## Power Relative to Windspeed and Kite Size [Reference]

forum for kitesurfers

taiguy
Rare Poster
Posts: 45
Joined: Mon Jun 23, 2008 2:13 am
Kiting since: 0
Brand Affiliation: None

### Power Relative to Windspeed and Kite Size [Reference]

Image may be cropped due to forum formatting. Right click on the image and open in a new tab to see full table

Yes, this is a table of values. Yes, it may not immediately make sense. Stick with me though.

These are relative "power" levels compared between kite size (in square meters) and wind speeds (doesn't matter if knots or mph, so long as you're consistent).
Several interesting things we can deduce from this.

For instance I want to figure out what my next quiver step size should be. Most of us know this through experience (read, trial and error) already but look how it breaks down. Say you wanted to work backwards from your largest kite size. For this example, I'll say it's a 16m kite. Let's arbitrarily set our step size to 75%. I want my 16m kite to have 75% more power than my next smallest kite. Looking at the 16 column, and the 12 row, I see that a 16m kite has 178% the power of a 12m kite. Great, so my first two kites are a 16m and a 12m. What's my next smallest after that? Looking at the 12 column, and the 9 row, a 12m kite has 178% the power of a 9m kite. So I'd buy a 9m, 12m, and 16m if I wanted to stay consistent. (further going down the chain would be a 7m). Obviously you can increase this to 100% and just say each kite size should be double the power (17, 12, 8 )

Let's use it a different way. Say I know that for my ability, riding style, and body weight, I really like riding a 9m kite in 28 mph because I feel powered up. To keep that power level in 20 mph winds, what kite size should I be on?

Looking at the lower table, the 28 column and the 20 row, we see that 28 mph is 274% of the power of 20 mph. So we need to make sure that whatever our larger kite size is, has roughly 274% of the power of our 9m. Going back up to the top table, we see that a 15m kite is 278% the power of a 9m. Strictly talking wind and kite size, you'd want to size up to a 15m kite in 20mph winds to maintain the same level of power you had with a 9m in 28 mph winds.

Yes, there's apparent wind, projected area, diminishing returns, etc. etc. however, this should be a good guide.

plummet
Very Frequent Poster
Posts: 5880
Joined: Sat Aug 29, 2009 11:25 pm
Kiting since: 33
Local Beach: EE
Favorite Beaches: NZ
Style: Terrain riding
Gear: Old wornout ozone.
Plummet hydrofoil and mutant
Brand Affiliation: None

### Re: Power Relative to Windspeed and Kite Size [Reference]

Yes confusing and it will only work if you run the same type of kite for all of your quiver.

Personally I have 5 kites. each kite is different. They have different designs, different power levels.

Also depending on the day. Wind conditions. gusty or clean, swell conditions big/small, the style of riding I choose all make a big impact on the style and size kite I choose.

Eg 20 knot small swell, clean wind. i'll go my 13m some sweet jumps.
20 knots medium swell. 10m ride some waves do some jumps
20 knots with big lulls. 15m
20 knots gusty squally wind spikes big swell 8m

Peter_Frank
Very Frequent Poster
Posts: 8450
Joined: Wed Oct 16, 2002 1:00 am
Kiting since: 0
Brand Affiliation: None
Location: Denmark

### Re: Power Relative to Windspeed and Kite Size [Reference]

It displays the effect of the wind squared quite well

But might be a bit difficult for many, to use when just "numbers" ?

I made a similar thing, where the apparent wind is taken into consideration (as is ALWAYS the case), three years ago:

viewtopic.php?f=1&t=2368840&p=721494

Then one can always change relative to his/her own specific kite, typically by using another personal weight.

I dont see much use for such a graph, at least now when out often and experienced.
But for the upper extremes it can be helpful sometimes, and some medium experienced has advantage of seing how it works.

Of course, the very low end sizes are not "accurate" as such, because special boards and wind shear etc matters a lot - but still, a good overall impression about how wind speed and kite sizes are connected

Peter

taiguy
Rare Poster
Posts: 45
Joined: Mon Jun 23, 2008 2:13 am
Kiting since: 0
Brand Affiliation: None

### Re: Power Relative to Windspeed and Kite Size [Reference]

Peter_Frank wrote:It displays the effect of the wind squared quite well

But might be a bit difficult for many, to use when just "numbers" ?

I made a similar thing, where the apparent wind is taken into consideration (as is ALWAYS the case), three years ago:

viewtopic.php?f=1&t=2368840&p=721494

Then one can always change relative to his/her own specific kite, typically by using another personal weight.

I dont see much use for such a graph, at least now when out often and experienced.
But for the upper extremes it can be helpful sometimes, and some medium experienced has advantage of seing how it works.

