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Upwind/Downwind Technique?

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Re: Upwind/Downwind Technique?

Postby Peter_Frank » Wed Apr 29, 2015 12:18 am

grania wrote:As I get more used to my foil, this is a similar question I have wondered about.
For pushing upwind as hard as you can, are you better to lean back and have the foil at a 45 degree angle in the water? (like leaning hard against a board rail)
Or are you better to stay more upright, but angle it "with the fins" like you might with a surfboard?

Seems like that might be a dumb question....but there it is. :?:
Not a dumb question at all.

Many think the mast/strut acts as a lifting wing, but it does not really.

You should angle the board as much as possible to windward, and use the "wing" to give you the upwind lift component :thumb:

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Re: Upwind/Downwind Technique?

Postby nickrh » Wed Apr 29, 2015 4:57 am

Randahl wrote:
Randahl wrote:What have you found are the best techniques for going upwind and downwind?

Aside from rider weight and kite size and wing size and wind speed, what are the best practices?

Say you are on a 15m Chrono and a Sword2 in 12-14 mph winds trying to get around a course.

For upwind:
How do you trim the kite? Fully powered, depowered a little?
From your trim setting how do you sheet? are you trying to let it fly or are you sheeting as much as possible without stalling it? I have been experimenting with depowering a little to sse if it would point higher, but I don't know.

How about where you hold the kite in the sky? down low? at 45 degrees? higher? I suspect 45 degrees...

How about how you heel over on the foil? heel over as far as you can?

Is it better to point as high as you can even if you feel like you are barely hanging onto foiling speed or is it better to go faster but not point as high?

For downwind:

Where do you hold the kite in the sky?
Sheeted in or let it fly?
heel the foil against the kite or ride more upright?

All good commentary but sort of off the topic. I used this equipment as an example because it's what I have and probably representative of the equipment that the top upwind downwind riders are using (the R1 and the other new kites and foils notwithstanding)

I am asking about technique, not equipment.
My bad, but the point was the downwind technique perhaps depends on the equipment's efficiency.

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Re: Upwind/Downwind Technique?

Postby dusta » Wed Apr 29, 2015 7:34 am

darippah wrote:Is it really possible to go downwind faster than the wind without sining the kite?
totally doable

monday i was out in around 10 knots and was hitting 20 knots downwind and i have only been on my foil for 4 hours . Parked my kite and just held on .

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Re: Upwind/Downwind Technique?

Postby Tone » Wed Apr 29, 2015 8:29 am

darippah wrote:Is it really possible to go downwind faster than the wind without sining the kite?
There is a vid somewhere of Robbie Douglas going something like 47 knots in 17 knots of wind. He is going off the wind, not dead downwind but very deep all the same. It's all about the resistance of the fins/foil and the performance of the kite (apparent wind)

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Re: Upwind/Downwind Technique?

Postby Tone » Wed Apr 29, 2015 8:31 am

grania wrote:As I get more used to my foil, this is a similar question I have wondered about.
For pushing upwind as hard as you can, are you better to lean back and have the foil at a 45 degree angle in the water? (like leaning hard against a board rail)
Or are you better to stay more upright, but angle it "with the fins" like you might with a surfboard?

Seems like that might be a dumb question....but there it is. :?:
going by how the racers go upwind, heel that sucka over and keep the kite at 30-45 degrees.
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Re: Upwind/Downwind Technique?

Postby JanneR » Wed Apr 29, 2015 8:59 am

Do I need to sine to go deep downwind with hydrofoil?
How can I go upwind / downwind more than speed of wind?
Why can I sail very deep downwind with a foilkite?

Please read following longish explanation with care. It may be helpful :)

Answer: Apparent wind speed + Apparent wind ANGLE (especially downwind)

When one is hydrofoiling with a race foil (very low hydrodynamic drag) and flying a sophisticated race kite (Elf, Chrono, Sonic etc.) with high performance (low aerodynamic drag, high lift from sailplane-like high-aspect ratio wing, low drag thin flying lines + bridle) then one is sailing upwind faster than the wind. How/why? At take off procedure, due to kites airspeed(sine/dive/loop)-produces power to pull rider + board through/out of the water. There is a lot of hydro drag from board / rider body when waterstarting, this needs a lot of pull to come over. Once starting to fly, the drag goes to minimal, perhaps to only 2-3% of the starting drag.

What happens then? The speed will accelerate, due to diminished hydro drag. Then, the kite will have increased airspeed. This results in increased lift=pull. This results in increased speed on water (boatspeed), which results in increased airspeed again, and increased lift and we are off!!! The acceleration stops, and max speed found only, when the hydro drag of the board and airdrag of rider, lines, bridle and kite will prevent further increase in speed, and therefore further increase in lift. The lift equals the drag, and topspeed is there.

Then one turns to sidewind and then continue downwind. What happens?

