Neil has been creating windsurfing magic with some recent innovations. Find out what happens when you sprinkle a tiny bit of the foiling dynamic into Windsurfing.

Top stuff...windtech board is on the shopping list this summer.

Cheyne Horan and Ben Lexcen designed "winged keel" fin.





Cheyne Horan's personal board recently on show at a French surf meet , mid to late 80s.

If you mean boards - not a problem

- regarding fins - Neil has got some kicking around her ein WA on the river and coast off Perth - but these fins are hand made and not commercially available. (its quite technical to bring these to market in volume with required tolerances) There is a lot of dynamic to be played with - size of wing, foil, angle of attack etc etc


I had a big 42cm fin with a larger wing tip on it on the river the other day - upwind lift is insane - and speed through chop / lack of terror is great because you can ride above it. But then again the flex tail and board balance already gives you some of this forgiveness through the rough stuff.

Takes a bit of getting used to off the wind as the lift makes it different to weight the tail going in to the back of chop - but the higher ride maybe means you dont need to - still so much to learn.



There is also a BIG benefit in the gybes with increased sustained lift through the arc - meaning exit speed is increased - as well as the chance to pull off a full planing manoeuvre in more marginal winds.

The wing fin helps keep the board composed in big chop over distance - super fast nautical miles

The board Active Trim Technology doesn't hurt either

Can't wait till the 57 gets here

I once made a large wing fin thing , ( try saying that fast three times in a row ) , It showed promise in fresh water , ( much slower planing ability ) , but not in salt water so i gave up . I dont know why , water density or just my density .???

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Reflex Films said..

Paducah said..
So, why is this a "wing" not a winglet like commonly found on airplane wings which works (largely - ignoring thrust aspect) by reducing tip vortex?

The surface area of that wing alone wouldn't seem to be providing much lift unless you are going insane board speeds, at which point, the drag of the extra surface underwater would seem to be a bit noticeable. I'm wondering if the improved upwind performance is because it effectively lengthens the fin rather than any "lifting" properties much as a winglet is designed to give a shorter jet wing the performance of a longer one that, because of gate space requirements, isn't practical.

I think the innovation is a good idea but just questioning the reasoning why it seems to offer an advantage.

There is so much to learn about blending different sizes of wings into different fins - we aren't claiming to know it all - just enjoying the journey and the riding feel.

1 thing is for sure - there are a lot of dynamics that can be taken advantage of. For a settled ride - the wing resists vertical movement so its easy to imagine how it settles the ride through chop.

Appreciate the reply and your candor. Good luck!

Not sure you want the board held down through chop, it would slam the board into it rather than letting it go over.

The lift of a planing hull is centred up front where it first strikes water. I don't think you could put too much lift back at the fin without major stance adjustment and footatrap shifting.

It's no accident that foil boards put the main wing forward on a fuselage to get the lift where we like it. Semi-foilers might have promise but the mini foil will still end up out front on a fuselage.

I always thought cut outs aided trim by lessening pitch forward and stickiness when the rear passes over a bit of chop. I won't know what to think if I see a winged fin on a board with cutouts?

Paducah said..
So, why is this a "wing" not a winglet like commonly found on airplane wings which works (largely - ignoring thrust aspect) by reducing tip vortex?

The surface area of that wing alone wouldn't seem to be providing much lift unless you are going insane board speeds, at which point, the drag of the extra surface underwater would seem to be a bit noticeable. I'm wondering if the improved upwind performance is because it effectively lengthens the fin rather than any "lifting" properties much as a winglet is designed to give a shorter jet wing the performance of a longer one that, because of gate space requirements, isn't practical.

I think the innovation is a good idea but just questioning the reasoning why it seems to offer an advantage.

You are right, technically it is a winglet, because one of its benefits is reducing the tip vortex of the fin, increasing the slope of the lift curve and increasing the effective aspect ratio (i.e. it feels like a deeper, more vertical fin). It also results in a net reduction in drag. This part of the design is not in question, with both data from aircraft wing research over the past 40 years as well as actual tank testing more than 30 years ago of fins with winglets confirming this (see photo below).

