Pretty common thing in yachting is racing to a polar plot, obviously there are a fair few more dynamic variables with winging, but I'm curious what are the theoretical possible top speeds of foils? & at what angles. Data is key here, and I guess we're all out free riding and enjoying ourselves, but not amassing this sort of data.
I was out yesterday on a HPS700 in 12-13 knots, gusting 16 with a 5m wing. I found the more aggressive I was in turning, the easier it was, so it really has opened a new setup for me. However, my maximum speed was only 21 knots. Surely I should be able to push and go faster, but I really couldn't get much more than 21. I assume the new ART 799 will probably tick a few more boxes for me, and I'll get rid of my light wind setup where I've managed to get the HPS830 to 20 knots quite easily in 9 knots gusting 12 with a 6m wing.

I've really noticed you can get to these speeds quite easily, but you hit a cliff in going any faster.


Background info - 75kg, 4"6 x 65L board.

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King Crash said..
Pretty common thing in yachting is racing to a polar plot, obviously there are a fair few more dynamic variables with winging, but I'm curious what are the theoretical possible top speeds of foils? & at what angles. Data is key here, and I guess we're all out free riding and enjoying ourselves, but not amassing this sort of data.
I was out yesterday on a HPS700 in 12-13 knots, gusting 16 with a 5m wing. I found the more aggressive I was in turning, the easier it was, so it really has opened a new setup for me. However, my maximum speed was only 21 knots. Surely I should be able to push and go faster, but I really couldn't get much more than 21. I assume the new ART 799 will probably tick a few more boxes for me, and I'll get rid of my light wind setup where I've managed to get the HPS830 to 20 knots quite easily in 9 knots gusting 12 with a 6m wing.

I've really noticed you can get to these speeds quite easily, but you hit a cliff in going any faster.


Background info - 75kg, 4"6 x 65L board.

In my experience it has a lot to do with conditions, if there is chop present, forget about setting speed records, the fastest runs I've had were in offshore winds, flat water.
I'm 75kg, 5m wing, 60L board, 85cm mast.
On my W1000/S399 wing/stab (980 cm2), if there is chop ~18 knots, regardless of the wind speed.
On my W671/S399 wing/stab (570 cm2) pretty much the same situation in the choppy water, + ~2 knots faster.
When it's flat water it's much faster, easily + ~3-5 knots.

The old story drag verses horsepower

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stroppo said..
The old story drag verses horsepower

can you not just counter this with a longer mast?

When I was doing some stuff with a Human Powered Vehicle while at uni the largest drag producer was frontal area.
Thick foils are slow.
Longer mast doesn't change thing a heap because percentage wise it's a lot less than the horizontal foil.
Sailing in chop the foil is badly aligned with the water motion most of the time due to the cyclic motion of the water particles and giving a greater frontal area exposed to the water particles than foiling in flat water.

Just my 2c

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Jethrow said..
When I was doing some stuff with a Human Powered Vehicle while at uni the largest drag producer was frontal area.
Thick foils are slow.
Longer mast doesn't change thing a heap because percentage wise it's a lot less than the horizontal foil.
Sailing in chop the foil is badly aligned with the water motion most of the time due to the cyclic motion of the water particles and giving a greater frontal area exposed to the water particles than foiling in flat water.

Just my 2c

Yeah makes sense Jethrow definitely food for thought
Kingcrash I use the 1m mast most of the time which is my favourite especially when sending it I ride Armstrong foils and two weeks ago I pushed my 2400 foil just over 20kts with a 7m Cabrinha wing I needed the extra horsepower for the drag and ended up just under 3kts faster than I've been on that foil as I would have normally used a 5m but it was a handful and the front foot pressure was a fair bit the lift created from such a big foil and the combined pressure from the sail loading was a real buzz when I realised I cracked 20 kts on 2400 foil I'm 112kg

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stroppo said..

Jethrow said..
When I was doing some stuff with a Human Powered Vehicle while at uni the largest drag producer was frontal area.
Thick foils are slow.
Longer mast doesn't change thing a heap because percentage wise it's a lot less than the horizontal foil.
Sailing in chop the foil is badly aligned with the water motion most of the time due to the cyclic motion of the water particles and giving a greater frontal area exposed to the water particles than foiling in flat water.

