Wyatt says
"One thing that all these Infinity wings have in common is they all have the downforce in the wingtips that kicks in at higher speeds. They're all really self-regulating wings that stop you from over lifting at higher speeds. On all these wings in the Infinity line, you have a lot of lift coming from the center of the wing at slow speeds. Then as you move to a higher speed, this sort of downforce in the wingtips, very similar to the twist-off in your windsurf sails, causes it to pull down a little bit at higher speeds. So instead of having to get further and further forward on the board, the faster you go, which is uncomfortable, you're actually able to get more under both feet at medium speeds and then get back onto your back foot at really high speeds as it wants to pull down just slightly and really drive it faster".

I've actually measured a 2 degree downward twist in wing from the root to the tip. Is this what he is talking about? And I do understand that at higher speeds, you do lower the angle of attack because you don't need a ever increasing abouts of lift. And it's probably nice that wing would stall first at root rather than at one of the tips.

My experience is limited. Are other brands doing the same thing? Does this feature delay the wing breaching the surface? Is Wyatt's less downforce in the wingtips a description of less lift in the wingtips at the lower angles of attack associated with higher speeds and wing twist?

Select to expand quote

lakeeffect said..
Wyatt says
"One thing that all these Infinity wings have in common is they all have the downforce in the wingtips that kicks in at higher speeds. They're all really self-regulating wings that stop you from over lifting at higher speeds. On all these wings in the Infinity line, you have a lot of lift coming from the center of the wing at slow speeds. Then as you move to a higher speed, this sort of downforce in the wingtips, very similar to the twist-off in your windsurf sails, causes it to pull down a little bit at higher speeds. So instead of having to get further and further forward on the board, the faster you go, which is uncomfortable, you're actually able to get more under both feet at medium speeds and then get back onto your back foot at really high speeds as it wants to pull down just slightly and really drive it faster".

I've actually measured a 2 degree downward twist in wing from the root to the tip. Is this what he is talking about? And I do understand that at higher speeds, you do lower the angle of attack because you don't need a ever increasing abouts of lift. And it's probably nice that wing would stall first at root rather than at one of the tips.

My experience is limited. Are other brands doing the same thing? Does this feature delay the wing breaching the surface? Is Wyatt's less downforce in the wingtips a description of less lift in the wingtips at the lower angles of attack associated with higher speeds and wing twist?

I don't have experience with other brands. My experience with Sling Shot foils is that these claims are largely hype -- in higher winds (gusts) my i76 has much more lift and will breach unless I'm proactive (head upwind and put a great deal of my weight and force forward or partially luff the sail). My i76 does not self-regulate and negate lift at higher speeds or, if it does, it's not much -- not enough stop a breach without some serious intervention by yours truly.

Select to expand quote

dejavu said..

lakeeffect said..
Wyatt says
"One thing that all these Infinity wings have in common is they all have the downforce in the wingtips that kicks in at higher speeds. They're all really self-regulating wings that stop you from over lifting at higher speeds. On all these wings in the Infinity line, you have a lot of lift coming from the center of the wing at slow speeds. Then as you move to a higher speed, this sort of downforce in the wingtips, very similar to the twist-off in your windsurf sails, causes it to pull down a little bit at higher speeds. So instead of having to get further and further forward on the board, the faster you go, which is uncomfortable, you're actually able to get more under both feet at medium speeds and then get back onto your back foot at really high speeds as it wants to pull down just slightly and really drive it faster".

I've actually measured a 2 degree downward twist in wing from the root to the tip. Is this what he is talking about? And I do understand that at higher speeds, you do lower the angle of attack because you don't need a ever increasing abouts of lift. And it's probably nice that wing would stall first at root rather than at one of the tips.

My experience is limited. Are other brands doing the same thing? Does this feature delay the wing breaching the surface? Is Wyatt's less downforce in the wingtips a description of less lift in the wingtips at the lower angles of attack associated with higher speeds and wing twist?

I don't have experience with other brands. My experience with Sling Shot foils is that these claims are largely hype -- in higher winds (gusts) my i76 has much more lift and will breach unless I'm proactive (head upwind and put a great deal of my weight and force forward or partially luff the sail). My i76 does not self-regulate and negate lift at higher speeds or, if it does, it's not much -- not enough stop a breach without some serious intervention by yours truly.

