Hey Guys,

Curious about how differences in design lead to differences in performance.

I was flying my newly purchased Twister 3.0 (thanks again rich!) and then switched to my CrossKites Quattro 4.5, and I honestly think they were pulling as hard as each other. The Twister was certainly faster, but I expected it to have less pull do to its size. I noticed that its aspect ratio is definitely higher than the Quattro (don't have any idea of what that number actually is, but it's obvious flying them that the Quattro is more squat looking and the twister more skinny).

There is no doubt in my mind that the Twister is better built kite, given that CrossKites is specifically a more beginner, budget friendly brand (that's what they market, anyways), and that the lines are simpler/thicker/heavier.

For reference winds were probably in the range of 6-10 mph. So my biggest question is, as I fly in higher winds, will the Quattro pull harder than the Twister, or will the two kites continue to have a similar output across any given wind range? For now I'll be using the Quattro as it gives me more time in the window to get moving (I tried landboarding again this weekend mainly with the Twister but by the time I got rolling it was already at the edge of the window, so I think the Quattro will be better for me now in that regard).

I also understand that my perception of pull is highly suggestive but I did expect more difference in how these kites performed, at least in terms of power output. Does it make sense for a better built, higher aspect ratio kite to pull as hard as a bigger kite? Will his hold true in higher winds? Lower winds? Is there a way to know this, or do I just need to fly them in different winds and find out for myself? I appreciate any and all input!

not for anything but was trying to bug this wkend in lite wind and couldnt get going w/ an 8.5 Blade my ultimate day saver...i broke out my 4.9 Blade had to work like a dog but finally got going...point being i dont know really...but seams yes the same kites act differently in different winds...i guess:dunno:
just keep throwing stuff up in the air till you get the desired result

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Is there a way to know this,

I don't think so. I have a set of Methods - a mid aspect kite. Put them up against a Reactor or Century (maybe slightly higher aspect ratio? ) and the results are completely different. I think the methods are bridled with a much lower angle of attack - and you don't really see that in a picture. A 2.8m Century will easily out pull and outperform the 4m Method under 16knots. Absolutely chalk and cheese. Above 18 knots, the Method still sits well forward and begins to leave the 2.8m Century - which by now is pulling a bit much to the side and causing the back end to kick out a bit. My point is, they are completely different performing kites...but to look at, they don't look that much different.

Static flying is the same - the 4m Method is quite mild whereas the 2.8m Century is explosive with much more power.

So similar looking kites can fly completely differently and I think you either have to fly them, or talk to people that have flown a few different types to try to get a feel for how they perform. I think there's a lot more to it than just aspect ratio.

Chalk and cheese... I love it,... must be an Aussie-ism...

Flight characteristic is a culmination of many factors. I would presume that the 2 kites will likely perform relatively similar in most conditions. To the best of my understanding, how strong a kite pulls and where a kite pulls is a function of the combination of Aspect Ratio, profile and angle of attack.

Your Quattro is designed to be a tame all-around beginner style kite. But the Twister is designed for lift and speed. The Twister's AR I believe is around 3.6-3.7 ish, combined with its specific AoA and profile, it is designed for LIFT... It's a jump-kite for sure (in the bigger sizes) (DO NOT JUMP WITH A 3M KITE). Typically higher AR kites have a stronger pull. The Quattro likely has an AR around 3.4 ish.

What you find with AR is that as the AR goes up, strength and speed increase, but stability decreases. Twisters are very stable as their AR is still low enough that stability as not really effected. But hen the AR gets over 4, then you start to notice the difference in stability.

