Don't know if this topic has been discussed elsewhere. If it was i'm sorry...

Hanging around the socials during these past last days i've noticed some pwa regulars showing signs of wind foiling crashes. Luckly nothing really bad but still...

Ueaj, they all try to push their limit (they need to) to reach better abd better level/performance.
High speed windfoiling is currently lot more better than few years ago but i wonder if this could improve re-thinking at the whole system.

I mean, for performance tools people don't foil same fin boards anymore.
So why don't design new different boards placing the foil somewhere else if this helps?

Hello, that is an interesting topic. I see two point of view, one related to general windfoiling, so not associated to competing , the other from a performance perspective.
Probably creating a system with a foil in front of the mast base could be more stable, but less manouverable I think, though for pleasure foiling I like the system as it is; too much of auto pilot would rouin that magic search of balance that foiling is all about. should not be needed to uphaul the sail, the perfect board would have the less nose possible and this makes the system more compact and 'on top of the foil', which for freeriding and having fun is all we need I guess; the less bulky equipment we need the better to me, more freedom, more playfullness. Moreover another gap I see in these days windfoiling is wind range, IQ sails can handle from 6-8 knts to 30 knots with 9 sqm sail, I was used to get in crysis with a 5.7 wave sail into 15-16 knt of wind, we shall do better than that, coming ashore to change sail is an hassle for foling boards..maybe we need to re-discover adjustable outhaul systems, they may enlarge that range a lot.

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w100 said..

So why don't design new different boards placing the foil somewhere else if this helps?

They do. The box is nearer the back of the board. Well, at least it is on my AHD freerace, 5cm from the back of the board.

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PhilUK said..

w100 said..

So why don't design new different boards placing the foil somewhere else if this helps?

They do. The box is nearer the back of the board. Well, at least it is on my AHD freerace, 5cm from the back of the board.

Or on the starboard race boards the box is over 20cm from the tail

Their course racing board is quite different from their slalom board in that respect. A stepped design on the underside at the tail.
Didnt they have something similar with their fin course boards, Phantom? Exocet had similar on their Kona long boards. From the top, it makes the straps look a long way forward, but they arent in reality compared to the foilbox. It makes the overall length long as well, 235cm.

windsurf.star-board.com/windsurfing-boards/foil-race-boards/foil-millennium-race-windsurf-board/
windsurf.star-board.com/windsurfing-boards/foil-race-boards/x-15-foil-slalom-windsurf-board/

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w100 said..
Don't know if this topic has been discussed elsewhere. If it was i'm sorry...

...So why don't design new different boards placing the foil somewhere else if this helps?

This has been discussed before a few times. In short, there have been attempts to put the foil elsewhere but the answer keeps coming back that where the foil is now is where it seems to work best for a number of reasons including how the board behaves while still in the water, at take off and as mentioned above, how the entire package, board and foil, behave in the air.

As for the Starboard boards mentioned above, the foil is still relatively in the same place vis-a-vis the straps ie the relationship between the rider, foil and mast is still pretty similar. The big difference being the tail above the water being extended to provide a smoother release for air coming off the back of the board. For recreational riding, I'm pretty sure the difference is minor to nil. For racing, since I spend a lot of time in the cycling world where even the drag of (edit) cables are considered so that of harness lines at 30 kts would be consequential, I imagine the small things do add up even if seemingly minor.

"The board is shaped like a water drop from the nose to the tail, reducing the drag from the water while also increasing aerodynamic efficicency. As a result, the board is very slippery and stable in the air."

Round hull is great

What brand and type board is this?

Reminds me of the CRIT 650 Div 2 board a raced in the early 80's. It was amazing in light air.

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barthbb said..
What brand and type board is this?

It is one of my other skills...

www.free-ride-addicted.fr/shape/

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WsurfAustin said..
Reminds me of the CRIT 650 Div 2 board a raced in the early 80's. It was amazing in light air.

This is part of the idea, you don't need a planing hull as at planning speed you are in the air... So having a minimum wet surface/volume ratio is best.

I would imagine with that bottom shape it would be quite tippy....?

Yup too hard to uphaul and then been trying not to say it but I really don't get it, flat is fast and low drag. Round is sucky.
In displacement mode a rounded bottom can be less drag but we want it to ride up out of displacement - granted we are not trying to achieve planing speed but still don't want a sucky round bottom.

Look at IQ and Patrik FoilOne.

Current downwinder wing foil and SUP boards are long and narrow with displacement hulls, so the theory works. A dirty great big foil underneath also helps with stability.

