First weigh the hatch in air. Then calculate the displacement of
the hatch, which is the weight of the water that would fill an equivalent
volume. Subtract the displacement from the weight. If you get a negative
number, the hatch will tend to "float" as you describe. I doubt very
much that would be the case for any conventional elliptical steel
hatch. In the case of an acrylic dome hatch like the K-250, I'd recommend
doing the math because I'm less sure of the outcome -- those might be
slightly buoyant.
Alec
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From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
Sent: Wednesday, February 17, 2010 11:50 AM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Hatch pressure
I've
brought up this subject before, but are tackling it from a differant angle.
How
much pressure is exerted upward on a hatch at the moment where the
submarine
just
submerges below the water? This is the point of most force before external
water
If
you took your submarine, filled it with water & hung it upside down, would
this be the
same
amount of force, or close to it.
In
wich case if you have a design like Franks flying saucer that angles up to the
hatch,
you'd
have a lot more force acting upward on the hatch than a K250 where the lifting
force
would
be spread more evenly along the hull.