[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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