tri fin speed board

i toying with the idea of adding some side fins to my slalom board and hopeing to use a smaller fin on speed runs, the problem is i havent got a clue on where to put them and at what angle to set them at,

keef,keef,keef


open the door in your shed and put the lid back on the thinners

careful,dont spill it on your board and dont get it anywhere near those plastic fins,they'll melt!

we'll talk later,it will make sence then

i'll be back on friday

lucky you mentioned those jocks choco ive been looking for those for ages im hopeing to cut the main fin down to maybe 16 to 18 on a 5/8 sail i'm not sure how it would go, im not useing the board so i thought id put a cutout in and the side finns
KA360 it sounds like youve bin in my shed those plastic finns are just a trial ill have to take the foil off the inside of the side finns and if it works ill make some glass ones , cu on friday

would be interesting to still see what happens with your setup.

what i haven't tried is symetric foiled fins as the ones i have are 80/20 so that may make a difference.

i also only had a 25cm centre fin so could be i was over finned.

for me the extra fins are for grip. i would think if the fins were very short they may end up doing nothing as the board lifts and they leave the water.

these side fins are 9cm and maybe a bit big, im not looking for lift just fins small enough for tracksion when bareing away and reduce the fin cavitation at high speeds, what i need to know is are they set strait or like surfboards that are offset, i tend to think for speed sailing they would be set strait and close to the rail

To save you time & with out punching numbers into the software that will say;
NO x 3.

1/ Use T-Plate cutouts, for wide/ normal tail board.

2/ Use single "small fin".

3/ Once feel comfortable in using the small fin", go smaller.

You will be surprise how small you can go,
Small fins is a learning curve, bit like learning to windsurf.

Small Fins are pressure sensitive, once you have overcome the fear & have an advance style of sailing go another size down.

Hi Keef, I have been sailing a hifly Madd twin fin board for the last 4 years or so and from my experience, they are no good for speed. You tend to get drag from one of the fins and when you try to drive the fins hard one of them will start to spin out while the other still has grip.

In Safety Bay for the last three weeks I found that I could go from sailing the Madd to sailing a 115L S-Type and straight away the speed was typically another 2 or 3 knots. It probably has a bit to do with the board shape too, but I suspect the drag of the second fin was a limiting factor.

Funnily enough I use two of Wolfgang's Chameleon weed fins in the Hifly. I initially tried it with two 23cm fins but they were too small and would break away into spin out easily, but with two 28cms it works okay.

With short fins you really notice how easy it is to spin out when there is a bit of chop. When you see some guys use 23cm asymmetric fins for speed sailing, keep in mind they are going downwind, way off the wind, and in very smooth water.

The one advantage to having two fins on my board is that for a 135L board it only has a fin depth of 28cm instead of 35 or more. If anyone has followed me over the sandbar at Safety Bay at low tide and wondered how the 'heavy' guy got over it and they didn't, I apologize It is great fun gybing in a foot of water though!

thought i might throw some comments on this. you might want to build a high wind b&j board one day.


on older surfboards, side fins were pointed at the tip of the nose.

on windsurfers they are pointed at a point usually an inch or 2 or more off the tip of the nose.

twin fins are loose, much looser than tri. if you wanted control i wouldn't bother with a twin, i'd look at either a tri or a quad. i am hoping to get a go on a fish twin soonish that has the fins right out on the rails. i was told this would provide a very loose feel.

i know there is a lot more to it but that's about the limit of things for me.

hi sailquick,

could you go deeper into why the twins would need to be parallel? i have been thinking about trying out parallel tri fin setup. is there any theory or anything you know of that may shed more light for me.

Hi Andrew, I think you might be too used to the 'choppy' water in Sandy Point
The first year I came down to SP it was interesting to see some people do really good gybes down the bottom of the course and truck upwind, yet others would do the walk of shame back up wind... I don't know why they were walking up as it is far more easy to sail up - I did it once; it's a long way to walk.

I am not sure I agree with your comment that it is not super flat - at least on the course anyway. Down the end it looks like it can get lumpy, but I think in parts of NSW we would still call that flat

I would say that coming the other way up the speed course is still pretty flat, although nowhere near the run down wind close to the sand.

I don't think you would see spinout at the bottom of the course anyway, as you are not really pushing that hard on the fin at that angle. Are they driving the fin hard on the way back up? Do you guys use the same asymmetric fins when you are out trying for distance or alphas?

