can you add a fin box after glassing?

I have a quad, "already glassed" and was wondering if I could add a center fin for a tri option.Wouldn't matter which system.

yes. it’s easier if it’s not a pre-glass system.

You will just need to sand rather heavily the area where you are going to insert a new box, then route out the hole, install the box, cover with a fiberglass patch, hot-coat, sand and (optional) gloss, fine-sand, polish.

Great. Now which system should I put in.Easier would be better.

Probox is the easiest IMO,and has an inexpensive install system.If your just doing one box your looking at 35$ for a box,an install jig and a router bit with a bearing.Whats your location I may be able to help.-Mike



I`ve only built two boards and repaired a few I am hardly an expert. But In getting advice from other posts here I thought you had to glass the board first before laying in the fin box.  I am using a Dion 10inch box for a single fin retro shape. The main trick is to position the box so there is still some stringer/foam and not to go all the way through the board.


good luck

I’d suggest taping off the area, giving it an extra hotcoat, then installing the box over that. Sand down as normal.

ProBox is easiest and made to be installed after the hotcoat.

Like nj surfer suggests, tape off the area first, it’ll help when sanding



I went back and re-read your post, but I guess I missed something.  On trying to decide what system or box to use;  I would first ask:  What system is already installed in your board?  You can install Pro-box, FCS, Standard(Surf Source) "after the fact" with little or NO sanding.  If you tape off as Brian mentioned in his above post and you are careful you may get away with only grinding the plug or box down flat to the board.  It will depend on how clean you can rout, set , fill and grind.   The other systems; Futures, O'Fishl, and Lokbox are either meant to be installed under glass at the lam or later with a cap or football over the top after the lam.  They can be installed retro, but a few extra steps will be needed in the process.  If you rout after the lam be sure that the box sets down into the lam ,not on top of it, that way the cap will lay down flat and blend well after sanding. Someone mentioned sanding the general area (4 or 5 ") around the routed hole.  This will enable the fiberglass cap to adhere to the exsisting glass job. Afterwards; hotcoat; sand, gloss and polish if desired.

Should have added;  You can install a Bahne or O'fishl 81/2 or 101/2" longboard box easily after the fact.  Just tape off and go easy on the grind.