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Calculating Aspect Ratios

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Hansen Design
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Re: Calculating Aspect Ratios

Postby Hansen Design » Sat Jan 12, 2013 8:08 pm

Hi Plummet :thumb:
Switch Kite Specifications.jpg

plummet wrote:it would interesting to know the changes in projected AR for different kite styles.
for example the projected ar of a C kite should be alot less than the project ar or an sle with the same AR......

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Re: Calculating Aspect Ratios

Postby plummet » Sat Jan 12, 2013 11:44 pm

Hansen Aerosports wrote:Hi Plummet :thumb:
Switch Kite Specifications.jpg

plummet wrote:it would interesting to know the changes in projected AR for different kite styles.
for example the projected ar of a C kite should be alot less than the project ar or an sle with the same AR......


interesting. its bizarr that the switch wave kite has the highest projected a/r. i would have thought the wave kit would have the lowest....

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Re: Calculating Aspect Ratios

Postby Hansen Design » Sun Jan 13, 2013 7:43 am

The Method is the least 'C' shaped or the models listed resulting in a higher projected span. In the realm of contemporary inflato traction kites, AR (projected or flat,) is not really a true predictor of performance unless all other variables are the same.
plummet wrote:interesting. its bizarr that the switch wave kite has the highest projected a/r. i would have thought the wave kit would have the lowest....

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Re: Calculating Aspect Ratios

Postby Kiteus Maximus » Mon Jan 14, 2013 10:07 pm

Peter_Frank wrote:
BWD wrote:Aspect ratio = ((wing span)^2/surface area)
So a hypothetical 12m kite shaped like a flat rectangle when unrolled, with a 5.4 AR has a span of 9.2m and chord of 1.3m.
Really kites aren't shaped so simply, and other factors are considered but that's the idea.


Formula is correct, and the easy way to measure (but numbers are not...)

Aspect Ratio = span / average width.

Area = span * average width.

Meaning AR = span^2 / area.

So your 12m2 kite with an AR of 5.4 has a span = sqrt(AR*area) = sqrt(5.4*12m2) = 8.0 meter.

And an average width = span / AR = area / span = 1.49 meter.


I dont agree that "numbers" are just marketing, so you simply lay your kite out flat on the ground and measure the span from tip to tip, and use the nominal size printed on the kite to calculate the AR.

That works fine - and most kites are relatively okay in their size measurement, is my experience.

Even if a 12m2 kite actually was 13m2 - the error in AR calculation will only be about 7 to 8% which is not bad really :rollgrin:


Of course, like others point out - the AR is only one parameter, as whether the area is in the middle or the tips, and how flat/c the kite is, means much more.

But for those interested in this number, using the written area and the measured span is fine IMO :thumb:

Agree that it is also interesting to measure a kite up precisely yourself, if you want to know the exact size.


Why do so many use the term "12m" about a 12m2 kite ?

The word constellation 12m does not exist as an area measurement in Danish nor German, and also lacking in most other languages, so why do so many english speaking say "12m" ?
Simple lazyness, or old bad habits or ?

:D Peter


This is not a true way to calculate the aspect ratio. You can have the same aspect ratio for different sized kites and if you use your calculation logic then different size kites will have different aspect ratios.

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Re: Calculating Aspect Ratios

Postby dyyylan » Mon Jan 14, 2013 10:17 pm

Peter_Frank wrote:Why do so many use the term "12m" about a 12m2 kite ?

The word constellation 12m does not exist as an area measurement in Danish nor German, and also lacking in most other languages, so why do so many english speaking say "12m" ?
Simple lazyness, or old bad habits or ?



Because there is no such thing as "12m2", it is 12m², but most keyboards do not have a way to produce that character. Everyone know what you're talking about when you say you have a 12m kite.

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Re: Calculating Aspect Ratios

Postby Peter_Frank » Mon Jan 14, 2013 11:39 pm

dyyylan wrote:
Peter_Frank wrote:Why do so many use the term "12m" about a 12m2 kite ?

