That’s the damage. I’m hoping that I don’t need to take the finbox out, and can just cut out the surrounding fiberglass and re-glass it but im hoping for some input. Is there something I should look for regarding whether or not I need to take the box out and replace it?
I would attempt to get the box out. Cut around and down on the box with a Stanley knife. Secure a fin in the box and see if you can wiggle it loose and out. Clean up the hole and reinstall the box using filler. I would use milled fiber. I wouldn’t cut too much of the damaged glass away around the box. Just the loose stuff. Do a little q-cell cosmetic treatment around the edge of the box. Put a couple of football patches of cloth and resin over the box. Hot coat and sand. It will obviously not be as strong if you don’t remove the box and reinstall it. Which means you could just clean up and fill around the box and cover with cloth. The problem with that is that if you ever hit it again it would most likely get knocked out.
First, try and put an fcsii fin in the box. See if the trailing edge is still above the lamination. If it is… Take away all that is broken. Then fix it with some epoxy and silica coloidal and few left over 6Oz mat pieces…
Since the foam underneath is now covered in compressed and hence actually stronger, it can work okay.
Conversely… Getting the box out is a bit of a mess. I usually go for a copy router bit and the original fcsii routing template. You route out the perimeter. Not the inside of the box, there is a metal rod inside! You can follow the circumference? And then pull the plug out. That way you get a really clean and good looking hole just slightly larger than the plug. The next thing you could then is to sand down the edge to the fibreglass. Do your patch will adhere and you get a perfect reinstall.
Then… Use old foam and shape it like the plug you want to install. Preferably smaller. Make a batch of slow hardening epoxy and microballoons. Put the fake foam in the middle and add the mix. Let it harden.
Then, sand down carefully and copy the installation directions from the other fin side. The distance from tail, rail cant and toe in (use a flat aluminum piece and tape as far up to the nose as possible to mark the toe in)
Install the box. Then later add fibre glass just past the sanded edge I spoke about earlier.
Then hand sand with a hard block and 80 grit till perfect. Add hotcoat. Wait, sand again. Hope you have not hit the weave and be done. Or just rattle can the remainder part. Wait. Sand wet with grit 1000 or even 2000.
Maybe polish it. Or not.
It’s a lot of effort, dedication time and money. But you do it for the love so tell us how it went. Make pictures.
Wouter Oosting
6oz mat is over kill. The only reason you would install a foam plug would be in the case that your removal of the box was not clean. Get the box out as clean as possible. Reset the box or use a new one. Thicken the resin with milled fiber or Cabosil. Put one 6oz and one 4oz. over the box. Hotcoat, sand and spray with rattle can Polyurethane Satin. Wet and dry to match. 1000– 2000# not necessary.