So, given that, it IS likely that the 2 will perform the same in most conditions, but don't be surprised if your Twister out-performs the Quattro, because as the speed increases, apparent wind increases and might give you even more oomph. Conversely, if the wind is very unstable, you might find the Quattro performing better, at least in the department of stability and ease of use.

so theres a nice muddles answer for you, hope it helped

It's not just A/R and AoA but also how rigid a kite is. The more cells a kite has the more rigid it will be and rigid kites definitely feel different than similarly sized and bridled kites with 2/3s the cells. Rigid kites can be a lot more punchy and explosive.

size and conditions are considerable elements far beyond quality, AR, brand etc.

design/brand/type can be a little difference in total power with relative sizes, but sensitivity would be more likely what your appreciating .

well made stuff is very sensitive, fires quick and early across similar design types

size and wind are the real players for sure in total power....design/type /brand all about CONTROL of said power which is directly associated with pilot skill, experience and knowledge in given conditions.

keep flying! you'll have answers in your experience

Makes sense, and thanks for all the input everyone. I suppose it's about what I expected - there is some theory to it but it'll be understandable after experience.

Soliver, don't worry, I have no intention of breaking my legs and am not even considering jumping right now, or any time soon. I'm focusing on basic landboarding right now, will try out snow kiting this winter if we get any snow here, and then will look to try the water out next year, where falling after a jump seems a lot less painful .

Quote:

The more cells a kite has the more rigid it will be and rigid kites definitely feel different than similarly sized and bridled kites with 2/3s the cells.

I do remember that the Century has a lot more cells than the Method has now that I think about it. I hadn't taken profile into account either (how flat or curved a kite's profile is in the air) - something not usually seen from the flyer's perspective.

Yes! It may seem that a 5m kite for example will have stronger pull than a 3m but that isn't always the case. The Twister will actually pull just as hard as the Quattro in higher winds. There is closed cell vs open cell kites, amount of cells, width/length of cells which obviously varies, material of kite, shape. List goes on.. There is a reason some kites are referred to as "jump" kites. The Twister is used for jumping due to its profile. Same goes with buggy kites. Kite safe and enjoy the sport!

Cheers, Ari

It would be interesting if there could be some type of graphic that could illustrate all the types, brand and how they relate or compare to one another. I can't even imagine how that could be pulled off.
Makes my head hurt just thinking about it.

My 2 c worth. Aerodynamically, there are several things which will affect the pull, lift and speed of a kite. These points refer mostly to normal bridled kites.
#...Wind speed.
Obvious, but remember that on 20-25m+ lines, the wind at the zenith can be a fair bit stronger than at ground level, so there can be a lot more power high in the zone than low down.
#...Aspect ratio.
High-aspect ratio, (much longer than it is wide-looks skinny) is much more efficient than a low-aspect ratio, (short and wide-looks fat or nearly square). High A/R kites (P/L Vapor) have much lower drag than low A/R ones (HQ Beamer) and will be faster, accelerate quicker and pull or lift harder than a low A/R kite of the same size.

#...Bridle and flying line drag.
Fewer bridle lines means lower drag which means more speed, better acceleration. Over-size and over-long flying lines also add a lot of drag sometimes seen as a big bow in the flying lines. This reduces responsiveness and feel as well. Most new high performance kites have greatly reduced the number of bridle lines compared to designs from 15+ years ago and are much better for it.

#...Kite area & design.
Again obvious, but consider the shape of the kite when it's flying. Does it stay fairly flat like a mattress or do the tips curl down heaps? Tips that curl down a lot add good stability, but don't add much in the way of lift or pull. This is one reason surf kites have heaps of tip curl, as well as some new race kites like the Ozone Quantum which has a very high A/R, lots of curve and apparently quite good stability.

#...Kite design 2.
Other good things are;
Rigidity-a more rigid/stiff kite that holds its shape is more efficient and has lower drag than a floppy one. Generally, adding more cells means the kite will hold its shape better, but this is more expensive to make. Low A/R kites can get away with fewer cells without losing shape too much.
Smooth shape-wrinkles caused by uneven bridle tension or poor cell inflation add drag, destroy lift and lower performance.
Clean leading edge-each designer has a different approach, but Ozone have a good one. Clean=more efficient.

#...Kite design 3.
Kite thickness-(best seen when looking at the kite from in front when it's flying at you. Hopefully someone else is holding the handles)
A thicker foil or wing section will produce more lift, but will be slower than a thin section which will have lower lift but more speed and pull.

#...Kite speed.
Speed increases the apparent wind across the kite which increases lift. More obvious with the higher A/R kites when some will not park very well, but stay inflated and pull hard if kept moving. One reason why most beginner power kites are low A/R.