The word constellation 12m does not exist as an area measurement in Danish nor German, and also lacking in most other languages, so why do so many english speaking say "12m" ?
Simple lazyness, or old bad habits or ?



Because there is no such thing as "12m2", it is 12m², but most keyboards do not have a way to produce that character. Everyone know what you're talking about when you say you have a 12m kite.


Sorry if explained wrong then - I meant that in "talk" many english speaking say 12 meter kite...

And this "term" is not used in most other languages, where it is named (translated of course) 12 squaremeter kite :thumb:

Just a silly thing I've noticed :roll:

:D Peter

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Re: Calculating Aspect Ratios

Postby Peter_Frank » Mon Jan 14, 2013 11:53 pm

Kiteus Maximus wrote:
Peter_Frank wrote:
Aspect Ratio = span / average width.

Area = span * average width.

Meaning AR = span^2 / area.

So your 12m2 kite with an AR of 5.4 has a span = sqrt(AR*area) = sqrt(5.4*12m2) = 8.0 meter.

And an average width = span / AR = area / span = 1.49 meter.

:D Peter


This is not a true way to calculate the aspect ratio. You can have the same aspect ratio for different sized kites and if you use your calculation logic then different size kites will have different aspect ratios.


I dont understand ???

It IS the very defintion of aspect ratio, so nothing one can change about that.

Just see the numbers Hansen uses - the very same calculation of course, and also giving approximately the same AR for different sizes :thumb:

Even though some brands also have lower AR for their smaller kites, so just different choices...

:D Peter

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Re: Calculating Aspect Ratios

Postby Peter_Frank » Tue Jan 15, 2013 12:26 am

Great so see some exact examples Hansen.

It shows that instead of the pre 2000 size scaling of 1.36 it is up to 1.8 for the most hardcore freestyle Switch C kites like the Combat.

And for the Method it is 1.42 so much closer to the pre 2000 "standard" sizing.

This is of course because the very first kites (Wipika Classic) were VERY wide in the middle, and tiny tips (and 2 lined) - so looking way more like present delta kites or the Method V2 or similar, thus having a similar projected factor, almost no matter how flat or not :D

The C or more C like kites with wider tips (really fast turning), like the Fuels and Nitro-Combat-Element has a factor between 1.6 and 1.8 apparently 8)

Nice to see some real numbers, thanks :thumb:


The Wipika Classic around 1.36 projected factor, actually quite low compared to later C kites:

Image



And another type with a REALLY low projected factor:

Image

Paragliders, to take a comparison to maybe the most flat types, typically has a projected factor between 1.1 and 1.2 only !

:D Peter Frank

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Re: Calculating Aspect Ratios

Postby oldschoolman » Tue Jan 20, 2015 2:07 pm

Peter_Frank wrote:Formula is correct, and the easy way to measure (but numbers are not...)

Aspect Ratio = span / average width.

Area = span * average width.

Meaning AR = span^2 / area.

So your 12m2 kite with an AR of 5.4 has a span = sqrt(AR*area) = sqrt(5.4*12m2) = 8.0 meter.

And an average width = span / AR = area / span = 1.49 meter.

Why to complicate you with calculations, when you can simply put your dimensions on an web tool like this and calculate AR? I'll always use this tool to calculate AR and never fail.

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Re: Calculating Aspect Ratios

Postby Laughingman » Tue Jan 20, 2015 10:36 pm

dyyylan wrote:
Peter_Frank wrote:Why do so many use the term "12m" about a 12m2 kite ?

The word constellation 12m does not exist as an area measurement in Danish nor German, and also lacking in most other languages, so why do so many english speaking say "12m" ?
Simple lazyness, or old bad habits or ?



Because there is no such thing as "12m2", it is 12m², but most keyboards do not have a way to produce that character. Everyone know what you're talking about when you say you have a 12m kite.


Actually every keyboard at least within Windows can do this ² .... the key combination is
Alt 0178 ² and Alt 0179 for ³ and Alt 0176 for ° etc.... you can pretty much use any character you want if you know the correct key combination.... note you must hold the alt key down while you enter the numbers


edit: just looked it up, you can do it with Mac as well but the key combinations are different.


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