Just my 2c

Yeah makes sense Jethrow definitely food for thought
Kingcrash I use the 1m mast most of the time which is my favourite especially when sending it I ride Armstrong foils and two weeks ago I pushed my 2400 foil just over 20kts with a 7m Cabrinha wing I needed the extra horsepower for the drag and ended up just under 3kts faster than I've been on that foil as I would have normally used a 5m but it was a handful and the front foot pressure was a fair bit the lift created from such a big foil and the combined pressure from the sail loading was a real buzz when I realised I cracked 20 kts on 2400 foil I'm 112kg

Pretty similar stuff to what the guys at Lake Geneva did this past regatta. Big sails for max speed, although you used a big foil, totally see the advantage.

Other factors come to play also. a lot of drag generated from big 5/6/7m wings. the greatest speed improvements will come when the LE is made smaller/thinner in my opinion

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stroppo said..
The old story drag verses horsepower

I'm guessing there is a speed where increased induced drag reaches a point where you can't apply enough power to keep accelerating.

Perhaps drag has a similar relationship to speed as wind speed and power and increases exponentially.

If you want to go faster you need a more slippery foil but then there is a price in terms of low speed handling and stability.

From what I've read the mathematics of wings is very well defined. You'd think that the designers would be able to tell us fairly accurately what the speed parameters of a wing would be. That's a little problematic because speed can drop massively with the slightest variations in wing and foil trim and water state and all the rest.

How fast can you ride your bicycle?

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waterlife said..
Other factors come to play also. a lot of drag generated from big 5/6/7m wings. the greatest speed improvements will come when the LE is made smaller/thinner in my opinion

Yep. If you've milked the foil setup for everything it's got, then you have to move down wing sizes to to avoid drag..wind permitting.....the smaller wings will produce the the same amount of lift at a higher speed if there is sufficient wind.

Now I've been at it for a while, I'd really love to try one of the Kitewing thingies they use in the snow to see how much more efficient they are.

It would be great to work out a graph of wind velocity vs wing size vs foil size just to visualise the relationship but I don't know where to start.

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Clamsmasha said..

waterlife said..
Other factors come to play also. a lot of drag generated from big 5/6/7m wings. the greatest speed improvements will come when the LE is made smaller/thinner in my opinion

Yep. If you've milked the foil setup for everything it's got, then you have to move down wing sizes to to avoid drag..wind permitting.....the smaller wings will produce the the same amount of lift at a higher speed if there is sufficient wind.

Now I've been at it for a while, I'd really love to try one of the Kitewing thingies they use in the snow to see how much more efficient they are.

It would be great to work out a graph of wind velocity vs wing size vs foil size just to visualise the relationship but I don't know where to start.

At the end of the day you're going to experience drag somewhere. The logic behind smaller foils is reducing the more dense drag. Eventually, maybe you could mill carbon plate into a wing shape, ultra thin, super powerful.
In terms of wings, smaller LE won't make much of a difference when you're reaching, at the end of the day, it's more sail area, just projected into the luff. I think we're seeing the upper end of what spinnaker cloth can do, I keep saying it but haven't had time yet. But I'll recut my 4m wing and replace the cloth with Dimension Polyant CZ cloth or light skin, whatever the loft has left over. This isn't an option really in the larger sizes, I've spoken to industry players, and they've tried the same thing, with it only working 4m and below.

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LeeD said..
How fast can you ride your bicycle?

Depends on how fast the car I'm holding onto is travelling??

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Gorgo said..

stroppo said..
The old story drag verses horsepower

I'm guessing there is a speed where increased induced drag reaches a point where you can't apply enough power to keep accelerating.

Perhaps drag has a similar relationship to speed as wind speed and power and increases exponentially.

If you want to go faster you need a more slippery foil but then there is a price in terms of low speed handling and stability.

From what I've read the mathematics of wings is very well defined. You'd think that the designers would be able to tell us fairly accurately what the speed parameters of a wing would be. That's a little problematic because speed can drop massively with the slightest variations in wing and foil trim and water state and all the rest.

