PMU sur KITEFORUM.COM a écrit

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Please don't even consider buying "foil" kites, they are hopeless. Inflatables are vastly superior to ram airs. I've summarised the reasons for the superiority of inflatables:

1: LIFT TO DRAG RATIO (L/D)
- Rams have a HUGE drag ("D") coefficient compared to inflatables, making them more inefficient. This is reflected in their poorer lift and inability to fly as close to the window's edge as inflatables. Large rams can pull steadily enough, but lack the aerodynamic finesse of good quality inflatables.

2: INERTIA
- Because large ram airs contain a much larger mass of air compared to inflatables within their pockets, inertia is HUGE. Large ram air kites contain OVER 11kg of air in their cells vs 2-3 kg for inflatables. It is very difficult to move this mass of air across the sky. This causes a multitude of problems including poor lift, slow turning, slow sining, and difficulty kitelooping. Excessive inertia also means that ram air kites to have a much narrower "sweet spot" for unhooking, which is one of the reasons ram air kites are poor choices for wakestyle riding.

3: RIGIDITY, STABILITY, & FOIL SHAPE
- Semi-rigidity improves consistency, stability, turning, and handling. It means inflatables are able to withstand gusty conditions better than ram airs. Ram airs often fold, collapse, and twist in gusty conditions. Kite makers are always looking for ways to make kites more internally rigid, eg by joining the struts firmly to the leading edge, adding fifth lines, and bridles.
- For stability problems in ram airs stemming from lack of internal rigidity, see: http://www.foilzone.com/phpBB2/viewtopi ... sc&start=0
- Inflatables have a consistent foil shape because they are semi rigid. Rams deform and change their foil shape which causes an inconsistent aerodynamic profile.

4: TURNING
- Far from being a hindrance, the tips of inflatable act as rudders, enabling faster, more controlled turns.
- When in the air, the semi rigid tips of inflatables create a "sled effect" whereby the kite sits stably and predictably above you. This effect is noticeably less in bow kites and ram airs.
- Rigidity facilitates turning. Bar input TWISTS the WHOLE kite, causing a rudder effect at the wing tips to accelerate turns. Lack of internal rigidity means that rams can't twist as aerodynamically as inflatos, meaning their turning and feedback is sloppier and less precise.

5: LUFF CURVE/DEPTH PROFILE
- Luff curves vary extensively. Inflatables with flat luff curves sit forward in the window whereas inflatables with deeper luff curves sit further back in the window. It is the same principle as sailing: If you want more "bottom" end with a sail, you deepen the luff curve (eg letting out the outhaul on a sailboard). If you want more "high" end, you make the luff curve shallower (eg sheeting in the outhaul on a sailboard). There is a lot of difference amongst luff curves on kites; this determines a lot of handling differences. It's a matter of trying different inflatables until you find one you like.
- The excessive drag and inertia of ram airs causes them to sit further back in the window compared to inflatables. Hence, there is less scope for ram designers to modify the luff curve.
- Because of the semi-rigid structure inherent to inflatables the luff curve is much easier to standardise and maintain. Semi rigidity actually enables variables like the luff curve to be really optimised. Ram airs don't have this capacity.

6: RELAUNCH
- Ram lovers make a big issue of this. It isn't a big issue. Beginners find relaunching inflatables easy after a few sesssions. Yes, some rams can reverse launch, but so what... a lot of inflatables can reverse launch. Rams can launch directly downwind in the water, but so what... so can a lot of inflatables. Anyway, downwind launches are dangerous for beginners because of the risk of being flung or carted downwind. For intermediates and above, relaunching should not even be considered in the equation because a) they won't be dropping the kite much anyway and b) Relaunching inflatables is EASY. Commonly, ram airs will not relaunch properly because of twisting, bridle tangles, or waterlogging. These aren't such big problems with inflatables.

7: SAFETY
Inflatables are safer than ram airs because:
a) Downwind launches are bloody SCARY and can be dangerous. Eg viewtopic.php?f=1&t=2359529 . Because only a small bunch of slightly odd people use ram airs, there is confusion about their correct use, leading to potentially dangerous situations eg viewtopic.php?f=1&t=2360971
b) Because they lack internal rigidity, rams deform, twist, wineglass, and jellfish in the middle of the power zone etc when they are downwind of obstacles, in rotors, and in VERY gusty conditions. This is VERY dangerous. Some of the most frightening kitemares witnessed have involved ram users in gusty conditions - their kites have been virtually uncontrollable and have endangered both the rider and other beach users.
c) Surf conditions
-- While it is always a gamble if your kite gets caught by a wave, at least you've got a fighting chance if it is an inflatable. If it is a ram air, it's all over.

