[PSUBS-MAILIST] Listing solved

Sat Jun 18 00:40:55 EDT 2016

Yikes, Hank.

Glad to hear that you got off the bottom.  Geeeez.  Would it be better to test the trim and buoyancy in 15 feet of water?  This would allow less time for Gamma to pick up speed during a crash dive or breach, and allow easier escape if it gets stuck in the mud.  Very tricky doing this testing phase solo.  There have been several times in history that when a sub breached all the compressed air in the MBT is lost and the sub crashed to the bottom.

I am not familiar with your ballast tank venting protocol, but most ballast tanks need to be vented slowly and carefully so that the sub's attitude remains level to allow all tanks to vent through the top vent(s).  If the sub starts to go down on one side or in pitch then the ballast must be blown to reset from level start attitude for another attempt. The conical ballast tanks fore and aft were likely much easier to control as only pitch trim was the issue.  Just a thought; several smaller ballast tanks, each with its own vent and blow valves, would make things easier to control.  The increased complexity would be worth it, just add to the procedures in your check list.

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of hank pronk via Personal_Submersibles
Sent: Friday, June 17, 2016 1:41 PM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: [PSUBS-MAILIST] Listing solved

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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