Work on the hatch lid ground to a halt due to being busy at work and then I had to do a 1500-odd mile road trip to pick up my cactus collection from where I used to live.
Whilst driving I did a lot of thinking about the boat and decided to pursue the idea to use foam for stiffening as suggested by
@Huntindave McCann
I managed to stop in at a hardware store and buy the $19.85 foam sheet mentioned earlier in the thread.
This is what I bought.
Back at work I ran a strip of the foam through the drum sander a few times to make it thinner and remover the smooth faces so that the epoxy would adhere to it. I was sceptical about using only foam to add rigidity to the lid so I cut some thin ply rib/stringer pieces on the laser cutter to glue in like you see in surfboards.
Laser cutting the ply.
Here’s the mock-up of the concept I thought might work. I didn’t think I needed to go full length as the lid gets narrower and is less likely to flex there.
Used commercially available thickened epoxy glue to stick it all together.
Needed some weights on the job pieces after firming up the clamps to stop them from buckling.
The next day I shaped the glued pieces with the saw and sander to fit semi snuggly against the central rib of the lid.
They were then painted with neat epoxy and I let them sit for about half an hour to give the epoxy the best chance of soaking into broken cells of the sanded surface. While they were resting I mixed small chopped glass strands and fumed silica into the leftover epoxy to make the glue that would stick them to the lid.
Chop strand glue mixture applied.
I’ve only ever used mixture like this to fill oversized holes for through-hull and deck fasteners, but I’m hoping it will work for this application.
Glue-up done.
Today I 40-grit sanded the set epoxy to prepare for adding the glass layer over the top. I wanted to do the glue-up and glass sheathing at the same time wet on wet and vacuum bag the whole shebang but I didn’t bring a large enough plastic sheet to work to make the bag. I’ve now made a large enough bag (which the lid is resting on in the photo) but I’ll use it when I sheath the top of the lid.
Here’s the foam sheathed with two layers of glass: 1x standard 200gsm cloth and 1x 265gsm +-45° biaxial cloth over the top. The sloping back edge (left hand side of the pic) also received two layers of 160gsm 3/4inch wide tape for a bit of added strength and to tidy up some of the loose strands along that face. Since I had the vacuum bag made, I did consider bagging this before I laid the glass, but due to the relative light weight of the cloth used it all conformed to the shape of the foam nicely, so I left it as is.
That’s it for now.