Induced drag goes down with increasing speed.Parasitic drag (friction,form,interference...) goes up.

In any asymetrical foil with twist there is a speed at which the AOA becomes so low (nosedown attitude) that the tips are going to create negative lift and lots of drag.
I do not think you can push too much against this "wall" of resistance no matter how powerful the sail or skilledthe rider is (Kai Lenny tried with a rigid frame wing).

Bigger rider,smaller foil,thinner sections and more symetrical profile will increase top speed at the cost of dismal low end perfo.

All the vids i have seen claiming +30kt on a wing were on 500-600cm2 kitefoils.

On flat water and well powered but very gusty and a bit turning wind I went with my Sab W1000+399 stab, AK5.8 strapless and Airrush3m 46.7km p/h /25knots and i,m pretty sure I can go faster but it felt freaking fast. With windsurf speeding I,ve done 10secc runs of 80km p/h+ that felt less scaryNext time I wanna go fast I will try it with straps. I love to surf strappless but when going really fast I miss them when trimming the angle at speed.

Zlab S with a good pilot is fastest in US.

I don't think the drag from the wing is significant compared to the foil. Ive gone 30+ with my 6m wasp on snow and ice. My huge naish 2400 foil seems to max out near 17, but I have had a few moments above 20 that resulted in a massive crash. Feels like its the liquid water slowing me down. Im 110kg and nearly 2 m tall. Im still on my first foil but imagine a newer foil will give me the most bang for the buck in terms of speed.

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Jeroensurf said..
On flat water and well powered but very gusty and a bit turning wind I went with my Sab W1000+399 stab, AK5.8 strapless and Airrush3m 46.7km p/h /25knots and i,m pretty sure I can go faster but it felt freaking fast. With windsurf speeding I,ve done 10secc runs of 80km p/h+ that felt less scaryNext time I wanna go fast I will try it with straps. I love to surf strappless but when going really fast I miss them when trimming the angle at speed.

I've had flat water with a HPS830 and 4m wing and done 20 knots without realising it, a super chill relaxed run. That being said, I've done runs in churned water on the HPS700 with a 5m wing gybing at 21 knots and that felt pretty loose. Pretty bold to be riding strapless! What happens if you vent? I guess you're going to really experience flight.

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LeeD said..
Zlab S with a good pilot is fastest in US.

Yeah.... I've seen around here 3300USD for one of these, or 4400 AUD. That's wayyy to much for the average bear.

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mcrt said..

Gorgo said..

stroppo said..
The old story drag verses horsepower

I'm guessing there is a speed where increased induced drag reaches a point where you can't apply enough power to keep accelerating.

Perhaps drag has a similar relationship to speed as wind speed and power and increases exponentially.

If you want to go faster you need a more slippery foil but then there is a price in terms of low speed handling and stability.

From what I've read the mathematics of wings is very well defined. You'd think that the designers would be able to tell us fairly accurately what the speed parameters of a wing would be. That's a little problematic because speed can drop massively with the slightest variations in wing and foil trim and water state and all the rest.

Induced drag goes down with increasing speed.Parasitic drag (friction,form,interference...) goes up.

In any asymetrical foil with twist there is a speed at which the AOA becomes so low (nosedown attitude) that the tips are going to create negative lift and lots of drag.
I do not think you can push too much against this "wall" of resistance no matter how powerful the sail or skilledthe rider is (Kai Lenny tried with a rigid frame wing).

Bigger rider,smaller foil,thinner sections and more symetrical profile will increase top speed at the cost of dismal low end perfo.

All the vids i have seen claiming +30kt on a wing were on 500-600cm2 kitefoils.

Yep. You're right. They're on 500-600. SAB and FONE look to be the only ones catering to this niche. I'm sure we;ll see some soon.
You're also forgetting the cavitation from any instability will reduce efficiency and increase parasitic drag. Hell, just a smaller moth foil could even work, unfortunately we don't have elevators to assist getting on foil, I guess you could get towed onto foil or go really overpowered.

