Sorry – this is kind of long, but I wanted to get some feedback.

I am thinking about installing flush hatches on my Chesapeak LT17 kit. I have read several (all?) the flush hatch postings for the past several months and have come up with my plans for flush hatches.

The Hatches

It seems like the challenge here is to get the hatches to follow the curvature of the deck – especially at the edges where the hatch stiffeners do not extend. I’m planning on using the covers provided in the kit as a template for cutting my hatches. Then, I plan on laminating the covers from the kit to the backside of the covers I cut from the deck. I plan of fixturing them at the same curvature as the deck and adjusting the stiffeners to the same radius.
I wonder if I should tighten the radius to allow for spring back? My thinking is that the stiffeners will hold the correct radius, but I am not sure if the laminated cover will be sufficient past the stiffeners. Maybe I should tighten the curvature of the forms past the stiffeners.

Flush Fit

Several of the posts refer to having trouble getting the hatches to rest at the same level as the deck. I am thinking of using a hard seat to solve this. My plan is to create a lip about ¼” smaller than the hatch opening and recessed a distance equal to the thickness of the hatches. The idea is that the hatches will rest on this lip and sit flush to the deck surface. This will require two layers of plywood below the deck surface. The first is a 4mm layer to match the extra layer on the hatch itself. The second layer is a ¼” thick layer that provides the resting surface.

Seal

There is a third layer of plywood needed for the seal to rest on. The plan is to cut this layer about ½” smaller than the opening provided by the lip (the previous layer). This is another layer of ¼” thick plywood. The idea is that the seal will be compressed to ¼” thick (equal to the thickness of the middle layer of plywood). I can make the last layer of plywood with a smaller or larger opening and that should change how much force is pulling the hatch against the lip.

Retention

I am planning on using an internal bungee system like Ross Leidy describes.

Materials

The first layer below the deck will be the 4mm hatch stiffeners provided with the kit. They will get cut away some to match the larger hatch opening. The next two layers will be some ¼” plywood I have in my shop. It has a birch veneer on one side and a luaun on the other with a thick core that I think is luaun. I am planning on setting each of these layers at 90 degrees from the previous one.

The Questions

Do I need to fiberglass any of this or will the epoxy (thickened) be good enough?
Will the plywood I have be OK?
Will the seal be sufficient?
Anything else?