However Neil's fins also have a couple of other effects that aren't immediately obvious. One is that they dampen both pitching and heaving motions, meaning that the board rides more smoothly and slams less.

The other is that because the wings are set at a neutral (or even negative) angle of attack, they don't tend to make the tail rise out of the water at speed, you actually get a net reduction in tail walking behaviour in chop at speed. If this seems counter-intuitive, keep in mind that the rear wing on a foil board is intended to produce neutral or negative lift, it's purpose is to keep the main lifting surface tracking at the correct angle of attack.

It's important not to think of Neil's wings as hydrofoils providing a constant upward force. While they may produce upward force when the board is at a reasonably high trim angle (such as sub-planing and early planing conditions), most of the time the upward lift component is fairly neutral. This means the winglets probably help a little bit getting the board on the plane and help to glide through lulls better. But the major benefits are increased efficiency for a given fin depth, and reduction in pitch and heave motions, allowing the board to be pushed harder at speed.

RichardG said..
Cheyne Horan and Ben Lexcen designed "winged keel" fin.





Cheyne Horan's personal board recently on show at a French surf meet , mid to late 80s.

I used to surf with a Horan/Lexcen starfin. I thought it was horribly draggy and gave up on it. But looking at the photo, I think I may have been using it the wrong way around with the back to front! Double face palm Fangy fail!

Sailing dinghies and cats have been using rudder winglets for decades now, using them to prevent nosediving and to ease motion through waves. It's amazing to see how tiny the ones on 18 ft A Class cats are, but they still work very well.

The largest fin with wing I made( wing because its at 90 degree to the surface of the fin ) used on a Rocket 135.
Feeling of lift was generated at the tail, no straight line degrade, turn were unaffected . I feel it helped speed when the wind was about 15mph and a semi planing condition, so almost. When the wind got above 15MPH the winged affair actually slowed the board down, the Rocket then performed better without it.
a back yard , shed project , that I measured to 1 degree AOA, and fitted the wings at a length I found acceptable. The wings bottom was sanded asymmetrical , somewhat. I feel it was a interesting experiment , it had little gain.
The wings were drilled at the bases to accept a carbon batten into them and through the fin from side to side. The glass and epoxy. Not placed at the tip of the fin. See post with photo Previous

We know T foils work - they've been working since the '90s on Moths, 14 Footers and cats. It's not a case where their effect will be proven by them exploding in popularity because there are other effects - they have been well proven in boats but they are also costly and problematic in some ways so most classes ban them despite the fact that that are often faster.

Given the tiny size of foils on Moths and A Class cats, not to mention windsurfers, it would seem that a foil must be making much more lift than you're calculating.

Here's a pic of foils from an 18ft A Class cat owned by Olympic silver medallist Andrew Landenberger. Notice how tiny they are. World champs in As (and they get far more sailors to world titles than FW does these days, including pros) reckon even these little foils have a huge effect in preventing nosediving even with boats with 30ft masts.

If they are so proven, then why dont they explode into windsurfing ?
Does problematic mean the performance gain is not worth the offset bad issues ?



Yes they work on airplanes as do a number of aerodynamic aids. The airplane fuselage is a little different to a board.
And uses moveable flaps, slats etc

forceten said..
If they are so proven, then why dont they explode into windsurfing ?
Does problematic mean the performance gain is not worth the offset bad issues ?



Yes they work on airplanes as do a number of aerodynamic aids. The airplane fuselage is a little different to a board.
And uses moveable flaps, slats etc

The problems include cost (not just of the winglets but the structure and hardware to take the loads, and the adjustment arrangements if allowed) and fragility. Most classes have banned them for these reasons. Interestingly, the classes that allowed them haven't maintained numbers any better than the classes which didn't, as far as I can see.

Chris and pacey, thanks I'm would be attaching to a wood rudder I think I will pass on making them.