You have made yourself a very stiff sandwich panel.  The best bet may be to go at the underside with a heat gun and see of you can remove the epoxy and glass on that side.  Then cut the correct camber into a couple of transverse hatch stiffeners and glue them to the cover thus pulling it into the correct shape.  You can then reglass the cover around the stiffeners.  You will then have the stiffeners to run the screw-eyes into for the hidden hatch hold-downs and a very stiff cover at the correct camber.

Good luck and tell us how it goes.

Paul

My WD12 hatch cover also ended up with a lengthwise curve which made it bow up when in place on the boat. So I cut a kerf laterally across the doubler, clamped the cover to a flat workbench, filled the kerf with epoxy/woodflour mix and glued a longitudinal stiffener to the doubler. The stiffener and hatch formed a t-beam, which strongly resists bending. The operation was successful, reulting in a perfectly flat hatch cover. Click on the picture to get a larger image.

Good luck,

Laszlo

Maybe we should trade covers because mine is perfectly flat but I need a bow put into it, about 4mm worth in the middle.  When I put the deck on it had a slight curve it it so the cover won't sit flat now.  I'm going to do what lazlo did, maybe a few more kerfs so it bends evenly.

If I was to do it again I would change the order of the plans and do the cover stiffner epoxy after the deck was on, which still gives room to fit the cover to the deck.

I would do exactly as Laszlo suggested and make a kerf or two in the stiffener.  That should release a bit of the tension and then you can flatten it out with some straps.

FrankP

Thanks for the advice.  I did a dry run and it should work out just fine.  I need to double check the length of the kerf in relation to the hatch and the spacing of the doubler.  It would be a shame to straighten out the hatch then have the kerf in the way.

Greg