Greater low end AND depower? Possible?

[R]

Hi, For years every new kite which has been release has had attached to it a blurb about "insane depower" and "awesome bottom end." Not one kite has ever delivered. Kites either have large range but sucky light wind characteristics (X3, Rhino4 types) or great bottom end and bugger all depower (X4, Rhino2 types). Once again the Hellfish is released making these claims.
My question is: is it actually possible for a kite to have both? Seems to me which ever way you look at it, a kite which kicks arse in the light stuff, the same characteristics are what makes them a handfull when the wind picks up. Why will the hellfish be any different? Hurry up and get them to Oz, can't wait to try one and find out.

[Dax]

I think the word is that high end is about the same as an equivelant sized Nemesis (which is confusing since the Nemi's all are even sizes and the HF odd.) It's low end that's really been increased.

So the trick seems to be going 1 size smaller than you normally would for a kite, then you give increased low end and high end.

This is all just hype based guesses on my part btw.

[Toby]

I wonder as well, but for me hangtime and grunt works against big depower.
e.g. X4 and R2 had a great lowend and hangtime, but the depower wasn't the best.
So I'm interested in that point as well...

[spork]

I think it's easy to get great low-end and great depower. You just make a medium to low A/R kite that flies largely on the back lines. To do this you change the planform a bit so the front lines are attached further forward relative to the center of pressure.

This should accomplish the goals - BUT it will be heavy on the arms. Now I've never ridden either a Globerider or a WindWing, but to me it seems they both have clever solutions to this. You tell me - how do they work?

Incidentally, depower alone isn't everything. You're better off riding a properly sized kite at reasonable wing loading than an over-sized kite that can be depowered in a big way. The depowered kite will be operating in a lousy region of it's polar. That's why sailplanes take on water as ballast for better performance. Without taking on ballast the only way I know of to keep a wing in the good part of the polar over a wide flight envelope is to vary the wing area itself. Not so easy to do on a kite in flight I suppose.

RC

[Innis]

Incidentally, depower alone isn't everything. You're better off riding a properly sized kite at reasonable wing loading than an over-sized kite that can be depowered in a big way. The depowered kite will be operating in a lousy region of it's polar. That's why sailplanes take on water as ballast for better performance. Without taking on ballast the only way I know of to keep a wing in the good part of the polar over a wide flight envelope is to vary the wing area itself. Not so easy to do on a kite in flight I suppose.RC

I agree with Spork in that it's better to ride a properly sized kite. However, high performance sailplanes have multiple polars based on multiple flap settings. They climb in thermals at slow speed in a positive flap setting and fly straight at high speed in a negative flap setting.

A kite with better depower is like a wing with better characteristics over a wider range of flap settings (e.g. the wing on an ASW-20 performs much better over a wider range of flap settings than a Blanik's does).

Taking on water shifts all polar's for all flap settings along the best L/D slope for better performance in better conditions. I agree that the kiteboarding equivalent would be to switch to a smaller kite. However, this doesn't mean a kite (wing) can't be made to perform better over a broader range of depower (flap) settings.

Nice to see I'm not the only Kiteboarder/Glider Pilot.

[jrobson]

Spork says:

I think it's easy to get great low-end and great depower. You just make a medium to low A/R kite that flies largely on the back lines. To do this you change the planform a bit so the front lines are attached further forward relative to the center of pressure.

This should accomplish the goals - BUT it will be heavy on the arms. Now I've never ridden either a Globerider or a WindWing, but to me it seems they both have clever solutions to this. You tell me - how do they work?

Incidentally, depower alone isn't everything. You're better off riding a properly sized kite at reasonable wing loading than an over-sized kite that can be depowered in a big way. The depowered kite will be operating in a lousy region of it's polar. That's why sailplanes take on water as ballast for better performance. Without taking on ballast the only way I know of to keep a wing in the good part of the polar over a wide flight envelope is to vary the wing area itself. Not so easy to do on a kite in flight I suppose.

RC

So is the new question then, "Better low end, high end and lighter bar pressures possible?"

[spork]

So is the new question then, "Better low end, high end and lighter bar pressures possible?"

I think it actually is possible. But it will be hard to achieve that combination in a significant way while maintaining a really good position on the polar in all conditions. I could tell you exactly how to do it - but that would render the Hellfish obsolete. It wouldn't be fair : )

I agree with everything Innis said regarding flap settings on sailplanes. I think the real secret lies in doing something like a fowler flap - in which both the camber and wing area change with flap setting. That would be difficult to pull off on a kite. As I'm sure Innis would agree, flaps are great for flying in certain conditions, but deployed flaps almost always decrease your L/D. They're typically used when you want or need more lift. In some of those cases drag is less important, and in some cases you use them because you want more drag (e.g. steep landing approaches).

I suspect we'll be seeing kites with at least a partial double surface before long. I think that will do us as much good (or more) than a thin L.E.


RC

[jrobson]

Excellent info.

I read that with great interrest as it is exactly what Armin said why they develop foils and not LEI's, in flight camber change, Jet flaps etc are not possible on single skin LEI's or briddle-less systems.

Maybe in the future cuben based kites can have double skins since the material is so light.

[Innis]

Fowler flaps on a Kite? Now that would be an engineering feat. Spork you may have given Best (or anyone else) their next challenge.

As I understand, there have been two major watershed improvements in the material construction of aircraft wings:
1. Going from Cloth covered wings to Metal wings (including ribs and spar).
2. Going from Metal wings to Fiberglass (or other composite) wings (+ spar but no need for ribs).

Both improvements resulted in significant reductions in drag (initially skin friction and, as a consequence, form drag).

I hope the move to Cuben Fiber construction will represent a similar improvement in the manufacture of Kites. If not, I'll send mine back.

The big question: When can we expect delivery?

[spork]

As I understand, there have been two major watershed improvements in the material construction of aircraft wings:
1. Going from Cloth covered wings to Metal wings (including ribs and spar).
2. Going from Metal wings to Fiberglass (or other composite) wings (+ spar but no need for ribs).

True enough, but there are trade-offs with everything. Some of the best competition aerobatic planes still use fabric wings (Pitts, Christen Eagle). When the Brits came out with the Mosquito during WWII people thought it was odd that they'd take such a big step backward to use wood and fabric. But it was a HUGE win for them. They had plenty of wood and fabric when aluminum was scarce, the could put all the furniture makers to work, and you can put a bunch of bullet holes in a fabric covered airplane before the ventilation becomes a problem.

Some of the real advantages of aluminum and then composites have more to do with the ability to control the wing shape (e.g. compound curves), and strength to weight ratio. At slower speeds the drag of cloth, rivets, etc. is essentially a non-issue.

You have to admit, going to double surface wings was a much bigger improvement though.

If the new material is lighter, can hold it's shape better, doesn't stretch, is durable, and affordable, it'll be the next big thing.

RC