First post, so I hope there's something useful in this stuff.
Cheers, Ian

Well that's definitely NOT your average first post... :o welcome Ian...

True Cheezy, though it is pretty typical for forum newbies to pull out old threads to comment on

Welcome to PKF Ian, sounds like you bring a wealth of knowledge!

Thanks Cheezy. Been static flying an old P/L 4m n'Gen that doesn't behave itself very well, but pulls & lifts like the proverbial. I'm about to get a buggy so I've got a lot to learn from you guys. The aero stuff comes from being a pilot for 35 years.
Also have a 2.5m Z1 and 4m Toxic. Looking at the new Reactor 5.5m to round things out.
Cheers, Ian

Ian, I've got a 5.5m Reactor II for about 1/2 the price of the new Reactor's if you're interested... From what I hear they are very similar. Main differences being the RIIs are more front line biased and the new ones can handle a little more brake input and the graphics are different. Check it out:
http://www.powerkiteforum.com/viewthread.php?tid=29727

and an 8.6m as well: http://www.powerkiteforum.com/viewthread.php?tid=29728

Soliver be pimpin' yo!

Where you from Ian?

Hi Soliver & MeatDriver.
Thanks for the kite offer, Soliver. I'm still considering options, as in not wanting to out-reach my ability, but I've been watching your posts for a while. I haven't got the hang of this posting business yet, so not much personal info. All new. I'm in Australia in New South Wales. Inland, but I get to the coast often. I appreciate the interest and hope to get back with some sensible questions about buggying.
Cheers, Ian

This may help < link > or not :puzzled:

Another welcome Ian D. Looks like you have a good grasp of the general theory behind kite / wing design, the problem is most of the wing theory is based on aeroplane wing design, very little seems to be available for kite wing theory. This is only my opinion... whilst a lot of it does directly relate to kite design there are fundamental differences: we need wind behind us to inflate the kite and get it in to a wing shape (obviously foils / single skin not inflatables etc), loose the wind and no matter how much speed you have the kite will stop as it approaches the edge of the window or over shoot and luff :D.

Sometimes even knowing all the theory it's difficult to grasp why a kite does what it does, I've tried many different things on what appears a very simple design the NPW and what appears to make perfect sense theory wise, doesn't always work on a kite. I do think though that kite manufactures should produce a performance spec on a kites power (pull) at a certain wind speed and the flying window size in degrees. I know the flying characteristics due to AoA, AR and wing depth will be different across models and difficult to quantify but at least we would have a good idea of the basic performance.

Another aussie :D Welcome. I'm a pommie myself.

Just to pick up on your post regarding High AR kites, particularly their acceleration and pull. Although a high AR is faster with its more efficient wing, it's initial acceleration is slower than that of a kite with a low AR, with all things being equal. This is because there is less power the further forward a kite sits in the wind window. A low AR kite will sit further back closer to the optimum zone of power generating more pull to out accelerate a high AR kite, initially anyway, to a point.

Welcome Ian...good call bringing this thread back..nice 2c

greetings , definitely have a grasp of basic foil design down.

just a mention, to remain on topic , it is a dynamic system, generating the bulk of usable power while the system is in motion. once in motion, the realization of apparent wind will be at hand ....this is where "point of sail", and navigation keep the the show going.

very nice Ian! way to show up with some knowledge! a little bit of sailing study and you'll stitch your first ride together no problem.

Quote: Originally posted by RedSky

Another aussie :D Welcome. I'm a pommie myself. Just to pick up on your post regarding High AR kites, particularly their acceleration and pull. Although a high AR is faster with its more efficient wing, it's initial acceleration is slower than that of a kite with a low AR, with all things being equal. This is because there is less power the further forward a kite sits in the wind window. A low AR kite will sit further back closer to the optimum zone of power generating more pull to out accelerate a high AR kite, initially anyway, to a point.

Redsky, I think he means the kite's apparent wind speed. I have noticed this in practice. I have flown some lower aspect kites, and still own a pretty low aspect Tensor. The difference between that and my Reactors or when I owned the big black Toxic is pretty huge. When the reactors hit an air pocket while flying through the window, they will sometimes get this quick surge. You don't really see low aspect stuff do that.

