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Posted: Mon Jun 24, 2002 8:15 pm
For selecting the kite size (in mÃ‚Â²) in relation to the wind (in knots) I propose a simple formula:

kn x mÃ‚Â² = constant (DetlefÃ¢â‚¬â„¢s Kite Rule)

The constant is in the range of 100 Ã¢â‚¬â€œ 300 and dependent on the type of kite and the capability of the rider. From my experience the following values hold approximately for the lower bound <sine bows> (MIN), the optimal range (OPT) and the upper bound <pros> (MAX) for kites with projected area (Proj.) and kites with developed area (e.g. ARX and X2):

........|... MIN ...... OPT ..... MAX
-------|----------------------------
Proj.. | ... 75 .. 110 - 150 .. 180
ARX . | . 100 .. 150 - 200 .. 250
X2 ... | . 150 .. 200 - 250 .. 300

A table as overview (also presentable as Excel graph):

_mÃ‚Â² | c100 c150 c200 c250 c300
------|-----------------------------------
_4.0 | 25.0 37.5 50.0
_4.5 | 22.2 33.3 44.4 ....... kn
_5.0 | 20.0 30.0 40.0 50.0
_5.5 | 18.2 27.3 36.4 45.5
_6.0 | 16.7 25.0 33.3 41.7 50.0
_7.0 | 14.3 21.4 28.6 35.7 42.9
_8.0 | 12.5 18.8 25.0 31.3 37.5
10.0 | 10.0 15.0 20.0 25.0 30.0
12.0 | _8.3 12.5 16.7 20.8 25.0
14.0 | _7.1 10.7 14.3 17.9 21.4
16.0 | _6.3 _9.4 12.5 15.6 18.8
18.0 | _5.6 _8.3 11.1 13.9 16.7
20.0 | _5.0 _7.5 10.0 12.5 15.0
24.0 | _4.2 _6.3 _8.3 10.4 12.5

I hope for an intensive discussion about the suitable constants for the many different kites on the market. On this basis the producers will provide their customers a comparable reference for their kites sizes.

Dr.-Ing. Detlef Teichmann,
Munich, Germany, June 24th, 2002

<font size=-1>[ This Message was edited by: Detlef on 2002-06-25 22:32 ]</font>

Posted: Mon Jun 24, 2002 8:51 pm
kn x mÃ‚Â² = constant (DetlefÃ¢â‚¬â„¢s Kite Rule)

....... | MIN | ....OPT... | MAX
------|------|------------|------
Proj..| _75 | 110 - 150 | 180
ARX .| 100 | 150 - 200 | 250
X2 .. | 150 | 200 - 250 | 300

A table as overview:

. mÃ‚Â² |c 100 |c 150|c 200 |c 250|c 300
------|-------|------|-------|-------|-----
_4.0 | 25.0 | 37.5 | 50.0 |
_4.5 | 22.2 | 33.3 | 44.4 | ........ kn
_5.0 | 20.0 | 30.0 | 40.0 | 50.0 |
_5.5 | 18.2 | 27.3 | 36.4 | 45.5 |
_6.0 | 16.7 | 25.0 | 33.3 | 41.7 | 50.0
_7.0 | 14.3 | 21.4 | 28.6 | 35.7 | 42.9
_8.0 | 12.5 | 18.8 | 25.0 | 31.3 | 37.5
10.0 | 10.0 | 15.0 | 20.0 | 25.0 | 30.0
12.0 | _8.3 | 12.5 | 16.7 | 20.8 | 25.0
14.0 | _7.1 | 10.7 | 14.3 | 17.9 | 21.4
16.0 | _6.3 | _9.4 | 12.5 | 15.6 | 18.8
18.0 | _5.6 | _8.3 | 11.1 | 13.9 | 16.7
20.0 | _5.0 | _7.5 | 10.0 | 12.5 | 15.0
24.0 | _4.2 | _6.3 | _8.3 | 10.4 | 12.5

Detlef

<font size=-1>[ This Message was edited by: Detlef on 2002-06-25 22:41 ]</font>

Posted: Mon Jun 24, 2002 9:15 pm
Hi,

for a better understanding two examples for my formula ( kn x mÃ‚Â² = constant):

If you fly an 11.8 mÃ‚Â² AirBlast in a range of 8.5 Ã¢â‚¬â€œ 17 knots, than your lower constant is 100 (11.8 x 8.5) and your upper constant is 200 (11.8 x 17). Therefore you can go with an 16.4 mÃ‚Â² AirBlust in 6 Ã¢â‚¬â€œ12 kn (100 / 16.4 Ã¢â‚¬â€œ 200 / 16.4) and an 8.4 mÃ‚Â² in 12 Ã¢â‚¬â€œ 24 kn ( 100 / 8.4 Ã¢â‚¬â€œ 200 / 8.4).

