: Hi everyone,

: I am curious if anyone out there has flush mounted hatches which are
: waterproof (incl. rolling). I looked at all the options I could find and
: there are only two which seemed to turn out at the end.

: Assumptions: ~2 lb of force per bungee (four in total) for sealing. I presume
: that I may need sone additional force to force the hatch into the proper
: position.

Waterproof is not as hard as it seems. You just need to have a gasket that seats down all the way around the hatch. You just need enough force to assure that the gasket achieves this goal and enough additional force that the hatch doesn't get knocked loose accidentally. As long as you acheive this putting the hatch under water will only seat the gasket tighter due to the water pressure pushing in on the hatch.

The gasket itself needs to be waterproof, so closed cell foam is needed. And it needs tobe strong enough that water pressure doesn't push it out of the way. This isn't hard as long as you don't put the boat 30 feet below the surface.

If you're hatch-hold-down system doesn't provide enough pressure to seat the gasket, you can increase the pressure per square inch on the gasket in two ways:

1: Increase the pressure generated by your hatch-hold-down system, or

2: Decrease the surface area of your gasket. If you use a narrower gasket, it will be easier to compress and thus be more likely to seat all the way around.

You could also choose a more easily compressible gasket material. The reason you use a compressible material in the first place is because the closure is somewhat irregular. If you make the hatch closure spacing more precise, you won't need as compressible a gasket.

: In case of Joe's designs the gives you 1/32"