Mark, I think the IQ and Patrik Foil Ones are flat because they are nearly 1metre wide.

With my body weight, sucky foiling skills, anemic pumping skills, choice of foil and sail, I depend on getting up onto a plane with the board BEFORE quietly lifting it up into flight. Therefore, a flat bottomed board with very little rocker works best for me.

Yes, once up in flight, bottom shape does not matter. Bottom shape before flight matters a lot.

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Mark _australia said..
Yup too hard to uphaul and then been trying not to say it but I really don't get it, flat is fast and low drag. Round is sucky.
In displacement mode a rounded bottom can be less drag but we want it to ride up out of displacement - granted we are not trying to achieve planing speed but still don't want a sucky round bottom.

Look at IQ and Patrik FoilOne.

I don't think this is quite true... Round rockers are sticky, yes... but rail to rail may be different... think about it in a static sense. Imagine a pc of plywood lying flat on the water there is lifting eye in the middle & you measure the force required to lift it out of the water. Now you have a semi cylindrical(half round) shape with the same surface area touching the water. Given they are the same weight with the same surface area which will take the least force to leave the water vertically? I think given sub planing speeds the displacement hull may release easier.... just a thought...

So why do i have a wing board that flies earlier than any other with many testers back to back with similar boards
Like two guys identical one gear can't even fly and on my flat board design they can? Swap over riders and same deal
Plus then touchdowns fly up again effortlessly which is a big one
Not theorists here - real world testing

People removing silly bevels and improve their board takeoff threshold greatly - real world experience

WS foil board likewise

Not saying round cant work but i am having people rave about early takeoff with flat, and they've used many boards.

And if round is so great why is nobody making race boards like that? 1m wide or otherwise.....

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Mark _australia said..
So why do i have a wing board that flies earlier than any other with many testers back to back with similar boards
Like two guys identical one gear can't even fly and on my flat board design they can? Swap over riders and same deal
Plus then touchdowns fly up again effortlessly which is a big one
Not theorists here - real world testing

People removing silly bevels and improve their board takeoff threshold greatly - real world experience

WS foil board likewise

Not saying round cant work but i am having people rave about early takeoff with flat, and they've used many boards.

And if round is so great why is nobody making race boards like that? 1m wide or otherwise.....

Maybe it depends on the circumstances. Likewise I have seen back to back testing.Wingers getting up on foil using long narrow round bottomed(but flat rockered) Downwind boards on a wing size they could never get on foil with their traditional boards. Maybe it is a matter of available power. The downwind style boards seem to be able to generate the speed needed to release quickly with less power, whereas a short flat board like you are espousing may take off very quickly given enough power.... just a thought. Here this is playing out over & over with people switching to downwind boards for lightwind winging. I think there's something to be learned there...

I never said short.....
My WS foil is crazy short at 170cm for 110L, and my wing board is very long for volume in these modern time (5'9" for 95L)

But my rocker is same as WS speed and slalom on both of those boards and they fly way earlier. And touchdown way better....

I'm talking same volume too, are some of these DW SUP board fairly voluminous compared to 'wing' boards? I' testing 3x 95L wing boards with 3 riders on same day all swapping gear and they are beaming and raving about it.

All I know is that all the bevels and stuff and egg shaped ouline things are slower to fly but it's a shame as the companies have created that image of batmobile-bottoms that ppl now expect to see

Take off depends among other things on technique, with cutouts or downwinder boards depend mainly on speed for take off, my board is 172*80 with large bevels, no cut out, but I don't see anyone taking off before me, and I do usually use smaller sail than the rest. My technique relays mainly on pumping and only minimal forward drive. Friend of mine getting a downwinder board with mast track + Gong Sirus 186(xxxl), I will report on findings in a couple of months

Heres what Starboard and Severne do with their race board cut outs respectively.






The starboard design is an interesting one. foil box looks to be further forward away from the actual tail, but footing position in relation to the foil looks to be in a more usual placement.

I'm wondering what the perceived benefit is of all that tail? They could easily lop off the round section without affecting anythingit would just be excess drag when you're trying to pop up as best i can tell.

The extended tail of the Starboard is for aero rather than hydro reasons - to have better airflow off the tail. That's why all the other dimensions vis-a-vis the foil box are conventional.

"Further aerodynamic features include a aero convex deck and a smooth exit at the tail to reduce high-speed drag as much as possible. " - windsurf.star-board.com/windfoiling-boards/freeride-racing-windfoil-boards/x-15-foil-slalom-windfoil-board/

I agree, the cutouts of the Severne are similar to Phantom, FMX, and others.

