[ksurf] Re: R: Aspect ratio .vs. performance
- At 08:08 AM 9/5/99 -0400, you wrote:
>> It is true that a C-Quad pulls more than a Peel, but this is notbecause of
>> aspect ratio difference. Many more things are involved, one of which isC-Quad is
>> speed. A faster kite will pull more than a slow one due to the factor that
>> power increase 4 times as the speed doubles. Peel is a slow kite,
>> a fast kite.The CQuad is faster because it has a higher lift-drag ratio. It gets that
>So what exactly makes the C-Quad a faster kite than the Peel and the
>N-Gen? Also, what are the other factors that make a C-Quad a higher
>If a low aspect ratio framed single skin kite has higher performance
>than a higher aspect ratio ram air foil kite, does it mean that framed
>single skin kite is the better way to make a kite?
from having fewer bumps across the back (which create "parasitic drag"
(whatever that means...)), a fairly high lift:drag profile, fewer bridle
lines, a very clean leading edge and probably some other stuff. It also has
a high coeffecient of lift, which means more lift at lower speed, which is
a function of the profile shape (the shape of the airfoil).
You could make a C-Quad-like kite with a higher lift:drag ratio. You might
start by increasing the aspect ratio, using unsleeved spectra for the
bridle, and tweaking the angle of attack. The thing is, the lift:drag is
already good enough that it overflies the edge of the window if the wind
isn't good. Higher L:D ratio would mean more overflying, especially for
less experienced users. The lower aspect ratio makes the kite steer quicker
and seems to generally improve handling (at least if you like a responsive
Like Roberto said, there are many factors that determine kite performance.
One interesting thing about a single skin kite is that it has less inertia,
which means it can accelerate faster. The air inside a foil can reportedly
have more mass than the kite itself (10 cubic feet of air = about 1 lb.).
So I think the CQuad can reach its top speed sooner, which might mean you
could use it on shorter lines, or at least have full power in a greater
portion of a "sweep".
Peter Lynn seems to think a good rigidly-framed delta can beat what we're
using now (CQuads, Qaudrifoils, etc), at least in some conditions. Here are
some quotes from the PL site:
>>>>>>>>>>>>>>>(from October 98 newsletter)
...by now three, large C Quads in Holland took the first three places in a
well attended 2 day club meeting- though observers noted that a 4 sq.m.
delta style 2 line kite was clearly fastest on the reaching legs (but not
the upwinds) in the gusty conditions on Sunday.
(from Buggies Boats & Peels, written in 1993. MMR is max. to min. pull
ratio across the window)
Rigid Frame Stunt Kites
Before developing the "Peel" range of soft stunters I used rigid frame
delta style stunt kites extensively for kite traction. They have
considerable natural advantages: control is good, kites can be made in
almost any desirable size (I built a series of 5.5m wing span stunters) or
smaller stunters can be stacked to get sufficient pull. They have a built
in mechanism to improve M.M.R.. By utilising spar flex and skin stretch,
delta style stunters automatically "twist off" at their wingtips as pull
increases giving very good M.M.R. This desirable characteristic can be
enhanced by building stunters with extra windtip area, held out by battens,
which only generates lift when the kite's apparent wind is low. Although
the recent trend has been for delta form stunters to tend towards long
tapered wingtips the reason for this has particularly to do with the rules
and requirements for "precision" stunt kite competitions. Kites for
traction don't need to follow this trend. One kite style that should have
considerable potential as a traction kite, for the reasons outlined above,
is the Volkensturmer 101 from Germany. Another design which should also
have very good inherent M.M.R. is the speedwing from Vlieger Op in Holland.
Lacking a spine, it contrives "twist off" in the middle of the skin again
by spar flex and skin stretch.
(from april 99 newsletter)
A major new product this month; We have purchased non-exclusive rights to
manufacture and sell the Bob Dawson (Leading Edge Kites, Coff's Harbour)
"Osprey" series delta style 2 line traction kites. Actually this is not a
sudden decision. We have been following Bob's work with close interest for
some years, looking for a traction kite that excels in strong gusty winds
to complement our Peels, NGens and C Quads. We believe that "D Wings"(our
name for this new range) will outperform all other traction kites in some
conditions, and not just in the Southern Hemisphere either! Their handling
is what sets them apart; somehow Bob has retained the power, speed and gust
responsiveness that delta's are renowned for while tightening the turns,
eliminating almost all oversteer and building in luff resistance that just
has to be experienced.
*DELTA style 2 line framed kite. These currently have the best automatic
depowering characteristics of all traction kites (by twisting off at the
tips in the same way that windsurfer sails depower by twisting off.), very
good lift coeff�s (power for size), excellent L/D (good upwind) and unique
On the down side, above about 5 sq.m�s, even with carbon it becomes
difficult to make frames for deltas that are strong enough within weight
limits for good light wind flying. Additionally, rigid frame kites like
deltas tend to break up when swilled around in breaking waves and the
bigger they are the worse this tendency is.