Tri-fin Conversion

DavidM · Post by **DavidM** » Sun Mar 08, 2015 10:34 am

I have had several request for information regarding the conversions I have been doing for the Mutts.

We have been using FCS Fusions Boxes. These are boxes designed for EPS Foam surfboards and they have a built in divinylcell bearing pad.

Eastside had this type of box installed to make his evil twin into a quad. He reported no problems using the box for this application, so we are trying them in the Tri-Fin conversions.

WSF has been testing his Fanatic conversion and has had it out several times. We will see how the FCS boxes work out for strength as he uses this board a fair amount.

Here is a link of the of WSF conversion. (Note WSF puts much prettier fins into the board that the ones shown on the link Ultra Fins Maui's)

http://1drv.ms/1A8QsSN

tempy · Post by **tempy** » Sun Mar 08, 2015 12:44 pm

Very impressive work!

Joostio · Post by **Joostio** » Sun Mar 08, 2015 7:38 pm

How do you decide on angles? Do they get a lot of toe in? I have put a mast track in a SUP and I have even contemplated a tri fin conversion on an old board I have. The mast track was pretty easy, I compared track placement on a similar board and it sails well.

nanmoo · Post by **nanmoo** » Sun Mar 08, 2015 8:43 pm

IMHO it's not the boxes that will be problematic, they'll hold the lateral loads fine, it's the fins. Standard FCS fins made for a surfboard don't have the right shape and are too flimsy for a windsurf board powered and planing. But if you can buy windsurf fins with FCS tabs then you're set.

DavidM · Post by **DavidM** » Sun Mar 08, 2015 9:38 pm

Joostio wrote:How do you decide on angles? Do they get a lot of toe in? I have put a mast track in a SUP and I have even contemplated a tri fin conversion on an old board I have. The mast track was pretty easy, I compared track placement on a similar board and it sails well.

Didn't do anything to trick. Just followed what most commercially produced windsurf boards have.... 0 cant, 0 toe. Trailing back of the fin just at the front of the back strap. Used Eastsides JP's as a guide.
I have heard that Witchcraft boards have some toe-in as do surfboards and sups.

The FCS can be bought with 0, 5, of 10 deg. cant.

DavidM · Post by **DavidM** » Sun Mar 08, 2015 10:03 pm

nanmoo wrote:IMHO it's not the boxes that will be problematic, they'll hold the lateral loads fine, it's the fins. Standard FCS fins made for a surfboard don't have the right shape and are too flimsy for a windsurf board powered and planing. But if you can buy windsurf fins with FCS tabs then you're set.

Nanmoo, agreed
The type of fin you speak of is available in FCS
Chris got a set of Maui Ultra Fins. They are for windsurfing. They come in mini tuttle, slot, FCS or US.
Here is the link of such a fin.
http://www.mauiultrafins.eu/index.php?o ... 46&lang=en

or K4 fins. http://4boards.co.uk/product/windsurf-f ... -mt-sl-us/

Udder is trying a set of small semi symmetrical FCS glass fins. We will see how that works, but the board he did is not his goto board (backup board) so testing is not progressing at a very fast pace.

C36 · Post by **C36** » Mon Mar 09, 2015 10:26 am

DavidM wrote:I have had several request for information regarding the conversions I have been doing for the Mutts...

Thanks for the thread DavidM and thanks to all involved for sharing their experiences (both building and testing)!

I particularly appreciated the comments on positioning (forward position, toe and cant) as well as profile (asymmetrical, semi-symmetrical, symmetrical) - all things I would have asked about.

Any thoughts (pros / cons) on installing mini-tuttle (my preference if I pursued it to be able to use the three sets of thrusters and set of cover plates I already have).

DavidM wrote:...Udder is trying a set of small semi symmetrical FCS glass fins. We will see how that works, but the board he did is not his goto board (backup board) so testing is not progressing at a very fast pace.

If you are looking for people to help with 'testing' just let us know - happy to help!

On second thought, given the limited conditions and lack of wind here on the Mainland,

that might actually slow down the testing process ~

C36 · Post by **C36** » Mon Mar 09, 2015 10:27 am

downwind dave wrote:the RRD [2007 Wave Swallow] is actually a tri but you are limited to what you can find as a wakeboard-style mount. i run 2" sides and a 8" middle.

Cross-posted in case anyone was considering using wakeboard-style fins.

DavidM · Post by **DavidM** » Mon Mar 09, 2015 12:55 pm

Mini Tuttle would be better with the following considerations.
- Finding mini Tuttle boxes. Only found 1 place in Europe that sold them on line.
- more invasive thru board installation. Patch on top of board and match graphics after conversion.

downwind dave · Post by **downwind dave** » Mon Mar 09, 2015 1:56 pm

Makani has some fcs fins but you would need to call and check if they can break up a set.
http://www.makanifins.com/collections/k ... urfing-fin
you guys finding symmetrical is better/faster or just more common?
looks like you have the process dialed in pretty well.. nice work with the vac setup!

with regard to what's out there for toe in, i found this useful chart at the K4 website:

http://www.k4fins.com/2013/09/pt-3-prod ... surements/
We’ve measured all of the 2014 production boards we could get our hands on. Thanks to everyone at the National Watersports Festival for letting us do this.

This is only a general round up of what we found (and in some cases an average), we recommend that you measure the boxes of your own boards and only use these figures as a rough guide.

