I’m fixing my friends board for him. Basically he got stuffed backward into a sandbar and broke his fin box. The fin ripped out most of the box and took a bunch of surrounding fiberglass and some foam with it. It’s ugly.
I plan to fill in the missing foam, replace the fin box, and glass it all in. At what point in the process does the fin box get installed? Before the lam? Between the lam and the hot coat? Does the glass from the fin box go under or over the glass I’m replacing on the surrounding area? On the Harbour Surfboards site there is a video of guy setting the fin box on a new board but I can’t tell at what stage he’s doing it.
I only do repairs here and there. I’ve never built a board so I don’t know the usual sequence.
Check out a book called “The Ding Repair Scriptures” by George Colendich. He has a chapter called Fin box disaster. Very helpful book when doing repairs like you discribe.
You had another question about sanders… I have a Black and Decker Buffmaster that I used to buff cars with. Works great on surfboards ,varible speed trigger ,speed control ajustment ,and lighter than most Milwalkies
I repair alot of these, especially 10" boxes. The first thing to do is get the box out so you can inspect the foam around it. Cut the box up into 5 or 6 sections but be careful not to cut the bottom too deep. Don’t attempt to router it apart, you’ll destroy the bit and the plastic will only melt. Use a dremel with a metal diamond wheel for best results. Cut the box around it’s perimeter as deep as your wheel diameter permits. Using a wood chisel and hammer, break the box up by hitting from the outside toward the fin slot on each side. Be careful you don’t smash up the surrounding glass and don’t be tempted to pry it from the sides. You have to whack it pretty hard, but it will eventually break up. Clean up the remaining pieces in the slot with the chisel. Finish cleaning up with a router. OK, now back to checking the foam. Very often the foam will split horizontally, and you’ll never get the new box solid. Check thoroughly for this. If too much of the foam is damaged the box won’t have enough support, and you’ll have to replace it. If this is the case , router out all of the damaged foam (including the box slot), cut a new piece of foam and glue it in with Gorilla brand glue (clamp the foam down). Trim the new foam level and laminate a layer of 6 oz. over it (2" overlap onto old glass). Hotcoat and sand. Cut a new slot for the new box using a router and template (see archives). Install the box (see archives again). After you sand the box flush, tape the slot and laminate another layer of 6 oz. over it and hotcoat. If you want a leash hole in the rear of the box, drill from the deck side on the stringer 1/2" diameter until you go about 1/8" into the bottom of the box. Fill this hole with cabosil/Q-cell and lam a small piece of 6 or 4 oz. over it then hotcoat. From the deck, mark the center of the filled hole and drill 1/4" thru everything. This is a big job, especially if you need to put in new foam. The worst part is getting the old box out. Attached is a photo of a typical foam replacement prior to being glassed/routed for the box.
Thanks for the feedback. I’ll follow-up on your archive recommendations
Unfortunately for my friend, almost all of the box was removed when it broke. Fortunately for me, the box is almost completely removed already. Actually he broke the tail of the board almost completely off. It’s just hanging on by a strip of deck glass. I just didn’t want to clutter up the issue with regard to how to set the fin box by bringing up the bigger issue of a broken board. It snapped between the front of the center fin and the back of the side fins. I’ve got a pretty good idea on how I’m going to fix the break and replace the foam and stringer. The router will definitely play a part. Once I get the board repaired to the point I’m ready to install the box, that’s where my plan ended. I just didn’t know when, or exactly how, to install the new box.
I’m kind of doing this to take my repair experience to the next level and to see if I can do it successfully. He was going to turn the board into yard art. Since I’ve done some decent repairs in the last year or so I offered to give a try at this major repair. He said he’d buy the materials so I’m gonna go for it.
Do you have a recommendation on where to get a good fin box for the center fin? It’s a longboard with a large center fin.
The boxes come in both 7 and 10" sizes. You can get them from Fiber Glass Hawaii. If you’re in SoCal , send me a PM and I tell you where to go. On the broken board, you don’t really have any stringer left in the tail because of the box; and I’ll bet the board had a thin tail and the box slot was routed all the way to the deck. Nothing wrong with that as long as the box is a good fit and glassed properly in. Most often it’s not, and then there’s a big discontinuity in the strength of the board. There are a number of posts in the archives about fixing broken boards, and I’ve had a lot of success using Gorilla Glue and a jig with bar clamps. The jig holds everything straight and tightening the clamps resets the correct rocker. Gorilla Glue is foaming urethane and is strong enough to hold everything in place while you glass it.
I’ve got the board in storage and I can’t remember exactly how deep the fin box went. I know there was some stringer left at the deck. I just can’t say how much. The board is 9’6" and not really thin. 3" at center. It’s a good shape so it has nice balance. There’s probably as much stringer left at the deck as you’d find on most. It’s a pretty wide stringer. I’d say 1" redwood. I has two smaller 1/4" stingers that are several inches off center. One design flaw I noticed was that the outer stringers run right through the side fin boxes. That makes the extra stringers useless in the plane of weakness that runs right through where the board broke. The outer stringers basically stop at the front of the side fin and start again at the back of the side fin. If those outer stringers were placed a couple of inches further to center, they would’ve added a lot of strength though that weak area.
I have Gorilla glue and have used it on several wood projects. Good stuff Gorilla glue. For cosmetic purposes I plan to join the tail to the rest of the board with Q-Cell. That joint only needs to be as strong as the tensile strength of the foam. I’ll splice the stringer with Gorilla glue. I definitely need a good bond there.
I’m going to use wood boards, blocks, and clamps to align and reattach the tail. I’m then going to put the firts layer of glass on the deck and the rails. I’m hoping this will make things secure enough to route and splice the stringer. Then I’ll route the bad foam to a flat bottom and filll it with some scrap foam blocks. Next, shape the replaced materials, then glass, and glass again.
I am in Orange County. When you say send you a PM, what did you mean? Is that like Yahoo IM. I don’t have it set up on my home computer. Is there a messaging system on this site? I just noticed “Messages” at the top of this page. I’ll check it out.