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Jeroensurf said..
On flat water and well powered but very gusty and a bit turning wind I went with my Sab W1000+399 stab, AK5.8 strapless and Airrush3m 46.7km p/h /25knots and i,m pretty sure I can go faster but it felt freaking fast. With windsurf speeding I,ve done 10secc runs of 80km p/h+ that felt less scaryNext time I wanna go fast I will try it with straps. I love to surf strappless but when going really fast I miss them when trimming the angle at speed.

Nice going dude that's cranking I'm also a strapless winger sending it I'm not going to do straps as I love the freedom you definitely gotta have your trim sorted but that's half the fun

Here's a video of some speeds for wind foiling, kite foiling and wing foiling. Looks scary to me!

I hit 22mph on my art999 then I tweaked my setup and found some flat water with my 6m. 24.5mph.
Got a 640cm wing which I should hopefully be able to clear 30mph. The glide is incredible but starting it requires wind in the top 1/3rd of your wings range.

you could go much smaller but there is a pract?cale point where you can only use it for speed runs as getting started requires too much power.


Curiously I didn't have a stall speed problem. Faster foils foil faster. it takes more to slow them down so maneuvers were just as easy but you were going faster. Incredible glide. Could still surf wind swell. I'd like an 800cm 10AR wing, probably the sweet spot.

Larger stab adds lots of low end.
My 600 sq cm foil is easy with a 310 stab.....very high end oriented with a 210 stab.

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JohnnyTsunami said..
I hit 22mph on my art999 then I tweaked my setup and found some flat water with my 6m. 24.5mph.
Got a 640cm wing which I should hopefully be able to clear 30mph. The glide is incredible but starting it requires wind in the top 1/3rd of your wings range.

you could go much smaller but there is a pract?cale point where you can only use it for speed runs as getting started requires too much power.


Curiously I didn't have a stall speed problem. Faster foils foil faster. it takes more to slow them down so maneuvers were just as easy but you were going faster. Incredible glide. Could still surf wind swell. I'd like an 800cm 10AR wing, probably the sweet spot.

2018 Starboard race foil with their 75cm fuselage and 255 tail could get that done for free.

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King Crash said..


Yep. You're right. They're on 500-600. SAB and FONE look to be the only ones catering to this niche. I'm sure we;ll see some soon.
You're also forgetting the cavitation from any instability will reduce efficiency and increase parasitic drag. Hell, just a smaller moth foil could even work, unfortunately we don't have elevators to assist getting on foil, I guess you could get towed onto foil or go really overpowered.

Interesting vid of foil ventilation.
Note that the tip vortex ventilation is independent of the full ventilation that happens around 00:50

I had never seen that tip ventilation,apparently as speed increases the tip vortex "tube" gets enough low pressure to suck air from downstream all the way to the tip,pretty cool :)

But it is not the cause of the main ventilation,that is air sucked from above at the foil pierces water surface.

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mcrt said..

King Crash said..


Yep. You're right. They're on 500-600. SAB and FONE look to be the only ones catering to this niche. I'm sure we;ll see some soon.
You're also forgetting the cavitation from any instability will reduce efficiency and increase parasitic drag. Hell, just a smaller moth foil could even work, unfortunately we don't have elevators to assist getting on foil, I guess you could get towed onto foil or go really overpowered.

Interesting vid of foil ventilation.
Note that the tip vortex ventilation is independent of the full ventilation that happens around 00:50

I had never seen that tip ventilation,apparently as speed increases the tip vortex "tube" gets enough low pressure to suck air from downstream all the way to the tip,pretty cool :)

But it is not the cause of the main ventilation,that is air sucked from above at the foil pierces water surface.

pretty interesting stuff. When I ride slightly bigger wingspans, you know when your ventilate a tip. Feels like you've caught a plastic bag, and you're spearing off with limited control. Often salvageable, but sometimes it just spits you out!

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King Crash said..