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Paducah said..
The extended tail of the Starboard is for aero rather than hydro reasons - to have better airflow off the tail. That's why all the other dimensions vis-a-vis the foil box are conventional.

"Further aerodynamic features include a aero convex deck and a smooth exit at the tail to reduce high-speed drag as much as possible. " - windsurf.star-board.com/windfoiling-boards/freeride-racing-windfoil-boards/x-15-foil-slalom-windfoil-board/

I agree, the cutouts of the Severne are similar to Phantom, FMX, and others.

reflecting on it, though, I wonder if a Kamm tail would be more efficient (or no less efficient) since the taper on the Starboard seems fairly extreme from an aero viewpoint. en.wikipedia.org/wiki/Kammback#Aerodynamic_theory Also, I imagine the air is pretty dirty going over feet, straps, etc at that point so excessive aero tinkering isn't that beneficial. I'd think at that point, there's as much to be gained by using thinner harness lines or other tweaks.

Board shape design in mostly guided by unproven theories, very limited testing, confirmation bias, and hype. Different levels of experience and background complicate things further - even more so for winging, where newbies may come from windsurfing, kiting, prone surfing, wakeboarding, or have no water sports experience at all.

Race boards in windfoiling seems quite similar to each other - very wide for early planing, sharp edges, and pretty significant tail cutouts. But in wing racing, it seems many racers are using downwind boards.

I'd theorize that downwind shapes work for foiling if you are using a relatively powerful but efficient foil - something like a 100 cm wide high aspect foil. With limited power, the downwind board shape will pick up an extra couple of knots due to longer board length and a lower drag coefficient. A fat beginner foil would counteract that with lots of drag, but might still work somewhat if it generates enough lift at low speed. But displacement speeds are limited, even for longer "wave piercing" displacement hulls, so a foil that's to small will not get up to high enough speed to generate the required lift. Such a foil will require a planing hull to overcoming the displacement speed limit.

So if you compare different board shapes in a test, it's quite important to take the conditions and foil type into consideration. In winging, you have the additional option to direct some of the "sail" power upward, which basically reduces the lift and therefore speed required for take-off. In GWA wing races, the requirement of the flagging/pumping leg limits how small a foil racers can use, which also favors a downwind hull shape. Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

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boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

Phantom Infinite

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azymuth said..

boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

I personally think momentum is there in both winging and windfoil, and is given by the rider body connecting sail to board transferring with his own body the force from the wing/sail to the board, and the hole si getting a wind force on the center of effort which is at a certain eight respect to the board, so the rider needs to counterbalance by leaning out and getting COG aside from vertical to get an opposite and equal in size momentum in search for equilibrium.
the only difference is that in winging the sail is not connected to the center of the board and you can move it out on the opposite rail, this you can't do in windfoiling since UJ is in the middle and fix, so the stance may be dirrent, in any case sail upright for maximum trust and body leaned outward farest away possible from the sail to counteract momentum...that is why so long lines on windfoil race.

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dimacced said..

azymuth said..

boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

I personally think momentum is there in both winging and windfoil, and is given by the rider body connecting sail to board transferring with his own body the force from the wing/sail to the board, and the hole si getting a wind force on the center of effort which is at a certain eight respect to the board, so the rider needs to counterbalance by leaning out and getting COG aside from vertical to get an opposite and equal in size momentum in search for equilibrium.
the only difference is that in winging the sail is not connected to the center of the board and you can move it out on the opposite rail, this you can't do in windfoiling since UJ is in the middle and fix, so the stance may be dirrent, in any case sail upright for maximum trust and body leaned outward farest away possible from the sail to counteract momentum...that is why so long lines on windfoil race.

We don't really experience rig induced roll moments in wind foiling, nor would a wing. The Americas cup boats and GP 50s do, as their rig is stayed to the boat. That's why they have their foils set much further forward, and outboard on the leeward side, to counteract the roll moment.

I believe what he's getting at is that wind foilers have to "share" the board platform with their rig, which means we generally need to be outboard when we're up at speed. Moving your feet away from the centreline means you lose some leverage over a foil that exceeds the board width. Hence the wider boards, so we can maintain leverage over the foil when we're outboard. Wing foilers don't really have their feet too far away from the centreline of the board, so roll moment is easier to manipulate.

