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Aerodynamically better leading edge

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edt
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Re: Aerodynamically better leading edge

Postby edt » Wed Jan 18, 2017 7:59 pm

You can absolutely make the leading edge much more aerodynamic and add just a tiny bit more weight. First of all, like Peter suggests, you do want to retain the original tube, same size and everything. But like Billie mentioned you add additional structure. The key point is that you can make a shape bigger and have huge reductions in drag. A pure cylinder is about as bad as it gets in regards to aerodynamics and I don't think we are getting anywhere with double cylinders. Still not efficient. So we have the original tube the same, holding all of the structure, but when we add additional structure what do we make it out of? Easy, just make it out of some super light compressible foam, that you can press a finger on it and it will fold up, but what it will do is create a better teardrop structure. If you look at an old school VW bug it is about half the size of a modern compact car yet pulls through the air like a mattress, coefficient of drag of .5 and a prius though ugly looking and twice as big as an old VW bug slips through the air with a coefficient of drag of .25.

You want to think about just adding more size to that leading edge and then you'll get dramatic improvements in aerodynamics. You don't want to make it smaller or sleeker with double tubes and such but to make it bigger by crafting light weight fairings that have no structural strength but add greatly to performance.

This would be a fun DIY home project, sewing on extra fabric to the leading edge and trying out new shapes or throwing the new shape on a computerized air tunnel.

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Re: Aerodynamically better leading edge

Postby jakemoore » Thu Jan 19, 2017 3:34 am

edt wrote: You want to think about just adding more size to that leading edge and then you'll get dramatic improvements in aerodynamics. You don't want to make it smaller or sleeker with double tubes and such but to make it bigger by crafting light weight fairings that have no structural strength but add greatly to performance.

This would be a fun DIY home project, sewing on extra fabric to the leading edge and trying out new shapes or throwing the new shape on a computerized air tunnel.
If only there was a way to get the wind to flow into this cloth fairing to hold its shape without adding weight. Maybe we could get a more streamlined kite without the weight and hassles of the high pressure tubes.

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Re: Aerodynamically better leading edge

Postby Don Monnot » Thu Jan 19, 2017 5:30 pm

Sounds to me like the physics guys on here are saying that you don't need the fairing--that there's no real issue with the space aft of the leading edge tube shape. They're saying that it's a dead space that really doesn't create much extra drag. Am I understanding this correctly?

Don

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Re: Aerodynamically better leading edge

Postby volume311 » Thu Jan 19, 2017 6:42 pm

This should be a relevant read to get an idea of some the principles involved and the flows around the leading edge of a foil (as in the wing, not a foil kite, calm down pumpy) and why you would want a streamlined transition vs just a tube.

https://sailwildling.com/2014/09/13/why ... ting-mast/

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Re: Aerodynamically better leading edge

Postby edt » Thu Jan 19, 2017 8:24 pm

Don Monnot wrote:Sounds to me like the physics guys on here are saying that you don't need the fairing--that there's no real issue with the space aft of the leading edge tube shape. They're saying that it's a dead space that really doesn't create much extra drag. Am I understanding this correctly?

Don
I am pretty sure the aero guys are saying the exact opposite. The issue is the shape of the tube. I'm just a regular physics/math guy though not an aero-science guy, so I could be wrong.

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Re: Aerodynamically better leading edge

Postby Bille » Fri Jan 20, 2017 5:54 am

edt wrote:You can absolutely make the leading edge much more aerodynamic and add just a tiny bit more weight. First of all, like Peter suggests, you do want to retain the original tube, same size and everything. But like Billie mentioned you add additional structure. The key point is that you can make a shape bigger and have huge reductions in drag.
A pure cylinder is about as bad as it gets in regards to aerodynamics and I don't think we are getting anywhere with double cylinders.

...

This would be a fun DIY home project, sewing on extra fabric to the leading edge and trying out new shapes or throwing the new shape on a computerized air tunnel.
Like i was saying , before marlboroughman hexed my flying trip with a bunch of fricken rain ...

Make a bladder like the inflatable SUP boards.
Forget the trip point on the cylinder, and point that extended dead-air were making, to
about 75-80% cord , and get ride of the blunt circle up front ; now you can adjust the pitching
moment, and the CLmax, by changing the canopy to reflex or under-camber, on the 75% mark.

75 to 80% cord, is where Ya get the most effective change, with the least amount of added drag
in-front and more drag behind that mark, if Ya hinge it there.

You just sped up your kite a Bunch, with way less drag ; and increased the lift at will, anytime
you add camber behind the 75% cord.

YOU would sell FEWER kites ; but so what , (everybody would Love them) !! :lol:

Bille

EDIT :
foilholio -- where is that camber changing apparatus, i ordered ??
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Re: Aerodynamically better leading edge

Postby Dimitri M » Fri Jan 20, 2017 4:51 pm

Hello guys,
All these info are great. Thank you for all your ideas and help. So what would you recommend for the next generation of kites. Working on few prototypes so let me know your ideas. You can always email me directly at: dimitri@epickites.com

:thumb:

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Re: Aerodynamically better leading edge

Postby edt » Fri Jan 20, 2017 5:16 pm

Sweet! That would be amazing if epic was out front on this idea. I like Billie's idea a lot. Just use the same stuff they use on sups to give that tube form.

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Re: Aerodynamically better leading edge

Postby Faxie » Fri Jan 20, 2017 6:50 pm

Weight is the biggest enemy of kites, and I have the feeling that the added weight (which gives you parasitic drag) for drop shaped LE's would not compensate for the potential slight decrease in aerodynamic drag.

You would also have to account for the decreasing structural integrity of the tube when you leave the round shape, thus having to increase it's size or amount of reinforcements, once again adding weight and surface area, resulting in drag.

Looking at experiments in the past with odd shaped tubes and added cloth behind the LE, I don't think significant improvements will be possible without a new kind of stronger and lighter material.

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Re: Aerodynamically better leading edge

Postby edt » Fri Jan 20, 2017 7:22 pm

Faxie wrote: Looking at experiments in the past with odd shaped tubes and added cloth behind the LE, I don't think significant improvements will be possible without a new kind of stronger and lighter material.
we didnt know what the f*** we were doing with kites 10 years ago. We have to take the knowledge we have now about how to build bridles, kites, shapes and such and add changing the shape of the tube to it. You know those experiments with cuben fiber? that's the wrong direction. You don't want to make the size of the cylinder smaller you want to make the shape of the leading edge better.


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