Hello, I am wondering what are the components that give glide to a foil.

AR? Thickness? Surface area? Weight? Shape of the front wing?

For example I have an F-One Phantom fct 1480 foil set and the front wing has an aspect ratio of 6.2, the thickness is not much for both front wing and stab, but I haven't measure it. When I try dock starts the glide doesn't last for much longer than a second before slowing down past the point of no return. I heard from the mouth of Tituan Galea that he uses this foil for dock starts but the difference in glide compared to one of those super high aspect sabfoils or axis foils that everyone uses for dock starts is just immense. I can't use this one for dock starts.

What do you say, if my front wing had an AR of 9 instead of 6.2, but always 1480cm2 of surface, would it have more glide?

In theory a higher aspect ratio would give you more glide. But possibly this isn't what you're lacking. Titouan will keep pumping at speeds a dockstart beginner won't be able to reach. Thick profiles tend to reduce stall speed, which is why dedicated pump foils have thick profiles regardless of their aspect ratio.
Go for something big and thick to learn!

In theory a higher aspect ratio would give you more glide. But possibly this isn't what you're lacking. Titouan will keep pumping at speeds a dockstart beginner won't be able to reach. Thick profiles tend to reduce stall speed, which is why dedicated pump foils have thick profiles regardless of their aspect ratio.
Go for something big and thick to learn!

Glide is ratio of the horizontal distance an unpowered foil will travel divided by the height loss. So a foil with good glide might travel 10 metres losing only 30cm, whereas a foil with poor glide might only travel 3 metres for a loss of 30cm.

It is determined by the maximum lift:drag ratio, which occurs at an Angle of Attack around 5 degrees. Glide is worse at higher or lower AoA.

To maximise it, you want to either increase lift without increasing drag too much, or reduce drag without reducing lift. Increasing the Aspect Ratio is the best way. However, reducing stabiliser size, or anything else that reduces drag without affecting lift will help.

You might think that thin foils have better glide due to less drag, but often they reduce lift more than reducing drag, so have a lower lift:drag ratio.

For a given foil and rider, there will be an optimum speed for glide, corresponding to the L/Dmax AoA. For pumping, it's ideal that this speed is low, as air resistance will be lower.

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BritWinger said..
Glide is ratio of the horizontal distance an unpowered foil will travel divided by the height loss. So a foil with good glide might travel 10 metres losing only 30cm, whereas a foil with poor glide might only travel 3 metres for a loss of 30cm.

It is determined by the maximum lift:drag ratio, which occurs at an Angle of Attack around 5 degrees. Glide is worse at higher or lower AoA.

To maximise it, you want to either increase lift without increasing drag too much, or reduce drag without reducing lift. Increasing the Aspect Ratio is the best way. However, reducing stabiliser size, or anything else that reduces drag without affecting lift will help.

You might think that thin foils have better glide due to less drag, but often they reduce lift more than reducing drag, so have a lower lift:drag ratio.

For a given foil and rider, there will be an optimum speed for glide, corresponding to the L/Dmax AoA. For pumping, it's ideal that this speed is low, as air resistance will be lower.

Hey great explanation BritWinger and do you think a longer fuselage greats a bit more drag than a shorter fuselage or is it about the same if everything else is unchanged?;-)thanks:-)

Hi Johndesu,

a longer fuselage would create more parasitic drag than a short fuselage, however the difference is relatively minor. The benefit of the longer fuselage though, is you can run a smaller rear wing (or less angle on the same rear wing) to produce the same effective stabilization of the front wing's pitching moment. It also makes the foil a bit slower to react, a negative for turning performance, but would dampen the flight oscillations from rider fore/aft movements. This would also increase efficiency, but hard to say by how much. I expect it would be considerable for a beginner but less so for a more experienced rider with better pitch control.

Eddy, have you tried playing with rear wing shims?

As Omen says, a tiny bit more drag, probably not noticeable for small increases in length.

Longer fuselage increases stability, but at the expense of maneuverability, especially yaw.

