Thursday, October 30, 2008

Dirk's quads

I received this email from my friend Dirk and I'm happy to publish.

I 've always been trying to make a board that sails more like a surfboard instead of a windsurfboard "shorter turns, easier to go under the lip more speed of the top,...." The boards I made at Richard Green 's place worked really well for me in the bottom turn (you can always ask Glenn this), but in top turns I was always wrong in timing, came out with no speed,... anyway I always missed the next section because of my bad top turns.So my answer to this was to make something more like a surfboard.

Windsurf shapers tried the thruster set-up but there was still one fin (also too big) in the middle that gave a lot of drag. Then Kauli came out with the twin fin set-up, here we go something new, lets check it out!
I continued my research on surfboarddesign putting some more energy towards twinfins
Let’s look at a small part of the short board history. Shapers started with making shortboards with a single fin set-up, this was not working well enough and they came up with the idea of using 2 "smaller" fins. This already made a big improvement on the performance of the boards but there was still a lot of room for improvement.
In the early 80's shapers came up with the idea of a quadfin, but the first quad fins where very similar in feel to the twin fins and so the thruster setup -what gave a nicer balance between single and twin fin- took over. Quad fins where put aside, and only a few devoted shapers continued the research.
Recently a lot of shapers have reevaluated the quad design and are trying it out on modern shapes and designs.

So mainly what are the strong points of a quad in comparison to a single or twin fin:

from Kimo Greene:
Why Do Quads Work Better?

Quads are way faster than standard thrusters or even twin fins. Most would think, how can they be faster with an extra fin…wouldn’t that create more drag? Actually, because both sets of fins are working together on the rail, there’s nothing to slow you down like the center fin of a thruster. Quads are a lot more efficient with speed.

Quads are much more responsive than twin fins or thrusters. The reason is that the fins are set further up the board which essentially puts the fins directly under your back foot. The end result is an ultra responsive board that goes where you want it to go and fast.

Four fins boast an extraordinary amount of holding power in larger surf. A large number of the world’s best big wave surfers use quads in giant surf at Jaws and Mavericks. Many of them claim that a quad fin board has better holding power and speed in giant surf. If it works well at Jaws, imagine what it could do at your local beach break?

From Bruce Mckee:
1. A faster board with all turns having an added boost
2. More security taking a higher line, so pulling out of a close out section is easier, also running high and getting speed or sitting high and deep in the tube
3. also slamming a bottom turn without fear of spinning out "No more 'nursing' a turn"
4. Much more control in floaters
5. Drive of the top instead of a stall.
6. rail to rail turning
7. Also what you will notice when the waves are bigger (with the same small wave board) is that you will have absolutely no 'nursing' the board trough a high speed bottom turn
Anyway You will be slamming or putting all you weight into everything. Not because you need to, but because you can!

For me this was enough info to convince me in trying out the quad fin setup instead of making boards that everybody was going to make, (this was about 3-4 years ago). So I called Alex Mussolini asked if he was interested in trying a few quad fins (at that time I was making his boards so it was easy to get him to try this out). I redesigned the outline (opposite from the trend of wider and rounder outlines), the bottom shape ( a little bit more v of the back,..) and the rocker, and off course instead of a single a quad fin setup.
He used it in Chili and loved, at the same time I made myself a couple of Quad fins and I was blown away with the result. The only thing that was left for me to do now is to get the twinfin master himself "Kauli" to try a quad fin out, so let's see what he thinks of his board.
For me it does all what is stated above (apart from the tube off course) and in terms of normal sailing I can add that it gets on a plane super fast, also very good upwind performance and even in choppy water I have no problems controlling the board "knowing that I only use 4'5 inch fins, about 11,4 cm in depth".

PS. Wonderful photos of epic California surf here. Sequence 23 is truly incredible.


Robin said...

Interesting stuff. Been riding Tri Fins now for nearly a year (the mid fin isn't that big anymore) and I can't see any downtrades over the single fin. Way better waveriding, way better upwind pointing (means more waverides at the end of the day!

Using the short Quad fins surely must mean trouble in (very) choppy conditions, is that what the added V is for? What about the railshape?? Just being curious.

B.T.W. sequence 14 is not bad either.

Missing Maui a lot by the way. Have fun, next beer at Jacques is on me G.P. ;)

andrew c said...

Good article. Would be interesting to try a quad. Yep, picture 14 of the California surf is amazing!

cammar said...

And how about 17? They are all amazing, really...