I'm riding the i76 since round a half year on a lake with gusty winds. Round 25-30 Sessions on a Wizard 125 wiith round 90 kg driver weight.I have also a view to the self regulating System. So my experience on it is a bit different:
At half wind the Wing get's easy more lift was you need. But half or a bit downwind I use most for start.
In the fly I just detected some different points:
1) When I have more pressure in the sail often I put the wing down that I can fly on half mast hight. This position enables to put more speed on it without getting more lift. In that position I can drive more half wind. There it't seems that I can feel a bit of self regulation.
2) If I have a lot of pressure in the sail and want to drive more half wind for me it's very difficutl to not get over lifted. When I have lot of pressure in the sail and don't want to pick up more speed two options:
- Fly directly in the wind with using the trapez.
- Fly a direction inbetween until half wind without the trapez, then open the sail very well and take it in the fron with "two fingers" (so very less force.

How the self regulation should work, I don't know. But in some situations it's easier for me to avoid overlifting with taking more spoeed on the wing. But moren then 21,59 knots I haven't reached until know.

Greetings....fly high....and have fun..
Michael

F-One Levo 900cm2 works with a similar concept (was 2 years earlier than slingshot with its introduction tbh) but works way better because the wings are higher aspect, smaller and the twistpattern have been in the R&D phase for a long long time with many many prototypes.

For the Levo, balance doesnt change with speed, for me speeds of 27-28 (and even 30+) knots are very accessible and achieved pretty much every session with a 4.9 wavesail and small (72x180cm / 105L) foilboard in 15-20 knots of wind.

Select to expand quote

WhiteofHeart said..
F-One Levo 900cm2 works with a similar concept (was 2 years earlier than slingshot with its introduction tbh) but works way better because the wings are higher aspect, smaller and the twistpattern have been in the R&D phase for a long long time with many many prototypes.

For the Levo, balance doesnt change with speed, for me speeds of 27-28 (and even 30+) knots are very accessible and achieved pretty much every session with a 4.9 wavesail and small (72x180cm / 105L) foilboard in 15-20 knots of wind.

You say it "works way better" - do you have any videos of wave-riding or carving windswells with the wing?

Select to expand quote

azymuth said..

WhiteofHeart said..
F-One Levo 900cm2 works with a similar concept (was 2 years earlier than slingshot with its introduction tbh) but works way better because the wings are higher aspect, smaller and the twistpattern have been in the R&D phase for a long long time with many many prototypes.

For the Levo, balance doesnt change with speed, for me speeds of 27-28 (and even 30+) knots are very accessible and achieved pretty much every session with a 4.9 wavesail and small (72x180cm / 105L) foilboard in 15-20 knots of wind.

You say it "works way better" - do you have any videos of wave-riding or carving windswells with the wing?

No, its a flatwater / pumpnjump / freestyle wing. In my opinion the wing is also miles ahead in those terms, but in the context of the post quoted above I meant to say the concept of the twistpattern, as worked out in the F-One, works better than the slingshots version, for the powerposition just does not move at all at speed, making the foil very stable also when going very fast!

In a slingshot type wing with such an almost logarithmic increase in lift over speed, its very hard to get exactly right, for your margin of error is way smaller than with a more linearly lifting wing. As you might understand? Since the lift curve of the slingshot wing over speed is logarithmic, the effect of the twist should also be logarithmic, which would be really hard to design correctly

www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

This U-2 airplane with the wing twist was designed 65 years ago so we can agree that its an old idea. Most airplanes have this feature, and its purpose is that in a stall the wing will stall first at the root and then at the tip. This controls the tendency to roll. If you stalled at the tip first on that side of the airplane the wing would loose lift. The airplane would roll severely and perhaps crash into the ground.

A foil wing is different. I think what F-One and Slingshot are doing with twist is changing the relationship between angle of attack and increases and decreases in lift . I suspect twist reduces the lift response to increases or decreases in angle of attack. I don't know who does it better, F-One or Slingshot. But there is no doubt that both do it.

When I started this post I was truly baffled. Thank you for your replies. They have been helpful.

Select to expand quote

CAN17 said..
www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

www.instagram.com/Bartkramer505/

There's enough on there, but you're right, marketing could be improved ;). In the videos you cite they use the 2016 model, which I think is no fair comparison. None of the 2016 windfoils were particularly easy. We dont have much video on the newer foils.

Select to expand quote

WhiteofHeart said..

CAN17 said..
www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

www.instagram.com/Bartkramer505/

There's enough on there, but you're right, marketing could be improved ;). In the videos you cite they use the 2016 model, which I think is no fair comparison. None of the 2016 windfoils were particularly easy. We dont have much video on the newer foils.

In your low wind pumping video, were you using a F-One Levo wing? Another?

Select to expand quote

WhiteofHeart said..

CAN17 said..
www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

www.instagram.com/Bartkramer505/

There's enough on there, but you're right, marketing could be improved ;). In the videos you cite they use the 2016 model, which I think is no fair comparison. None of the 2016 windfoils were particularly easy. We dont have much video on the newer foils.

