I could use a little advice. I have a longboard with a badly cracked fin box. The box has separated and cracked out of the end closest to the nose. I have taken my dremel advantage and routed out the majority of the box. The problem is I have the base of the box left to remove but it is glassed tight to the inner stringer and foam. My main concern is that the fin box is sitting too close to the deck, as it is a fin box with a leash hole. If I try to tear it out I am afraid I will take out too much of the foam and possibly part of the deck with it. Any advice on how to get this thing out and maintain the integrity of the deck. Chisel, Grinder, What do you think?
If you can SEE the actual finbox from the deckside, then you will take out some of the deck upon removal of the box.
That’s the way it is, when attached to the deck skin.
If you only see the resin hole the leash goes thru, then 50/50. You can always reglass 3 layers on the deck back there.
Install a beater fin, take a 2x4 about 2’ long, and whack upward trailing edge slowly at first…or beat it with a rubber mallet so you don’t totally destroy you fin. That should lift the box and some deck out.
Reglass the deck first, then put in new box with woodies on the sides, and one layer of glass.
Before hotcoating, make sure to add one layer of glass about a football sized patch.
If I read your original post correctly, the sides of the box are gone? Just the base still attached at the very bottom with a through box leash hole going through to the deck?
I think I might try a drill bit slightly larger than the resin plug the leash hole is through. Drill out the remains of the leash hole resin from the deck side. Try a punch or narrow chisel through the new hole you’ve drilled from the deck - try to catch a corner of what’s left of the box and give it a whack or two. It might knock the remains of the box free. You might accidently take some foam with it. If you’re lucky, you can reset your new box, refill the leash hole, drill through that and it’ll be clean as new.
Maybe screw a couple of big screws into what’s left of the box base, grab with vice-grips and pull. Maybe put some pieces of wood along the sides of the box slot and crowbar against the vice-grips? Don’t break off the tail!
You are correct John, only the base of the fin box is intact. I do have a plung router but was afraid that the rpms might be too high and cause more harm than good. Also I was not sure of the effect of a router bit on plastic vs. wood. If you think the router is the best way to go let me know. I like the drill out the hole idea. Do you think the resin from the orig box insert might be too soaked into the stringer and cause the stringer to fracture or is that just me being paranoid.
Any advice you can give and have given is much appreciated.
The router is definately the way to go. Use a 1/2"bit and make a jig if you don’t have one.
Simplist and quickest for a one time use jig is wood clamped, hotglued or taped to the board to keep the bit oriented to the original box hole (set the wood up to contain the router base ie: the base slides along the wood). Trick is to not try and take the full depth of the box or its remnants in one pass.
Take it about an 1/8" at a pass until you get all the box and you should be able to do it without any - no-none -zip - damage to the foam, stringer, glass.
I use a router to shave down FU boxes after unstall per Cleanlines video and the bit has no problem with the plastic box whatsoever.
It might take a little stringer with it but I would be more concerned with the connection to deck glass via leash hole. Drill that out regardless - router or not. The box might tear up your router bit but that is a good way to go. Just for kicks, I would still try drilling out the leash hole and putting a punch or chisel through the hole and whack it. The whole thing might just pop out.
I replace these all the time, and I currently use the following method: Wear a face shield cause there’s going to be shrapnel flying. Use a portable circular saw and set the blade depth to about 1/16 less than the box depth. Set the saw blade along the side of the box, tip up on the front of the shoe and lower the blade. Repeat for the length of the box and the other side. Next, use a 1/2" chisel and a 1 lb ball peen hammer and hit the box between the cut and glass toward the inside of the box all around. It will break right at the pin groove. Once the sides are gone, chisel the front and back inwards towards the box. This leaves just the bottom left. Use the chisel (bevel down) and cut and break the bottom out. The bottom will invariably take out pieces of foam and stringer which need to be leveled for the new box. I use a slightly larger template for box repairs to clean up the damaged glass around the old box hole. Set the router template and router the bottom level as much as possible while still leaving about 1/8" before you hit the deck glass. Check this depth against the box depth; make it about 1/16" deeper than the box. Level the tail area and pour a layer of lam resin thickened with cabosil to just fill the voids. Put a piece of 5/16" plywood in the box at least 6" long for alignment later. Wipe the outsides of the box with acetone and set it in place using lam resin mixed with milled fibers, leave about 1/8" below the glass level of the bottom (some guys use a strip of cloth under the box at this point). Check the vertical alignment of the box using the plywood and a square, put a piece of tape across the top of the plywood going rail to rail to hold it. Check to make sure the box isn’t floating up, clamp with strips of wood across if it does. After the resin sets, fill the remaining gap around the box with colored sanding resin and grind the whole thing flush with the original bottom glass. Lam a piece of 4 oz over the box, hotcoat, sand, finish to your liking. Using a router to remove boxes results in a wrecked bit and gooey mess of melted plastic.
So I went the plung router route and it worked like a charm. I took it slow at 1/8" or less depth increments with a 1/2 in bit and it went smooth as can be. My router is a new black and decker firestorm router. This was my first chance to test it and I must say it is one of the best routers (of the three I have used) I have ever used. The thing has a variable speed gauge and a list of speed recomendations for material types (wood, plastic, laminate, etc). So I set it to plastic and let her rip. I bought it at Lowes for about 75$. Anyone who needs one for boards should really look one up. As for the bits, I bought a set of some 20 odd bits from costco on sale for about 40$. The bits were a great deal too, all carbide, all good.