Luffing is not a bad thing you know. A kite, like any wing is a foil shape for aerodynamics. The fuller the foil & the less sheeted(depowered) the more it is prone to luffing. The alternative to luffing is backwinding, resulting in the kite tumbling out of the sky. The Slingshot Link was the classic example. 9 struts, a stable & rigid foil, as well as being heavy it was prone to tumbling, no matter what the wind strength.
Col
Great question that I have no idea what the Answer is. All I know is I remember the kites in early 2000 causing me and my crap flying skills a world of pain. Love someone who understands wings really well tell us an answer.
I know that even standing on the beach if you let them fly overhead (and these were the days you were told to put your kite at nuetral) turbulence over the wing would cause that horrible Hindenburg out of the sky and to be sure it would power up right before it hit the ground and take you on a scary ride. They seem to fall back now gotta be something to do with the wing shape and even more so the bridallling surely.
Lufting is from airflow not flowing evenly over and/or below the kite. Kite designs have improved over the years by using batterns and more taunt materials, but in some conditions lufting is simply inevitable. Aerodynamically, manufacturers still have a handful of easy tweaks they can do to improve kite stability, but I havnt seen any brands trying what I think would work. Some brands even go as far as giving u a bigger bar to help with stability
^ ^ ^ + 1 Kamikuza & Eppo
From a sailing perspective.... it is a supported sail becoming back winded, going to close to the wind direction UPWIND. i.e. tacking through the direction of the wind.
"Luffing" or back winding is when the trimmed structure (main/jib or other sail) points with the vessel to close to the wind. Simple example tacking from port to starboard "bow through the wind".
For kiting, fold the bit of the canopy closest to the inflated leading edge towards you, making like an "S-shape" of the wing, then lose pull on the lines and kite falls out of the sky.
It could be created by accelerating the kite across the power zone in the wind window to the edge then to "go to far' and the wind gets on the other side and it falls out of the sky & towards you on the other tack. As a kites' leading edge would rarely if ever act like a forestay on a sailing boat with a mast, the luffing effect is rare, undesired and seen perhaps as poor flying (poor AoA for flight, no Lift, no control = fall of kite & Oh S**t, care of power zone).
Yeh but a lot of kites don't even have battens. There has been a huge change in the ability to not luff a kite. I think I recall the first kites to really show this stability were the rhinos, which are now the rebels of course. They have done something pretty concrete to all kites for this stability but I haven't the foggiest.
Before u bring out ur own brand eppo, throw this page some thought
www.aerospaceweb.org/question/aerodynamics/q0228.shtml
Select to expand quotedorothyinste said..
How do kite designs evolve to reduce luffing?
To answer the original question, the most common way to stop luffing is to simply improve the balance of the kite. Kites used to luff because they were leading edge heavy. Once the lift faded the kite would simply fall over forward. By making the kite more balanced it could float in the air and drift back rather then fall down nose first.
There are other ways to fix luffing and for other causes. You can make reflex profiles so that the centre of effort naturally moves forward as the wing tilts forward. Reflex profiles are naturally resistant to luffing but they are also less efficient. Simplistically described a reflex profile is a wing where the trailing edge kicks up slightly. They are also called S-curve wings. Google reflex profiles and have a read.
Adding pulleys and bridles also helped to bring the tow point forward whenever a kite luffed so that it would recover instead of crashing.
L/D ratio and balance. As you sheet out the L/D ratio improves and if the center of gravity is ahead of the center of lift it can glide out of the window. Improved balance and increase drag when depowered through kite flapping has largely eliminated it.
