[PSUBS-MAILIST] Listing solved

Fri Jun 17 17:57:40 EDT 2016

Sounds exciting stuff Hank, can you repeat it so we can see it on video?Looking at the segmented design of your saddle tanks, it would be hardto get trapped air to move out of the top of the center segment without having it's ownventing valve (which I can't see). There might be up to 20 liters of air trapped in each ofthose center segments. That would contribute to making you 40kg light,but at a 100ft when the air compressed to 1/4, you would be 30kg heavy.You could check how much air we are talking about by blocking an endsections drain hole, pouring water in to it until it spills in to the next sectionthen unplug & drain the water in to a bucket & measure how many liters you have.The water in liters would equate to air in liters that would be trapped up the top.Does that make sense?Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Saturday, June 18, 2016 8:40 AM
 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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