Contact   Imprint   Advertising   Guidelines

Trapped air in double skin foils?

For all foil kite riders
Regis-de-giens
Very Frequent Poster
Posts: 1380
Joined: Thu Jul 31, 2014 2:58 pm
Weight: 62 kg
Local Beach: France: St Laurent du Var, Cannes, Almanarre
Style: 62 kg , light wind, waves
Gear: Conceptair pulsion 18&15&12S, OR Flite 10m , Airush One 9&6, peak 5M , Rally 6, Elf 11 &7, 19m2 single skin proto.
foil Ketos, RCS Supreme, TBK Mana, snowskis, kite-boat
Brand Affiliation: None
Has thanked: 83 times
Been thanked: 80 times

Re: Trapped air in double skin foils?

Postby Regis-de-giens » Sat Jan 09, 2021 7:19 pm

Tomlutz wrote:
Thu Jan 07, 2021 11:16 am
Regis-de-giens wrote:
Tue Jan 05, 2021 12:03 am
There is however one big advantage of entraped air : the internal pressure provide an additional stiffness that allows more efficient foil profile, like less "twisting" of wingsfor exemple. On the contrary on a SS (so, without internal pressure ) you need to impose more Angle of Attack on wings (to avoid their collapse), and you loose some efficiency (drag) and thus less speed and pull during the travel of the kite, very useful in lightwind.
I don't think the stiffness is the main reason for better performance. I am also paragliding and fly single skin paragliders. However, unlike the kite market there are high AR single skin paragliders (AR of 6), I don't know of any high AR single skin kites (not counting LEI, which in fact are also single skins). The main obstacle is the increased drag due to the fact that there is no skin on the bottom for better aerodynamics. Hence single skins just do not fly fast, otherwise they have quite good performance, in some respect even better performances and even better stability than double skins even though they are not at all stiff. Tom
Not the stiffness in itself, I fully agree ; but the fact that designers can use the increased stiffness of double skin (and same for LEI's) to optimise the twist at tips locations, and decrease the AoA of the tips, leading to a better L/D ratio overall, which is called Performance ; for a similar aspect ratio, a double skin will have a better L/D ratio than a single skin (also the turbulence behind the leading edge , it is true); if you take a well deigned double skin and cut the intrados, most will collapse at tips if you do not change massively the local twist ("vrillage" in french) by changing the bridges around the tips .

slide
Frequent Poster
Posts: 441
Joined: Tue Nov 27, 2018 12:54 pm
Kiting since: 2003
Weight: 75kg
Local Beach: Brancaster Norfolk 46 miles- just need a hard beach
Favorite Beaches: mablephorpe , cleephorpes uk-just need a hard beach
Style: landboarding with a petzl work harness
Gear: old blades and old flysurfer's , ckb/dex carbon landboards, modified airdeck and a home made snow board with barrel wheels ,soul's , spd5's
Brand Affiliation: None
Location: east anglia, uk
Has thanked: 51 times
Been thanked: 21 times

Re: Trapped air in double skin foils?

Postby slide » Sun Jan 10, 2021 10:03 pm

well you can try to be quiet or if not cough at the same time , and then move away very quickly , :out: but 2 Rennie normally sort me out , sugar free of course


Return to “Foil Kites”

Who is online

Users browsing this forum: No registered users and 6 guests