2014 PATRICK TRAILER WAVE, US FRONT BOXES 0.6 degree

2014 RRD WAVE CULT, SLOT FRONT BOXES 0.3 degree
2014 RRD FREEWAVE, SLOT FRONT BOXES 0.3 degree

2014 FANATIC FREEWAVE, SLOT FRONT BOXES 0.7 degree
2014 FANATIC QUAD, SLOT FRONT BOXES 0.7 degree
2014 FANATIC TRIWAVE, SLOT FRONT BOXES 1.1 degree

2014 JP FREESTYLE WAVE, MT FRONT BOXES 0.6 degree
2014 JP SINGLE THRUSTER, MT FRONT BOXES 0.6 degree

2014 TABOU POCKET, SLOT FRONT BOXES 0 degree
2014 TABOU DA CURVE, SLOT FRONT BOXES 0.1 degree

2014 STARBOARD BLACK BOX, SLOT FRONT BOXES 0.1 degree

2014 NAISH, 95 TRI WAVE, US FRONT BOXES 1.5 degree

2014 GOYA CUSTOM, MT FRONT BOXES 0.7 degree

2014 SIMMER FW, QUANTUM, FLY, SLOT FRONT BOXES 1.5 degree (2013 1.3 degree)
2014 SIMMER FRUGAL, SLOT FRONT BOXES 1.8 degree (0.7 degree rear)

2015 QUATTRO CUBE 98, US REAR, MT FRONT 0.3 degree

DavidM · Post by **DavidM** » Tue Mar 10, 2015 8:09 pm

The toe-in K4 measured on production boards is very small and in some cases 0 or nearly undetectable.

K4 say that they feel toe-in is very important and will gladly sell fins with toe-in built into the fin (1, 2 or 2.8 deg). This is to enable someone with a production board to get toe-in if they feel they need it.

They further say, in their opinion, that toe-in for symmetrical fins should be up to 1.5 deg and toe-in for asymmetrical 2.5 to 3 deg.

I think that is the point of their measurement of the production boards (which you listed) is to demonstrate that production boards have very little or no toe-in whereby supporting their case for the need to buy their fins with built-in toe. It is a good option they offer if you want more toe: with their fins you can experiment with toe-in to your heart content and get all the toe you want.

Here is a quote from their site.

"With our k4fins we’ve found that 2.5 to 3.0 degrees is best for most boards. We’ve produced our fins with the heads at different angles, with 1, 2 and 2.8 degrees (marked as 3). So if your board has straight boxes you need the 2.8 degree k4s to give 2.8 degree toe, if your boxes are at 0.2 to 1.0 degree you’ll need the 2 degree k4s, and if you’re boxes are 1.0 degree plus you’ll need the 1 degree."

On another topic, is anyone interested in step by step pictures of a soft deck rebuild? I can post a thread on a deck rebuild if there is interest.

eastside · Post by **eastside** » Tue Mar 10, 2015 10:17 pm

I put 1.8 on my conversion of the SB Evil twin into a quad. I also added a centre US box. This was about 3-4 years ago I can't say whether the toe in helped as I didn't have a no toe in option to compare it with.1.8 seemed to be the consensus on the Boards Forum at the time. The whole conversion worked great. I never had any problems with regular FCS fins. The fins were about 12 DM and asymmetric. I also tried symmetric which were a bit smaller and the rear fins from a quad set.. I don't think I could tell the difference Symetric v. Asymetric I weigh about 175 lb. I used the same type of FCS box DM used. Mine was done by Aftanas Surfboards in Tofino. DM did a great job. I would recommend doing it. It will give your board a new feel and definitely loosen it up for waves.

C36 · Post by **C36** » Wed Mar 11, 2015 7:11 pm

Others from the mainland have been enjoying this thread.

AdrienGrelon on www.wtfbc.ca responding to a link to this thread wrote:Sweet, thanks for hooking it up!

DavidM wrote:...On another topic, is anyone interested in step by step pictures of a soft deck rebuild? I can post a thread on a deck rebuild if there is interest.

I think I might know how the story ends, but would still enjoy it!

You do awesome work and I'm sure others would appreciate you (and others) sharing your (their) knowledge.

stokeometer · Post by **stokeometer** » Mon Mar 16, 2015 10:17 pm

So I've been toying with the idea of converting my JP FSW 92l to a thruster, in the hopes of more wave riding performance come the O coast this summer.

My question to those who have converted their boards: Is it worth all the trouble? Do those little side fins really make an appreciable difference when on the face of a wave?

I've also heard from another windsurfer that as a fairly inexperienced wave sailor, I may be better served with a slightly better pointing and earlier planing single fin setup, as that's going to help me get out the back and position myself easier. Not to mention more power for hucking into big airs and rotations

Would love to get some thoughts on this. Cheers!

nanmoo · Post by **nanmoo** » Mon Mar 16, 2015 10:46 pm

your JP FSW like my RRD FSW has a rocker and rail outline not really suited as well for multi fins IMHO. They are designed for different things. Put an 85 fsw beside a 85 quad or thruster and you'll see what I mean. Presumably the shapers have done that for a reason. For the o coast you'd be best suited by a higher volume (85-105 depending on your weight) multi fin that will feel way more planted in high winds compared to your single but allow you to not get destroyed when its light or gusty.

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