I can easily spin out my 23cm fins, but this is on a reach pushing a lot through the fin, and I suspect the same fins would be fine going downwind as there just isn't anywhere near the same pressure on them.

When sailing in shallow water, weed fins are definitely an advantage to give that softer feeling when you hit bottom!

P.S. please feel free to send me some spare Time Machine foils so I can conduct my own testing I may have to convert to tuttle box, but I think I can live with that.

Have a look: www.designlessacher.com
For pics of rake 30° please mail me. Wolfgang

What about the Bonzer boards? I rode one years ago in the Columbia River Gorge. It was a lot different to other boards of that era, being quite short and thick. Not a bad board to ride though I don't really remember it being particulary fast. This sort of setup would be good for riding in shallow waters.

Well, I guess it depends on your definition of 'Super Flat'. To me that is what you see in the pictures taken at the top of the course and on days with less than 25 knots of wind. At 45+ knots, rolling chop 15-30cm high is certainly not super flat and definitely gets your attention! If you haven't seen it you haven't been broad enough in strong enough wind.
Coming back in the channel when the wind is 30 knots against an incoming tide can kick up horrendous washing machine chop 2 feet high and really close. Again, you have obviously not been there.......

There is absolutely no 'shame' in walking back up the speed course. Many times it is the safest and most reliable way back, and often the quickest. When the wind is quite west it is very difficult to sail up and involves a lot of tacks back and forth for little gain and a lot of energy expenditure. Quite a few times I have been walking up the bank as another sailor set of to sail upwind, only to arrive back on the next tack at the same place as me a few minutes later. We will often walk the first couple of hundred meters to where we can make it back to the top of the course on one tack.

When Mal Wright pulls 46 knots at 120 off the wind he has maximum pressure on the fin! I usually need to go broader to get max speeds but even then I have quite a lot of pressure on the fin.
Coming upwind I have as much pressure as the fin will take which means I vary it all the time. Less as you bounce through a wave, more when you can run in a trough. Remember we are often sailing way overpowered with a bagged out sail. It is hard work on the sailor and the fin.

We use the 26cm TM Speed26 symmetrical for Alphas and 1 hour as well as the KA symmetrical 23 cm speed fin which has about the same area but is steeply raked. Max pressure beam reaching!

Sorry mate, don't have any 'spare TM's' :-) All the ones I have I have developed a deep personal relationship with. And anyhow, I don't know of any real speed boards that don't have a Tuttle box. [}:)]

On a speed board it would be critical that the fins were parallel with each other. If they are not they will be working against each other creating massive drag. The working angle of attack of the foil at top speed is less than one degree so it is critical. And they would have to have identical foils.

Surfboards and windsurfing wave boards are working in a different environment.

Hi Craig, from anyone else I would ask 'when did you fall through it'.

With you, I think I am more likely to ask 'who did you run down while you were sailing your 5.8m?'

Did ya have to chase them onto the sand, or were they just floundering around in the water?

I worked in 39 years 155boards for Windsurfing. Only for myself. Only some boards
for Lechner. The last years make I only in front broken boards shorter. 2m long
no problem. I tried from one to five fins all it. I am a friend from concaves at the
bottum. The last years no time for boards, only fins.
What should a fin can do? Speed and no spin out. So I worked only asymm.fins
so how they do it in Sandy Point. Only for one way. Leewards flat. That was okay
later leewards a concave from the thickest point of profile to the end,2mm deep.
That was faster and no spin out. So there were 2fins. A right and a left.
There I are windsurfing in Netherland Srand Host, was it it always the same. In
front fast and back slowlier. Over 4km 20m in front, the first.
So I said , 10m in front, thats the half, but i am the first. So I worked the
concaves diagonal. A concave left and one right do not work. Diagonal works it good. The half concave for in front works leeward, the other works on the way back. 40cm fin, 20cm concave from the base to the middle, on the other side
from the middle to the tip. What happend? The concave for the way back
reduce the vacuum on the other side so good, that there was no difference.
Not 10m in front, 20m. Thats all. Cut out at the base? Helps to start very big
sails, witout to get spin out. Thats only for the first meters where you have not enough speed. Select asked me for Prototypes, they got some, they said to thick,
I said no, but now they work the Weedfins with cut out. They are the first who
wake up. Wolfgang