There might be a small difference in performance.
I've had this with some of the demo boards I've had over the years.
It's an easy fix really.
If you have a fin that fits in another board flush with the bottom of the
board, try that fin in the fin box you are having trouble with.
You have 2 choices as to how to fix this problem.
1/ If the board is fairly unique to one or 2 fins (i.e. you don't use the fins
that fit this board in other boards and vice versa) then the easiest way
to fix this is to take the fin heads that go in too far, and simply wipe a
thin layer of thickened epoxy filler (Marine Tex works.... so does JB
Weld or JB Weld Quick... or you can mix up some epoxy resin with
microballons or foam dust as a thickener.
Try to work just the back taper first.
Put a dab of the filler on the radius on the back of the fin root.
Spread it with a gloved finger or with a plastic spreader/spatula.
Take some masking tape and carefull tape over the filler, being
careful to keep the filler on the radius.... do not alow the filler to
flow around to the sides of the fin root.
It only takes a little filler as you are only wanting the "build up"
to be < 1/16" per layer.
When the epoxy has set, remove the tape and smooth out
the layer you have added.
Try the fin in the fin box.
If it's now above the bottom surface of the board more that 1/32"
to 1/16", do a bit more filing to drop it into the fin box.
Ideally your fin should slide into the fin box quite snug (a push fit)
on the sides and the front and rear tapers regulate how far it goes in.
Pushing in by hand should leave the fin root between 1/32" and 1/16" proud
(above the bottom surface) of the bootom of your board.
The last little 1/32'-1/16" is the "draw" on the front/rear tapers and you pull
the fin root in that last little bit with the fin screws.
The idea is that you get a very tight and solid fit so the fin screws are not
supporting the fin in the box, but simply holding it in.
To remove a perfecty fitting fin, you must take out the fin screws, then use
a rubber hammer or your hand to "pop" the fin head taper loose from the
2/ If this board sees alot of different fins, then it may be better to build up the
back taper in the fin box.
This is tricky, but uses the same materials.
Mix up your epoxy filler, get some waxed paper (borrow some from your
Smear the epoxy in the rear radius of your fin box, but not all the way down to
the bottom (say about 1/2 the distance to the bottom).
Now cover the epoxy with the waxed paper, making sure the wax paper covers the
Now install your fin and tighten the screws very lightly so the bottom of the fin head
(what you see when it's installed correctly) is parallel with the bottom fof your board.
Let the epoxy set up hard.
Remove the fin and the waxed paper.
Try your fin.
If not enough... repeat the process.
Ultimately you need to "fit your fin" using a bar of soap as your "contact marking
Rub the soap all over the fin head.
Slide it into the fin box.
Pull it in lightly with the fin screws.
Remove the fin and look for the "shiny/dark spots" along the front and rear tapers.
Use a single cut file to remove just the shiny spots.
Rub with soap..... repeat process... until you have at least 75% contact (top to bottom)
on both the front and rear tapered radii.
Now your fit fits the way Larry Tuttle intended it to fit.
Hope this helps,