fin question/observation exocet windsup

outhaul · Joined: 27 Sep 2011 Posts: 254

The stock fin on the 11'8 is 44cm which I've found to be a decent all-around length. Yesterday I tried a new Makani 49cm freeride fin in about 17 mph winds and 3-4' swell with an 8.5m sail.
As one would expect the board felt less maneuverable but seemed a bit earlier to plane and able to point higher than the stock fin.
I then switched to a used but mint 35cm JP Carve fin that I picked up on E-Bay.
To my surprise the 35cm seemed faster, or at least as fast, pleasingly loose and able to point as high as the 49cm.
I know there's many variables at work here but why did the 35cm perform so well? Should I be surprised?

U2U2U2 · Posted: Mon Oct 05, 2015 6:20 pm Post subject:

Without supporting numbers, GPS...
The seems speed could be wrong. Is this a board that speed is desire Able?

Just a guess, the Standard fin may be large, the Makani even more and the JP
Just right. Just a guess.......

joethewindsufa · Joined: 10 Oct 2010 Posts: 1190 Location: Montréal

length in a fin is only ONE factor of MANY
thickness of fin may affect speed
the chord (or length front to back) affects fin as well
there are VERY short weed fins with HUGE chords that work with large sails
Hatteras is known to push people to such fins
however, as a BIG guy on big boards, I still prefer long slalom fins ....

Sailboarder · Joined: 10 Apr 2011 Posts: 656

The way I understand it, the smaller fin you use, the faster you go on a beam reach. (Provided you manage to plane and not spin-out).

My experience is with a K1 board, with 46 and 40 fins (same model as yours, they are similar to MFC Liquid Pro) and with 28 On-shore wave. As you go down in size, you can feel that the fin provides less resistance in water, allowing you to go faster. You also get a looser board that doesn't hit the chop as hard, reducing the braking effect from the chop.

I find strange however that the 35 points as high as the 49. This is opposite to my experience. Maybe I have yet to use a fin too big for the situation? If I stick to the bigger is better theory, here are possible reasons why you didn't see this:

-Size. As Joe pointed out, chord and area are also important. I estimate my 28 provide a lift similar to a 34 MFC LP. Your 35 could be equivalent to a 41 or more, so the fin can be close to your stock fin. Still the 49 should be better, unless it's design is quite different from the LP.

-Technique and setup. If you are well experienced in using small fins, it's possible that you are not exploiting the upwind capabilities of your longer fin. That's an art by itself that I have yet to master. Sometimes I go upwind on plane way better than others, sometimes not. I think the setup is critical.

U2U2U2 · Posted: Tue Oct 06, 2015 8:35 am Post subject:

If weed fins were involved here, I think the OP would have said.
Joe you bring up good points in that the length is just one aspect that effects the performance, area being another.

outhaul · Joined: 27 Sep 2011 Posts: 254

My comments about speed being similar with the 35cm was achieved on a beam to broad reach and the board did seem to be freer.
Although the wind sensor at my location didn't show a shift I did detect a slight offshore component creeping in to the previously side-onshore conditions.
Again, this was all very unscientific but the 35cm did perform well and I loved the looseness. It's not that the 49cm was disappointing but rather how the 35cm was surprisingly good.

boardsurfr · Joined: 23 Aug 2001 Posts: 1266

The fin size will matter most when you need every little bit of help to get onto a plane or upwind. In 17 mph on the 11'8 with an 8.5, you had plenty of power. In 17 mph, I can usually plane with a 6.5 and a 110 l FS board (but our wind meters may differ by a few miles, and you may weigh more than my 190 lb). I may need a 30 cm weed fin to get going in 16-17; if it's 20, I can go down to a 24 cm fin, without having to adjust my style much. And I'm using huge fins compare to the freestylers.

The big fins can be useful to get going in marginal conditions. But when you are powered, you may want to try even smaller fins. I use an 11 cm on my 10'6 SUP. With the two side fins that are about the same size, it works perfectly fine for light wind. It is a bit too small for planing, but I switch boards when I can plane, anyway.

U2U2U2 · Posted: Wed Oct 07, 2015 10:27 am Post subject:

jingebritsen · Joined: 21 Aug 2002 Posts: 3371

I have caught tons waves with my 11'8"

The fin I like best for it is the kona 38 cm. Planes well, turns great on wave rides with wind below 15 mph. When surprised by upticks in winds beyond forecasts, & the wind is sideoff,I get an even smaller free ride fin @ 32-34 cm.

BTW, the stock fin is fabulous on a early planing large free ride to. I sailed mine to death in that mode. Priceless, all those after market fins, for earned $$$ or the molded stock fin for
the windsup that I found too large for the Intended board to use much anyway