There you go very cool Bart. You should start being in more f-one vids
Particularly liked the foiling 360 video.

How cold is it in feburary there?

Select to expand quote

lakeeffect said..

WhiteofHeart said..

CAN17 said..
www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

www.instagram.com/Bartkramer505/

There's enough on there, but you're right, marketing could be improved ;). In the videos you cite they use the 2016 model, which I think is no fair comparison. None of the 2016 windfoils were particularly easy. We dont have much video on the newer foils.

In your low wind pumping video, were you using a F-One Levo wing? Another?

The one with the racing sail was with my racefoil, which is 872cm2 for the largest wing. The Levo is roughly equally quick to fly though, just not as powerful when up in the air, which has to do with the overall fuselage geometry, and twist funnily enough.

This years coldest session for me was about 5 degrees C, which is relatively warm for winter, haven't had to use boots yet. Last few winters have shown it can both freeze and be 12-14 degrees C from December up to March and change from the one to the other within 2 days.

(That rocket was on flat water in a little bay area, only 30m after I got flying hahah)

I have some really cool 15 pic jibe sequences too, but I haven't figured out the format in which I want to post them..

But yeah, to write an "on topic" conclusion to the question:

Twist in the wingtips are meant to decrease power as speed increases. Without the twist the wing would power up more and more as speed increases an would have to require you to shift way forward alot to keep the wing in the water. When speed increases, you automatically also start riding more and more "flat" to decrease power, this goes for any wing, but with twist in the tips you basically gradually reduce the wings "active" surface as the speed increases / angle of attack decreases, making for a more stable ride.

With "too little" twist you get a similar effect as with the "right" twist, albeit a little too little so you'll still have to shift your weight forward if you accelerate. With "too much" twist the wingtips will eventually start lifting in the wrong direction or causing ventilation, depending on the profile. Both is bad. Downward pull in the tips gives the wings an "overly stable" sensation, I think we all know what ventilation feels like. (Same as when you have too little speed and drop out of the air, or breach a wingtip) additionally I feel a wing with a little twist is slightly faster than a wing without across the wind, but I'm not sure if thats purely due to the wing being faster, or a sideeffect of the added controll so to speak.

The downside of adding twist in the wing, is that you loose some power (duh), thats why most racefoils dont have any twist in them. They rely on greatly increasing power over speed to achieve ridiculous up/downwind angles. A wing with more twist will never reach the same angles up and downwind.

I think that except only for freeride, twist in the wings is the direction the "slalom" focussed wings are going to take in the future, when a clear division between "race" and "slalom" wings are going to form.

Select to expand quote

WhiteofHeart said..

lakeeffect said..

WhiteofHeart said..

CAN17 said..
www.google.ca/url?sa=t&source=web&rct=j&url=https://www.f-one.world/product/levo-900/&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAB6BAgAEAI&usg=AOvVaw1Bg8M6sxVEMmuAeBK0IN-T

www.google.ca/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DXpAZCP_hBXs&ved=2ahUKEwjX49qh7J3oAhVBZN8KHd0EDdUQo7QBMAJ6BAgAEAY&usg=AOvVaw3WXujnOMZ3VcV70GZNoeOg

JJ I think you need to start making videos for F-one because these ones needs help!

I don't see Flatwater, pump and jump, freestyle moves or wingtips. The proof needs to be in the pudding.

www.instagram.com/Bartkramer505/

There's enough on there, but you're right, marketing could be improved ;). In the videos you cite they use the 2016 model, which I think is no fair comparison. None of the 2016 windfoils were particularly easy. We dont have much video on the newer foils.

In your low wind pumping video, were you using a F-One Levo wing? Another?

The one with the racing sail was with my racefoil, which is 872cm2 for the largest wing. The Levo is roughly equally quick to fly though, just not as powerful when up in the air, which has to do with the overall fuselage geometry, and twist funnily enough.

This years coldest session for me was about 5 degrees C, which is relatively warm for winter, haven't had to use boots yet. Last few winters have shown it can both freeze and be 12-14 degrees C from December up to March and change from the one to the other within 2 days.

(That rocket was on flat water in a little bay area, only 30m after I got flying hahah)

I have some really cool 15 pic jibe sequences too, but I haven't figured out the format in which I want to post them..

But yeah, to write an "on topic" conclusion to the question:

Twist in the wingtips are meant to decrease power as speed increases. Without the twist the wing would power up more and more as speed increases an would have to require you to shift way forward alot to keep the wing in the water. When speed increases, you automatically also start riding more and more "flat" to decrease power, this goes for any wing, but with twist in the tips you basically gradually reduce the wings "active" surface as the speed increases / angle of attack decreases, making for a more stable ride.

