Joined: Sat Feb 05, 2005 3:22 am Posts: 1237 Location: PBKiteboarding.com Sales-Repair-Lessons Ozone, Aboards, Flysurfer, OR, Canada USA Worlwide
Yeah thanks going good... lots of happy guys smiling now..
I always stick with the real deal... and physics always wins... much of it is weight in lulls that drop kites. I sell Inflatables too... great Kite Ozone Zephyr 17m (I used to ride a 19.5 and 22.5m Inflatable. Phew, Good thing I ride both... and is biggest needed as an inflatable with since weight becomes a huge factor in lulls.
I wish Inflatables could be lighter but it's because of the pressure in the Leading Edge that require a certain strength of Dacron and the bladder weight. Combined that make the kite heavier and more weight on front than on trailing edge as well...
I'm on a 17m Zephyr and Aboard Lightwinds Video... Lots of Fun and just taught a New Customer one as well and sell many. Some just want this and don't need lighter winds or more power.
But, I will get in trouble when any Customers is on an inflatable I sell and if I don't tell them that one day all the other guys will be kiting when they can't or Screaming up wind on their Flyrace and 21m.. happens all the time here.... Yikes...!
But Reality is there is a whole other level... in low wind areas (Lulls) or heavier guys... even like this old video holds true...
hhmmmmm...Keep thinking for sure.... But at least we're all having fun Kiteboarding..! What a Sport!
I had a 21 and it weighed at 8.5lb without bridle.......well the XR2LW 19 10.5lb "with bridle system"
SupaEZ, you must also measure mass of air you pump up to your kite! I don't know the bladder volume and pumping pressure you are pumping into your Core, but pumped air has estimated mass of 2-3kg. You convert it to a non SI (standard unit) weight.
Now we can go to gas buoyancy in atmosphere. Atmosphere is in 1bar so you can reduce that from the mass of air (or pressure) at your kite. This also involves the 21. So for flying the 21 has mass of air kite_volume times 0.01bar (ram air pressure) times air characteristics (density etc). So 21 is still light when flying. But Core is even heavier. Or are you flying an empty kite?
I had a 21 and it weighed at 8.5lb without bridle.......well the XR2LW 19 10.5lb "with bridle system"
SupaEZ, you must also measure mass of air you pump up to your kite! I don't know the bladder volume and pumping pressure you are pumping into your Core, but pumped air has estimated mass of 2-3kg. You convert it to a non SI (standard unit) weight.
Now we can go to gas buoyancy in atmosphere. Atmosphere is in 1bar so you can reduce that from the mass of air (or pressure) at your kite. This also involves the 21. So for flying the 21 has mass of air kite_volume times 0.01bar (ram air pressure) times air characteristics (density etc). So 21 is still light when flying. But Core is even heavier. Or are you flying an empty kite?
With your logic the 21M would be heavier than my 19
This huge twinskin as a LOT more of air inside (volume) at 1 PSI
The 19 is pumped at between 6 & 7 PSI
I do not think that pumping air inside the 19 adds 5 pounds to it
Do you even kite in light air....when the wind is 8 knots i can keep up with the 21
And at 10 knots the 21 is basically not necessary anymore
Joined: Mon Aug 12, 2002 1:00 am Posts: 1593 Location: Miami @ 6" Flat Butter!
joriws wrote:
you must also measure mass of air you pump up to your kite! I don't know the bladder volume and pumping pressure you are pumping into your Core, but pumped air has estimated mass of 2-3kg. You convert it to a non SI (standard unit) weight.
