Major Fin Box Blunder!!!!

helped my friend put a fin box in his board, and it seems that resin leaked into the box through the bottom. it latched onto the fin we used to set the box, and it doesn’t seem to want to let go. we’ve tried to get it out, but to no avail (even going so far as to drill a hole through the fin, run metal wire through it, and pull like hell).

anyone got any ideas??

whats goin on

if there is any space between the box and the fin try pouring some acetone in there and see if it will loosen up.

l8r on


Hey Soulstice,

There are probably several ways to approach this. Start by saturating the inside of the fin box with Acetone to see if you can get the resin to degrade and let loose. The solvent chemistry might work. There may not be much resin holding the fin in place. Try several applications. If this doesn’t work. I guess you have to cut the fin off, grind it flush with the box and route it out. However, if the groves in the side of the fin box are full of resin then I’d guess that you’ll have to route the whole fin box out. You might be well advised to just cut the fin of and route the whole fin box out and start from scratch again but if you take it one step at a time you may save the orginal installation.

Hope this helps.

Mahalo, Rich

If you find the above solutions don’t work, and short of routing the whole box out, try dismantling the fin by drilling and chisseling carefully.

Maybe route a slot down the middle of the fin to give it room to collapse inwards.

The reason I suggest this is occasionally the resin won’t fully bond and may chip off the inside of the box.

You might sacrific a fin, but you may be able to save the box and board with little or no damage.

The acetone disolve sounds best to me, as long as it’s pe resin.


The acetone disolve sounds best to me, as long as it’s pe resin

that would be too easy…it’s epoxy.

Hey soulstice,

The solution has to be a mechanical one. If you can set a perimeter fence up for a plug router you cut the fin out and not touch the walls of the fin box at all. Just leave a little of the fin on the wall of the fin box and peel it out with a chisel.

Mahalo, Rich

Try a heat gun and a hammer. Warm up the box and fin then tap on the screw side of the fin, should come loose. If that doesn’t work maybe alternating hot and cold water in the box may break the bond. I’ve never tried either method, just theorizing.

If you end up routing out the fin. Don’t forget the steel pin in the fin. You hit that with a router bit and it’s gonna leave a mark!

I dunno what to tell you about your fin. I hope it rides good where it is at, and you probably don’t need the $.50 plate and screw anymore. The bases of fins are usually grinded out with 36 grit and usually not finished, unless you bought from Fiberglass Fin Co. The one guy who suggested heat might be your best bet. You can always repair the finbox.

Next time if you have to use something for eyesight, get a stick the same width as the base of your fin. Cheap wood at that. The Bahne boxes have tabs on the sides so you can settle it against that, but most people still like having an eyesight guide. And if you did the o’fisl’l center box route, you should be using raised tabs at the corners of your jig.

Awright, the fin’s sticking to the box, but not all of the box? Try taking a putty knife and a hammer, smack the putty knife into the fin box alongside the fin, both sides. That will loosen up the sides, break them free from the fin box.

Then, take your hammer and smack the fin, upwards, from the back. This should cause the fin to break free and maybe become removable.

By the way - either one of these moves is likely to bust the fin box too.

That’s ok, cos when ya think about it, the fin box is phucked anyhow, on account of the resin that leaked in will keep it from ever accepting a fin again unless it’s in exactly the same spot as the stuck fin. Bummer, huh?

If that’s not a problem, then leave things as they are and don’t try to get the fin out. Heaven alone knows it’s in there securely already.

If the current fin position is a problem, you will need to take it out and replace it. This is where a Roto-Zip or equivalent tool comes in handy, like the sheetrock guys use. Run that carefully around the box, cutting it free, and replace the box. You’ll want to add filler, cos when it comes out it’ll take some foam with it. I might use a diamond-shaped patch of contrasting colored/pigmented glass on the reinstall for an 'I meant to do that" look.

Hope that’s of use


Geez, being anal, I had to read from post 1.

Then Docs post came up, exactly what I’d reco.

Putty knife, hammer or composite mallet, strike fin from trailing edge tip away from box, but first place a piece of wood against the trailing edge of the fin.

Will come out, it’s only resin holding it in place, and we know resin without glass is not all that strong or solid.

Doc has it. Use a thin wide (4") flexible high quality taping knife. Round off the front edge and up the sides with 120-150 sandpaper and smooth it out. NO sharp or square edges. If you get the right kind of taping knife it will have a metal head on the handle and you can tap this gently with a 16 oz. hammer. Start trying to work a corner point of the knife in between the fin base and the box and then gently work the rest of the flat edge in tapping slowly. Go slow. You are asking plastic to release it’s grip and it may not want to do this without a fight, but if you are slow and persistent you will prevail. Work it to the bottom of the box. Do this soon dont wait till tomorrow, because the epoxy is still soft within the first few hours and still brittle after a day.

Once the sides are free the bottom will take a different approach. Go with Docs plan. Use a block of wood to absorb the impact so you dont over stress everything. You may want to try a shot straight down on the fin too, but be careful not too hard. But it could shatter the resin on the bottom. Gentle taps will do the trick. Imagine you re trying to make sma;; cracks in it. I know if I was there I could get it out and save the fin, box and board. Think along the lines of working with glass.

actually, we got it. after trying brut force (unsuccessfully), i filled the box with mineral spirits (it was all i had) and let it soak in for about 24 hours. the fin popped right out with little difficulty, and the remaining resin in the box was easily chiseled out with a screwdriver.

And the blunder turns to wonder. Well done.

Well done, to get it out… but I have to wonder, having set a good many FU boxes, how it came to be that you missed the flaw that let the expoxy in through the bottom? I ask cuz epoxy is viscous enough so it wouldn’t want to flow in just any little pinhole.

If someone without considerable experience and credibility had reported this, I’d have simply assumed they spilled the epoxy in from the top.

Has anyone else seen poorly made FU boxes with this problem? I know I have to shave each one of them somewhat before installing (I like a snug fit in the foam) but I’ve never seen an actual hole in a box.

Clever. I’ll have to remember that one.

what an adventure

as I ead along the exothermic heat expanding the box an clampng the fin into permanent place struck me…


hole in the box ? wow…

i’ve never had any problems with the 10.5, and i actually noticed it beforehand with this and for some reason didn’t even give it any thought (i’ve been a bit sleep deprived lately). anyhow, you know how the sides of the box are a single molded piece and then the bottom is glued on…well it looked like they had only glued it at the four corners, and all along the length of the box it could easily let resin through. i don’t know why, but this just didn’t click inside my head, and i put the box in like any other. resin made it’s way into the box through the unsealed area on the bottom, and made quite a mess of things. like i said, i’ve never had any problems with an FU box…the kid i was helping out bought it from a surf shop, not a surfboard material supplier, so there’s no telling how long it had been sitting there. maybe the glue just deteriorated over 10 years of temperature changes while sitting under the shelf at this surf shop…who knows?!

and just for another kick in the ass,

this was the kid’s first board that he shaped, and while it was a great

learning experience for him, it wasn’t the best of boards. i told him

to read the archives…he didn’t. i told him what tools to buy…he

figured he could manage with a 120-grit sand sponge about 4" long and a

5.5" surform. end result…the foil was all wrong and it’s about 4"

too short. he rode it once and decided it just isn’t working out for

him, so he’s going to try and sell it and build another. maybe this

time he’ll do his homework first and better prepare himself.