SUBSIM Radio Room Forums - RFB needs your help re: decoys

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It's in the game but I don't use them, depends on the player at the end of the day.

From Norman Friedman's US Submarines Through 1945, p. 247 (Naval Institute Press, 1995 ISBN:1-55750-263-3)...

Quote:

...decoys could be released from a submarine's 3-in signal ejector tube and from her torpedo tubes. NAC was a barrage jammer with only limited output at any one frequency band. After tests on board an S-boat in February, 1944, 450 NACs were ordered in June 1944; that increased to 5,450 in August. Another 5,000 NAC-1s were ordered in June 1945. A total of 4,308 were supplied to the submarine force during the war (contracts were cut back drastically at the end of the war.) NAC proved only partially effective against experienced sonar operators. Its successor, NAH, used a high-velocity tape or disk recorder to pick up the sonar ping, then retransmitted it for 15 sec, beginning 0.10 sec after it arrived. It worked over the 10-15 kHz band. Developement began in May 1945.

NAC did not move through the water like a real submarine. Work on a self-propelled NAD began in May 1943. The 3-in NAD-3 simulated a submarine running at periscope depth at 120 turns. It could not accomodate a sonar repeater. A 6-in (diameter) decoy ejector was proposed; beginning in December 1943, an enlarged NAD-6 (6 in x 48 in) incorporating a repeater was designed to fit it. The new ejector was then canceledm and NAD would have to be fired from a torpedo tube. UCDWR {Univeristy of California Division of War Research} enlarged NAD again (the 10-in NAD-10 was made from an M30 mine body). The first NAD-6, carrying a sonar repeater, was completed in August 1944. BuShips demanded a simulator; a redesigned NAD-6 was tested in October 1944. Contracts for 500 NAD-6s and 500 NAD-10s were let late in 1944 and doubled in 1945; at the end of the war they were cut back to 500 each. These decoys held a straight course within 2 degrees so that the launching submarine could know where they were and evade away from them; gyro angle was present to within plus or minus 90 degrees. NAD-3 ran at 5 kt at a depth of 50 ft and slowed to 3 kt to begin noisemaking at present distance. NAD-6 ran out of a torpedo tube at 4 kt; noisemaking began after 35 sec, and last 30 -35 minutes. NAD-10 ran out at 7kt, then slowed to 3.75 kt after 1 min; it last an hour. At least some NADs were in fleet service in the summer of 1945.

4300 NACs were supplied to submarines from (estimating here) late July or early August, 1944 til the end of the war. That is a pretty good rate of distribution amongst the active fleet boats. One would have to conclude that they were being used. Of course, this conclusion has faults...unknowns such as size of NAC and available storage space aboard ship are not factored in.

Still pouring through my library and war patrol reports...hopefully, I will find something definitive.:ping:

Good find Donner. Now we are cooking with steam!

USS Barb deploys decoys

Perhaps I can be of some use here.

Been reading Fluckey's Thunder Below! and during Barb's 12th war patrol he recounts that on June 29, 1945, Barb was close inshore in shallow water, tracking merchants who were 1500 yards inside of the 15- fathom curve. After firing nine (!) torpedoes at a single ship for no hits (deep runners mostly) Barb was attacked by a destroyer.

From Thunder Below!, page 340-341:

Time 1332. "Sonar reports all torpedoes passed directly under target. Now fading out on same bearing...

Time 1333. "Gierhart says he heard side throwers firi..."WHAM! WHAM! WHAM! WHAM! "All ahead one-third. Max, I can't hit him! How many evasion devices do we have on board? Bubblers, swim-out becons, everything."
"Seventy-six."
"FIRE THEM ALL!"
"All?"
"I said all. I need them now, before he attacks again. We have no other weapons for these depths. Barbas gpoing to leave here alive and kicking. Get cracking!"
"Aye!" Max and Chuck sped off.
"Jim, to delay the next attack until we get some evasion devices in the water, let's throw her a couple of full-speed knuckles. These will give her something to ping on until the beacons simulating a sub swim away from the tubes and make their own submarine noises. We're only 5500 yards off the beach, so don't let us run aground...

Time 1340. Max returned breathlessly. "Captain, all five beacons are on their way and will be sounding off momentarily, as are the Pillenwurfer bubblers and gassers."
"Sonar reports that there is so much noise in the water it has blanketed our all targets. Sonar is useless."

Hope this helps.

I'd say it's a fair bet they were in common use towards the end of 1944.

Quote:

Originally Posted by tater

I'd say it's a fair bet they were in common use towards the end of 1944.

I'm with Tater on this one. The info above looks good to me concerning the round about time the decoy could be used.

76 decoys are a lot of decoys for one boat. So, if we want to be accurate, we shouldn't start using the pillenwurfer modeled in the game until mid-'44.

Quote:

Originally Posted by M. Sarsfield

The the sub sims from the early days, including SH1, let you jettison debris out of one of the torpedo tubes to fake your death. I'd would like to see that get added back in.

(I realize that this is off topic.)

Couple years back I think I asked Diveing Duck if he could make a mod of debris, like oil ,a matress , or some other sub stuff. And even got a little morbid and said a crewman or two. :lol: for uboats before decoys were availble. And use decoy launcher to send stuff out. I don't remember how he responded. He was working on alot of kool projects then.

This would be great for SH4.

BTW Sansfield I don't think you were OT at all.

Thx for reminding me of this. :up:

Nice find, epower!

From USS Barb's Twelfth War Patrol Report...

Quote:

29 June 1945, 1333-34 : Ten or more depth charges to starboard and astern, above and below. Released 5 NAC beacons set on 3 minutes delay at about one minute intervals. Threw a couple of full speed knuckles then slowed to 70 RPM and withdrew tactically and tacitly from the coast. Several escorts made sweeps around us occasionally but never picked us up again. Consider ourselves extremely unfortunate to only get a draw in this beautiful fight after all the punches we threw.

And Thunder Below is my favorite sub book... This crow sure is good!:yep: Want some?

Donner, thanks for that great information. It will help a lot in making a final decision.

Ive always been a fan of the oilslick idea. But from info provided, looks like they existed from sometime 44 onwards. I almost wish i remembered to remove decoys in TM. I never use them, but i diliberately "forgot" about it in hopes it would cut down complaints about my AI settings from the less experienced users. :lol:

I cant post the documentation for this, however while at the Batfish I watched a documentary with the torpedoman of the Batfish, and they said that they would launch decoys out of the signal flare tube. They said these decoys were just alkaseltzer which when introduced to water fizzes, and on the hydrophone they said it would sound like propellers swishing through the water which would cover up the sound of their propellers moving. Also they said they would launch a dummy wooden periscope painted black about 3 inches in diameter out of the same place and hope it would float in the opposite direction they were going. I am taking this straight from the documentary with the crew of the Batfish, the documentaries are down at the Batfish museum.

I guess they kept a lot of alka seltzer and dummy scopes on hand. :)

They never actually specified how many alka sektzer tabs they had, I think they said they had like 3-4 dummy periscopes, but they were not very big so they could store them.