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?



A photo might help but based on a couple of assumptions on my part:

  • Individual plugs (vs Fusion vs FCS II)
  • No major damage to surrounding foam

Try installing the Fusion (peanut/hourglass hi density with plugs attached) plugs.  With some careful detailing it might be a nearly invisible repair.  

In answer to your questions:

  1. Glass-on fins are always an option.  Structurally?  Likely more so than individual FCS plugs.  Foam plugs or bog - either way.  Don't skimp on fillet at base.  Consider a bunch of fiberglass patches cut on the bias.
  2. Worth the effort?  Definitely.  Or, a good excuse for a new board!
  3. Check online for fiberglass fins.  Tabs on your basic FCS interface are easy to cut off.  Or check Fiberglass Supply, FoamEZ, etc.....

PS - Or like gdaddy recommends.  Didn’t see his comment!


Not worth the effort performance wise.  Repair it back to original and shape something new.  I don’t know why so many want to cut up boards that seem to work fine and were designed to be what they obviously are.  Most of the time they cut them up out of impulse.  I often wonder how pleased they are with these “dog” morphidite cross gender boards after surgery.  Most of the time you don’t hear anything in the way of aftermath.  Too embarrassed to admit that they wish they had the board in original condition.