[PSUBS-MAILIST] Listing solved

[Stephen Fordyce via Personal_Submersibles]

Wow Hank, that sounds like one epic experience! At least you know the cause
though and can do something about it.

Cheers,
Steve
On 18 Jun 2016 8:01 am, "Alan James via Personal_Submersibles" <
personal_submersibles at psubs.org> wrote:

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 hard
to get trapped air to move out of the top of the center segment without
having it's own
venting valve (which I can't see). There might be up to 20 liters of air
trapped in each of
those 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 end
sections drain hole, pouring water in to it until it spills in to the next
section
then 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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