[PSUBS-MAILIST] Need advice, new builder.

[Stan Muller <smuller@iland.net>]

Hi All,
   I have been visiting your web sites for the past six months, and now
I'm trying to apply some of what I have learned. I am building my own
dry submersible. (Diving Duck)
   I have two aluminum cylinders (tanks) one is 24" by 75" and the other
is 21" by 62" The larger is to be the hull and an end of the other is to
be the conning tower. When assembled, the 1/8" aluminum will be covered
with several layers of hand laid 6 oz. fiberglass epoxied on. There will
be five, lexan 1/4" by 6" diameter portholes in the conning tower. two
six gallon ballast tanks will be mounted on the exterior of the hull,
and will be blown with CO2.
   I have built a 6' articulated arm with a grabber that will be mounted
on the port side of the hull along side and below the conning tower,
where it can be seen from the inside. It is built with pivots at the
wrist, elbow and shoulder, and will follow the movements of my arm
inside the sub. There will be no through hull mechanical fittings, for
the arm, as it operates with hydraulics. 
   Maximum depth of operation will be twenty feet, being at one
atmosphere with a surface air supply through an umbilical from a tender.
It will be sealed and pressure tested to thirty feet, before any trials.
Emergency air will be onboard, as will drop ballast, and the other
safety measures, that are outlined so well on your many web sites, will
of course be included. 
   Now for the questions; Am I on the right track so far? Is there
anything that I should be concerned with that I haven't mentioned? Do
you think that 12 gallons of air ballast will be enough if everything
else is properly engineered?
  Any and all assistance will be appreciated. 
Thanks and best regards, Stan in Missouri.