rtz - 14-9-2015 at 11:14 PM
A mental exercise(for now):
On a non or light wind day, get a kite up in the air static. Then attach the strop line to a vehicle and have the kite driven to it's top speed while
another controls the kite.
My thinking and feeling on this is at a certain speed the kites leading edge will roll back or collapse from the drag and air resistance at some
speed.
There is no way a kite has unlimited top speed.
So with this said; and if true; it would be fascinating to know what a kites true top speed is. So maybe a Vapors true top speed may only be 90 mph
or some number? Will be interesting to see what kite could be used to break 100 mph in a buggy.
Feyd - 15-9-2015 at 03:55 AM
My feeling is that the speed at which the drag would start to induce frontal collapse is pretty high. At 70+ I've never seen any of the kites I ride
give any indication that we were close to what would I guess be a kite equivalent to Vmax. Especially with moderate high AR wings like a Vapor to
higher AR wings like Chrono or F-arcs which just want to charge the window edge, they just seem to want to go faster and faster.
In my expirience the kite is just one factor in achieving high speeds. The pilots ability to feel what is going on and make rapid adjustments to get
the most out of the kite is easily more critical. The surface conditions and the equipment beneath you is important as is obviously the wind.
Last season we did a little test. We compared the 9m Chrono to the 8m Access. Too see how much of an advantage a High AR wing has over a low. We
found it to be a lot less than we had imagined. In fact the Chrono only managed 5mph more than the Access. What we found was the Access generated
more grunt which with our edging ability can be translated into speed. The Chrono was faster across the window but if we edged too hard it would just
sort of max out. It looked fast, but really wasn't much faster.
We were surprised. In a buggy things may be different. You guys expirience drift and that may change things quite a bit. Holding a solid edge
depends on your surface, your wheels and the pilot I imagine.
I guess I shouldnt be surprised about the low AR vs high AR . Most of my fastest runs have been on low AR kites on surface conditions that we would
assume would be slow because they were soft. But they allowed for digging a deep edge and converting all the grunt the kite had to forward motion.
A grunty hi AR kite is what we all need.:D
Bladerunner - 15-9-2015 at 04:14 AM
I suspect that you would blow something before you found the kite reacting as you envision? A bridle or cells or wherever the weakest link is. The
test might be " at what speed does said kite self destruct " ?
While I am not speed demon I agree with Feyd. The real impediment to hitting 100 is more related to pilot and equipment.
If I have it correct in my head the trick to maxing out in the buggy is to get up to max speed on a reach and then run it slightly more down wind for
that extra boost?
I sure hope Beamer Bob throws some insight into this discussion. I know he has put a lot of thought into what kites run fast for him and if I'm right
he has been surprised by the speeds he gets with some low aspect ( LEI ) kites.
BeamerBob - 15-9-2015 at 05:20 AM
I agree that the kites have little variability after the wind gets cranking assuming we are talking mid to high AR. I've been over 60 with a 2.5m
Uturn Butane, HQ Montana 8m, PL Vapor 2.7m, and HQ LEI Ignition. 3 different styles of kites and all of them need about the same wind to do it. The
Ignition had more (in my head) top end range than the others with the best match with my skills to possibly take me over 70.
I don't think towing a kite is a true measure of it's top speed. That is different than running with a kite driven by wind while feeding it apparent
wind and attached to a vehicle with limited grip. As speeds increase, the kite just drops back to it's equilibrium point. That point would be skewed
by towing it with a car. Adding real wind would have the kite pushing more forward in the wind. At the limit, either the lines or bridle tabs would
start to fail before the fabric gave way IMHO.
As I think about this more, driving straight into the wind without edging could mimic wind speed, but not give an indication to how fast you could
buggy with the kite. I imagine all kites are stronger than they can fly pulling a buggy.
In a buggy, the highest speeds are done with only the load your tires can provide traction for which means the fastest runs are some angle off of
perpendicular to the wind as much as 45-60 degrees.
abkayak - 15-9-2015 at 05:39 AM
BeamerBob....in hitting those speeds w/ very different kites i assume all these fly/feel very differently
also guessing the small ones are getting seined like crazy while the larger ones your looking for a sweet spot?
BeamerBob - 15-9-2015 at 06:28 AM
The only big difference at speed is that the LEI I have has a sweet spot angle that was more downwind than the others.
If there is enough wind to get over 60, your entire consciousness is dedicated to keeping that kite vertical and going the same direction you are.
Sining is not necessary, and you are guarding against direction changes, not adding them in.
abkayak - 15-9-2015 at 06:30 AM
yea i guess...i feel the same at 30, and dont even relate to 60
BeamerBob - 15-9-2015 at 06:40 AM
I had only been 34 mph on a beach before riding at Ivanpah. It's a different world than you can imagine. 30 mph will have you bored and wanting more
wind so you can get going.
ssayre - 15-9-2015 at 06:41 AM
I'm hoping to bump my speed up some on my ever changing new found, temporary outlaw locations :D
skimtwashington - 15-9-2015 at 07:18 AM
Speed=pilot weight x kite size x wind speed + beer....
Nope...nope.... wait...
nope..nope... wait....
E=MC Hammer + a(b + c)/WTF!
Nope...nope...wait..
Kapwoohhhh! (...part of brain explodes)
Demoknight - 15-9-2015 at 08:08 AM
I feel like if you have a bridle and line set with infinity strength to test this, you would blow a cell before the LE ever collapsed. My reasoning
is that on foils, closed and open cell, the internal pressure is fed by the LE external pressure. The greater the speed, the higher the internal
pressure goes and creates a more rigid shape. I feel like you could take this as fast as you want and it would just scale itself up to the point
where the kite would disintegrate before it would collapse.
ssayre - 15-9-2015 at 08:53 AM
I'm no engineer but wouldn't towing a kite from a car turn it into a parachute and tear itself apart at a certain speed? Not sure that would be a
good test of the speed of a kite.
ssayre - 15-9-2015 at 08:58 AM
I think you would need high wind not low wind so the car wouldn't be trying to outrun the kite if you really wanted to try it. In other words you
would still want the kite in the pulling position which would require the actual wind to be on the high side.
PHREERIDER - 15-9-2015 at 10:06 AM
tow force will produce different tension thru canopy , most likely choking the kite, so drag will be distorted and very hi...effectively "dragging"
rather than "in flight"
the apparent wind would be killing it (thru drag) more like para sail, rather than feeding it
WELDNGOD - 15-9-2015 at 12:50 PM
Demonknight FTW
WELDNGOD - 15-9-2015 at 12:56 PM
Google the "Bernoulli principle". It has a lot to do with how our wings fly.