[PSUBS-MAILIST] cabin pressure

[Alec Smyth via Personal_Submersibles]

Hi Brian,

D'you have an over-pressure valve? I just stick the shop vac hose over the
valve (which is slightly smaller diameter than the hose) and that'll pull a
small vacuum in the cabin. If you can see a cabin pressure gauge through a
viewport, just pull the vacuum and then see if it persists over say ten
minutes after removing the shop vac. If it does, your hull is air-tight.

Best,
Alec

On Tue, Apr 3, 2018 at 10:48 PM, Brian Cox via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi All,          I did an experiment today with my hatch because I'm
> trying to get a handle on the sealing capability of my hatch.  My hatch
> dogs are on a wheel that I turn to secure them, they are only a friction
> progressive seal, where the dogs push the hatch down tight from the
> underneath the rim of the hatch rim.  I'm concerned that if I were
> lingering right at where the water level meets the hatch ring that there
> might not be enough pressure to seal and I would have a leak.  I also
> wanted to see my cabin pressure gauge move as well so I brought a scuba
> tank inside the cabin to build up pressure inside.  I used some ratchet
> straps to secure the hatch from the inside and was able to build up some
> positive pressure inside the cabin.  Then I tried just holding onto the
> hatch closure wheel with my weight to see if I could get a pressure
> increase that way, which I did.  Do you experienced submariners ever have
> an initial leak at the hatch before there is sufficient pressure to seal?
> It would be nice to do a negative pressure like Nuytco does but I can't
> figure out how to do that while I'm inside the sub.
>
> Brian
>
>
>
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