So with my single-fin boards, I’ve always followed the “Andreini Rule” (though I think he got this from somebody else) of positioning the fin in the box, and they all felt great. In this case, optimal placement is where the fin, placed on its side from the fin box to either side of the board, has about 1/3 of its height extending past the rail.
Do you think this works for boards with side bites too? I’m guessing it doesn’t. If anybody has (single) fin-sizing info for these 2+1 setups, I’m all ears.
Welcome to the forum.
Your question seems to be more about size of fin(s) than placement of fins on the board, is this correct?
Last time I had a 2+1 fin sizing issue, I called up Robin Mair at Hanalei and we talked through what I was building (odd sized board) and I ordered his recommendations. The fins and check crossed in the mail…
Maybe with some more details from your side (board, conditions, etc) , more people can comment on this.
some 2+1 placement diagrams from Hanalei and Greenlight:
Thanks! Yes, mainly choosing the right height fin. I’ve just always wondered.
My intuition says maybe use the Andreini formula to get the right height with a fin pushed all the way back in the box. Then you could slide it up and let the side bites “make up the difference,” but who knows…
Dear friends, i too have seen both graphs from hanalei and greenlight, and they are very usefull, now please take a look at both for the thruster setup and look how much the rear fin position differs for example?
I’ve been having fun riding my 2 +1 boards (mid-length or longer) as twins for several years now. In many of the boards, the fins are much further up than where they should be for a twin, so I make fins with the tabs set where the fin is as far back as possible.
I recently saw something from Jim Banks, who makes a lot of twins, placing his side fins for a 2 + 1 mid-length where twins would go, further back. They are more in line than ahead of the single. I think that setup is worth trying, so I plan to do that and be able to ride my 7’ boards as a single, 2 + 1 with small side bites or a twin.
so lets say for example for a 6.8 x 2 1/2 x 22 twin like the one on the photo.
and its just twin fin, no side bites, no big fin.
where would be the best place to put the back of the twin fins?
7 inches from tail? further? i think more back is no good but maybe???
i have a hand-written table of a pro shaper where he has the adjustments of a trusther setup as the size of the board increses in size.
it is in cms but i will look for it and publish it.
I put the back edge 9 inches from the tail, but I think I might go as far back as 7 inches in the future. I think it is dependent on the individual, I stand further up on my boards.
looks like a pretty big tail on your board. Usually a twin will be anywhere from 8.5 inch to 9.5 inch from the tail and on a middy maybe around 10 inch. It all depends if you want to ride with a fin with a longer base or not. On a more upright twin, the base of the fin will end pretty much on your shaper dot but with a keel, the base can end as far as an inch further than the shaper’s dot. With this in mind, you can play on the fin placement. The same box placement can have a totally different feel because the longer fin will extend closer to the rail and tail.
