Hi Dean. Ya, pin holes can be hard to find. You can put duct tape over
the bottom holes and pump up the tanks with a small compressor. It doesn't
take hardly any pressure to make bubbles at a pin hole. Just squirt soapy
water all round and bubbles will form at the leak.
Hope you're having fun testing.
Some of the guys are putting poppet or mushroom valves on their tanks to
let the air out quicker, so submerging doesn't take so long. I'm like you in
that respect. I'm not that concerned with how long it takes to flood the
tanks. I'm using 1 inch valves and the bottom holes ( 2 on each tank ) are
about 3 inches in diameter. I'm putting little diverters on the holes so water
won't be forced into the tanks if the sub needs to be towed at relatively high
speeds.
With 2 holes on each tank I should be able to "blow ballast" and get the
water out fairly quickly. The tanks are 12 gage so a little pressure build-up
when dumping air into them shouldn't be too risky. Worst case scenario would
be to "bulge" the tanks a little if I added air too quickly. Expensive to
replace but not life threatening.
Are you going to take any video of your sea trials? That would be a real
kick in the ass to see.
Be careful and have LOTS of fun. Frank D.