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Subsonic said..

dimacced said..

azymuth said..

boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

I personally think momentum is there in both winging and windfoil, and is given by the rider body connecting sail to board transferring with his own body the force from the wing/sail to the board, and the hole si getting a wind force on the center of effort which is at a certain eight respect to the board, so the rider needs to counterbalance by leaning out and getting COG aside from vertical to get an opposite and equal in size momentum in search for equilibrium.
the only difference is that in winging the sail is not connected to the center of the board and you can move it out on the opposite rail, this you can't do in windfoiling since UJ is in the middle and fix, so the stance may be dirrent, in any case sail upright for maximum trust and body leaned outward farest away possible from the sail to counteract momentum...that is why so long lines on windfoil race.

We don't really experience rig induced roll moments in wind foiling, nor would a wing. The Americas cup boats and GP 50s do, as their rig is stayed to the boat. That's why they have their foils set much further forward, and outboard on the leeward side, to counteract the roll moment.

I believe what he's getting at is that wind foilers have to "share" the board platform with their rig, which means we generally need to be outboard when we're up at speed. Moving your feet away from the centreline means you lose some leverage over a foil that exceeds the board width. Hence the wider boards, so we can maintain leverage over the foil when we're outboard. Wing foilers don't really have their feet too far away from the centreline of the board, so roll moment is easier to manipulate.

I've just posted some questions about how a speed foil board should be and why.
I will be very keen to any comment added

www.seabreeze.com.au/forums/Windsurfing/Foiling/Medium-to-strong-wind-foil-board-to-blast-around?page=1#5

p.s. my question comes after having seen a 195/71/58 ofo cm board supposed for gps foil speeding vs all other current speed foil boards being longer than 200 cm x 71 x 64 ofo.

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Subsonic said..

dimacced said..

azymuth said..

boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

I personally think momentum is there in both winging and windfoil, and is given by the rider body connecting sail to board transferring with his own body the force from the wing/sail to the board, and the hole si getting a wind force on the center of effort which is at a certain eight respect to the board, so the rider needs to counterbalance by leaning out and getting COG aside from vertical to get an opposite and equal in size momentum in search for equilibrium.
the only difference is that in winging the sail is not connected to the center of the board and you can move it out on the opposite rail, this you can't do in windfoiling since UJ is in the middle and fix, so the stance may be dirrent, in any case sail upright for maximum trust and body leaned outward farest away possible from the sail to counteract momentum...that is why so long lines on windfoil race.

We don't really experience rig induced roll moments in wind foiling, nor would a wing. The Americas cup boats and GP 50s do, as their rig is stayed to the boat. That's why they have their foils set much further forward, and outboard on the leeward side, to counteract the roll moment.

I believe what he's getting at is that wind foilers have to "share" the board platform with their rig, which means we generally need to be outboard when we're up at speed. Moving your feet away from the centreline means you lose some leverage over a foil that exceeds the board width. Hence the wider boards, so we can maintain leverage over the foil when we're outboard. Wing foilers don't really have their feet too far away from the centreline of the board, so roll moment is easier to manipulate.

I am not sure wether I got your point correctly. On foiling we are subject to torque generated by the sail, it is our body that connects the force source (sail) to the board, if you let the sail go it will fall downwind. We do not perceive that much force due to the poor power our sails/wing generates and the very low drag the foil has. Should you take off the foil and do windsurfing instead, immediately consequences are, more drag, so more sail needed, and more torque generated and you need to lean much more outboard to compensate and you perceive more clearly that your body is the connector and force, torque transfer to the board.
As a matter of fact the sail surface and efficiency of an america's cup boat is enormously different, so that they are much more efficient and get 4 times faster than wind speed, while on foiling we get almost as fast as the wind or slightly above 1,4-1,6 times the wind in the best conditions (racers with big sails and very small foil).
So less power generated =less torque, but still torque is there both in winging and windfoiling.
Should leverage being needed to compensate for torque generated by the foil underneath we have this both in winging and windfoiling alike, though wing foilers stay quite centered on the board while windfoilers need some width to counteract that.
While this is generally true, some windfoilers these days claim they feel better with straps located more towards the center of the board, I think the difference is the kind of riding you want to do: should you go faster with more power you may need leverage, and the balance you get is totally different (lean out much, longer fuselage for more power and upwind ability, more sail cloth, more board width), should you go for a more manoeuver oriented ride, you get a totaly different set up, that very much resemble the wing one (Balz muller riding the Pegasus 108 that is 60 cm wide with very mych centered straps).
I start believing that wingers need less forces to get moving, so that even poor source of pure as the wings are are able to let them go; and less forces means difenet stance on the board.

I am afraid many of the difference in stance are coming from our eritage, we have been windsurfers before getting into windfoiling so we have that kind of stance engrained, wingfoilers come from many different sports, some from kiting and they have wider stances, some from windsurfing and they tend to use the wing as a sail...there is a component of physical motor patterns we are somehow linked to and have diffciculties in abandoning. Experimenting is the only thing we can do to explore and understand.

