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Lightwind Kite Aspect Ratio

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davesails7
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Lightwind Kite Aspect Ratio

Postby davesails7 » Mon Jan 30, 2012 7:00 pm

There seems to be two totally different styles of lightwind kite available:
High aspect ratio with 6 or 7 struts like North Dyno, Ozone Edge, Crossbow, and Speed 3 (no struts, but High AR)

Low Aspect Ratio with 3 or 4 struts like Epic Infinity and Blade Fat Lady

Seem kind of weird that they are designed for the same thing, getting you out in as little wind as possible, but are totally opposite in design.

What are the benefits of each?

In a recent post people were saying obviously low AR is better for low end, but I don't think that's true. It seems to me that the high aspect ratio will have better upwind and slightly lower on the low end, but will have worse relaunch and smaller wind range. Is that right?

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Re: Lightwind Kite Aspect Ratio

Postby davesails7 » Mon Jan 30, 2012 7:02 pm

By the way, just want to talk about high aspect ratio vs. low aspect ratio, just gave names of kites for examples of each. No need to say which single kite design you think is best because you own the company :D

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Re: Lightwind Kite Aspect Ratio

Postby voodoospirit » Mon Jan 30, 2012 7:59 pm

high aspect ratio are way better at edging upwind/parked but can be sensible to wind variation as they are very close to the edge of the window ( collapsing/hindenburg), the situation is reduced as u develop apparent wind.
on the other hand, if u have a fast board , u can go with smaller aspect ratio , the kite stay a bit deeper in the window and will handle the wind variation better, the board speed will allow to go upwind ( even if u have to sin the kite) and u might use them for surfing, where the high aspect ratio are not meant for.

if my wind is unstable/gusty, i might prefer a smaller aspect ratio (despite i ride with a speed3 which si very stable in gusty winds unlike its predecessor the speed2)

if i have a lamilar wind or close to regular, higher aspect ratio all the way.

question of preferences or choices..

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Re: Lightwind Kite Aspect Ratio

Postby stefaans » Mon Jan 30, 2012 8:04 pm

Ozone Edge is 5 struts BTW.

Keep in mind that when going in super light winds going upwind is one of the most important aspects.
So HAR goes upwind better than LAR. HAR doesn't feel like it has the initial power but build more power by apparent wind once up to speed. LAR kite will never get close to you once you get going.

LAR kite feels like it has more power just by having it in the air and flying it. imo prob better in waves as you don't ever build up apparent wind just some raw power turn turn turn. probably pretty bad upwind.
As far as wind range the HAR kite has a better range. Better top end for sure and then the low end is debatable depending on what you want to do with it.

It's all just about where the kite is in the window.
These kites are not designed to do the same thing. Get the one for what you will be using it for.

all just opinion!

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Re: Lightwind Kite Aspect Ratio

Postby Tiago1973 » Mon Jan 30, 2012 8:24 pm

better persons could explain this better. there are 2 forms of resistance: the form resistance and the induced resistance

induced resistance is the one created by lift => higher lift (weight) will drive higher induced resistance

induced resistance is also inverse proportional to aspect ratio => higher aspect ratio will drive lower induced resistance

thus if the idea is to go up-wind like crazy it make sense to reduce weight and maximize aspect ratio, as possible.

But then i don´t think either the Epic Infinity or the Blade Fat Lady were designed with the idea of maximizing up-wind, i.e., they are not race kites. In consequence Epic/Blade didn´t went with the high aspect ratio solution as i guess this could limit other flying characteristics being persuit. As a low wind kite they kept an eye in the weight and thus the 3 struts solution.

having this said if Momi drops a line saying this is all wrong please believe Momi :lol:

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Re: Lightwind Kite Aspect Ratio

Postby Cespo » Mon Jan 30, 2012 8:32 pm

Hi guys! First time here! Nice to meet you!

Back on the thread!! I'm not experienced with those kites and can't compare.

Talking academically about aerodynamics you can compare this case to airplanes: gliders (high AR) vs fighters (low AR).
At low speeds a higher AR guarantees a better lift/drag ratio due to the reduced importance of induced wingtips vortices, while a low AR gives more maneuverability.
In Italy we call it "having a short blanket": if you want a good lift/drag ratio you have to forget quick maneuvers, and if you want quick maneuvers you should forget about the lift/drag ratio.
Now, beeing in certain fixed conditions (materials weight and stiffness, kite area and wind speed) I think it's matter of every producer choice to elongate or shorten the kite span to have more lift or better maneuvering.

Again: academically! In fact I don't know exactly how do theese kites differ.

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Re: Lightwind Kite Aspect Ratio

Postby fdvj » Mon Jan 30, 2012 8:36 pm

Low aspect kites work better in light onshore conditions as you don't get the chance to build up the apparent wind needed to get high aspect kites to work, especially if you throw waves into the equation.

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Re: Lightwind Kite Aspect Ratio

Postby davesails7 » Mon Jan 30, 2012 8:42 pm

Cespo wrote:At low speeds a higher AR guarantees a better lift/drag ratio due to the reduced importance of induced wingtips vortices, while a low AR gives more maneuverability.
In Italy we call it "having a short blanket": if you want a good lift/drag ratio you have to forget quick maneuvers, and if you want quick maneuvers you should forget about the lift/drag ratio.


I thought that in general high aspect ratio kits turned faster, is that not the case?

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Re: Lightwind Kite Aspect Ratio

Postby Hansen Design » Mon Jan 30, 2012 9:15 pm

More to it than AR alone.
Tube size, profile and profile morphing over the span along with built-in AOA are highly determinant factors in where a kite with a given AR and canopy curve ('C'-ness & projected area) sits in the window and how eager it is to fly at the edge for upwind VMG. You can have a relatively low AR swept 3-strut fly aggressively to the edge even though most kites of that type do not. With regard to turns, a kite that turns outside the wingtip (non-pivotal) and holds power in the turn will help the rider maintain speed and stay upwind. Turning speed and type of turn is also not necessarily a matter of pure AR. There are a lot of variables blended into a kite that can negate pure AR as a predictor of light air performance so if you are looking for a light air kite, you need to consider your board, weight and type of use you desire - ultimate upwind or doing tricks that may put you downwind? On water testing with your gear is the only way.
Cheers!
:thumb:

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Re: Lightwind Kite Aspect Ratio

Postby tautologies » Mon Jan 30, 2012 9:33 pm

davesails7 wrote:
I thought that in general high aspect ratio kits turned faster, is that not the case?


Nope. Not the case. Too much wing to turn around.



Now, I think a kite with low ar is almost useless for light wind kiting, unless your doing downwinders. Hansen is talking about what we call grunt, the kites willingness to go to the window. Most low ar kites will not do that well. For light wind, IMO, medium and high ar kites are the way to go. There are many many other parameters that will influence how it does in light wind..weight is a huge one. Diameter of LE...but if the LE deforms out of design it is too thin.

Light wind design is really a fine balance of parameters that has to be just right. In addition the tradeoffs on choosing one solution over another, will greatly impact the kite handling.


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