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Re: [PSUBS-MAILIST] Center of gravity Vs. Center of Bouyancy
Lew Clayman wrote:
>
[snip]
> Not to get too pedantic here, but if you move weights so as to to change trim, have you not in
> effect changed CG? And if you move other weight (water, below) to compensate, haven't you changed
> it back? Or do I still not get it?
You do get it. You are correct. The center of gravity deals with balance
and if you move water, lead, or people fore or aft, the CG has also
moved.
[snip]
> I had forgotten about trim tanks, shows I'm a newbie. Eases design when you have a mechanism to
> correct things. Duh. Never realized it could be a toy, too.
Everybody is/was a newbee at one time. That's what's so beautiful about
this groups list. We all benefit from a conversation between you and I
and I benefit from conversations between another two on the list. Great
learning tool.
I think all PSubs should have a trim system. It is so easy to set up on.
Here's what you need for a simple one.
-------- -> ----------
| Aft |=======>===||==(pump)===||===<=======| Fwd |
| | || || | |
| tank |=====<X====|| ||===X>======| tank |
-------- 1 |=============| 2 ----------
The pump always pumps water in one direction. It is by opening and
closing two valves (or one mixing bivalve) that water is pumped fore or
aft from one tank to the other. To pump water forward, open valve #2
(X>) and shut valve #1 (<X). Reverse the valve status to pump forward
aft.
Another idea is to have a wire or "closeline pulley" running from fore
and aft with a seight suspended on it. Want more weight forward, run the
weight forward on the line until you get the desired trim. I suppose
this could be internal or external of the pressure hull but outside
would require a small motor.
Ed
> Thanks for the lesson.
>
> -Lew
>
> =====
> "Yo no soy marinero / Soy capitan"
> - Traditional Mexican Lyric (La Bamba)
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