So here is what I’m working with. Had a longboard fin that was broken around the screw hole in the back. Hard to describe what happened, but I’ll do my best. if you look at the first picture, you can see where the fiberglass delamed from the graphic layer that was sandwiched in the fin. Where the green box is, there was no glass. the missing sectioned had chipped and fallen off. You can also see in the first picture that the delam actually starts forward of the screw hole. I was only able to get resin in that space, as it is just to tight to be able to fit glass inside of it, without breaking this tab off.
What I’ve done so far is taken 60 grit to the surfaces inside of the damaged area, taken multiple layers of 6oz glass (just enough to fill the gap with out with a bit of outward pressure on the pre-existing glass), saturated with lam resin, and stuck it in where the missing section had left a gap, lightly clamped, and let cure. I sanded everything to shape, and then took a drill bit the appropriate size for the screw, and started drilling out a new hole. I thought I was in the clear right when the drill bit caught, and separated again, causing the crack you can see in the picture.
The new glass (inside the green box) actually stuck to the graphic layer, but seperated from the fiber glass on the other side of the repair. Now, as you can see in the second picture, there is enough material there, but some shattered fiberglass has created enough debris to leave a gap, even when squeezed together with my fingers. I’m nervous that if I fill this with more lam resin (even with some cabosil), or even more resin-saturated glass, that I’m going to have the same crack happen again.
I am going for the strongest, and most “original to product” repair that I can here, because this is for a friend and I really want to give him something back that is well done (I dont like it when my work looks like a hack did it). I would really like to avoid the same crack happening again.
I’m wondering if there would be a (strong) way to cut off the damaged parts, and somehow rebuild that part of the fin with new glass, and drill a new screw hole.
Here’s a tip I taught myself after splitting a fin I made… use a set of vice-grips and clamp both sides of the tab as you drill. It’ll help keep it together while you drill. Obviously try not to twist the drill as you’re drilling.
If Bill Thraillkill says to use Super-Glue, give it a try.
Make sure to get the broken/cracked area well saturated, before clamping. From what I could see, in your photo, this is the simplest answer to the problem. If it doesn’t work, there are other labor intensive ways to address the issue. Always try simple first, if the circumstance allows it.
I found drilling the hole for the fin screw to be a bit of challenge too. I always clamped it as I knew it could grab and split all too easily. Eventually I settled on using very small drill bits to make pilot holes, expanding their size, then moving to the dremel with a small stone grinding wheel. Slow speed and let it cool, and keep it from getting smoking hot.
It is also all to easy to drill the hole at a slight angle which can make getting the plate to thread on the screw quite difficult. Progressively larger drillbits allow one to get it more perpindicular.
David Town (Warrior1515) recently made a fin for me. He ditched the screw tab altogether and inserted a row of spring loaded ball bearing gizmos that ‘pop’ into the slot in which the screw plate would ordinarily fit. A ‘Click Fit’ kind of thing(?) I’ve also seen them on SUP/windsurf fins.
Thanks everyone for the advice. Bill, I used the super-glue, and now it’s super strong. John, I clamped it before drilling the hole again, and it came out perfect and centered, no cracks!
My buddies have been using the fin and are stoked I got it in the water again.
I’m super intrigued! I’m a bit more of a traditional/minimalist when it comes to design and functionality, but I am always open to new ideas (everything was an innovation at one point in time). Do you have pictures? I want to see how this is done!