Now we can go to gas buoyancy in atmosphere. Atmosphere is in 1bar so you can reduce that from the mass of air (or pressure) at your kite. This also involves the 21. So for flying the 21 has mass of air kite_volume times 0.01bar (ram air pressure) times air characteristics (density etc). So 21 is still light when flying. But Core is even heavier. Or are you flying an empty kite?[/quote
Pump me up wrote:
MASS & INERTIA Ram airs contain a huge mass of entrapped air; consequently inertia is HUGE. Large ram airs (eg Flysurfer 19m & 21m) contain >11kg of air in their cells vs 2-3 kg in the tube structure of inflatables. The huge inertia of ram air kites causes a multitude of problems including poor lift, slow turning, difficulty kitelooping, and diminishes the "sweet spot" for unhooking (one of the reasons ram airs are a poor choice for wakestyle riding). Poor turning and acceleration results in inferior dynamic power (the power generated with sinusoidal kite movement).
I'm glad people are shedding light on this issue Looks like PMU figured out the pumped air estimated mass right on an L.E. I. but his calculation is way off on huge foil kites I'm surprised he hasn't chimed in yet......
@SupaEZ, I agree at 10 Knots minimum I can use a 12m SP3 with the 6m line extension to make it work on a Mutant.
DrLW
PS. Foil Kites still outweigh some known negative side-effect in certain needs & circumstances. Like having the advantages for better self launch & land and when you need better weight & pack up for traveling at the end.
I'm glad people are shedding light on this issue Looks like PMU figured out the pumped air estimated mass right on an L.E. I. but his calculation is way off on huge foil kites I'm surprised he hasn't chimed in yet......
Well I told it to PMU on some of the threads. I also tried to educate him about subject flying mass versus inertia. Or in general what is acceleration (inertia).
Now to SupaEz. What did I say about buoyancy. Air in air in same pressure/density is weightless as it is buoyant AFAIK. It means that most air in 21m is buoyant. Ram air pressure is 0.01bar so volume*ramairpressure*airdensity = mass of non-buoyant air. On inertia side you need to accelerate all the air what is in the kite, so on inertia side 21m has more air mass than 19m. But we were talking about flying weight, didn't we?
*edit* And to the SupaEz's question, I do light wind. I even do zero wind kiting in winter with kite flying only with apparent wind. If you are far away on the ice and wind dies because of atmospheric inversion, you need to get back to your car.
Very interesting thread! Thinking about masses of airs in tubes and foils and theire influences to the way of working of these mashines is an intresting base of discussion. I didn't thought about the mass of compressed air in my kites befor reading this... A few month ago, I bought a dyno 18 and had a realy nice light wind session regardless of my 105kg. I realy liked the dyno but it needs to be sined 2 or 3 times before flying well. And by the way, the dyno produces less stearing forces and bar preassure than my 12m switchblade (2011) while it is reacting more precise on stearing input - this is amazing. I realy like this kite and looking foreward for some sessions with more wind in it to ride my twin tip instead of a big door... Two weeks ago I tried to ride on a landboard the first time. It was not enough wind to stear the dyno from the one side of the wind window to the other without looping it. At the same time a (experienced) rider did some old school tricks with his fs 19 dlx. Backrolls Board Offs ... I packed my stuff and watched the show. After talking a lot about the fs, he gave me his flysurfer to play around a little bit. It was amazing how these kites stay in the air, relounch and what power they produce. One week ago, there was a little more wind and the dyno stayed in the air. I did my first runs, was great fun. But the dyno need the traveling speed I can't handle with a mountain board yet to produce reliable power. I found two used 15m and 21m speeds for my light wind land boarding. Don't want to destroy the dyno while landboarding. These ultra light weight tubes can't handle the rough job on land. On water it is different. Experienced light weight riders can do a lot with modern tubes. Great what is possible today! Sad that I am heavy - pounds eats knots Next season is gonna be a test season for sure, especialy on the water!
Joined: Fri Jan 09, 2009 4:49 am Posts: 2775 Location: Japan
mr_wilson wrote:
Sad that I am heavy - pounds eats knots
I know what you mean! My biggest kites and biggest boards have reduced that disadvantage though, to the point where I'm still riding when the little guys are walking
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