RE: [PSUBS-MAILIST] Hatch pressure

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

Hi all,

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

pressure helps close it.

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.

Am I thinking right?

Alan