Of course, the very low end sizes are not "accurate" as such, because special boards and wind shear etc matters a lot - but still, a good overall impression about how wind speed and kite sizes are connected

Peter
Someone else just informed me of Jim's calculator as well (http://jimbodouglass.blogspot.ca/2011/0 ... lator.html).

Cool stuff!

edt
Very Frequent Poster
Posts: 4939
Joined: Fri Jul 16, 2010 6:27 am
Kiting since: 2010
Local Beach: ford lake Michigan
Gear: slingshot liquid force wainman pansh naish north cwb burton

### Re: Power Relative to Windspeed and Kite Size [Reference]

not a real useful chart too many numbers.

Can you redo it like this?

175 pound rider on a 12 meter kite is considered the default

Now what is the kite size for equivalent power for kite speed in 15, 25, 30 knots

Now what is the kite size for equivalent power for 200 pound rider in 15,20,25,30 knots

And the same for a 150 pound rider.

That would be a more intuitive way to display the information.

taiguy
Rare Poster
Posts: 45
Joined: Mon Jun 23, 2008 2:13 am
Kiting since: 0
Brand Affiliation: None

### Re: Power Relative to Windspeed and Kite Size [Reference]

edt wrote:not a real useful chart too many numbers.

Can you redo it like this?

175 pound rider on a 12 meter kite is considered the default

Now what is the kite size for equivalent power for kite speed in 15, 25, 30 knots

Now what is the kite size for equivalent power for 200 pound rider in 15,20,25,30 knots

And the same for a 150 pound rider.

That would be a more intuitive way to display the information.
Mine wasn't setup to take rider weight, board size, or skill into account. It assumes you have at least one data point for yourself and then you can work from there. I believe Jim's spreadsheet (linked above) does what you're looking for though.

edt
Very Frequent Poster
Posts: 4939
Joined: Fri Jul 16, 2010 6:27 am
Kiting since: 2010
Local Beach: ford lake Michigan
Gear: slingshot liquid force wainman pansh naish north cwb burton

### Re: Power Relative to Windspeed and Kite Size [Reference]

taiguy wrote: Mine wasn't setup to take rider weight, board size, or skill into account. It assumes you have at least one data point for yourself and then you can work from there. I believe Jim's spreadsheet (linked above) does what you're looking for though.
It doesn't do what I'm looking for. Not unless I have a calculator, and if I have a calculator I can just multiply v^2 mass and kite size myself, don't need the spreadsheet.

UKSurf
Frequent Poster
Posts: 326
Joined: Wed Feb 22, 2012 9:09 pm
Kiting since: 1999
Local Beach: South Coast of UK
Gear: Slingshot Rally
Brand Affiliation: None

### Re: Power Relative to Windspeed and Kite Size [Reference]

Why does a 10m kite have 4x the power of a 5m in your first chart? I would think it would have 2x approx. also the power seems to be increasing with the power of 4 not power of 2 for wind speed. We need Bill Hanson to confirm these figures before they are used to purchase a quiver

edt
Very Frequent Poster
Posts: 4939
Joined: Fri Jul 16, 2010 6:27 am
Kiting since: 2010
Local Beach: ford lake Michigan
Gear: slingshot liquid force wainman pansh naish north cwb burton

### Re: Power Relative to Windspeed and Kite Size [Reference]

UKSurf wrote:Why does a 10m kite have 4x the power of a 5m in your first chart? I would think it would have 2x approx. also the power seems to be increasing with the power of 4 not power of 2. We need Bill Hanson to confirm these figures before they are used to purchase a quiver
u r right UKSurf, 10m kite has twice the power of a 5 meter kite. He also has wind speed wrong, he's got them going as the cube or v^3 which is incorrect. v^3 is only true for wind turbines but not for kites. For wind turbines when the wind doubles in speed the turbine also spins twice as fast. This is why instead of v^2 a turbine gets v^3. Kites feel v^2. I might make a chart in the format I mentioned previously after I get back from vacation.

taiguy
Rare Poster
Posts: 45
Joined: Mon Jun 23, 2008 2:13 am
Kiting since: 0
Brand Affiliation: None

### Re: Power Relative to Windspeed and Kite Size [Reference]

UKSurf wrote:Why does a 10m kite have 4x the power of a 5m in your first chart? I would think it would have 2x approx. also the power seems to be increasing with the power of 4 not power of 2 for wind speed. We need Bill Hanson to confirm these figures before they are used to purchase a quiver
I haven't seen any information that would corroborate edt's claim.

Power increases with respect with the square of the area and cube of the windspeed. But please have Bill come and give us all a short course