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Author: Subject: Fluid mechanics, I think...
geokite
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[*] posted on 5-1-2011 at 02:41 PM
Fluid mechanics, I think...


I was wondering what is the relationship, in order to plane a kite board, between rider weight and the minimum required kite pull. I suspect it is not a linear relationship. Does anyone know any fluid mechanics graphs for this? Might there be one used to describe the planning ability of certain boats that could be used?



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[*] posted on 5-1-2011 at 04:07 PM


deffo not linear, as speed increases the pull can be less than starting from a stop. And sq. area of the board has alot to do with it. Specific gravity of the water(salt vs. fresh)would also factor in. I have no clue where to look or what to look for.



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[*] posted on 5-1-2011 at 04:35 PM


There are alot of factors to consider such as propulsion power ( kite power) , resistance, bottom profile of the board, the length to beam ratio ( fat board compare to skinny board) and of course the weight is most important. Your weight will affect how much displacement the board have which will make it harder to plane. If you trim a boat correctly, it will plane easier so some rider can plane earlier than others base on their skill.



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[*] posted on 5-1-2011 at 04:44 PM


kite Projected area per rider weight was varied by skill.

.8/10kilos for advanced and 1.2/10kilos beginner. best i remember

power required ??? rate would peak at drag limits of kite, surprisingly low i would think. land, ice would maybe 1/2 -2hp. water maybe 1-5hp.

starting would be like boat with 75hp kinda range for water. there's a vertical vector which would reduce that by some??

snow ??? in between

but this is a quick guess


sorry no simple graph either ..def not linear it would follow fluid principles though



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[*] posted on 5-1-2011 at 04:46 PM


it would be an interesting graph but I agree that board width would play a big part.
I think if you have the board width that will get you riding in lightest wind it's then what the minimum wind is to get you ass up out of the water and standing on that board. As soon as I have enough wind to get me up out of the water, even if it involves more of pulling myself up (as opposed to a straight forward lift onto the board), as soon as I'm standing on the board I can ride, even if it means working the kite like hell and going downwind. So that amount of surface to support my weight at the minimum amount of forward speed - plus just enough power in that kites initial dive to pull myself up onto the board.
We have a lot of doming in the spring so there will be wind inland all the way up a few hundred feet of the water and then it can be dead calm - throwing long line extensions on gets us up into the higher elevation wind as well as that long power stroke makes a big difference for getting up and riding. Cheapest way of gaining more than a kite size. But if the wind picks up - beware it takes a lot longer to get out of the power.
So is it rider weight, board width, wind speed, salt vs fresh water, air temperature, line length etc?
Also, colour of board shorts is very important, just like kites, some colours are slower;-)



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