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RalfsB
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 Joined: Mon Jan 09, 2012 2:45 pm
 Kiting since: 2010
 Local Beach: Beaches close to Riga, Latvia
 Style: Freeride
 Gear: Kites: Ozone, Naish, RRD; Boards: Alpine foil, some surfboards I shaped myself, Machado Moonbeam
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 Location: Riga, Latvia

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Postby RalfsB » Wed Sep 12, 2018 9:28 am
Sorry, my post is not about Turbines but an observation about kite flat areas in general. One day, I happened to lay down on the ground my 17m kite and my 12m kite on the top of it. The 17m was larger but only slightly, it did not look like there is 5 square meters difference between them. I was intrigued and decided to measure the flat area of my kites. Results:
My 6m kite is actually 5m
My two 9m kites are actually 8m
My 17m kite is actually 14.6m !
I am not sure how manufacturers are measuring the flat area (maybe the total area of the cloth before it is sewn together, not sure) but the difference seems to be significant.
My method of measuring was:
 find the middle of the kite (because I need to measure only a half of the kite)
 divide the halfkite into triangles, so that the outer edges of triangles are close to the actual edges of the kite.
 measure the edges of all those triangles
 calculate the area of triangles (Heron's formula works fine) add them up, multiply by 2 to get the whole kite.
I assume my method could give like 5% error but the actual differences are much much bigger.

Janus
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Postby Janus » Wed Sep 12, 2018 10:07 am
No Wind?

RalfsB
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 Posts: 173
 Joined: Mon Jan 09, 2012 2:45 pm
 Kiting since: 2010
 Local Beach: Beaches close to Riga, Latvia
 Style: Freeride
 Gear: Kites: Ozone, Naish, RRD; Boards: Alpine foil, some surfboards I shaped myself, Machado Moonbeam
 Brand Affiliation: None
 Location: Riga, Latvia

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Postby RalfsB » Wed Sep 12, 2018 10:25 am
Janus wrote: ↑Wed Sep 12, 2018 10:07 am
No Wind?
Yeah, no wind for the last 2 weeks...

Slappysan
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Postby Slappysan » Fri Sep 14, 2018 1:18 am
RalfsB wrote: ↑Wed Sep 12, 2018 9:28 am
I am not sure how manufacturers are measuring the flat area (maybe the total area of the cloth before it is sewn together, not sure) but the difference seems to be significant.
My method of measuring was:
 find the middle of the kite (because I need to measure only a half of the kite)
 divide the halfkite into triangles, so that the outer edges of triangles are close to the actual edges of the kite.
 measure the edges of all those triangles
 calculate the area of triangles (Heron's formula works fine) add them up, multiply by 2 to get the whole kite.
I assume my method could give like 5% error but the actual differences are much much bigger.
The trouble with this is that the kite isn't a 2D object like you are measuring it, it's very much a 3D object and that's what makes it a wing and gives it lift. So you are basically ignoring one of the 3 dimensions.
The surface area of a hemisphere is 2*pi*r*r (6.28 for r=1) while the area of a circle is only pi*r*r (3.14 for r=1). Now the dimension you aren't counting is no where near the other two in size like a sphere but it still has an effect.

RalfsB
 Medium Poster
 Posts: 173
 Joined: Mon Jan 09, 2012 2:45 pm
 Kiting since: 2010
 Local Beach: Beaches close to Riga, Latvia
 Style: Freeride
 Gear: Kites: Ozone, Naish, RRD; Boards: Alpine foil, some surfboards I shaped myself, Machado Moonbeam
 Brand Affiliation: None
 Location: Riga, Latvia

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Postby RalfsB » Fri Sep 14, 2018 8:59 am
Slappysan wrote: ↑Fri Sep 14, 2018 1:18 am
The trouble with this is that the kite isn't a 2D object like you are measuring it, it's very much a 3D object and that's what makes it a wing and gives it lift. So you are basically ignoring one of the 3 dimensions.
The surface area of a hemisphere is 2*pi*r*r (6.28 for r=1) while the area of a circle is only pi*r*r (3.14 for r=1). Now the dimension you aren't counting is no where near the other two in size like a sphere but it still has an effect.
Yeah, but the kite cloth itself is flat, not really spherical. What gives the kite the 'sphere' is how its seams are laid. If I place the edges of my triangles along the seam lines (as I did) I do measure the area of the cloth with very little margin of error.

Slappysan
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Postby Slappysan » Fri Sep 14, 2018 7:15 pm
RalfsB wrote: ↑Fri Sep 14, 2018 8:59 am
Yeah, but the kite cloth itself is flat, not really spherical. What gives the kite the 'sphere' is how its seams are laid. If I place the edges of my triangles along the seam lines (as I did) I do measure the area of the cloth with very little margin of error.
Only if you did it while the kite is inflated.
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