[PSUBS-MAILIST] inside trim tank

Sun Aug 16 11:06:54 EDT 2015

Be careful with bladders. When they leak (not if, but when) the water will run to one end of the sub or the other. A small sub here locally had that issue and ended up standing on its tail with no way for the pilot and passenger to flood down and get out. Happily, they were in shallow waters on a test dive, and the Coast Guard was able to fish them out.

Historically, we didn't use bladders. PC-8 originally had one (that leaked!) so it was replaced with a flat top fiberglass tank curved to match the hull radius which fit under the deck. That tank held, and one supposes still holds, a couple of hundred pounds of seawater. With internal ribs, the single tank was replaced by individual, interconnected tanks (usually 4 of either fiberglass or SS, depending on the customer) that would sit down between the ribs and could be pumped in and out, as well as fore and aft. Great for commercial payload changes, but probably overkill for us little sub guys.

Keep in mind. Two dozen of the most successful submersibles in history. And no VBT bladders. Ever. Something to think about.

Vance

-----Original Message-----
From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
To: PSubs <personal_submersibles at psubs.org>
Sent: Sat, Aug 15, 2015 11:08 pm
Subject: [PSUBS-MAILIST] inside trim tank

  I'm thinking that it may be easier for me to have a variable tank inside after all, if I make it out of a rubber material I could make a big bladder bag .  That way all I would have to do is have one line going to it with a reversible bilge pump on it to vary my weight.  

Brian  

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