Jeroensurf said..
On flat water and well powered but very gusty and a bit turning wind I went with my Sab W1000+399 stab, AK5.8 strapless and Airrush3m 46.7km p/h /25knots and i,m pretty sure I can go faster but it felt freaking fast. With windsurf speeding I,ve done 10secc runs of 80km p/h+ that felt less scaryNext time I wanna go fast I will try it with straps. I love to surf strappless but when going really fast I miss them when trimming the angle at speed.

I've had flat water with a HPS830 and 4m wing and done 20 knots without realising it, a super chill relaxed run. That being said, I've done runs in churned water on the HPS700 with a 5m wing gybing at 21 knots and that felt pretty loose. Pretty bold to be riding strapless! What happens if you vent? I guess you're going to really experience flight.

An big splash.

trimming al the time limits it speed right, but riding strapless is soo much fun in the waves so I accept that.Besides: if I wanna go really fast I grab an high wind windsurf slalomset from one of my buddies.

Well.... I went through my 5m WASP twice in a week in two very non-event circumstances. I figured there was no better time than the moment, and decided to do a comparison test. I bought 2m of CZ cloth from Dimension Polyant for $42, and went about replacing panels before work. I did this in two hours over two days, I wouldn't call it an amazing job, but it'll get me on the water and offer a bit of R&D. If you zoom in on my photo, you can see the hack job I did in places. I've done a leach take up on one panel and I'm happy, I'll just ask the loft to do my 4,6 and complete this 5 if I'm happy on the water. Otherwise I'll just ride it till it explodes or tears itself apart. First two panels I completely replaced into the frame, then tracing to the wing tip, I was lazy and just did a cut out panel for final two.

The wing is no different in weight, if anything I probably lost a little weight as I didn't bother with a clew or luff patch on the center strut. A critical error? Maybe who cares, if I need to replace the entire right side of the wing, it was <$50. When I make the call, I'll ask the guys to get heaps of leach tension, this seems to be the path F-ONE has followed.

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King Crash said..



Well.... I went through my 5m WASP twice in a week in two very non-event circumstances. I figured there was no better time than the moment, and decided to do a comparison test. I bought 2m of CZ cloth from Dimension Polyant for $42, and went about replacing panels before work. I did this in two hours over two days, I wouldn't call it an amazing job, but it'll get me on the water and offer a bit of R&D. If you zoom in on my photo, you can see the hack job I did in places. I've done a leach take up on one panel and I'm happy, I'll just ask the loft to do my 4,6 and complete this 5 if I'm happy on the water. Otherwise I'll just ride it till it explodes or tears itself apart. First two panels I completely replaced into the frame, then tracing to the wing tip, I was lazy and just did a cut out panel for final two.

The wing is no different in weight, if anything I probably lost a little weight as I didn't bother with a clew or luff patch on the center strut. A critical error? Maybe who cares, if I need to replace the entire right side of the wing, it was <$50. When I make the call, I'll ask the guys to get heaps of leach tension, this seems to be the path F-ONE has followed.

Wow, very impressive.
Wether it works or not it looks killer!.

Starboard/Airush had a wing with similar cloth in a catalogue i was shown before last summer but i do not know if they made any.

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King Crash said..



Well.... I went through my 5m WASP twice in a week in two very non-event circumstances. I figured there was no better time than the moment, and decided to do a comparison test. I bought 2m of CZ cloth from Dimension Polyant for $42, and went about replacing panels before work. I did this in two hours over two days, I wouldn't call it an amazing job, but it'll get me on the water and offer a bit of R&D. If you zoom in on my photo, you can see the hack job I did in places. I've done a leach take up on one panel and I'm happy, I'll just ask the loft to do my 4,6 and complete this 5 if I'm happy on the water. Otherwise I'll just ride it till it explodes or tears itself apart. First two panels I completely replaced into the frame, then tracing to the wing tip, I was lazy and just did a cut out panel for final two.

The wing is no different in weight, if anything I probably lost a little weight as I didn't bother with a clew or luff patch on the center strut. A critical error? Maybe who cares, if I need to replace the entire right side of the wing, it was <$50. When I make the call, I'll ask the guys to get heaps of leach tension, this seems to be the path F-ONE has followed.

