Re: Center of gravity

[Subscuba <Subscuba@aol.com>]

Hello Marcel,

I am not really qualified to answer your question, perhaps someone else on
Psubs can answer it.

My thoughts are that you would want the difference between the center of
buoyancy and the center of gravity to be as far apart as possible consistant
with the construction of the Sub. My Sub is a wet sub and I have the battery
box as low as I can in the rear of the Sub. I am presently putting in the
floatation primarily over the battery box. My assumption is that I need this
righting moment so I don't need the diving planes to operate like an Airplane
to counteract the motor torque. My planes operate together such that in the
dive position both planes point lower simultaneously. I'm planning to put my
fixed floatation in (primarily Flotech Techspheres with microballoons and
epoxy) and then by trial and error adjust the trim for horizontal and vertical
stability to achieve neutral buoyancy. If I could I would put the center of
gravity in the bottom center of the Sub and the buoyancy in the top center.  I
know I will have to solve a number of problems when I get it in the water for
the first time.

In reference to pressure compensation of the motor. I have the compensation
port on my battery box and the motor compensation port at the other end of the
battery box. I have placed the ports as far apart as possible to avoid
entrained seawater from getting into the motor. I believe that the motor
brushes are very sensitive to having seawater corroding the hell out of the
brush to communtator interface so the battery box ,hopefully, will take any
seawater droplets out before they get to the motor. I may add an absorbant in
the hose going to the motor after I get the thing launched.

I hope this helps, don't forget I think there is more qualified people on
Psubs.

Ken Martindale