8: BRIDLE TANGLES & FAILURES
Bridle tangles are disturbingly common with ram airs. Check this thread viewtopic.php?f=1&t=2354115&start=30
In particular, note the statement by "schmoe" that goes: "A bridle tangle on flysurfer can mean that you do not go out... For me I had many lost hours where the wind is cranking because of the bridles. I rather inflate 5 tubes and know that the setup time is exactly 10 minutes, no more no less, than have setup time that is 70% 5 minutes and 30% an hour. And now with one pump, the setup time of a tube is less, so it is not an advantage of the foil anymore."
Ram air bridle tangles can be very dangerous. A lot of riders have reported how their ram airs caught seaweed in their bridles, causing their kites to wineglass and spin out of control.

Bridle breakages occur surprisingly frequently with ram airs. They can be expensive (US $500 plus) (eg see the thread titled "Flysurfer Warrior Exploding:" phpbb/viewtopic.php?t=4612 ) .

9: PRE-INFLATING
- Ram users struggle to pre-inflate their kites in a lot of situations eg cross- offshore conditions. I once witnessed a Flysurfer lover trying to launch at a point break in cross offshore conditions. He had to get a friend (inflatable rider) to grab one tip while he grabbed the other tip and they both ran up and down the narrow strip of beach, trying to pre-inflate - to no avail. He had to pack up and go home while the inflatable riders were able to do drift launches. Without pre-inflation, ram users find it very difficult to drift launch, a skill that is often required eg Promontory/headland launches.

10: RESALE
- Contrary to the propaganda of ram lovers, ram airs and inflatos have similar lifespans. The major determinant of lifespan is obsolescence. In 2-3 years, whatever you're using now won't be worth much and will be superseded.

11: REPAIRS
- Ram air repairs are generally a LOT more expensive. For example, this phpbb/viewtopic.php?t=4612 required a PARACHUTE repairer to fix his kite, costing well over $1000. Bills over $1000 are common, eg viewtopic.php?f=1&t=2348790
- In the first example above, Flysurfer refused to honor the warranty, even though the kite was less than a year old.

12: COMPETITION
Ram lovers frequently make ridiculous claims about upcoming competitions that they will "dominate." They then go on to get blown out of the water. For example, they said that various kites from Flysurfer (Psycho, Silver Arrow, Warrior, Voodoo, Titan, Insert Name Here..... etc) would dominate the pro kitesurfing circuit. It has never happened. No ram riders have ever made it into the top 20 on the PKRA - ref http://www.pkra.info . Ram lovers said ram airs would dominate the Cabo Verde Wave event... They didn't. They said ram airs would dominate the "low-wind" showdown in San Diego - They didn't. The top pro riders ALL ride inflatables because of their superior aerodynamic properties. It's interesting that ALL the world records in hang-time, as well as unofficial records like Eric Eck's crazy jump, are held by inflatables. Ram airs aren't even on the same page.

13: LAND & SNOW
Check out this thread viewtopic.php?f=1&t=2355153 Not only are inflatables superior on water (because of better aerodynamic performance, jumping, stability, and safety), they are also superior on snow and land for the same reasons.

14: LIGHT WINDS
Ram airs are inferior light wind kites for the following reasons:
1) Excessive drag (bridles, lack of internal rigidity), compromising the Lift/Drag ratio
2) VERY slow turning
3) Inertia. The Speed 2 19 contains over 11kg of air in its pockets, compared to about 3kg in the largest inflatables.
4) Bridle failures and tangling
5) Wind dropouts and gear failure
--EVERYONE experiences a few gear failures (eg broken lines) and COMPLETE wind dropouts every year. You're usually safe with an inflatable. It can be used to "self-rescue" or you can swim in with the kite. If things go REALLY bad, you can just use the inflatable structure to support your weight.
--ALL ram airs become hopelessly waterlogged after 45 minutes - unlaunchable and certainly unable to support your body weight. viewtopic.php?f=1&t=2346569 viewtopic.php?f=1&t=2358958&p=608890#p608890
6) 8 knot limit
-- Despite what anybody tells you, you won't really have fun on any kite (ram air OR inflatable) unless the wind is over about 8 knots. This is the starting point for BOTH ram airs and inflatables, but because of the reasons I've outlined above, inflatables are vastly superior. And this is just the starting point. You won't really be having fun until it hits about 10 knots on an inflatable OR a ram air.
- Ram lovers are prone to exaggeration and just plain misinformation about light winds, eg see the following thread: Ram airs jump 8m in 8 knots ("The future is bright, the future is foil") https://www.kiteforum.com/viewtopic.php ... &view=next
7) Objective Testing
-- A variety of kites were tested in light wind conditions in San Diego a few years ago viewtopic.php?f=1&t=2319439&hilit=ram+a ... +san+diego . Despite the ridiculous over-hyped claims from Flysurfer reps like Ted Bautista, Flysurfer ram air kites crashed and burned. The overall consensus was that Flysurfer ram air kites are ok in light wind, but they turn VERY SLOWLY. The overall impression was that there are much better inflatables. It's interesting that a lot of the ram air guys who were excited about this showdown were remarkably SILENT afterwards, in particular, Ted Bautista, the U.S. rep for Flysurfer. His alpha-male chest-beating rants in the lead up to this showdown almost defied belief.
For an example of the LIES that ram lovers tell about their kites, checkout viewtopic.php?f=1&t=2350141&p=539227#p539227
8) Flysurfer and Light Winds
See the thread about the poor light wind properties of Flysurfer viewtopic.php?f=1&t=2349064