I think this is attributed to a higher volume of air passing over the high AR airfoil from LE to TE. The air makes that trip faster, because the total distance is shorter. Along with the air making the trip faster, it is a wider wing, allowing more air to pass at the same time. Imagine a two-lane road, with a 55mph speed limit, that is 5 miles from start to finish. Now imagine a four lane road, with the same speed limit of 55mph, but the length of this road is only 2.5 miles. You will be able to get way more cars from start to finish on the four-lane road. The cars are air molecules

Quote: Originally posted by Demoknight

Quote: Originally posted by RedSky   Another aussie :D Welcome. I'm a pommie myself. Just to pick up on your post regarding High AR kites, particularly their acceleration and pull. Although a high AR is faster with its more efficient wing, it's initial acceleration is slower than that of a kite with a low AR, with all things being equal. This is because there is less power the further forward a kite sits in the wind window. A low AR kite will sit further back closer to the optimum zone of power generating more pull to out accelerate a high AR kite, initially anyway, to a point. Redsky, I think he means the kite's apparent wind speed. I have noticed this in practice. I have flown some lower aspect kites, and still own a pretty low aspect Tensor. The difference between that and my Reactors or when I owned the big black Toxic is pretty huge. When the reactors hit an air pocket while flying through the window, they will sometimes get this quick surge. You don't really see low aspect stuff do that. I think this is attributed to a higher volume of air passing over the high AR airfoil from LE to TE. The air makes that trip faster, because the total distance is shorter. Along with the air making the trip faster, it is a wider wing, allowing more air to pass at the same time. Imagine a two-lane road, with a 55mph speed limit, that is 5 miles from start to finish. Now imagine a four lane road, with the same speed limit of 55mph, but the length of this road is only 2.5 miles. You will be able to get way more cars from start to finish on the four-lane road. The cars are air molecules

Interesting post.

You're right of course and I think PHREE hinted at it, it's a dynamic system with kites being more akin to sailing than flight. Your high AR kites may well surge to produce more power but this is normally a single event that cannot be easily and reliably replicated, in fact a trick to give a high AR kite more power is to limit their efficiency by applying some brake input.

When Ian mentioned acceleration I immediately and perhaps wrongly thought about acceleration from a standing start and not as perhaps you and most people thought, when a kite is already in motion. That's where our ideas might be conflicting. I've put it down to me watching too much Top Gear on TV.

If a kite is already at speed and able to take advantage of its efficiency and to build on apparent wind then you are correct.

However I stick by my guns :frog:, that a low AR kite will out accelerate a high AR kite with all other things being equal from a standing start to some low initial low speed, say 20mph, if only to prove the theory that a low AR kite that sits further back produces more initial power.

My foil experience isn't up to date however. My experience is coming from LEI's. Whereas kite buggying normally concerns itself with upwind efficiency and top speed, kitesurfing kites are perhaps more clearly defined with less efficient kites that pull strongly downwind being more desirable for extreme and powerful riding.

Hi guys and thanks for the additional welcomes. Much appreciated.
I'm glad I was able to kick this thread into gear again, and when I talked about high A/R acceleration, I did mean when the kite was already moving. High A/R = low drag. Most of my kite experience has been with a cranky old P/L4.0 n'Gen that always needs to be kept moving to avoid the dreaded wrap-up's and bow-ties, but can pull and lift really hard, even in light breezes.
My 90kg body has had some scary air in 25+kts on a Gold Coast beach when I thought the zenith would be a safe place to park the monster.
I am just now discovering the pleasures of stability and hope that if I go with a Reactor, it will be reasonably stable as reports suggest. I do like the efficiency of high A/R foils. Any additional comments on the Reactor?

