Foolkookio & Ridiculous Light Wind Claims

[alamos_kiter]

Glide ratio

When flown at a constant speed in still air a glider moves forwards a certain distance for a certain distance downwards. The ratio of the distance forwards to downwards is called the glide ratio. The glide ratio (E) is numerically equal to the lift-to-drag ratio under these conditions; but is not necessarily equal during other manoeuvres, especially if speed is not constant. A glider's glide ratio varies with airspeed, but there is a maximum value which is frequently quoted. Glide ratio usually varies little with vehicle loading; a heavier vehicle glides faster, but nearly maintains its glide ratio.

Glide ratio (or "finesse") is the cotangent of the downward angle, the glide angle (γ). Alternatively it is also the forward speed divided by sink speed (unpowered aircraft):

Glide_ratio.gif (3.73 KiB) Viewed 859 times

L/D = Δs/Δh = v_forward / v_down

Glide number (ε) is the reciprocal of glide ratio but sometime it's confused.

[foilholio]

I am certain I read of someone doing 4x wind speed on a hydrofoil. or maybe buggy, I forget

I would love to see what a rigid wing with L/D in the 50-70+ could do on strings.

Glide ratios with a higher sink rate ,i.e. like from more weight, could be considered higher wind.

[sabraxas]

The glide ratio (E) is numerically equal to the lift-to-drag ratio under these conditions

Thats it. I didnt know. Thanks.

Will you call the apparent wind we generate when we kitesurf the same as glide ratio?

For example if a kite has a L/D ratio of 7 and it achieves that moving at 14knots it then only need 2knots wind to achieve it. For every 2knots it moves through the wind it can move 14knots sideways to the wind. 2x7 it's simple math.

L/D ratio of 7 in 2 knots= 14 knots... And then you load the system with a surfboard with 80 kgs guy standing on it...

[sabraxas]

I am certain I read of someone doing 4x wind speed on a hydrofoil. or maybe buggy, I forget

Glide ratios with a higher sink rate ,i.e. like from more weight, could be considered higher wind.

Well, now you low your bet.

Real wind: 2 knots. Apparent wind with surfboard: ¿2? ¿3? x .

You wont get any traction with that final speed.

[PullStrings]

Wow your kite would be out of tune .
There is tuning options to make it static fly below 4knots,
21 was out of tune.

We believe your brain is out of tune

[alfredo68]

Kiting sucks in under 10 knots, no matter the board or kite.

There are absolutely those who CAN go in less, but the size of kites and type of riding required are a bore.

in 2016 the real deal on switch for freeride fun is 10 knots. Were lucky, a few years ago it was 15, years before that closer to 20.

Might take some flame for that, but I'm a true addict and if it ain't a convincing 10 knots on the water. I'll pass.

In reality, 10 knots is low enough to make a real go of it as a sport. Rideable 5/7 days a week so far this summer.

Life is good.

[Bille]

I am certain I read of someone doing 4x wind speed on a hydrofoil. or maybe buggy, I forget

I would love to see what a rigid wing with L/D in the 50-70+ could do on strings.

Glide ratios with a higher sink rate ,i.e. like from more weight, could be considered higher wind.

On a High-performance sailplane , the open door for the wheel will account for
1/2 the parasitic drag of the entire ship, (which will reduce it's top speed) ; so until you figure
a way to reduce line drag of a kite, a higher AR wing is kinda useless.

On glide ratios --- the heavier you are , the higher the speed you go to max glide ratio ; but
the actual glide ratio is the same, (only the speed changes with wing loading). It's why they
add water ballast, to expensive sailplanes.

Bille

[Starsky]

Thanks for the reminder Alfredo,

I'm so done with this light wind bullshit.

Let's get back to kiteboarding.

[foilholio]

Why do you read or post in these threads then?

Will you call the apparent wind we generate when we kitesurf the same as glide ratio?

I think we can equate it in certain situation i.e. straight across the wind it makes obvious sense. Downwind it makes sense too. Upwind I think requires some thought. It seems like the wind increases but that is powered off the wind so :-/

L/D ratio of 7 in 2 knots= 14 knots... And then you load the system with a surfboard with 80 kgs guy standing on it...

Yes but that 7 was just an example and 2 knots was for standing not riding. If you load the kite it needs to make more lift, so possibly a higher AoA and with it worse L/D. But 80kg is a reasonable amount for a paraglider to support with a 2knot sink rate, you just need to get up to the 14knots. But the question is how much pull (sink rate) translates into lift at the board? because it is mainly the board (and a bit of kite) that supports the rider.

Well, now you low your bet.

Real wind: 2 knots. Apparent wind with surfboard: ¿2? ¿3? x .

You wont get any traction with that final speed.

Whhhhaaattt what bet did we have? A surfboard has bouncy so this make a big difference helping to get on plane not so sure it makes a difference when on plane. Say in 3knots I think 10to 12 knots riding is possible maybe even 15. So that gives 3,4 or 5 times wind speed.

Kiting sucks in under 10 knots, no matter the board or kite.

There are absolutely those who CAN go in less, but the size of kites and type of riding required are a bore.

in 2016 the real deal on switch for freeride fun is 10 knots. Were lucky, a few years ago it was 15, years before that closer to 20.

Might take some flame for that, but I'm a true addict and if it ain't a convincing 10 knots on the water. I'll pass.

In reality, 10 knots is low enough to make a real go of it as a sport. Rideable 5/7 days a week so far this summer.

Life is good.

10knots is heaps, it is already mid range with 2 of my kites on a surfboard (and the kites drift easy in that wind) and it's the top end on some kites with hydrofoils. For me the easy riding stops around 6-7knots. But I wouldn't go for a kite unless it said at least 10knot there. That way I am almost guaranteed to kite. The wind does stop occasionally then you can surf mmmmm glass.

On a High-performance sailplane , the open door for the wheel will account for
1/2 the parasitic drag of the entire ship, (which will reduce it's top speed) ; so until you figure
a way to reduce line drag of a kite, a higher AR wing is kinda useless.

Yes but how much is the drag of the wheel vs the kitelines? are they equivalent? And if you double the drag and so halve the L/D 50 becomes 25 which is still fucking awesome. Even a hangglider at half is still good and consider all other kites must deal with the same line drag and rider drag etc, it'll still be awesome too.

On glide ratios --- the heavier you are , the higher the speed you go to max glide ratio ; but
the actual glide ratio is the same, (only the speed changes with wing loading). It's why they
add water ballast, to expensive sailplanes.

Bille

Yes that is why I talk about sink rate, the ratio stays the same but the sink rate increases because the speed is increased. So a kite that achieves maximum L/D at a higher speed will too achieve that in a higher wind speed. And the sink rate doesn't change much for these faster wings so potentially for a small wind increase you are getting a massive speed increase. It is one reason I think thinner is better, add that a foil can change it's camber to make more or less lift very effectively quite stunning performance is possible.

[Bille]

...

Yes that is why I talk about sink rate, the ratio stays the same but the sink rate increases because the speed is increased. So a kite that achieves maximum L/D at a higher speed will too achieve that in a higher wind speed. And the sink rate doesn't change much for these faster wings so potentially for a small wind increase you are getting a massive speed increase. It is one reason I think thinner is better, add that a foil can change it's camber to make more or less lift very effectively quite stunning performance is possible.

Yep !

Bille