I don't know. I'm not a sub guy, so I'm not sure of the terminology. No chambers or air systems involved, this was from spares and stash.

I had all the guttywuts (brick, motor and aileron servos) from a 2 cell foam microplane. I had a Revell 1/144 Type VII/41, so I figured I'd have some fun (which was why I brought it up, hobbies are about the fun).

So I bought 6 AA NiMH cells and soldered them together into a string in the hull bottom, installed everything else, building stuffing boxes for both the prop shaft, rudder and dive planes and sealed the entire thing up with an external switch and charging port. It was trimmed to sit low in the water and I figured the planes would push it under, release them and it would rise and since it was positively buoyant, when it went under 6 inches and lost signal, it would pop up.

It all worked better than I could have hoped. We were having too much fun to really work out control, it needed a good bit of momentum to dive, then it's lose signal and pop back up stern first. It dove real fast in reverse. I could set travel adjust, expo to get more subtle control on the dive able, but I didn't bring the multimeter and wasn't sure how much run time to expect off a 1800 mAh since the motor is design to drive a big AC prop on lipo. I didn't want a LVC blackout 100 feet offshore.

On the way to the car after the session, we heard the water inside, a very small amount, but still distrubing since there is no way to get it out. I assumed it was getting in through the shaft since we were doing some hard reversing, but while shaking it, there was a drip from the conning tower. That turned out to be the whole problem, what I thought was a solid piece where the flak guns would attach, was actually a shallow opening, so the twenty minutes or so it spent underwater it took on a few ounces of water.

Once it dries out, I'll seal it up again, put the detail parts on, paintit and have more fun. I definitely see a serious sub build in my future, with real systems in a 1/72 VII or IX.

Or maybe I should just go over to the sub forum and rant about how much they suck and I spent $15 on batteries for a wet plastic model and all you guys can go...