Q bout replacing fin box.......

Loaned a single fin longboard out sometime back…it came back with a damaged fin box 

Bought a new box…paid $100(±) to have it installed

Just noticed a lifting of bond along the edge of box…often I will put some tape along the bottom of a fin and push fin into box… with no bolt…It can be very tight and I remember when removing the fin that something moved or did not seem right…but did not look close at the time…

So now I see that the repair did not have any glass over the top of the box…as I have thought was the the proper method for installation…

Maybe on new boards the glass over the box is not quite as critical…but am I correct in assuming that that would be standard proceedure for new box on old board?






Glass wouldn’t stick well to the top of the box.

a 100 $ (±)

dang that sucks

that sounds like alot

was there alot of damage around the box and the deck as well

sdrepairman…no… not alot of damage…but discolored foam and I think the box was cracked as I recall other wise I would not have bought a new one(this was probably a year ago)…I don’t have my camera with me or I would post a piccy

Just looked at 3 other boards and 2 for sure have cloth over box…the other I cant tell for sure…

I can clearly see where he had taped off the box…and the resin coming in about half way to slot…Not sure if he would have put cloth under box as the video shows but even if he did…seems like he should have gone the extra step(glass over box) to add to the integrity of the expensive repair…

This is one of the boards I keep on Oahu…I can and will bring it back for a conversation…he is a very experienced ding repair guy…I want to give him the benefit of the doubt…but I gotta say I am ticked off…


Roger I like to glass over box but not mandatory and on a proper install shouldn’t make much difference anyway - I think your beef is with the cracked bond IMO the glass over is a non issue if neither one of you specified ahead of time. For that price it’s a warranty issue take it back and give him chance to remedy. Hope all is well with you my friend!

Yea…Huck…but with probable degradation of Foam due to leakage…it really should have been been all tied tight with glass…I am not sure if he did not just cut old box out…put a little filler…and hot coat…

Snowy looked at it and did not think it was done right either…

I’ll bring it over to show him next week…and see if my warranty is still good…




Yeah def sounds like it was not done right - my thinking is that if it wasn’t done right I don’t think glass over the top would have saved it. Glass over the top adds a seal but I don’t think it adds much strength.

Hi all -

Regarding “proper” box installations vs box installations “not done right.”

There are several ways to analyze the issue.  If you’re going to make meaningful comparisons, it’s not enough to say “proper” or “right”…  too subjective.

It can be argued that a proper box installation might start with the number and spacing of the stringers when the blank is ordered.  In my opinion, a good start to a solid box installation is a blank ordered with double stringers spaced just far enough apart to allow a box to be dropped in between them.  This prevents the removal of nearly the entire stringer directly in front of the box when the hole is routed out on a single stringer board.  I’ve seen countless boards cracked, leaking, or even snapped in two right at that spot (immediately in front of the box) where the stringer has literally been routed down to 1/4" or less to make way for the box.

On boards I do with double stringers, I score the foam on sides inside the routed box hole so there is a connection from the hole directly to the wood.  This, in turn, provides direct resin/wood support to the sides of the box when the box is installed.  I.E. the foam isn’t going to be compressed by side-to-side fin pressure against the box.

Bruce Jones (RIP) used to run advertisements in magazines showing two ‘mini-stringers’ - one installed on each side of the box.  This is a good way but might not be as structurally sound as two stringers from nose to tail.  It could argued that the ends of the mini-stringers might contribute to a ‘hinge point’ while a full length double stringer avoids that.

Actual box installation can vary from factory to factory and from board to board.  I’ve always liked a fiberglass ‘liner’ inside the hole, followed by a fiberglass patch (or two) over the top.  Some guys like a complete tail patch (very obvious with a tinted lamination) extending from edge to edge in the tail.  They look neat but if the box hole is routed in after the hotcoat, you still won’t have any glass over the box/foam seam unless it is applied as a separate step.

I’ve done many single fin box repairs where it appeared as if the box was simply installed (over a single stringer that had been cut away in it’s entirety) with a batch of thickened/pigmented resin only… no glass liner and no glass over the seam.  It saves time, saves money and provides for a board that will likely need repairs or replacement much sooner than anticipated by the new owner. It can even be argued that pigment added to the installation resin weakens the overall product.

Stuff like what I’m talking about might help explain the difference in price between a $500-$600 longboard and a $1000-$1200+ longboard.  It might also help explain why a solid longboard built to last is going to weigh more than a disposable cheapie.

With finbox replacement, the installation process can follow any of the above methods and with equal results as a ‘new’ installation depending on the method.  The single stringer board will still be missing almost all of the stringer at the front of the box.  The choice of mini-stringers, a fiberglass liner, or a cap is usually left to the repair guy.  If I were to ‘do it right’ and route 2 additional slots for mini-stringers, line the hole with glass and do a feathered-out ‘cap’ on a box replacement, I’d definitely be charging extra.  It’s a lot of work!

