Monday, November 9, 2009

Kite Size Calculator / Weight Translator

**Note: This is old now. I have an updated version of the calculator, which incorporates wind ranges and board sizes and a graphical chart, at this link.**

**Note #2: My famous WINDSURFING CALCULATOR is available at this link.**

Most kite manufacturers make wind range recommendations for their kites based on a "typical" kiter who weighs about 170 lbs (77 kg). I made this table so people of different weights can translate those recommendations for themselves, or figure out proportional kite sizes relative to what their lighter or heavier friends are using. E.g., if 110 lb Tina is perfectly powered on her 8 msq kite, then 230 lb Lars should use his 16 msq kite.



I also included approximate wind speeds in the right hand columns that you can match to your weight and kite size. BUT the particular relationship between kite size and wind speed depends on the style of the kite, the quality and direction of the wind, the type of board, length of lines, etc. So take the wind speed versus kite size recommendations with a grain of salt, and be careful.

15 comments:

TonyWind said...

I'm not into kitesurfing but something seems missing from your table...There shouldn't be a column with the wind speed (in your case decreasing from top to bottom of the table)?
I would say that, for a given wind speed, the right size of kite to rig should scale linearly with the mass of the kiter. Hence, if I'm half your weight I should rig a half size kite which is what your table suggests....

James Douglass said...

Hey Tony- The relationship between kite size and wind speed obviously matters, but it's kind of complicated, so I left it out for now. You're right about the scaling linearly with body weight, though.

James Douglass said...

Tony- Ok, I went ahead and did what you suggested.

TonyWind said...

Hey James, good work, did not mean to give you a hard time...just wanted to get the table right. As I said I'm not into kiting ;)

Angelo said...

Is there any windsurf size calculator? Thanks!

James Douglass said...

Angelo- Yes, I made one of those, too. Check the link I just put at the top of this post.

Brian said...

James,
The windsurf calculator seems to work well for my body weight, but is way off for my girlfriends weight (105lbs). It predicts much too small of a sail for her. I see the formulas you used, but how did you calibrate for different weights/winds?

James Douglass said...

Hi Brian-

That's interesting that the calc isn't working well for your gf. Is that your observation or hers? There's a couple reasons I can think of why that could be the case.

1. The weight of rig, board, harness, etc. are a greater portion of the total weight when the rider is light, so it becomes a problem that the calculator doesn't consider gear weight.

2. Small sails that your gf uses are shaped for heavier riders in higher winds, maybe with not enough belly for light air planing.

3. A bigger sail integrates the gusts and lulls from a larger section of wind, and a bigger rider has more inertia to coast through lulls once up to speed. So a small person may need to rig a bit bigger than recommended to keep power and momentum in the lulls. Maybe you could try using a handheld wind meter in conjunction with the calculator, and rigging your gf for the lulls?

4. Your gf's technique may be adapted to sailing overpowered if she is used to always being on sails a bit big for her weight. I.e. she may let the wind do the work more and not do the same kind of pumping and stuff that you do to get going.

Grzegorz said...

Hi,

Thanks so much for the kiteboarding calculation Jim. Very helpful.

I'm 200 lbs, live in NYC - I bought a 12m kite since it's supposed to be the avg sized kite for where I live, only to realize that that 12m is good for a guy that's 25 lbs lighter. I think I'm going to get a 16m kite based on my experience (cannot ride on 12m kite in light winds), AND, based on your calculator.

Thanks again,

Greg

James Douglass said...

Hey Greg!

I'm glad this worked for you. Yeah, 12 m is too small for a 200 lb guy unless it's quite windy. :)

-James

Colton said...

Hey this looks like a good chart to have around. Obviously there are a ton of other variables to consider (gusts,lulls, current and board sizes)I'm just learning to ride on the water, been trying closed cell foils, but think they are more suited to someone who already has riding skills. So I'm looking at a North Evo. Can't decide whether or not to get a 12m or 14m. I'm 185lbs and the only other rider in my area is 225 riding a 15m naish cult. From this chart, I'm thinking the 12m will be okay in most of my conditions.

James Douglass said...

Hey Colton- Yeah, I'd say you're right about foil kites. I had one that worked fine in steady wind, but was a big pain if you ever dropped it in the water. Since I made this post I've updated the kiteboarding calculator to incorporate board size and stuff, so you might want to check that out. http://jimbodouglass.blogspot.com/2011/01/interactive-kiteboarding-calculator.html

Deli said...

thx James

Anthony O'Neill said...

This is a real help for me as I'm still a beginner and wasn't sure what the best conditions would be for my 11m Nobile N62

Stefano said...

Has anyone an idea for the actual pull (in kgf or lb) kites of different sizes exert at different wind speeds?