angles for both the surface and beneath the ship.

http://i14.photobucket.com/albums/a3...arpatterns.jpg