Fcs fin box patches

Hi people. Sorry, there might be a thread for this but I haven’t found it. I’ve made about a dozen boards always using FCS Fusion fin boxes. They recommend puting a patch over each box for strength. I’ve tried multiple methods when doing this, but in the end the patches are always visible through the glass. Any suggestions? 

I have used those boxes. I put a tail patch of glass first, then I installed the plugs. Then I covered the plugs with glass when I glassed the bottom of the board.

I have done a few…

And prefer to lam 1st (1 layer 4oz) then rout and add boxes.

Then add 2 “dog bone” patches…

Although I have gone a bit further…


put the patches on top of the lam  box/board - full bottom lam - patches when you grind your laps feather the patches in. You end up removing the hard edge that shows the outline of the patch making it far less noticable

I just put the footballs over the boxes and makes sure they are tight with no air or resin voids and pulled smooth on the foam.  After setting up, I then sand down any football edges that are pointy or raised (5 mins max).  Then I glass the bottom normally.  

So I do a kind of pre-glass step.  I don’t see the patches and if I’m doing a tint, the area doesn’t get darker.  And I’m not a professional.  YMMV.

Could be the cloth the OP is using.  Some cloth does a better job of vanishing than others.  Also if you do your patches separately and your wet-out is too resin rich you will see them as well.  Keep in mind that a resin rich wet-out is heavier, weaker and will stand out.  I’ve not had any issue on clear boards.  I do my patches under the cloth so that over the fin boxes I’m wetting out two layers of cloth simultaniously.  This also keeps the edges perfectly smooth.