Re: [PSUBS-MAILIST] Re: high speed subs

[VBra676539@aol.com]

In a message dated 2/27/00 1:35:08 AM, heyred@email.msn.com writes:

<< Vance,

My old dusty books describe squat (aka "settle butt") as a surface
disturbance phenomenon. You're saying this occurs in mid-water, so that's no
help. Does it become any less pronounced with depth? Please tell me more
about the velocity relationship. Your butt settles as you start from a dead
stop? And settles more the faster you go?

Joe
 >>

The subs squat from the start, and recover somewhat at power so they can be 
trimmed for controllable forward motion. All of them do it to some degree, 
even the JSLs. The subs with the biggest props are more pronounced, and the 
subs with the shortest lengths are the least. It has to do with the distance 
of the thrust from the CG/CB. The longer that lever is the more pronounced it 
can be. Even WW II Fleet Boats did it. The point is that this is a common 
thing. Not theoretical. Side thrust subs don't suffer from it because they 
are being pulled through the water, rather than pushed. Anything that uses 
dive planes and a rudder changes attitude underway to some extent, I expect, 
and that motion is multiplied a bit by the push.

The numbers you didn't like on the K had to do with its resistance through 
the water when we towed it around with the scale in line. It burns up thrust 
due to unnecessary losses due to the ballast shell and so on. Your crib notes 
say I'd be better off with tubular tanks and no attemped streamlining of the 
bow at such and such a speed. We didn't do anything with the boat under power 
that day, although the stern settled a bit when I was surface maneuvering, 
just like they all do.

Vance