Very cool. Id love to see a separate thread all about what you did. How did you attach the cloth to the leading edge? Looks like you have an additional panel towards the tip. I think a radial pattern will be needed to get higher tension, which would be tricky to create the right shape. Did you use the old panels as a template for cutting out the Dimension?

An update from first session. I tried to make this as clear and in depth as possible. My wife just bought me a new apple watch, so I used the water speed app, but I ran the watch out of battery, so I have no definitive max speed, the app did announce my distance up until it died. So last I remember was 59kms foiled, then it died and I did another 15-20 mins. So I assume, 65-70 km's in 2.5 hour session.

Conditions: 13-15 knots building to 25, NE breeze.
Foil: HPS700 and 420 tail
Board: Starboard 4"6 x 69L

Initially got out in moderate conditions, didn't take much effort to pump up, I would say easier to pump up in this lighter stuff. Immediate full power on foil. Wing was very, very light on my arms, I will circle back to this later. I was cruising around, I did 35kms distance foiled in 1hr. So I had the hammer down and was just chilling.
I found some very flat water and did two tests here, maximum speed and sail out of the wind. The second to see how far could I pump the wind and stay on foil in no wind.
When the wind did build, I was really left to only speed runs and keeping off the breeze, I need another leach take up, the leach was flapping like mad. Also..... I need a luff patch, the cloth started tearing off the bladder, I kept purposely crashing to review everything and this is the only point that needs remedying. The 'tearing' was very minor and really just a point to keep this wing going forever, if I wanted to, I could never do this, but I want this now on all my wings.

Speed runs - This was absolutely insane. I have never taken the HPS700 to its limit like this, I had my primary foot in the foot strap, back foot had my toes in the front strap and majority of foot over the centreline. I was using full body weight to stop the foil breaching. Lesson, I need a smaller foil. I have no idea how fast I was going due to the watch dying. But if anyone has tow foiled the HPS700 and maxed it, there you go. I assume I was doing 25 knots +. But I don't know. I was very comfortable at these speeds, very balanced and the wing just wanted to keep accelerating.

No wind pump: The HPS700 isn't really for pumping and you need power for lulls. On a normal wing, I would try and find myself falling off foil. I was within touching distance of the wind line, I doubled my distance in no wind. If you pump, the response is immediate and powerful. I also tried a zero wind pump up, the wing was no heavier in my arms in no wind, I was curious on the point. I could not zero wind pump up with only half the wing replaced. I got very close though, I was porpoising but was just missing that final point, keep in mind, this was zero wind.

I carried the 5m much higher in the wind range than I would usually, I swapped down only because the leach was flapping. It was annoying and I thought I had performed my experiment well. I swapped down to the 4m and did another 20kms. This was an interesting point, the 4m was more taxing on my body on the than the 5. My forearms and back straight away felt the additional load, I hardly felt doing 50kms on the 5m, I'm sore today from the remainder on the 4m.

I was jumping on both the 5m and 4m, the 5 was bloody easy, I flew up and was doing huge jumps and tricks, when the breeze built for the 4, there were even ramps in wind swell, I wasn't getting anywhere near the height, and the strain was much higher.


Take away - I need a smaller foil. HPS700 is too big, rumour mill tells me I'll be sorted on this point soon without having to get the 650. Even then, I'll take a 650 in the meantime.

Wings - I'll be replacing all my wings with CZ cloth now. I need to work a bit more on leach shape and make a luff patch, but apart from that, this ticked every box.

As others have said, if you want to go properly fast (25-30+ knots) you will need a foil that is designed for those speeds . From what I've read the SAB W1000 ( windfoil racing ) is good for 25kts, the local guys who have cracked 30kts were using SAB 671 wing ( kitefoil racing- small) , the guy who cracked 30 knots at Lake Garda during the racing recently was on a Levitaz R5 - top end current racing kitefoil. The rest of us can forget hitting these speeds on our regular winging foils, they are simply too thick and draggy , even the HA ones. Most people will be doing well to crack 20kts fully powered up. So the issue seems to be the foil , not the hand wing, even though we think the latter is relatively crude it is clearly capable to getting you to 30kts if the rest of the package is low drag and designed for speed.