LA Towed array ??

[steveuk]

This might be a very short thread.. but I have never seen this question asked before and it is puzzling me.

On the outer hull of the LA's there is a raised cowling that runs down the length of the boat. It is known as the "Towed Array housing". Presumably the towed array is payed out from a winch from this when under way.

Here is what puzzles me - Fistly there appears to be no hole or door at the sternmost area of this housing for a towed array to exit. It fairs in neatly to the hull. But more importantly it seems that this is probably the worst area to have what amounts to a very long cable paying out - ie any such device exiting here at the stern would surely foul the prop!?
Tell me I'm not being stupid. There must be a rational explanation..I just haven't read it in any books!
Or is it a military secret?

[boss subfixer]

Steve,
It comes out the center

Steve,
It comes out the center of the prop... Just Kidding, I'm being stupid.This is a good question.The exit area is located on the outer most edge of the stern planes, and yes it could foul the prop if your not careful. There are procedures that should keep this from happening if followed.

[PaulC]

Steve,

It is an interesting question.

Steve,

It is an interesting question. Some of the data below is from Clancy and Gresham's "Submarine".

The tube for the TB-16 array runs down the length of the exterior because the boat is of single hull construction. The winch that pays it out is in the forward ballast tank and therefore cannot be seen. Aft, the fairing ends where the tube enters the stern ballast tanks. It snakes through the stern plane stabilizers and exits a tube built into the outboard edge of the starboard plane. The cable is 2,600 feet long with a 240 foot hydrophone array at the end.

In the 688i there is an additional array, the TB-23. It is a thin line array housed on a winch in the stern ballast tanks and fed out of the port plane. The hydrophone array is 960 feet long and is designed to detect very low frequency noise at very long range.

Prior to the LA class, Sturgeons had fairings added with an external tube which exited the fairing and curved out to the top of the vertical stabilizers on the end of the stern planes. It was a lot less elegant in application, but it adds a lot of character to a model (see Bill Lambing's USS Trepang, image courtesy ThorDesign).



Hope this help!

[steveuk]

You guys are so knowledgable.

You guys are so knowledgable.

Yes that helps a lot. Thank you very much. Who would have guessed it snakes through ballast tanks and the stern planes!

I had my own theories that those tubes on the tailplanes were not part of the towed array as I couldn't see how a cable might run through them. I thought the tubes contained countermeasures and that the Navy wanted us to believe otherwise. BUT! Your descriptions have blown all that away. Wow, two sets of towed arrays. This all makes alot of sense.

One last thing then about the towed array housing - Looking at my closest pictures of this casing I woulsd say that it is not sealed against the hull. There seems to be a small gap and a shadow where it joins the hull, top and bottom .. like a long free flood hole. I rekon you could get your fingers under it on the real thing. This would make sense as the whole thing needs to flood and not trap air bubbles in it.
Am I right about there being a gap?

[boss subfixer]

steve,
Your correct. It is free

steve,
Your correct. It is free flood.

[PaulC]

The gap between the fairing

The gap between the fairing and the hull is a little more pronounced on Permits and Sturgeons than the LA but it is definitely free flooding.

Originally, towed arrays were clipped onto boats as they headed to sea. However, this slowed down their transit times as they crossed the Pacific -- high speed tended to damage the array or cause it to be lost.

The countermeasures are mounted on a rotary pod on the end of the anhedrals of the 688i. They can be seen just forward of the starboard stern planes on Jamie Howell's USS Hampton (image courtesy ThorDesign).

[steveuk]

Ok Thanks guys. http://www.subcommittee.com/forum/icon_smile.gif

Ok Thanks guys.