RedSky makes a good point that kites, being held captive by their lines, do behave more like sails than wings, although the airflow dynamics are similar.
Referring to Demoknight's post, the latest line of thinking from aerodynamic-type persons, is that the percentage of lift produced by lower-pressure airflow across the top of the foil, (Bernoulli's theorem) is fairly small compared to that produced by the simple pressure difference between the lower side and the upper side. (Kite area presented to the wind) For a kite, this might explain the large difference in pull between a low downwind position and steady at the zenith.
In other words, the difference between an almost stalled AoA downwind and a very flat or low AoA overhead. In theory, (and mostly in practice), a kite cannot fly further forward than the overhead position since the lines would then be causing it to follow a down-curve that presents a negative AoA the the wind.

It would also seem that the foil shape and bridle design will have a considerable influence on how well the kite behaves close to the edge of the window and how easy it is to enter a stalled condition by too much brake. The brake lines, of course, are just changing the camber of the foil, something that birds do really well and rigid-wing aeroplanes can't do very well. For a given airspeed, an almost flat foil (brakes off), will produce less lift than a more curved one. (brakes on a bit)

I suspect that the P/L n'Gen I have does not have a well-adjusted bridle, as the slightest touch on the brake lines causes it to fold instantly, although it flies well when kept moving. Does anyone have any experience with one of these old things? Any thoughts would be appreciated.

Cheers, Ian

I can tell you that in my (somewhat limited) experience with high-ish AR kites (4.5), the Reactors are much more stable than others. My experience is really only in comparison with the HQ Toxic which is HQ's very comparable version. I have flown/owned a 3m Toxic in my winds and I currently own the 3.5m, 5.5m, and 8.6m Reactor IIs all of which would out fly the Toxic on all accounts. The Toxic was wiggy, twitchy and would constantly luff in my inland shifty wind. In comparison the RIIs were noticeably more stable inspire of the unstable winds. I would say that if you fly more inland wind, Reactors are a good choice. However, be forewarned that they are very powerful and considered an intermediate level kite for good reason.

Just my 2 cents...

Thanks Soliver. Excellent advice and greatly appreciated. I'm soaking up the collected wisdom of you guys and it helps a lot. The short time that I've had my 4m Toxic up in inland winds confirms your assessment. It appears to have a slightly lower A/R than the Reactor.
Getting a bit off topic there, but to get back on line, would the stability thing be because the Reactor has slightly more curl-down on the wng-tips?
Cheers, Ian

Actually the AR on Toxic and Reactor are the same ... Both at 4.5 on all sizes except the 8m Toxic is 4.8, whereas the Reactor 8.6m is still 4.5. The differences discussed in the marketing jargon of the 2 kites may be notable though. Reactor is marketed as a "low lift" kite very specific to buggying. Toxic is marketed as a buggy kite as well, however they say it's also a good jump kite.... With that said, maybe it is a function of of the Angle of Attack (AoA) or the profile of Reactor, or perhaps the happy culmination of all of the above.

Just in case you may have it backwards lower AR = a MORE stable but SLOWER kite whereas higher AR = a LESS stable but FASTER kite (usually with more LIFT)... That's why most beginner kites are low AR.

I would say (based on my limited experience in comparison and things I've read other people say) Reactor is one of the more stable kites in this "class" (4.5-ish AR Intermediate level), from what I've read, the Flexifoil Blurr is really good too, but I've only flown one of those for a few minutes and can't tell you how they compare.

Do be aware though that even though Reactor is marketed as "low lift" it will still lift you, just ask the 2 titanium plates in my heel

Since participating in the Global Hardwater Speed Ranking the past couple years, I've learned that the guys with the fastest speeds usually are not using kites with high aspect ratio's. That kinda blew my theory out of the water that "faster kites" = faster speeds. Neat to look back at all the entries and see what kites all the fastest guys are using. Only trend I see here is that it's the same guys that bag the top speeds year after year, not the same kites. Interesting thread!

I've been hearing this a lot lately too Cheddar in particular that lower AR kites give you better speed inland and that totally makes sense to me. I think that it is primarily a function of the stability of the kite. If you are fighting with unstable wind and the kite is not performing at its best because of your wind then you are not getting top performance out of the kite. Whereas, if you account for bad wind with a more stable kite, then you are getting more performance out of the kite than you would if you had up the high performance machine.