Details and pics below Hi Fos, I am going to frankensteinize an old windsurf waveboard (70Curious about your build. -What did you use for the tracks?. Shapers do the 2 tracks in a foam block ready to go. I later found out the fibreglass shop here stocks the same ones from shapers.
-Did you use any tricks to reinforce or just the bottom carbon layers in the pic? I am nervous about the side loads given the formula board at 1m wide, but the foam block inserted into a tight fit with the carbon over seems to be working.
-How many layers/cloth weight did you use?. 2 glass top and bottom, 2 carbon sandwiched.
The thought was that the glass will stick better to the existing carbon and paint, not sure if it's a thing but it cant hurt.
So the base layer is glass. 6oz from memory
Then Carbon for strength, 2 layers,
and finally glass to protect and shield the carbon from scratches or if sanding smooth(which I didnt)
-Did it gain a lot of weight by adding the foil box?
No where near the weight of the foil and mast, so nothing I've noticed, maybe up to 1KG but guessing hard.
Phase 1I got the tacks in a foam block, they weren't glued in I used surf epoxy and qcell mix to place them in, with masking tape over the tracks to enable easy cleaning.
Phase 2With a router and a vacuum cleaner I cut out a fairly precise hole, shapers forums led me to how far from the tail to cut. When I got close I checked with the foam block for fit. Then with the mast in I set this in qcell mix as per above. Using tape I ensured the to sides of the masking tape were the same length to get square.
Phase 3I removed the mast and sanded this all flat (didn't look for square), also sanded the plastic from the fin boxes to ensure all smooth, so the glass layers will attach well and it will be flat.
Sand out past where the widest piece of glass/carbon is going to go
Phase 4I remasked the tracks, but with very minimal cover, so the fiber glass will cover the plastic tracks. Then mixed up around 2 cups of resin(no qcell). Poored a reasonable amount on the board where the first glass 6oz goes, out that down and got it all wet, the carbon layer 1, carbon layer 2 and finally a glass layer for protection, if something hits it it won't hit the carbon. Left that about 12 hrs, when not sticky, but still soft enough I used a Stanley knife to cut out the basic shape of the tracks.
Phase 5,Wait 24 ish hrs from final application, Using a sander or dremmel cleanup the fin tracks so they are the correct shape and have no fiber edges - also sand any daggy bits around the edges, where fiber glass gathered etc
Pic1 - the block is set and now a combo of chisel to remove excess lumps and sanding to get smooth - I wear a face mask and use the vacuum
pic 2 (out of order) pencil marks for foam block location and routed box, before any resin is mixed

Pic3 Setting the block - with mast for square
Pic4 Setting the block - with mast for square
Pic5 after initial stanley knife cutout, after it had gone off but not set