I asked Dirk to post comments here to answer questions.

Dirk Vankerschaver said...

I got an update from Kauli and apart from the fact that the shape was
completely different from what he is used to sail the comments were very good.
He especially liked the extra drive the fins give and the speed you have in the cut back.

Now to reply on Robin regarding choppy conditions. When I made my first quad fin, this was the main concern I had. Anyway 2 days ago we had some very windy fully overpowered 4.3 conditions and I had no problems what so ever to stay upwind, to plane and I did not even once have a spinout. The fins are positioned very close to the rail, so they keep good contact with the water.

On top of this I can play around with a lot more different fin positions (Both fins forward or backwards, or more distance in between fins), and this gives me a good setup in any type of condition.
The upwind performance of the quad setup is better than any other setup I have tried. Getting on a plane takes nothing.
If I would have to put a down side to this setup it would be the low end speed on a straight line "not on a wave, on the wave it just accelerates more and more".
The added V is because the quad fin setup performs better with a wider tail (otherwise the fins will come too close together and lose their effect), and so the V will help the transitioning in to the cutback.

Hope this helps, let me know.

Anonymous said...

Great read. "no more nursing a turn" really hit home. I'm sold. I love my retro quad surfboard for the drive and speed I can get even on mush.

One more advantage for us east coasters is smaller fins. Fins that short would allow more access to sandbars and beach break.

giampaolo - love the site.

Jeroensurf said...

Hi Dirk,
I love the idea but if the quad work better with a wider tail, how do you see this on smaller boards?
The way i read it the quad makes you able to sail smaller as usual but at the same time you need a weed tail with looks a bit like the oposite.

Dirk Vankerschaver said...

in reaction to:
-I love the idea but if the quad work better with a wider tail, how do you see this on smaller boards?-

How small do you want to go? At the moment I use a 7'6" and it is easy to make the boards even smaller without changing the tail or the outline too much. At the end a wider tail does not effect the length of the board!

-The way i read it the quad makes you able to sail smaller as usual but at the same time you need a weed tail with looks a bit like the oposite.-

I don't know where you got this from, might be in the section from Bruce Mckee were he is talking about taking the same small wave board out in bigger surf and still being comfortable in the turns, this instead of having to take a bigger board out when the waves get big.
Again a wide tail does not mean the board can't be small.
Hope this helps,

Robin said...

Thanks Dirk for your explanation, will definitely try one (a quad) when I get the chance to!

Dan said...

Hi Dirk,

I live in Reunion Island...worldclass surf and surfsailing,'s been 12 years since I got customs and find that single boards won't let me drive closer that I'm now from curl...not convice with the twins, I was searching infos on quads as it grows here too in the surf...already knowing Mac kee stuffs... do you know pretty cool set the quads...and they 're going to make an under fiber box in a couple of months using 4 us box would be too heavy and nonhydodynamics...
did you try ? as I think that FCS would not fit the windsurf pressure.

do you put angles on you're quads vert/horiz ....closing/opening...a surf board is not often going staight line...personly I'don't care if there is more drag and less speed on straight lines if it goes upwind better.
I have nothing to do with production stuff but will be very happy if you accept to share a bit of knowledge as the local shaper isn't convinced ...

keep the curve you're closer to the curl than production marketing.

Dirk said...

Hi Dan,

Nice to hear you are also looking for something new. I did know about the 4way fin system and Future fins but I indeed doubt if this fin systems can handle the pressure. I personally have good experience with Lokbox they have a wider base and so far I had no problems.
You can only move the fins back and forward, but as I have my angles set I have the same play like on a normal windsurfbox.
You can always write me back in French but I would have to answer in english as my French is limited to talking and reading.

Best regards,

Anonymous said...

Hi all,
I do not personally push for wider tails on quad boards.
In fact that is why I introduced the M5Multisystem idea and formulas after the M4 Quattro concept, so that people could convert their 'Thrusters'.
The key is the proportion of width between the back fins in relation to tail width.
Too close to center and drive is lost, too close to the rail and other problems appear such as rail grabbing, delayed re-centering or 'stuck on one tack' feel.
Fin direction is important to balance up the mix.
Too much toe-in is remedied by increased Vee, though with the correct toe-in, for the board length and distance between the back fins, any type of bottom should work.

I have just released a new 'Width between back fins formula' to combine with the ' February 2009 Shortboard and Guns Formula'.
The positions will cater to sailboards.
Both can be found at..