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kiterbiker
Since 12 Jun 2010
65 Posts
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 Wed Sep 21, 11 12:52 pm pounds of force created by kite? |
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| Ok, science peeps out there. Today I was wandering around town running errands, and as usual, thinking of kiting. Then I started wondering how many pounds of force is the kite is producing to boost, say 20feet in the air. If kiter+board weighs 175lbs, or maybe the torque created by the kite. I'm sure theres an equation to bust this value out. Since we all kite, and anyone who jumps can say "a lot", and could give me an answer like "go tie yourself to a quad runner and have it pull you around". I was curious if anyone had any real values out there, and am not just some kook saying "how powerful is the kite really?" Which I know we've seen on the forum, and it ends up with the "go tie yourself to a bus" sort of answers, but wondering if any engineers or physics enthusiasts out there had an actual number for curiosities sake to an experienced kiter who loves pulling the trigger and feeling the power.
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Blaine
Since 06 Aug 2010
96 Posts
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| Wed Sep 21, 11 1:47 pm |
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What I have seen before is
Force=Wind Speed Squared * Kitesize
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cosmodog
Since 06 Oct 2005
203 Posts
Stoked
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| Wed Sep 21, 11 2:18 pm |
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Lift on a wing:
L = 1/2 * rho * V * V * A * Cl
Where:
rho = air density
V = air speed over wing
A = area of wing
Cl = lift coef
So for a 10m kite in 20 m/s wind + kite speed (~44 mph) and a lift coef of 0.8 you get:
L = 0.5*1.2*20*20*10*0.8 = 1920 N = 420 lbf
Lots of assumptions but I think its in the right range.
This sim I wrote years ago is closer but lacks accounting for the speed of the kiter when you jump:
http://www.flysim.com/kitesim/kitesim_features.html
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Youkai
Since 08 Feb 2010
553 Posts
Beaverton
Addicted
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| Wed Sep 21, 11 2:53 pm |
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You could just calculate your potential energy at 20 feet. 4742 joules or 3497 foot-pounds of energy based on your numbers. However much potential energy you have at 20 feet is how much energy it took to get you up there.
I found this potential energy calculator: http://www.ajdesigner.com/phppotentialenergy/potential_energy_equation.php
The acceleration of gravity on the surface of the Earth is 9.8 m/s(squared).
I got a significantly different number than cosmodog though. . .
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Captain kook; always wrong. |
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chrissmack
Since 08 Jun 2005
526 Posts
portland
Addicted
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| Wed Sep 21, 11 3:20 pm the answer |
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throw something like this on each of your front lines, and go ride...
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scale.jpg |
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Nak
Since 19 May 2005
4280 Posts
Camas
Site Lackey
CGKA Member
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| Wed Sep 21, 11 3:33 pm |
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Kites do not produce torque. Impossible given flexible lines. Kites produce lift. Translated to you as pull.
Gentle water start: 75% of your body weight.
Aggressive water start: up to 120% of your body weight, more for something super aggressive.
Dragging across sand with your heals dug in: 100% of your body weight. (Level ground. )
dragging across wet mud: next to nothing.
Dragging across sand while prone and trying to stop: anywhere from 50% to 80% of your body weight. Level ground.
Jumping & tricks: A minimum of 100% of your body weight. On up to whatever.
Just cruising. Depends on the board. 50% of your body weight on down.
Yep, I've done all that with a force gauge.
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DangleMaster123
Since 01 Aug 2010
38 Posts
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| Wed Sep 21, 11 4:22 pm |
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Youkai, you're always wrong. It's about 20,136 killonewtons. Pretty amazing if you ask me.
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I love to Dangle |
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SalmonSlayer
Since 27 Nov 2005
648 Posts
Addicted
CGKA Member
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| Wed Sep 21, 11 4:38 pm |
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| Nak wrote: |
Yep, I've done all that with a force gauge. |
that is slightly geeky, but, I think you know it. 
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Nak
Since 19 May 2005
4280 Posts
Camas
Site Lackey
CGKA Member
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| Wed Sep 21, 11 4:56 pm |
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| Yeah, I know. There was a reason. I needed to know those numbers for some work I was doing. Nothing like getting beat all to hell being drug behind a truck in the name of advancing technology.
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kitezilla
Since 22 Jun 2006
453 Posts
gorge
Obsessed
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| Wed Sep 21, 11 7:04 pm |
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| Nak wrote: | | Yeah, I know. There was a reason. I needed to know those numbers for some work I was doing. Nothing like getting beat all to hell being drug behind a truck in the name of advancing technology. |
Some of us remember that very admirable project... one of the many things we respect you for. Some day I would like to hear "the rest of the story".
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scottman
Since 08 Jun 2007
150 Posts
hillsboro
Stoked
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| Wed Sep 21, 11 7:43 pm |
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| i always heard the angle of the dangle was proportional to the heat of the meat
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arkay
Since 06 Jun 2008
192 Posts
Manzo/Hillsburrito
Stoked
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| Wed Sep 21, 11 8:46 pm |
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| No wind day, force meter, tether, car... don't try this at home
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Scriffler
Since 03 Jul 2005
581 Posts
LYLE
Addicted
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| Wed Sep 21, 11 9:18 pm |
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| We did it one time testing for North. If I remember right the kite exerted almost nine hundred pounds of force being towed up to 40 MPH behind a truck in no wind, that was the highest reading when turning a 14 M. Never broke the thousand pound mark but were very close a few times.
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arkay
Since 06 Jun 2008
192 Posts
Manzo/Hillsburrito
Stoked
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| Thu Sep 22, 11 6:53 am |
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wind tunnel time is too expensive for most kite makers... it's pretty insane what a thin sheet of nylon can do, ain't it! 
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kenja
Since 19 Jun 2008
179 Posts
Stoked
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| Thu Sep 22, 11 7:02 am |
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| I snapped two 600lb test lines while unintentionally looping my '02 fuel back in the day. Thank god they broke or I wouldn't be here to tell the story. So at least 600lbs... Probably more.
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Aeolus
Since 20 Apr 2010
354 Posts
Gold Beach, OR
OR-SoCo-Aficionado
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| Thu Sep 22, 11 7:44 am |
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| Nak wrote: | | Yep, I've done all that with a force gauge. |
I had a feeling that post was going to end like that. Sickness! 
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