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Marginal wind kites ?

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muitomaluco
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Re: Marginal wind kites ?

Postby muitomaluco » Fri Jul 27, 2018 7:44 pm

tomtom wrote:
Fri Jul 27, 2018 7:08 pm

BTW where you can buy strutless GONG 17 for 500?

I also think that it possible to make good restartable LW lei - but thats future and there are good LW foils NOW!
Mixed up the prices: new some 590.-
Used 17m² Demo-Kites you can find in section "great deals" on their homepage for 509.-
https://gongsupshop.com/epages/box1707. ... SSV2DEMO40


Video about the relounch abilities looks just great to me... But of course they wouldn´t put it in the video if theyd fail couse of too low wind one day... ;-)
http://www.gongkite.com/Strutless-relaunch.html?lang=fr

tomtom
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Re: Marginal wind kites ?

Postby tomtom » Fri Jul 27, 2018 8:03 pm

Thanks.

About relaunch - It was SO SO and in best position for that particular kite - and not in marginal - they are LEI kite riding in background. Most problem with relaunch MONOS and ZEROS are leading edge up. Lack of structure makes them lay on water flat and they just stick to the water. I can relaunch foil kite in any wind where it flyes stable on zenith - there will be NO LEIs riding then. Of course according to Pedro it is still not marginal :) You need much much less resistance to restart foil - almost no difference if you can or cannot resist pull /ie. shallow water/.

kitexpert
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Re: Marginal wind kites ?

Postby kitexpert » Fri Jul 27, 2018 8:10 pm

tomtom wrote:
Sun Jul 15, 2018 3:48 pm
I think that AIR mass traped in kite is much dominating factor to kite reaction but maybe im wrong. Also in mediterran sun air in kite is very hot and now im believer in hot air baloon effect which keeps kite stable on zenit. I has very surprised about air temperature in it. It was like 60-70 hot.
Air inside of foil kite makes them slower to react, but it is not that much a problem with small kite sizes. Small foil kites are in general fast enough.

But if you double kite area you almost triple the volume (and inertia) of it.

"Hot air balloon effect" is nonsense, everyone who bothers to find out air density in different temperatures knows it. And it should be remembered air is constantly moving through the kite, there is leaks and also draining vents which are open all the time.

Interesting topic however.

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Re: Marginal wind kites ?

Postby tomtom » Fri Jul 27, 2018 9:00 pm

40 degree difference makes 200g per m3. I know 40 degree is little extreme but just little :) So in 3m3 kite it CAN be 600g uplifting force. I know this is very optimistic estimate but even half - 300g can make difference - especially in full line slack situation.

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Re: Marginal wind kites ?

Postby kitexpert » Fri Jul 27, 2018 11:58 pm

tomtom wrote: 40 degree difference makes 200g per m3. I know 40 degree is little extreme but just little :) So in 3m3 kite it CAN be 600g uplifting force. I know this is very optimistic estimate but even half - 300g can make difference - especially in full line slack situation.


At 30 degrees air density is 1.16kg/m3, at 50 degrees it is 1.09kg/m3, about 70g/m3 difference. 9m AR 5 kite has volume of about 1.2m3, so in that case this effect would be 84g. Compared to kite weight and lift forces kite has when it is possible to kitesurf this kind of help is insignificant.

I was kite surfing on Thursday, no clouds and temperature peaked 26 degrees C. There was three foil kites on the water, Sonic2, Matrixx3 and Speed5. I helped Speed and Matrixx down but I didn't notice anything warm in them. With Sonic2 I had a nice low wind session, but I doubt it had any more hot air inside than those other two :)

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Re: Marginal wind kites ?

Postby tomtom » Sat Jul 28, 2018 12:16 am

I was using this https://www.engineeringtoolbox.com/air- ... d_600.html
Online Air Density Calculator - and use little extreme 20 and 60. I was kiting whole June in Croatia and while it wasnt particular hot - about 25 whole time /unusual cold/ the air in kite was very very hot - im mean not warm but like hairdryer hot. It is my first foil kite after long time and also first time i noticed this. Maybe its little related to particular latitude and particular day IR intensity. But by no means I insist on hotballoon theory :)

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Re: Marginal wind kites ?

Postby tomtom » Sat Jul 28, 2018 12:28 am

Anyway. What about dream marginal wind kites? Im still think it is possible to make very good LEI for marginal freeride. It just must be clearly produced with warning about "maximal canopy load"
So for freeride HF only. Quite conventional multistrut with minimum reinforcement and from very light cloth. Also tube and struts should be from lighter material - in bigger sizes LE diameter should be big enough so lower pressure LE will not be such problem for rigidity. Bridles should be much denser almost foil like to distribute load better and also on TE for better reverse relaunch.
But maybe todays foil kites are just as good - who knows. For now they are better in this condition for me.

foilholio
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Re: Marginal wind kites ?

Postby foilholio » Sat Jul 28, 2018 12:53 am

Hot air balloon effect is real. Why because astute flyer can notice it. Two because the air in the kite can actually get warm or even quite hot compared to surrounding air. You can not escape physics, if the air is warmer you have increased buoyancy.

The hot air balloon effect is most noticeable on the largest kites, in the lightest wind. 4 reasons for that. Larger kites have least weight per m2 or m3. Largest kites have the most m3. Light wind reduces air exchange inside the kite. Light wind reduces skin cooling.

The notakitexpert is just proving his idiocy by arguing against this. This is basic physics and some simple observations. Something I would think not a high IQ would be needed to grasp. But in that maybe I am wrong.

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jakemoore
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Re: Marginal wind kites ?

Postby jakemoore » Sat Jul 28, 2018 4:04 am

foilholio wrote:
Sat Jul 28, 2018 12:53 am
Hot air balloon effect is real.
Hot air gives lift to Kiteforum! Especially when the wind is light.

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Re: Marginal wind kites ?

Postby foilholio » Sat Jul 28, 2018 4:27 am

Come on you can do better. Personally I am waiting for a Pullstrings reply and a kitexpert cad render.


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