I really dont know how many layers of glass there it but its about Ό inch or so thick. Mine had those plywood blocks attached and another very thin layer of glass over the blocks to complete the lamination.
When I replaced mine I removed the blocks from the inside replaced with ½ inch plywood and epoxy and put one layer of glass over it. Then use fairing compound and paint.
Other guys have used composite material for the lamination and still others used 2 inch pvc pipe cut long ways and then they glued approx 3 of those pvc pipes along the inside for stiffness then they added a couple of layers of glass then faring and paint.
The rim where it rests on the deck needs to be strong enough that no cracks start showing up over time around that rim. The lamination inside is for stability and strength when you walk on it.
I would also grade the edges on the inside lamination to approx a 45 degree angle so the glass will follow that curve and adhere to the top glass with no air bubbles because of a 90 degree angle edge was used instead of a 45 degree edge.
FellowShip
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Just for the Grins
Official 23 SF Antique Classic SeaCraft Owner