rossb63 - 6-5-2011 at 11:57 AM
higher aspect ratio means more climb and power right?
BeamerBob - 6-5-2011 at 12:43 PM
generally means the kite flies faster through the air. In general, most beginner friendly kites have a low AR, and more advanced kites that require
more skill, yet provide more performance will be a higher AR. There are exceptions on both ends though.
awindofchange - 6-5-2011 at 12:54 PM
The aspect ratio is the span of the kite vs the width. Higher aspect ratio kites tend to be much longer and narrow than lower aspect ratio kites.
Generally, this means faster flying through the air. The faster flying is what produces more power, but it comes at a great cost to stability.
Bladerunner - 6-5-2011 at 05:55 PM
To get going you want to avoid high aspect ratio small kites. = 2 race kites. They will be unfriendly to fly. The only people who gain from a high
aspect ratio small kite are folks going for high speed runs.
I have flown for years and still am not fond of how finicky race kites can be.
Just go OZ and get flying ! 
acampbell - 6-5-2011 at 07:34 PM
Simply put, Higher A/R (aspect ratio) kites are more efficient, so they generate more power and acceleration for a kite of the same area but of lower
A/R. What happens is this: A certain percent o the area of a kite's wing near the wing tip is not as efficient because the high pressure of air
under the bottom skin spills out sideways towards the wingtip (path of least resistance) instead of being swept past the airfoil. It curls over the
wingtip from bottom to top and that creates a vortex of air that induces drag. So a portion of the span is "wasted" or not producing as much power.
When you see vertical "winglets" at the wingtips of airliners, they are redirecting that vortex to spill the vortex behind the wing rather that keep
it churning, thus reducing induced drag. That increases efficiency.
With a higher A/R wing (kite), a smaller percentage of the wing area is "wasted" at the tips and more of the span and area are left to produce lift
and power. Because overall induced drag is reduced, you get the increased acceleration and power build up.
But the trick there is to keep the long and spindly span stable. Designers are getting better at that. You don't' hear the modern racekites called
"bastards" as much as you used to. But I myself still refer to the Flexifoil Blade as a "violent" kite because of what it can do in gusts.
Hope that made sense.
krumly - 9-5-2011 at 10:08 AM
A bit late to the table on this, but Angus is right on with the physics.
The affects of aspect ratio on 3D wings vs 2D airfoil sections was documented in theory and verified through wind tunnel tests by the aerodynamcicst
Ludwig Prandtl in 1921 at Gottingen. The attached scan of his test results show the lift curves for different aspect ratios at a range of angles of
attack for a wing of rectangular planform.
Note that the higher the aspect ratio, the steeper the lift slope. The higher aspect ratio wing will develop more lift per degree change in angle of
attack than a lower aspect ratio wing. A super high aspect ratio wing - think along the lines of a 50:1 AR competion sailplane wing - will have a
lift slope almost that of an ideal 2D foil section, where there are no pressure losses around the end of the airfoil.
But also note that the higher aspect wings start to stall at lower angles of attack. The AR 7 wing lift slope falls off around 12-13 degrees. AR 3
starts to stall around 15-16 degrees. The AR 2 and 1 curves are still straight at 17 degrees, beyond which there is no more data. The drop off for the
lift curve is sharper for higher aspect ratios - their stall will be more abrupt.
Consider this for wings with identical foil sections, equal projected areas, and proportional planforms: a high aspect ratio wing will develop the
same lift at a lower angle of attack than a low aspect ratio wing. Operating at a lower angle of attack means less drag, so the high aspect ratio
wing can fly faster. Power = force X velocity, so the faster wing develops more power. But the higher aspect ratio wing will have a narrower range
of useful angle-of-attack and a sharper, less forgiving stall rate.
Bottom line, a higher aspect ratio kite will generally fly faster and develop more power, while being more difficult or 'finicky' to control.
krumly
acampbell - 9-5-2011 at 12:21 PM
Krumly I always enjoy reading your learned, lucid posts