Multi-fins for freeride

[acalhounguy]

I have a new 109L FSW board that comes as a Tri-fin setup - 10cm side fins and 23cm center fin. I have ordered a 30cm blade-weed fin to use as a single with my 6.5L sail. My reasoning is that I thought I might plane a little sooner with less drag and more drive off the fin. The lakes I sail at have weeds and my weed fins in larger sizes (38,43,48 ) generally work pretty well with larger boards. Fortunately the tri-fin setup that came with my board sheds weeds adequately so I can go single or tri and use the stock fins which are a nice MFC g-10 set. So what advantages are there of a tri-fin if you are on a lake? Any? Obviously I'll check it out for myself but I'm curious what the advantages of single vs thruster are in a flat-water setting. What advantage/disadvantage to larger side fins and a smaller center fin? Thanks.

Another question - this is my first board with a US box - I'm assuming fin further back in the center slot you get more stability with less lift, further forward more lift but more directionally unstable / quicker turning. Is this right?

[cgoudie1]

Greetings,

Thruster fins can have varied effects depending on their placement and such. I have 2 boards with thrusters that are toed and canted, an OO and a HiTech. Both were designed for where I sail them, which is the Gorge. Here
they provide stability and traction in rough unsettled conditions. and at least with my
HiTech (on which I had them added custom) they increased the range
one sail size larger, than without. It's probably similar on my OO, but
I've never found a reason to remove the thrusters to try it that way.
In my conditions, they provide considerable bite when leaned over
hard in a jibe.

Neither of these boards is bigger that 80 ltrs. A 109 ltr board seems huge
to me these days, and thrusters on a FSW could only be useful in the
W part of the function, so, on a lake, probably not too useful unless you get
a lot of disorganized chop in the 6-8M sail range. I don't imagine you get
much wave action on a lake with 109 ltr conditions, maybe if it were a Great Lake.

One possibility might be to try a an actual tri-fin setup, where the Center
and side fins are close to the same size. That might help you carry a big
sail in shallow launching conditions. It'll be weirdly loose if you try and
back foot it though.

In your described conditions, a single fin (without too much weed) might
be a better choice, but you should try it both ways, because sometimes thrusters can have unusual effects (both good and bad).

and yes, moving you main fin forward tends to loosen up turning, and
back tends to improve straight line stability.

.02

-Craig

[acalhounguy]

Thanks for the reply. 109 is small for here but practical. We had a day last Saturday where it was averaging 20 knots but would drop to 0 and gust to 40 pretty regularly. It was funny watching guys try to decide what board / sail combos to use. I can still uphaul it and slog it but it's not too huge in the nasty chop we get at my main city lake which has some concrete shoreline. Anyway, it is far more "slashy" than my bigger boards but I don't have a similar board to compare to. I did spin out a couple times - more or less spin out with a multi-fin all other things being equal?

[cgoudie1]

Again it depends on the setup of the thrusters. If they're very close to the
rails, it won't have much effect on spin-out (but should help with hard
jibes), but if more inboard, and canted, then they really help reduce spin out. Remember we're talking a thruster set-up here. I say this because
I had a quad that could be set-up for Quad, Single with thrusters,
Dual, or Single. It was spin-out prone in quad mode which surprised the
heck out of me. It was most enjoyable for me and my conditions in the
single plus thruster, where it was spin out resistant.

With your conditions, a short wide floater with thrusters sounds like the
perfect board, for that nasty chop and your dramatic wind range.
Don't let that keep you from trying it with a bigger single fin though.
I ride with a guy here who took his thrusters out of his Cascade 70 ltr
and never wanted them again.

-Craig

[U2U2U2]

If your MFC fins she'd weeds, ok, then why a single weed Fin ?

Soon you will have the single to try and see how they differ.
Your thinking IMO is correct for all you surmise. How does the tri fin feel, anything dramatic ?

More area with 3fins vs 1fin "generally speaking" increases drag, hence slower to Plane and less top speed. ( my quad conversion/ revamp is 95liters done off a Freeride board, has NO drag ) the fin size shape area on multi fins is critical to optimize performance, they compromise a huge amount of character .

Your FSW, is not a Freeride, it's a wave board compromise, and in its own niche
Can plane early, compared to a Freeride platform, it won't, no matter what, under like circumstance.

Use 3fins you lose some top speed, again in a FSW class of boards. You gain some upwind, ( more area) and a Flicky loose , while the same time grip. Some notice some instability in straight line, only some. It's a give take episode.

I made a tri fine Tabou Rocket 135, it's been tri capable since new. The purpose was less fin depth , to sail in rocky areas in Maine, and shallow ones in Hatteras. I generally use a weed center that reduces depth somemore, CNC fins, I remember once since 2011 using a single center fin, it offered some plus that I mentioned, or suppressed the tri fin negatively, I luv the way it feels in tri fin, it carves like a 100liter, jibes nicely.

If speed is your need then single.

I have used a multitude if fin sizes on the Rocket, and other tri fins. Using 3fins of similar size, just say on yours all 15s, the board will become very Twin like("generally speaking again " it will be loose, very skate line in feel.
Top speed may increase some, stability more likely less, turns Way cool.

I find it me now, that a longer center is the feel that is the most comfortable .
I do try instead of say, 23 and 10...go to 20 and 12.

I could figure out your board company, probably Fanatic ..but it so it's unknown .

You may of course PM me , be happy to help with K4 fins.

[isobars]

A fin > 12" is usually considered hazardous to the health of a U.S. box. Does your board mfr or dealer recommend bigger fins for that board?

Whether you're on a "lake" isn't the issue, as many lakes get useable, maybe even big, swell in conditions suitable for a board that size. What matters is the terrain and what you're doing with/on it. If you're turning extremely tightly at high speeds (whether slashing or jibing) in rough water, thrusters may help near the limits. Spinning out in lesser conditions is usually operator error unless the fin is loose, damaged, or too small.

[U2U2U2]

32 cm is the largest I see for a USBox.
For a 109 single something like 32-35, with a 6.5m sail is about right.

30cm would be my choice if nicely powered up on a 100liter.

One may find a longer USBox fin , and explore the area compared to other sizes, a 30cm weed may have a large area, or have one built.

Your board is not so ideal as a large single. The USBox over powerbox, has plus minus. ISO has a point on size, going to large on that box could bring structural problems, too large is the question..what IS ?

[acalhounguy]

Somewhat moot now. Fin arrived and it's too long for the box (looks like my board has a relatively short slot). May still look for another single but maybe ask Quatro what they would recommend (something MFC I'd guess which is fine). Mostly I was thinking earlier planing with a bigger single but I may have been misguided anyway. I'm not looking for more speed per se. The thought about the box not being strong enough for the longer fin is a worthwhile consideration in any case. Thanks

[U2U2U2]

Quattro

Way more wave oriented than other FSW.
A phrase that applies here, actually 2.
Live and learn.
The operation was a success but the patient died anyway.

Wish you the best of luck, and thanks for thanking .

Meanwhile back at the ranch

[acalhounguy]

Tetra - it isn't that wave oriented but it is longer than average for its size and it crushes chop both things that I wanted. Very happy with it so far. Not the fastest board of this type I'm confident but I was going for control in wacky reflected chop so I think the patient will survive after all. Doesn't hurt me to have something new to play with in terms of the thruster setup which is the origin of the questions. The new fin can / will be returned - no big loss.