[PSUBS-MAILIST] Listing solved

[hank pronk via Personal_Submersibles]

Hi Brian,The sub was spinning like when a helicopter loses its tail rotor.  It seemed pretty fast also, I am guessing four revolutions but I was't counting.  I have never experienced that, it was very weird.  Its funny though because in the few seconds it took to surface I said to myself "I wonder if this is what Alec was talking about"  because he had an issue with Snoopy rotating but under different circumstances.  Hank 

    On Saturday, June 18, 2016 2:58 AM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 Hank,  When you say you did " 4 full rotations"  Do you mean rocking from one side the other on the way up?   What maximum angle from center do you estimate you were swinging?  If I'm understanding you right. That extra air was no doubt compressing on the way down , making you accelerate. Brian   

--- personal_submersibles at psubs.org wrote:

From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: [PSUBS-MAILIST] Listing solved
Date: Fri, 17 Jun 2016 20:40:55 +0000 (UTC)

Today I dove Gamma to 80 feet and the cause of my list became clear.  First off I extended my bottom vent tubes on the front MBT's and that fixed the list once surfaced.  But the real problem was quite scary.  It turns out that I am not evacuating all the air from my MBT's because there is not enough height difference between the vent valve and the tanks.  I added about 200 lbs more weight than my calculations called for and that compensated for the trapped air.  Now, I am no math wiz, so I chalked it up to a math error.   When the sub is on an angle the air does not escape fully.  I did my dive and vented till the sub was under and let her sink.  I was not paying attention to the sink rate because I expected it to sink slowly thinking all the air was out of the MBT's.  I was more concerned about the first time diving after all the modifications I have done.  I have not done a deep test yet.  Well I hit the bottom like a ton of bricks and Gamma went into the mud pretty deep I guess, because I had to use up 500 psi of air get it loose from the bottom.  Once it was free, I was a rocket heading to the surface and the sub did about 4 full rotations on the way up and then It breached.  Man that was freaky, so now I know the sub is too heavy because the air is trapped in the MBT's.    There is an easy solution, I will mount manual vent valves to the tanks and rotate them with linkages from the main vent valve.  I will leave the existing lines in place to get the air into the tanks but the extra valves will do the venting as well as the original vent valves.Hank
Oh ya and my hip waders had another leak.
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