I got myself a 92 Litre Tabou free style wave board that came with a 24cm fin. I mostly use it with a 5.7mt in bump and jump style conditions ocean / choppy harbour etc. I have been suffering a lot of spin out and decided to get a larger fin.

Fin arrived yesterday and went to go for a sail today but the head was just a little bit too big!

First question is how many types of US box sizes are there?

Second question is how to make it fit? Do I drill out or route the fin box on the board or attack the fin?

If I do the board can I simply drill the hole out a bit and then what do I coat the newly exposed area with?

US boxes are all slightly different sizes go figure heh!
I usually just sand the fin down a bit to suit the box generally they don't need much, but as I said all boxes are slightly different.
As long as you leave enough meat on the fin should be good.

Yeah, don't mess with the fin box, other than making sure it's clean. They are all supposed to be the same size, but sometimes the resin used to install the box will get too warm, putting a very slight warp in the box, or there might be some schmutts on the inside of the box, left over from the production of the board. Make sure the box is clean, if it is but the fin still won't go in, sand the fin a bit, evenly.
If you want to use the same fin on a different board, but now it's too loose, that can always be built back up with a variety of things, anything from tape to the thin, clear, stiff plastic that is on boxes for a toy, or almost anything. The plastic makes the best shims.

Give the fin box a sand with fine wet and dry, get the hose out and go for it. This will get some of the black paint and any imperfections out of the fin box.

Buy a file.

Test fit and calculate amount and location of fin mod.
Begin modification with file, clean up with one of those sanding blocks, test fit, repeat till perfect.

BTW Is this a Makani fin ?, I had a a couple of where I spent over an hour getting the fin to fit , still good fins though

US Boxes can be a bit is a pain. I suppose that's why Midnight Oil wrote the song about them.

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da vecta said..
US Boxes can be a bit is a pain. I suppose that's why Midnight Oil wrote the song about them.

"Redneck Wonderland" ?

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da vecta said..
US Boxes can be a bit is a pain. I suppose that's why Midnight Oil wrote the song about them.

"The boxes are borderline"

I have sanded the fin as much as Possible at both ends of the head and can now actually fit it flush into the box.

Problem now is that the screw hole is still too far forward of where the nut hole can get to. So the base of the fin would need to be sanded back at least 1-2cm so a new hole could be drilled.

I'm not completely sure, but shouldn't that nut slide forward to meet the bolt?

The groove that the nut rides in stops short of going that far forward.

But, it's all good. My mate Benny came to the rescue with a grinder and a drill and he took off a sufficient amount from the rear of the fin and re-holed the brass pin. It now fits!!!

I'm off to try it out now :)

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gregob said...

da vecta said..
US Boxes can be a bit is a pain. I suppose that's why Midnight Oil wrote the song about them.

"Redneck Wonderland" ?

Very funny!

Oh sorry, US Forces, thought they were singing US Boxes.

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mr love said...

da vecta said..
US Boxes can be a bit is a pain. I suppose that's why Midnight Oil wrote the song about them.

"The boxes are borderline"

ha ha

That's weird. I always thought the feature of US fin boxes was that you could adjust the fin position forward or backward a number of centimetres. Forward for a looser board.

That it didn't fit at all is very odd, there's no denying. Seems to me too many trying.

US boxes come in several different lengths. The boxes that are meant for a tight fit (length wise) better be in the perfect spot for that board.
I don't like those boxes of that size for that very reason, longer ones are much better, it gives you options.
The same goes for Power boxes and Tuttle boxes, no room for adjustment, so that being said, I prefer US boxes, so long as they are longer than your typical fin base.

the kode wave i've got has a centre US box, but one side of the slots that the pin/plate slides in hasn't been routed out far enough. So if the fin base is too long, you can't even get the fin in there.

Even the twin fins wobble and slide around when done up tight. I think I got the lazy friday afternoon @ starboard edition, to go with the lazy afternoon at JP with the complimentary trampoline deck

The issue is that this board has a short US box designed for wave fins basically. The 24cm was already about right, sorry to say greg I think it was a back foot pressure issue (unless the fin had chips and gouges). Sticking a big weedy in (which presumably is quite wide based?) will help but then you are losing some of what makes it a nice FSW

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Haircut said..
the kode wave i've got has a centre US box, but one side of the slots that the pin/plate slides in hasn't been routed out far enough. So if the fin base is too long, you can't even get the fin in there.

Even the twin fins wobble and slide around when done up tight. I think I got the lazy friday afternoon @ starboard edition, to go with the lazy afternoon at JP with the complimentary trampoline deck

Just wait until the deck grip start falling off. Starboard and North must sniff the same glue.

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Mark _australia said..
The issue is that this board has a short US box designed for wave fins basically. The 24cm was already about right, sorry to say greg I think it was a back foot pressure issue (unless the fin had chips and gouges). Sticking a big weedy in (which presumably is quite wide based?) will help but then you are losing some of what makes it a nice FSW

Bit of a catch-22 in that I don't have an enjoyable session when it keeps sliding out. I end up having to head more downwind to avoid it but then I just lose ground down wind. If it was happening every now and then I can live with that but with it happening every leg it just ruins the session.

Ideally I would experimented with fin brands and slight size adjustments but I can't afford to buy half a dozen fins so I opted for a sure fire fix :)

I'll keep my eye out for cheap fins between 24-30cm as well.

Hey Greg, I had the same "non enjoyable sideways sliding sessions" with my 94 Kode. Basically I was too back foot heavy for the standard 26 cm fin in it. I ended up putting in a 26 cm Ono weedfin. My idea was to tame the board a bit and reduce the spin outs. The new fin does both perfectly. It still turns way better than I can, and now has good rear drive in lighter winds. The weedie works a treat on the lakes and river also. PS- and no issues, fin slotted straight into the box.

Nice looking fin Phil.

Benny's handy man skills worked a treat on mine! I got out this afternoon after work in a 20knot ish North easter off sawtell beach and had one of the best sessions ever. And no spin out!

Good one Greg. Glad you got it sorted, and glad you guys got some wind! You must be sailing well by now. We had a teasing 10-14 knots here. Tomoz is looking sweeeet. Catch ya mate.