In this photo of a Bruce Jones ad it might be noted that the ‘mini-stringers’ are actually inside of full length double stringers.  :slight_smile:

PS - In the Harbour video, it might be pointed out that in severe side-to-side pressure situations, the edges of the fiberglass liner are still going to compress the foam on either side of the box.  I’ve even seen the supposedly superior “Chinook” sailboard boxes easily stuff up the foam along the sides of a box… The resin adheres to the Chinook edges around the box just fine but nothing prevents the resin block itself from compressing the foam.  That’s where double stringers come in to play.







Very well stated.



I am pretty sure it was a $100 price tag…Had we discussed options, I would have chosen an option that would not have had the bond with resin and box break, while trying to remove a fin from box…

Proper is proper unless I make a conscience decision for something less…

John…it does have a double stringer…so box is 1  1/2  inch away…

Should I be able to see the edges of the fiberglass liner(if it was used)…I see no sign of it…


Hi Roger -

Yes, you can usually see the edges of the liner glass in that resin gap around the box.

If the wood is 1 1/2" from the box, there is no stringer support to speak of unless they carved 1 1/2" horizontal channels for the resin bridge (doubtful.)

I agree, a box installation should stand up to a fin insertion although you still can’t force a fin that is too tight without risking some sort of damage.  Boxes frequently distort a bit while the resin heats up and expands.  Try one fin on several boards and you’ll likely find minor fit differences on each.  Too tight?  Don’t force it.  Filing the box slot or sanding the fin tab should do the trick.  For that fin in that board anyway.

In the Harbour video they sand the box a little before installing.  I use one of those 36 grit Rol-Lok discs and grind the entire outside surface of the box, including the bottom.  There still is no chemical bond but it does seem to help.

Hey Roger,

For what its worth, I always cap boxes with fiberglass.  Even proboxes.  I would be very unhappy if I paid someone to do it and it wasn’t capped. Of course, I wouldn’t pay someone and would do it myself and you would be able to see the glass line easily because my glass work is pretty mediocre.  Your boards are beyond bitchen and deserve the best. 

Damn that was good, John!  Used the Rockwell on my first long board by the way.  Love it.  Mike

Borrowed camera…this is the front of box…the discoloration was from the original problem…you can see the resin line just under the damage. Looking closely at glass pattern…I suspect there was no glass put under box and lapped out…

Threre are three ways a box is installed in most Professional glass shops.  These three methods are what you would call most common;                                       1. Rout the hole for the box after the hotcoat and install the box with ground milled fibers and resin(most common install)       2.  Rout for the box after the hotcoat and place fiberglass in the channel (usually 4 oz.)  .Use a chip brush to wet it out, sink the box in the slot.  Trim excess glass with a razor when it jells.      3.  Rout the slot after lamination, blow of particles etc. from lam with air nozzle, set the box using either of the above mentioned methods and cap the box with a layer of glass.   Their are other options as mentioned by John etc.  Woodies can be installed on either side of the box.  A strong box like the one Futures makes.  My favorite;  the Chinook box.  The worst install is a box sunk in Q-cell after the hotcoat, no glass cap.  I did way too much ding repair during my time on Maui.  The foam and glass is usually crunched around the box from impact, so it’s always a good idea to put glass under and over a repaired box.  If you just Q-cel it in the, first little bump on an Hawaiian reef will loosen it up.   And that is most likly what happened in your case.  Lowel

Hi Roger -

If you are able to shift or move the box with fin in place, it should be removed, cleaned up, and reinstalled.  I can think of some good reasons to reroute the hole as well… get all the busted up resin out of there and give the foam a chance to dry out really good.  Make sure the new install is attached to clean dry foam and not to some free floating pieces of broken resin.  I would go ahead and carve out some horizontal channels at about mid hole depth and make a ‘resin-bridge’ connection to the stringers.  They don’t have to be huge gaping channels… just something to make contact.


And when you have done as John said;  you will be able to see how the fin was installed ie.  whether or not it was installed with. glass under it…  If it is loose take a Stanley knive to it and cut around the edge before trying to pull it out.

…often I will put some tape along the bottom of a fin and push fin into box… with no bolt…It can be very tight.

Imo doing that is p robably not going to help.

I have removed a number of fu boxes from old windsurfers to reuse. The ones with woodies or dcell inserts are alot more solid. Glass under or not doesnt make a huge difference to strength. Resin does not stick to the boxes very well at all. Once out of the board it just peels off leaving them looking like new.

Rough the box up with sandpaper as shone in the Harbour video or wipe it down with acetone.  It will stick better.  Fin box manufacturers understand that it is much easier to remove and repair a box that has struck a reef than it is to put a new tail section on a destroyed board.