As you can see in the table: If you can fly a 10 mÃ‚Â² kite in 20 Ã¢â‚¬â€œ 30 knots, than your constant is 200 Ã¢â‚¬â€œ 300 and you can fly the 20 mÃ‚Â² kite in 10 Ã¢â‚¬â€œ 15 kn or the 8 mÃ‚Â² in 25 Ã¢â‚¬â€œ 37,5 kn.

Detlef

<font size=-1>[ This Message was edited by: Detlef on 2002-06-25 22:25 ]</font>

Posted: Thu Jun 27, 2002 1:14 am
sounds great but I'll get sand in my sliderule

Posted: Fri Jun 28, 2002 6:13 am
Typical engineering thinking... donÃ‚Â´t kill anyone in boredom. No wonder marketers take care of marketing and engineers take care of numbers.... Why canÃ‚Â´t you go to the beach, check the wind, rig the right kite straightaway and have fun? The wind will be varying anyway so... pick the 11.5 or 15.5 and rip. So f...king what if the kite is 0.88 m2 too small or big? Some people only have one or two kites and tell me, what does a calculator help? Nothing. Dank U.

Posted: Fri Jun 28, 2002 6:17 am
and furthermore... who the hell is measuring knots when trying to manage the boldly under/owerpowered kite? Use your eyes, check the wind and go. Those who measure are on the beach and those who rip donÃ‚Â´t measure...

Posted: Fri Jun 28, 2002 10:43 am
Deltef, I did a similar exercise a few years back regarding windsurf sail size and rig settings as part of my computing degree. I went for the full monty - electronic scales and a real time wind feed. As soon as I passed the course, I chucked it in the bin - nothing beats the human brain!

Posted: Fri Jun 28, 2002 10:56 am
Detlef, did you take in consideration the different weights of the riders?

For beginners it is interesting so they could feel more comfortable in their selection of kitesizes.

Toby

Posted: Fri Jun 28, 2002 4:59 pm
Toby,
the simple formula (kn x mÃ‚Â² = const.) is especially a help for the decision of beginners. Their range will be rather in collumns c 100 - c 200, the pros will go up to c 200 - c 300.

A good average is: kn x mÃ‚Â² = 200

The weight will decrease or increase the constant. I have no experience about the equivalent of -/+ 10 kg in the rage of knots you can fly.

. mÃ‚Â² |c 100 |c 150|c 200 |c 250|c 300
-----|------|-----|------|------|-----
_4.0 | 25.0 | 37.5 | 50.0 |
_4.5 | 22.2 | 33.3 | 44.4 | ........ kn
_5.0 | 20.0 | 30.0 | 40.0 | 50.0 |
_5.5 | 18.2 | 27.3 | 36.4 | 45.5 |
_6.0 | 16.7 | 25.0 | 33.3 | 41.7 | 50.0
_7.0 | 14.3 | 21.4 | 28.6 | 35.7 | 42.9
_8.0 | 12.5 | 18.8 | 25.0 | 31.3 | 37.5
10.0 | 10.0 | 15.0 | 20.0 | 25.0 | 30.0
12.0 | _8.3 | 12.5 | 16.7 | 20.8 | 25.0
14.0 | _7.1 | 10.7 | 14.3 | 17.9 | 21.4
16.0 | _6.3 | _9.4 | 12.5 | 15.6 | 18.8
18.0 | _5.6 | _8.3 | 11.1 | 13.9 | 16.7
20.0 | _5.0 | _7.5 | 10.0 | 12.5 | 15.0
24.0 | _4.2 | _6.3 | _8.3 | 10.4 | 12.5

Detlef

Posted: Mon Jul 01, 2002 11:49 pm
Although I also would only trust the "good human brain" check at the beach, I think your table could be used as great help to choose the kite size one wants to purchase.

Your table, when used in the c150-c300 range, corresponds remarkably well to my typical ranges with the Fone 18 and 12 !

Cheers,
j.

<font size=-1>[ This Message was edited by: Jido on 2002-07-02 00:51 ]</font>