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Author Topic: sport kite roll bars  (Read 1775 times)
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chilese
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« Reply #15 on: January 01, 2019, 05:14 PM »

Mathematically...

Assume: 15 psi ambient (really about 14.7 psi) Immaterial as we are using a differential pressure
Assume: Kite surface area of 1600 sq inches (approximately 1 sq meter)
Differential pressure front to rear surface: 0.1 psi
Pull on lines: 160 pounds force, 80 lbs per line

I would be surprised if the pressure differential on a sport kite skin ever got past this.

Flow across any part of a kite skin will always be non-laminar, but
it can still appear smooth to our eyes.

KaoS: A pleasure to read your inputs sir.

« Last Edit: January 01, 2019, 08:48 PM by chilese » Logged

Frazer
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« Reply #16 on: January 01, 2019, 05:52 PM »

If Bingo's going all Pythagorean on us I'll go empirical.

I have a DSUL which remains efficient enough to be flown (on short lines) in SUL winds - with the rollbars intact.

Ergo, any associated drag is insignificant.

Q.E.D

-Frazer

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Allen Carter
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« Reply #17 on: January 01, 2019, 05:58 PM »

Trick kites are so inefficient, drag-wise, that this is a pretty silly conversation...  Smiley

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Allen, AKA kitehead
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« Reply #18 on: January 01, 2019, 06:19 PM »

Trick kites are so inefficient, drag-wise, that this is a pretty silly conversation...  Smiley
So says the original owner of my DUSL Smiley

-Frazer
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Allen Carter
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« Reply #19 on: January 01, 2019, 06:36 PM »

Trick kites are so inefficient, drag-wise, that this is a pretty silly conversation...  Smiley
So says the original owner of my DUSL Smiley


I think that particular DSUL is a bit magical...
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Allen, AKA kitehead
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« Reply #20 on: January 01, 2019, 10:08 PM »


KaoS: A pleasure to read your inputs sir.


...and yours  Smiley
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Kevin Sanders

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« Reply #21 on: January 01, 2019, 11:09 PM »

 The area behind the sail on a kite has almost no pressure due to the fact that the wind is redirected along the face of a kite.  


You are confusing pressure and wind speed.  A sport kite pulls away from the flyer because of it's airfoil properties, not because of Newtonian force against the "front" of the sail.
Yes, there is lower pressure at the rear of the kite, just as there is lower pressure above the top surface of an aircraft wing when compared to pressure below the wing.  But to claim there is "almost no pressure" is wrong.

If you have ever flown a stack with the link lines too short or through the wake of another kite at close range you would understand what void I'm talking about.



No, that's because of turbulence, not a "wind void".  Watch any of the many videos that explain how wings really work e.g. http://youtu.be/UqBmdZ-BNig and you might understand what I'm talking about.

There was a video of Mark Reed doing a wind tunnel test years ago where he had short ribbons attached to the back of the sail and you could see some of the ribbons laying flat with little to no movement.


Little to no movement of the ribbons merely indicates smooth airflow in that region.
Yep your right, I was getting them mixed up. Different pressure effect when parked vs forward movement air flow.
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