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Take Off Speed

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UKSurf
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Take Off Speed

Postby UKSurf » Tue Sep 19, 2017 12:30 pm

What are the minimum speeds needed to "Foil Up"? I have read that some people say you only need 8 knots of board speed to foil up on the Liquid Force rocket fish but I finding it hard to get up on the foil unless I am travelling at quite a speed (I would say 12 knots at least). Is the lift created by the foil related to the square of the speed in the water in a similar way to a airplane wing is related to the square of the windspeed? I am thinking that being a heavy weight (95kg) I need more board speed than most.

I also find that once on the foil I can go slower than the speed I need to foil up on, Is this related to the extra lift needed to suck the board off the water surface tension?

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Re: Take Off Speed

Postby Lokihel » Tue Sep 19, 2017 12:55 pm

UKSurf wrote:
Tue Sep 19, 2017 12:30 pm
Is the lift created by the foil related to the square of the speed in the water in a similar way to a airplane wing is related to the square of the windspeed? I am thinking that being a heavy weight (95kg) I need more board speed than most.
It works exactly like an aeroplane, but in water instead of air.
This also means that more weight means more lift required, which translates into a higher takeoff speed.

UKSurf wrote:
Tue Sep 19, 2017 12:30 pm
I also find that once on the foil I can go slower than the speed I need to foil up on, Is this related to the extra lift needed to suck the board off the water surface tension?
Probably not. I would say it is either that you're now running the foil at a better angle of attack, or the kite is helping more since it is most likely higher up.

dylan*
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Re: Take Off Speed

Postby dylan* » Tue Sep 19, 2017 1:21 pm

forward speed is kind of a useless measurement because you have a kite pulling you up at the same time, i can often water start straight into foiling with 0 kts of board speed. obviously there is some speed measurement for the foil there because that's how wings work, but i dont know how you would measure it or if it really matters

just keep riding and you will get it figured out. maybe try a bigger kite, you can't always go off the windspeed:kitesize numbers you see on this forum because they're going to be completely different for everyone

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Re: Take Off Speed

Postby pj sofine » Tue Sep 19, 2017 1:40 pm

I'm only 7 hrs in ,but the ss hoverglide comes up on plane as soon as I waterstart(on my good side),no idea the speed,except its very low if not non existent.It actually feels like its coming up on foil as I'm getting up.

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abel
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Re: Take Off Speed

Postby abel » Tue Sep 19, 2017 9:54 pm

Board speed is an odd, single and not enough parameter to describe water start features of an HF.
There are so many other parameters in the water start equation, that referring only to board speed is difficult to measure and not enough.
Under the limits of light wind everything thing is highly influenced by a mere 1 knot lull.
The kite thrust can decrease between 20 to 30% in the middle of a water start. :-? :-x
Because of that, the way that works for me is water starting like the wind is dying on me on every start trial.
You have to take into account that the wind window is significantly smaller than with normal winds, so you have to point the board quite downwind.
I start with my body leaning towards the front of the board (while pulled by the mid downstroke of the kite), keeping the wing aft.
That gives me an extra length to 'swing' the wing forward with the legs, giving it an extra speed for the start.
While the wing gets the speed (not your body) you try to fly so the weak thrust from the kite is enough to maintain the tack.
Just to emphasize the "trick", you increase the wing speed by striking the mast with your legs, while your body is forward.

I hope I managed to explain how to gain some "Take Off Speed" under very light winds. :roll:

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Peter_Frank
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Re: Take Off Speed

Postby Peter_Frank » Wed Sep 20, 2017 4:23 pm

dylan* wrote:
Tue Sep 19, 2017 1:21 pm
forward speed is kind of a useless measurement because you have a kite pulling you up at the same time, i can often water start straight into foiling with 0 kts of board speed. obviously there is some speed measurement for the foil there because that's how wings work, but i dont know how you would measure it or if it really matters

just keep riding and you will get it figured out. maybe try a bigger kite, you can't always go off the windspeed:kitesize numbers you see on this forum because they're going to be completely different for everyone

Spot on, it is the weight of you combined with the kite lift component that makes the forward speed "obsolete" regarding how little speed you require for take off :thumb:

And no, you dont need more speed while the board is on the water, for takeoff - but you need a he.. of a lot more power from the kite, till the board is free, so this might be what makes you think you need more speed :rollgrin:

Also, the more experienced you are, the slower you can ride on ANY wing, everything else being the same - incredible but true :D

The LF can start at really low speeds, compared to many other foils, but a number dont make much sense, unless you know your weight and windspeed and kite too.

8) PF


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