Eddy, most of the dockstarters say it takes about 300 tries to get it right, so there may be some practice sessions ahead, but I'm sure a good foil will always help out

The glide is determined by the lift to drag ratio. Wing shape, surface area, AR, foil section, anhedral, and tip washout will all affect the lift to drag ratio. Higher AR reduces the induced drag, and therefore improves glide, but it's not the only variable.

From your description the foil you've got sounds like it should be pumpable. I've seen videos on Youtube of people pumping the Slingshot i76 foil and that thing is draggy. AR of 3.7 and area of 1534cm?.
That said, pumping is hard and takes lots of practice.

Thanks everyone for the great answers!

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BritWinger said..
Glide is ratio of the horizontal distance an unpowered foil will travel divided by the height loss. So a foil with good glide might travel 10 metres losing only 30cm, whereas a foil with poor glide might only travel 3 metres for a loss of 30cm.

It is determined by the maximum lift:drag ratio, which occurs at an Angle of Attack around 5 degrees. Glide is worse at higher or lower AoA.

To maximise it, you want to either increase lift without increasing drag too much, or reduce drag without reducing lift. Increasing the Aspect Ratio is the best way. However, reducing stabiliser size, or anything else that reduces drag without affecting lift will help.

You might think that thin foils have better glide due to less drag, but often they reduce lift more than reducing drag, so have a lower lift:drag ratio.

For a given foil and rider, there will be an optimum speed for glide, corresponding to the L/Dmax AoA. For pumping, it's ideal that this speed is low, as air resistance will be lower.

Amazing explanation thanks! I'm curious to know: why max L:D ratio happens at 5 degrees?

Also I'm not sure I understand correctly, but when you said L/Dmax AoA corresponds to optimal speed for glide, what did you mean? L/Dmax basically is equivalent to saying maximum glide, right? So max glide angle of attack corresponding to optimal speed for glide... I don't follow I'm sorry.

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Omen said..
Hi Johndesu,

a longer fuselage would create more parasitic drag than a short fuselage, however the difference is relatively minor. The benefit of the longer fuselage though, is you can run a smaller rear wing (or less angle on the same rear wing) to produce the same effective stabilization of the front wing's pitching moment. It also makes the foil a bit slower to react, a negative for turning performance, but would dampen the flight oscillations from rider fore/aft movements. This would also increase efficiency, but hard to say by how much. I expect it would be considerable for a beginner but less so for a more experienced rider with better pitch control.

Eddy, have you tried playing with rear wing shims?

Hi Omen, forgive my ignorance but I don't know what shims means. I'm gonna assume it means just stabilizers, and nope, I have only 1 stab for now

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RAF142134 said..
Eddy, most of the dockstarters say it takes about 300 tries to get it right, so there may be some practice sessions ahead, but I'm sure a good foil will always help out

Hey Raf! Thanks for the heads up hehe, yeah I know it's not so easy, but I think I have a good few hundred tries under my belt. Although I'm sure I can improve my technique more! I have seen a guy on YouTube dock starting with my exact foil so I know it's doable. The thing I'm wondering is how long he can keep it going for... Certainly doesn't look as easy as other foils though.

I would like to buy a foil set to do pumping very easily and keep it going for a long time (like a few minutes at least). I was thinking either an Axis PnG or a Sabfoil leviathan. I weight 50kg and my father weighs 85kg. It would be great to find something that works for both and was wondering what wingspan would be the best middle ground for us both.

I play a lot with stab and fuse, fuse has a lot of incident on turning, stability, but I do not feel a lot on drag. However stab with good HA foil it's insane, a bit less noticeable with thicker mid aspect more draggy foil. You can feel it with bulkier foil, but you are used at the slowing down when you just stop pumping...or when you flag a wing. A good glider with a slower ticker stab is like having something on your foil...like weed..you just feel the steady deceleration!

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eddyjmthewll said..
I would like to buy a foil set to do pumping very easily and keep it going for a long time (like a few minutes at least). I was thinking either an Axis PnG or a Sabfoil leviathan. I weight 50kg and my father weighs 85kg. It would be great to find something that works for both and was wondering what wingspan would be the best middle ground for us both.

Leviathan is a significantly newer foil. I'd go 1350.