With "too little" twist you get a similar effect as with the "right" twist, albeit a little too little so you'll still have to shift your weight forward if you accelerate. With "too much" twist the wingtips will eventually start lifting in the wrong direction or causing ventilation, depending on the profile. Both is bad. Downward pull in the tips gives the wings an "overly stable" sensation, I think we all know what ventilation feels like. (Same as when you have too little speed and drop out of the air, or breach a wingtip) additionally I feel a wing with a little twist is slightly faster than a wing without across the wind, but I'm not sure if thats purely due to the wing being faster, or a sideeffect of the added controll so to speak.

The downside of adding twist in the wing, is that you loose some power (duh), thats why most racefoils dont have any twist in them. They rely on greatly increasing power over speed to achieve ridiculous up/downwind angles. A wing with more twist will never reach the same angles up and downwind.

I think that except only for freeride, twist in the wings is the direction the "slalom" focussed wings are going to take in the future, when a clear division between "race" and "slalom" wings are going to form.

As usual, your explanation is top notch! Thanks, Brant

On my i76, I have not noticed the pulling down of the wing at higher speeds that wyatt mentions, maybe I just do not let myself reach a high enough speeds for that too happen, or perhaps it is a more subtle effect

But yesterday I did notice an interesting reduction in lift with my i99 in a strong gust. The board powered up and there was a noticeable need for less front foot pressure to keep the board level, only one data point though...

I dont know what the Infinity wings trailing edge looks like exactly, but this is the twist in my wing ;).

I dont think the goal of the Infinity's twist is to create a downward pull at speed, rather to have the tips just do nothing at a certain point. A downward pull at the wingtips leads to some bad behavior in my experience and is something we aim to avoid.

I think it would be very hard to notice the effect of the twist by using only that wing. Its not an effect which "kicks in" at higher speeds, but if done well works gradually. If you were to compare your Infinity wing to the same wing with no twist I think you'd feel a noticable difference, where the wing without twist overpowers very quickly compared to the Infinity you're using and requires a lot more front foot preassure to keep down at speed.

That twist is called "washout" in aircraft and it's to promote safer stalling characteristics at the expense of efficiency.

What Slingshot (probably F-one too) is doing is using an airfoil with a reflexed trailing edge which creates a stable center of lift across a range of speeds. This is why the foot pressure changes less.

Compare that with the original H2 wing which has an undercambered foil, which creates a lot of lift for it's size but has an unstable center of lift. So foot pressure changes a lot with speed changes.

Select to expand quote

Grantmac said..
That twist is called "washout" in aircraft and it's to promote safer stalling characteristics at the expense of efficiency.

What Slingshot (probably F-one too) is doing is using an airfoil with a reflexed trailing edge which creates a stable center of lift across a range of speeds. This is why the foot pressure changes less.

Compare that with the original H2 wing which has an undercambered foil, which creates a lot of lift for it's size but has an unstable center of lift. So foot pressure changes a lot with speed changes.

thanks

Select to expand quote

Grantmac said..
That twist is called "washout" in aircraft and it's to promote safer stalling characteristics at the expense of efficiency.

What Slingshot (probably F-one too) is doing is using an airfoil with a reflexed trailing edge which creates a stable center of lift across a range of speeds. This is why the foot pressure changes less.

Compare that with the original H2 wing which has an undercambered foil, which creates a lot of lift for it's size but has an unstable center of lift. So foot pressure changes a lot with speed changes.

I transferred the I84 profile with profile gauge used to cut flooring to a piece of paper. I can't say it doesn't have a reflexed trailing edge, but I can say I didn't see one. The exercise was only accurate enough to say the profile has a 14% thickness relative to the cord and a 3.5% camber.

Perhaps you are right, maybe what I saw as reflex is just washout.

The Infinity wings definitely use a better airfoil compared with any of the undercambered ones.

Select to expand quote

thedoor said..
On my i76, I have not noticed the pulling down of the wing at higher speeds that wyatt mentions, maybe I just do not let myself reach a high enough speeds for that too happen, or perhaps it is a more subtle effect

But yesterday I did notice an interesting reduction in lift with my i99 in a strong gust. The board powered up and there was a noticeable need for less front foot pressure to keep the board level, only one data point though...

Out of my experience you need to put speed on it to get the down force effect. With high pressure in the sail in low speed I also don't feel it. My advice:- Open the sail A BIT...
- go halfwind----
- Then sheeting the sail in AND in the same moment press on the front hand the board a bit more down
- normally you should pick up some speed with this little action ....then push your course more again the wind....and bring it slowely more a bit out of the water....- Perhaps it helps to keep the back foot before the back straps....


Have fun....