Problem with making fins for boxes

Guys: in the past I have made a couple fins for the Fins Unlimited/Bahne boxes, but had trouble getting the exact thickness for the insert part. Anyone have any suggestions that don’t involve kinda expensive tools?

I saw the post a couple weeks back about making the insert part first then forming the rest of the fin onto it, but that doesn’t “feel” right to me somehow, though it was a very inventive solution.

The problem is to mill the base of a fin to the 0.375" needed for a tight fit. If by hand, I can’t keep the sanded surfaces flat and parallel. Something like a milling machine would be nice. I have heard of putting a router bit on a radial arm saw, which I don’t have. Maybe a router table? I don’t think the fence on my table saw will work, and fiberglass dulls blades pretty quick.

Anyone have a creative solution?

The fence on your table saw will work fine. You just need to clamp a piece of wood to the fence that’s less than 7/8" tall in case the foil of your fin is wider than the base you want to cut. Then just crank up your (oldest) blade to 7/8" and go. I cut one side with the fence 1/16" proud of where I want final thicnkess to be, then move the fence in 1/16", flip the fin, and make the other cut.

Tape a square to the fin with the base of the square at the level of the top of the fence and run it along the fence as you cut. That will keep it plumb as you make your cuts but won’t interefere with the blade as it would if you put the square down on the table side.


I stick the fin in the box. If it is too thin, I add layers by laying up on a flat surface. If it is too thick, I block sand on a flat surface until it fits.

I have a full-time mill, but have never used it to make a fin fit. Waste of time jigging it up when I can sand it in 5 minutes. The specs on the fin are 0.350 inches, the Bahne box should be 0.375 inches in the gap. The fit is just not that tight.

I use the same technique making fins for my boxes, easily to within 0.005 inches.

A pair of $16 calipers helps, too.

This is a tool I made for putting bases on fins. It takes about 1 1/2 oz of resin to make a base. After lining the base mold (made from an oak 2x2) with parchment paper, I pour some resin into the bottom of the mold. I then put several strips of 8oz tape in the mold making sure the are saturated with resin. Next, put the fin in the mold and fill the rest of the way with the remaining resin. the base comes out a little over size which allows for final sanding to fit. Cut a notch on one end of the fin and drill for a screw. Use 3/16 brass rod for the pin, however, I find that screws on both ends of the fin make for a better fit.

Hi Charlie,

        Rod on the Gold Coast how all in paradise you lucky bastard,Mate when I make panel on the very rare occasion I make it 32 layers of 6oz and 2 litres of resin for the wet out give or take a little. And the tagges are spot on and fit into the box with no extra work at all.

The perfecto fin which is 12’’ and a glass/on for Gordon&Smith limited edition mal takes 40 layers of 6oz.

If you need to thin out the tag on current panel fins I got

my-self a 5 speed drill press ‘‘cheap is best’’ and got a

12mm bolt and cut the head out it so it will fit the 13mm

chuck on the press get two nut’s to fit the headless bolt

buy a diamond blade and two penny washers put the blade,washers & nuts together place into the chuck. Table

of the press put a thick peace of timber, screw from bottom

on top put hole to take the bottom bolt on blade shaft, on timber put thin peace say max 5mm thick as fin base guide,

use finished fin to set drill press thickness and away you go.

    Regards Rod


I’ve also used the tool I showed above to put bases on plywood fins. On plywood, I use epoxy. I saw the use of two screws on Paul Jensen’s site, It solves the problem of getting the pin placement just right on a single screw fin. It also allows for easier adjustment. Just loosen up both screws a little and the fin slides easily. I found that if I used 8-32 x3/4 screws with allen heads on them (the same size allen head as the FCS system) I eliminate the use a screwdriver and the damage I can do with one.

parchment paper for mold release? that’s a new one on me… makes sense, its silicone-impregnated, right?

thanks for the tip!

I don’t know what the parchment paper is made of, but not much will stick to it. I was faced with the problem of treating the oak base mold with some kind of release agent I was going to have to buy when I decided to try the parchment. It works great as long as I don’t puncture a small hole in it that allows for a leak. It happened once and ruined the mold. I made another mold (which is nothing more then an oak 2x2 with a groove cut in it) and have been more careful with good results. The stops on each end are wood. I then fold up the remaining ends of the paper to make sure no resin leaks onto the mold.