Converting 5 fin shortboard to 2+1 w/glass-ons

Hey gang. So I was down in Baja last week and some damn reef just appeared out of nowhere in front of me… musta jumped at me when I wasn’t looking or something… 

Anyways, I ran aground as it were, and completely crushed in the two front FCS fin boxes on my daily driver shortboard. Its a 5’10, flat rocker, wide squash tail. Pretty typical for a groveller. I go to my ding repair guy here in San Francisco and he quotes me $200 to replace the two fin boxes. If the board were crispy and new… sure. But this board is in decent, but by no means spotless condition. 

Ive done my fair share of decent ding repair and my new neighbor shapes, so what I’m thinking is this— Rip out and fill in the holes where the front two fin boxes were and just glass on some performance twins. Thinking something like the MR power twins. The rear box is fine, so I could rock it as a twin on the smaller days or a 2+1 when it gets decent. 

A few questions for you wise folk. 

  1. Will this work structurally? What would it take to get this strong enough to surf? Would I need to drop in some new foam and glass over that or could I fill in around the fin box with resin and q-cell and then just glass the fin on top? 

  2. Think that’s worth the effort? ie, will a board like this go well as a 2+1, and if so, what cant and toe-in should I do on the glass ons?

  3. Where the hell do I buy glass on performance twin fins?



Parts is parts, so you certainly can pull the damaged plugs out, fill and glass on twins.  You can use a resin+filler, but I prefer not to when it comes to big repairs.    Personally, I’d use a dremel or a router to rout a cavity, cut an oversized plug to fit using foam from a dead longboard and glue it in.   Reshape to fit the bottom contour of the board and glass over that before doing glass ons.   But there are also other ways to handle that fill.  

Here’s a pic showing what I’m talking about, except that this is a raw blank that I prepped prior to shaping.   The darker foam is high density foam that I cut to fit.   They get shaped down flush with the rest of the blank when I shape it.   




Foam EZ has a decent selection of glass on fins specifically for Twin Fins.  Check their website.