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dimacced said..

Subsonic said..

dimacced said..

azymuth said..

boardsurfr said..
Another thing that's absent in winging is the roll momentum from the rig and mast foot, which requires wider tails to counter-act it for stable rides.

That's interesting - I feel it with smaller extreme HA wings.
Can you explain the roll forces that are unique to windfoiling please

I personally think momentum is there in both winging and windfoil, and is given by the rider body connecting sail to board transferring with his own body the force from the wing/sail to the board, and the hole si getting a wind force on the center of effort which is at a certain eight respect to the board, so the rider needs to counterbalance by leaning out and getting COG aside from vertical to get an opposite and equal in size momentum in search for equilibrium.
the only difference is that in winging the sail is not connected to the center of the board and you can move it out on the opposite rail, this you can't do in windfoiling since UJ is in the middle and fix, so the stance may be dirrent, in any case sail upright for maximum trust and body leaned outward farest away possible from the sail to counteract momentum...that is why so long lines on windfoil race.

We don't really experience rig induced roll moments in wind foiling, nor would a wing. The Americas cup boats and GP 50s do, as their rig is stayed to the boat. That's why they have their foils set much further forward, and outboard on the leeward side, to counteract the roll moment.

I believe what he's getting at is that wind foilers have to "share" the board platform with their rig, which means we generally need to be outboard when we're up at speed. Moving your feet away from the centreline means you lose some leverage over a foil that exceeds the board width. Hence the wider boards, so we can maintain leverage over the foil when we're outboard. Wing foilers don't really have their feet too far away from the centreline of the board, so roll moment is easier to manipulate.

I am not sure wether I got your point correctly. On foiling we are subject to torque generated by the sail, it is our body that connects the force source (sail) to the board, if you let the sail go it will fall downwind. We do not perceive that much force due to the poor power our sails/wing generates and the very low drag the foil has. Should you take off the foil and do windsurfing instead, immediately consequences are, more drag, so more sail needed, and more torque generated and you need to lean much more outboard to compensate and you perceive more clearly that your body is the connector and force, torque transfer to the board.
As a matter of fact the sail surface and efficiency of an america's cup boat is enormously different, so that they are much more efficient and get 4 times faster than wind speed, while on foiling we get almost as fast as the wind or slightly above 1,4-1,6 times the wind in the best conditions (racers with big sails and very small foil).
So less power generated =less torque, but still torque is there both in winging and windfoiling.
Should leverage being needed to compensate for torque generated by the foil underneath we have this both in winging and windfoiling alike, though wing foilers stay quite centered on the board while windfoilers need some width to counteract that.
While this is generally true, some windfoilers these days claim they feel better with straps located more towards the center of the board, I think the difference is the kind of riding you want to do: should you go faster with more power you may need leverage, and the balance you get is totally different (lean out much, longer fuselage for more power and upwind ability, more sail cloth, more board width), should you go for a more manoeuver oriented ride, you get a totaly different set up, that very much resemble the wing one (Balz muller riding the Pegasus 108 that is 60 cm wide with very mych centered straps).
I start believing that wingers need less forces to get moving, so that even poor source of pure as the wings are are able to let them go; and less forces means difenet stance on the board.

I am afraid many of the difference in stance are coming from our eritage, we have been windsurfers before getting into windfoiling so we have that kind of stance engrained, wingfoilers come from many different sports, some from kiting and they have wider stances, some from windsurfing and they tend to use the wing as a sail...there is a component of physical motor patterns we are somehow linked to and have diffciculties in abandoning. Experimenting is the only thing we can do to explore and understand.

Think of it this way.

If you could blink and instantly turn yourself into a statue whilst out windfoiling, then you would begin to get rig induced roll going on. That's because in turning into stone you are suddenly providing a solid linkage between the rig and the board (and foil). Any gust that hits the sail, and the leverage gets transferred to the board and sail through your solid body. The board and foil will then roll to leeward. Any lull in the wind and the sudden loss of power in the sail gets transferred to the board , and the board rolls to windward. That's what rig induced roll is.

but we, and wingers are not made of stone. Nor are our mast bases a solid connection. They're a universal joint that allows the board to roll and be put on a set angle, regardless of whether the sail is bolt upright, leant over to windward, or about to fall in the water to leeward. We get to manipulate the amount of angle that our boards sit on, regardless of gusts and lulls, and our boards don't capsize (without a concerted effort)