When one turns towards downwind, one turns to a bigger true wind / apparent wind angle (the moment of reaching, before downwind). This is the key moment to one's coming downwind performance! What happens? The angle of attack on the kite's leading edge increases dramatically due to changing course, and the lift it produces, shoots up in great amount. Speed through water (boatspeed) increases greatly, one accelerates like a sportscar. What happens during that acceleration? Since TRUE windspeed / windangle stays the same, our apparent wind angle will move again to smaller numbers, much closer to upwind angles. Why? Because, we are already sailing faster than the wind, and the kites leading edge will meet the airflow from the front, rather than from very high angle of attack, that some people call "drifting". These some people also say, that a wave kite can be good for hydrofoil, since they "drift" downwind well, and one can sail very deep angles downwind. Yes. It is true. But only if you sail SLOW! Then the apparent wind angle comes from "behind" = very big angle of attack. The kite "drifts" (sits deep in the window, near stalling).

Now back to one's reaching moment, with proper high performance kite. A lot of acceleration made (in just 1-2 secs, now one starts to turn more and more downwind:
When the speed increases, the lift will increase, and tolerate then this new lower angle of attack, and we turn down more, and same happens again. More lift, more speed. Ok, so when one keeps the high performance kite going downwind, the kite is actually sailing almost upwind. This means, that one can turn more downwind, since one wants to sail as deep as possible, straight to the mark, if possible. When one sails deeper, and deeper steering angles, in the end, the apparent wind speed decreases on the wing, and the increased hydro/aero -drags again meet the lift, and then we have found our max downwind performance. This performance is a mix of many, many little things that matter ( how deep is the foil in the water=less mast in water= less drag, how is the bar? More bar pressure = more aerodynamic drag on kite, if pulled beyond optimal profile for downwind. How is the steering angle, compared to wind speed / boatspeed, kites angle of attack and lift produced?

All these little things matter, and they can be summed up as a skill of sailing fast.

Sine, in general is only working when boatspeed = speed through water is very low. By flying the kite in sine wave style up and down creates airspeed and additional lift. A high performance hydrofoil does not benefit from this, since at highspeed the steering movements on the wing to produce the sine create aero drag that partially ruins it, and the rest is ruined due to general decrease in speed when kite flown to a direction which is not forward, and therefore diminishing boatspeed, and airspeed, and again lift. Sine is needed, if one is shitting the pants with high speed transition from upwind to downwind. If there is no speed going downwind, then one has to sine to produce some airspeed and lift. One can accelerate only by sailing higher angles fast. There is no acceleration possible, if driving deep angles dead downwind.

So, how Do I maximize my light wind hydrofoil downwind angles/performance? Use a BIG high performance kite with a lot of lift against the aerodynamic drag it produces. More lift with low airspeed is the definite key here. It is a big foilkite btw, as long as someone reports, that a LEI can outperform a foil kite in light downwind performance.

My very longish 2 cents. Please bear with me. But, this is not easy to unfold with just 2 lines. This is quite complex, and combines both aerodynamics and hydrodynamics. It has many things in common with flying a seaplane.

Janne
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Re: Upwind/Downwind Technique?

Postby Peter_Frank » Wed Apr 29, 2015 11:56 am

dusta wrote:
darippah wrote:Is it really possible to go downwind faster than the wind without sining the kite?
totally doable

monday i was out in around 10 knots and was hitting 20 knots downwind and i have only been on my foil for 4 hours . Parked my kite and just held on .
I think darippah meant downwind speed faster than the wind in its very direction, meaning VMG and not board speed.
You need to know the precise angle to the wind, in order to know if faster than the wind in the dead downwind vector.

So you are actually overtaking the air/wind and getting downwind before the wind arrives :rollgrin:

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Re: Upwind/Downwind Technique?

Postby Aspiremr » Mon Oct 21, 2019 1:24 pm

Thanks for the information. I’ve jsut started on my racing journey. Does anyone know of any good videos or similar tutorials on correct stance for downwind.

I find upwind I have no problems. BUt downwind I jut can’t seem to get pointed anywhere near enough down wind, and the crashes I am having at speed when heading downwind are really painful to say the least. I must be standing wrong or similar.

When i look at racing videos the board still seems to be angled over but when I head down wind i tend to be standing upright on the board and it’s a fine balance act. How do I get the right stance ?

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Re: Upwind/Downwind Technique?

Postby davesails7 » Thu Oct 24, 2019 1:45 am

What kite and foil are you using? How much power are you riding with?

Keep the kite low and pick up speed, then follow the kite downwind.

You need to have enough power to get a good downwind angle.

If you get overpowered turn more downwind towards the kite. If you dont have enough tension. Turn upwind a bit til you get back up to speed again.

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Re: Upwind/Downwind Technique?

Postby Aspiremr » Tue Oct 29, 2019 12:44 pm

I’m using different sizes, but in 10 to 14 knots on a 15 Mt soul, a Moses T60 board, with a Vorace mast (101 Cm) and a 590 wing. Weight 95 Kg’s.

My angle to the wind is ok, but on the downwind run I always seem to be vertical, upright on top of the board, which is not so stable.

How do you get the board to lean over on an angle like when going on an upwind tack.

All the good kiters do it but the minute I head downwind I don’t seem to be able to hold an angle against the kite.

Thanks.


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