School of the boat for 31 Jan 09 (SONAR)

[Darrin]

Folks, the school of the boat has slowed down for a reason... we are in an area now where very few of the museum submarines are the same as to which time period that they are being shown as now compared to when they were built and when they for the most part were alike..

For me these last few blocks have been the hardest to have you all work on because the fact that your submarine maynot have the same gear onboard that is discussed in the Fleet Manual.. With Radio it showed that almost all of our boats are different in what years and what kinds of gear they are supposed to have onboard for the period that they are trying to get to... i.e. COD, Pamp, Drum and Bowfin are still pretty close to their WWII timeframe and then you to the extremes which are the Marlin and soon to be the Dolphin who's time frame is soo different that it isn't funny.

SO, with that being said it is time to get back to work... The basic principles of SONAR have not changed only the gear that is used has changed with time.

What are the basics principles of SONAR and how did the SONAR work on a WWII fleet boat?

[Tom Bowser]

A look out would yell Down "contact off stbd bow" and sonar would say "yep something over there.
Tom

[Mark Sarsfield]

For the green horns, I just want to point out that sonar and hydrophones are two completely different animals.  The hydrophones use the sonic listening method, which is analyzed through the JP sound gear in the FTR.  Sonar uses the supersonic listening method through the WCA sounds heads and sound gear in the CT.  With that said...

The WCA system of sonar gear is used for supersonic listening, and also for echo-ranging and depth-sounding. It consists of three main divisions: QB, JK/QC, and NM. In this chapter we shall be concerned with the use of QB and JK/QC for supersonic listening. However, to keep things straight, we shall start with a brief description of the whole WCA system.

Projectors
The QB projector is a spherical hydrophone mounted on the lower end of the starboard training shaft. One face contains rochelle salt crystals, which change shape when a sound wave strikes this face of the projector. The other side is empty.

The JK/QC combination projector is mounted portside. The JK face is just like QB. The QC face contains small nickel tubes, which change size when a sound wave strikes this face. (The NM projector, mounted on the hull centerline in the forward trim tank, is used only for echo sounding.)

Change in shape of the salt crystals (QB, JK) or in the size of the metal tubes (QC, NM) generates a small electric current in connecting cables.

Receiver-Amplifier
In the receiver-amplifier, the small electric current is strengthened and changed so that it is heard as sound in the phones or speaker. Two receiver-amplifiers, QB and JK/QC, are in the conning tower. There is also a receiver-amplifier in the forward torpedo room for emergency use with either system.

Remote Control Units
In the conning tower are two remote control units, one for the QB, the other for the JK/QC projector. These operate the training motors, and also show the direction in which each projector is trained.

Hoist-lower-train mechanisms   
Both shafts are equipped with hydraulic mechanisms for raising and lowering the projectors. Training motors and reduction gears turn the shafts and projectors. Power is supplied by two motor generators. All of these units are in the forward torpedo room.

Other Parts
The remaining parts of the WCA are concerned with echo-ranging or depth sounding. For echo-ranging there is a QB driver and a QC driver in the forward torpedo room, and a range indicator in the conning tower. For echo-sounding, there is a depth indicator in the control room. (The QC driver is also used for NM in depth sounding.)

In the conning tower
The photograph below shows a WCA stack, in which five units are grouped for efficient supersonic operation. There are separate remote-control units for the starboard (QB) and port (JK/QC) projectors, each with its receiver-amplifier. During routine search only one type of supersonic gear is manned. But when a contact is reported, QB is taken over by the sonar operator whose battle station is at the stack, and a second operator mans JK/QC. Normally during an attack, QB tracks the target, while JK searches for other ships. The range indicator is not used for listening.



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The photographs above give a general picture of the WCA gear in the forward torpedo room, looking aft, with projectors raised. These are lowered by a torpedoman, operating the hoist-lower mechanisms. If for any reason, the conning tower has to be abandoned, supersonic listening can still be carried on from the spare units in this room. These include a receiver-amplifier, which can be connected to either JK or QB, and a training control for turning either shaft. Relative bearings can be read directly from the scale and pointer on each hoist-train shaft. True bearings cannot be read.

Limit switches prevent training either shaft more than 2 1/4 turns, as a protection to the cables. If you train far enough to hit one of these switches, the training motor automatically stops. You must then train back one full turn. Where slip rings have been installed, the training shaft can be turned continuously in either direction without damage to the cables - eliminating the need for limit switches.

 

[Darrin]

VERY GOOD, thank you for the detailed version on how the gear was used

[Mark Sarsfield]

Thanks.  I feel bad for being gone for so long.  So , now I have some sub school karma in the bank.

[Lance Dean]

Good grief what an answer.

And thanks for clarifying between SONAR and hydrophones.

So you have to be in the FTR to use the hydrophones?

[Mark Sarsfield]

That is correct.  On German boats, the hydrophone operator was near the radio operator and the control room.  I don't believe that German subs had supersonic gear.

[JTheotonio]

Great information!