15: GEEKS
Amongst inflatable riders, there is a certain amount of collegiality. Inflatable riders tend to hang out together and help each other on the beach and on the water. If you fly a ram air, you'll always be a bit on the outside; regarded as a bit weird and not really part of the group. Part of this is because you will always be in a minority on the beach, part of it is because ram airs are so rare that inflatable riders are a scared/unsure of ram airs, and part of it is because, as a group, ram rides ARE a bit weird. Anyway, one of the problems with being part of a weird minority on the beach is that it can be very difficult to find people to help launch and land your kite, eg http://www.seabreeze.com.au/forums/topi ... C_ID=51465

marshone a écrit

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Denis,

pour avoir fait du caisson une seul fois sur l'eau je confirme qu'il est possible de rider avec seulement 6knt. Mon experience était avec la Pulsion 18m et ma Sector. Je ne me serais pas aventuré très loin avec cette configuration mais techniquement il est possible de le faire. Avec un Hydrofoil et un caisson la combinaison est surement redoutable, par contre il ne faut pas être un adepte des changements de direction humide (les fesses à l'eau) puisqu'une simple erreur de pilotage devrait résulter en une imminante perte de controle du kite...

Comme confucius dirait, il ne faut pas mettre le doigt entre l'arbre et l'écorce

Mais que dirait le Yoda du LW (Use The Force?)

Qu'on organise le challenge ultra light wind au plus vite et qu'on confonde les capitaines bonhommes

À mon poids je ne crois pas que le matériel aurait fait une différence

Il devrait y avoir une formule pour diviser le poids du rider par le pouce carré de la voile diviser par la surface du board... non?

SebM a écrit

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Je ne suis pas d'accord avec toi Flysurfer64 quand tu dis que la limite pour rider en foil est le vent requis pour redécoller en eau profonde. Sauf dans ton cas vraiment spécifique ou tu décolle habituellement au large via ton bateau mais ça ne représente pas ce que 98% des rideurs font. Et j'ai pu très bien démontrer ce point la semaine passé ici au LSP. Vent nul au niveau de l'eau, vent de 5-8 noeuds sur l'anémomètre à 45' et j'estime un vent de 10-12 noeuds un peu plus haut via mes lignes de 30,5m. Je suis donc sorti en Core XR5 11m et j'ai rider mes deux plus belles heures de foil à date! Dont une heure fin seul. Et trois autres gars en foil sont venu me rejoindre par la suite. C'était tout simplement magique.

Bref si tu échappe pas ton kite (assez facile avec un caisson si on ride prudemment sans essayer de trick) le vent au niveau de l'eau je m'en fou ce qui compte c'est le vent dans ma voile. Et on ride dans quoi comme vent? Le vent au sol, le vent à 25', à 75'? Facile, on ride avec le vent qui frappe notre voile. Et par expérience je crois fermement que ça prend stict minimum 6-7 noeuds dans la voile entre les mains d'un expert avec un hydrofoil. Et pour ma part avec mon niveau plutot intermédiaire mais également en hydrofoil je dirais que ça me prend 8 noeuds et plus et encore, je suis pas certain.

Donc tout comme Denis, je ne crois nullement aux histoires de capitaine bonhomme de gars qui ont ridés dans 4-5 noeuds

PS: En passant Denis, t'es aller chercher ça loin le vieux post de PMU

Qu'on organise le challenge ultra light wind au plus vite et qu'on confonde les capitaines bonhommes

flex23 a écrit

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Pour l'instant, le record est toujours tenu par KiteRider...

flex23 a écrit

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D'après la référence, on a eu une heure de vent entre 5 et 10 knts (de 14h à 15h). Pas facile et pas convaincant.
Sylvain est sorti en FS Sonic II 18 m +foil, et, oui, on l'a vu remonter efficacement le vent, et puis, perdre son vent apparent sur un virement de bord....pas réussi a redecoller le kite ( ça correspond à ce qui a été décrit plus haut. ). Même chose pour Gemini I en R-I 17m, retour à la plage avec un chiffon mouillé.
Pendant ce temps, Astuce je crois, en baloune Turbine 17 m + galette maison se maintenait en vie laborieusement, et on l'a même vu progresser sensiblement au vent autour de 14h45.
Mention honorable à Astuce.
On a pu verifier la grande efficacité de la combinaison FS 18m + foil. Mais, dans des vents sous 10 knts, on est à la merci des deventes
Pas beaucoup de plaisir sous 10 knts dans nos conditions continentales. (pas maritimes.)




a grand voile et du foil, mais on