Fin base/box fit advice

[lokomotiv]

Hi all, I picked up a Techno 148 that sat in someone's storage shed for a while. But the stock 48cm fin does not fit totally flush to the bottom of the board - the base sticks out ~ 1/8 of an inch. I've cleaned out the finbox thoroughly so there's no obvious grit or sand in there.

I assume I want the fin base to be flush, and that torquing the fin screws to jam it in would be a bad to terrible idea.

Next step would be to lightly sand the sides of the base. But since this is the first time I've dealt with a Deep Tuttle box and this kind of issue, worth a check with the iWindsurf community before going an irreversible path.

[Ugly_Bird]

[Brian_S]

If your fin has a black base, you can use a yellow or orange grease pencil on the base. 'Color' the base with the grease pencil and push it into the box. Remove the fin and you'll see where the pencil rubbed off. That's where you'll need to sand. You'll have to repeat this process many times until you achieve the fit you need.

[isobars]

If you have a bud or shop with a Tuttle fin and/or board, try before sanding to determine whether the problem lies in your fin or in your board. It would be a shame to sand the wrong thing if you ever wanted to acquire another Tuttle fin or board.

[lokomotiv]

Great advice - thank you all.

Since the fin is the stock one that came with the board (2006 Techno 2), what are the chances that the lack of fit is due to some deterioration of the board / fin box?

And how much performance am I losing with that 1/8th of an inch of the base sticking out?

Any feedback appreciated.

[Brian_S]

It may not have deteriorated, it may just have never fit. I've had a couple boards with tuttles or deep tuttles and the fins have never fit as new. The previous owner may have never 'fit' the fin.
I think the 1/8" will make a difference, but maybe not enough that you'll notice. Give it a try!

[swchandler]

As a variation on what Brian_S offered, instead of using a grease pencil, you might want to try regular bar soap. It's slippery, will show interferences, and it's easily removable before sanding, thereby avoiding lots of clogged up sandpaper.

[isobars]

When I tested hundreds of boards for a Gorge gear magazine, we spent WAY too much sanding cavity fins and boxes (e.g., Powerbox, Tuttles) to match. We finally told the manufacturers that if their supplied fins and didn't fit their boards as delivered, we weren't going to test their boards. Some cooperated, others less so.

(The same went for the huge variety of mismatched mast top and sail top hardware.)

If you're spinning out, or if guys you could outrace now beat you, MAYBE the 1/8" protrusion is at fault.

[U2U2U2]

Sand the fin.
1/8" is not much to be concerned with.
Echo others statements , fins are frequently off some and need some gentle finesse to fit perfect.

Take care and slow as you go, I would use a machine sander, like palm unit.

Worse case is you now need to add some shim .. Unlikely but possible.

[bred2shred]

Tuttle box on a Bic? Thought that would be a trim box.

Anyway, if it is a Tuttle box, then sanding the sides will not help. You need to sand the ends of the fin (where the taper is). You can use a grease pencil or other marker to help see where the interference is. Remove a little bit at a time and check the fit frequently by fully installing and torqueing the screws. If you go too far, you'll have to add material which is a whole other exercise.

The other thing to double check is the length of the fin screws. If the screws are too long, they may be bottoming out inside the fin before the fin is actually drawn completely into the box. Throw a couple washers under the heads of the screws and try re-installing to see if the fin gets pulled in the rest of the way.

sm