*Geek Alert*
I recall an earlier thread regarding canted fins and found this recent research paper titled:
"The application of canting keel concept in racing
windsurfing fins: does it lead to superior performance?"
http://www.theplymouthstudentscientist.org.uk/index.php/pss/article/viewFile/109/157

BTW - It mainly deals with Formula racing as opposed to smaller speed fins

Are canting fins class legal for formula?

Well that was an interesting read,....what's next!

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Katapult said...

Are canting fins class legal for formula?

If you had a fin made that flexed near the base and was stiffer in mid section, then you would/could achieve the same effect as the canted fin........ maybe.

Who's going to build one as a test model.
It would save having to deal with the canting & securing in the fin box.

You are right Ads, good reading.

Nice to see some scientific research in windsurfing. I was also thinking of contacting a university for research related to fins.

Like wineman says it should be possible to make the hinge elastic instead of mechanical. Only difficulty with formula fins is that we are dealing with some serious forces. So before building this kind of fin i would recommend to perform some serious strength analysis on the design.

I was thinking of what physics are behind this concept, and i almost think it is about the same story as with stiff fins vs soft fins.

The lift and drag generated by the fin are not influenced by canting the fin. Only the direction of the lift is changed which cause the vertical lift to increase and lateral lift to decrease. When you look at the case of a stiff fin vs a soft fin you will see the same difference. Soft fin will bend more, causing the vertical lift to increase and the lateral lift to decrease. And since today a lot of formula riders prefer the soft fin, this could mean that the increased vertical lift have a positive effect on performance. From this point of view the results of this research are not very surprising.
Comparing the very soft fin to a stiff canting fin will probably not make a big difference in the forces and directions of these forces acting on the fin. But we will definitely see a difference in dynamic behavior. Maybe this is what makes the canting fin concept better than the original concept.

I only have a little doubt about the quantitative data collection method. Only one test rider was used for this part. First the standard fin was tested for an 2 hour session running a simulated racing course. And after that the canting fin was tested in a similar 2 hour session running the same course. So we don't know if there was any difference in wind speed or wind direction. A little increase in wind speed would definitely have an effect on upwind / downwind angles and board speed. And i could think of some other extraneous variables which can introduce some kind of noise in the experimental results. I think it would be better to use more test riders, so it is possible to test both fins in the same time window.

Didn't IanK try out a reboxed fin to see what changing the angle does.

Ian? What was the result?

Yes took this one for a spin. Was thinking that splitting the hydrodynamic forces into two orthogonal components, as we do with fin and hull, is not the most efficient way to go about it. The fin is more efficient at generating lift than the hull so using it to relieve the hull of a bit of work should be a win. As Michie says it's a trade off of horizontal lit for vertical lift. But because of the way sines and coses work it's a win. For this fin at ~ 18 degrees you lose horizontal lift with the cos of 18 = .95 ie lose 5% but gain vertical lift with the sine of 18 = 0.31 ie 30% and the fin only has to be 5% bigger to get back the lost horizontal lift. ( Or run at a slightly higher AOA).



I had a bit of a win in that many said it'd be unsailable, I'd break an ankle. In fact it was surprisingly easy to sail, a little prone to spin out on the lifty side and heaps of traction on the digging in side. Did about 30 knots I recall. But I felt that I'd lost a bit of steerablity and feel. Maybe you'd get used to it. Only sailed it once.

The sailrocket speed machine makes good use of this idea by eliminating the planing surface altogether in favour of two fully immersed foils. One in water and one in air - both of which should operate at a better lift to drag ratio than a semi-immersed planing hull. It's getting close to the perfect sailing machine ie - one foil in the air connected by an ultra thin, ultra strong wire to one foil in the water.
Control will be the issue, the old planing hull is hard to beat for dynamic stability.

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Wineman said...

Katapult said...

Are canting fins class legal for formula?

If you had a fin made that flexed near the base and was stiffer in mid section, then you would/could achieve the same effect as the canted fin........ maybe.

Who's going to build one as a test model.
It would save having to deal with the canting & securing in the fin box.

You are right Ads, good reading.

Thanx Wine Man but I was being a tad cheeky,...sarcastic, all be it, facetious I think I made it through the first page then skimmed to the pictures!
As to that fin design, it reminds me of myself really. I could do with some stiffness in the mid section? I'm going a tad soft with this 'no wind' business!

Hi,

I experimented with canted fins 2 years ago with Ron van den Berg and Martin and I had the same comments but found that you do not need to go to a big angle for the concept to work best. made 2 of the exact same fins with 2 different canting angles (we called it camber) and the spinout sensitivity on the lifting side is caused by too much canting. What I think happens is that when the fin gets out of the water and the angle is rather big, such as seen on the picture, the side of the fin starts planing. I expected difficulties upwind on the wrong side, but it was amazingly efficient and pretty fast. The speeds I did with the canted fin were consitently around 5km/h faster than with the regular 0 degree canted fin, which we had as a benchmark. We have a proto which can shift sides after jibing. Worked pretty well and during the jibe when you would not give consistent pressure on the rail it was a bit nervous as the fin was shifting sides back an fourth but never getting in a spinout. But when you would give good pressure it would go though the turn without you noticing it shifting sides. We tried it on a kite raceboard as well. We put it in the fridge as we have bigger projects going on now.

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Ads72 said...
[Thanx Wine Man but I was being a tad cheeky,...sarcastic, all be it, facetious I think I made it through the first page then skimmed to the pictures!

Yes, I know you like pictures - but a budding teacher must read as well!

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I could do with some stiffness in the mid section? I'm going a tad soft

Don't listen to TFord - he's only winding you up.


Thanks to Ian K & Serge for a great (& practical) response to the tecknical side of the discussion.