What makes a kite auto-zenith? For those that don't know, auto-zenith is a quality that makes a kite automaticly return to zenith(12:00) without user input. Peter lynn Twinskins are the only kites that do this. There are 2 main reasons why they do this.

The most prominent cause is the spars in the wing tips. When the kite drifts to one side, gravity pulls the spar downward. This increases the angle of attack in the upper wing tip and decreases the angle or attack in the lower wingtip. The angle of attack change causes the upper wing tip to have more lift than the lower wing tip, lifting the kite back to zenith. It also causes the upper wing tip to have more drag than the lower which turns the kite upwards toward zenith.

The second prominent effect is the distribution of canopy. When the kite veers off to one side, there is always more canopy pulling upwards than downwards. This returns the kite to zenith from to balance the forces. This also causes stability in arcs and other power kites. The downward curve of the wing tips causes more of the lift to pull the kite upwards, counteracting the force of gravity on the kite, adding stability.

There are other effects but they don't add much to autozeinth. I hope you found this interesting little write up interesting. I am planning on makeing more articles about other kite related things in the futre.

Great post. Knew the "what" about auto-z but not the "why."

Keep the info rolling. I for one will read every word. One of the greatest aspects of kiting is learning!

Thanks for the info. It seems relatively similar to why a sail boat will head up if you let go of the tiller, it is the position where the least wind energy is.

That is a good description.

I am still stuck for an explanation as to why some folks say their arc sits at 1 or 11 ?

Bladerunner, Arcs might not autozenith becase sand or water is in the kite weighing them down on one side. My 18m guerilla was full of about 5 pounds of sand when I got it. 3 pounds was on the surface when I first unrolled it. I shook out another pound before I flew and about another pound came out after 30 minutes of flying. It would not auto-zenith before I emptied the final pound of sands from inside.

Another reason may be damage or repairs. My venom does not auto-zenith because of a repair on the right side. It always flys to the left when I am flying static but it doesn't when I am in motion. The damage or repairs increases or decreases the lift and drag of one side, causeing the to veer off to one side.

Bent or broken spars can also cause the kite to not to auto-zenith, but broken spars can be dangerous. They can cause the kite to become unstable and not respond to user imputs. You should always check if your spars are straight before you fly to prevent damage to your kite and yourself.

Gusty and shifty winds can cause a kite not to auto-zenith also. My 15m guerilla with be happily siting at zenith and will move side to side alot before going back to zenith, some times as far as 10:00 and 2:00.

Differences in line length too. I've experienced this on a couple used bars.

Quote:

Originally posted by Snake The most prominent cause is the spars in the wing tips. When the kite drifts to one side, gravity pulls the spar downward. This increases the angle of attack in the upper wing tip and decreases the angle or attack in the lower wingtip. The angle of attack change causes the upper wing tip to have more lift than the lower wing tip, lifting the kite back to zenith. It also causes the upper wing tip to have more drag than the lower which turns the kite upwards toward zenith.

Hey Snake, Is this from info researching back through arc material? It was my understanding that there were other things that were a bigger factor than the rods including the slight recurve on the trailing edge and that bulge of the upper skin just back of the leading edge that produces more lift in the centre than there is at wingtips.
i do understand the tendency for the wingtips to drop but in reality flying an arc if it flares wide open and goes into a float it is very rare that the wingtips drop. It's only when the lines get some tension that the top skin arcs back away from the tension on the lines and that tension is not always as a result of the wingtips dropping first. If the wingtips dropping were a major contributor to auto zenith then why didn't early C shape kites and other kites that are bridled by wingtips and taking a natural curve auto zenith? Take the high a.r. paraskiflex or many LEIs with fixed curve shapes, they do fly at the zenith nicely but do not auto zenith.

Good discussion - and lets also remember that auto zenith and stability at the zenith are separate.

Mark

My F-arc will lock into position anywhere from 10-2:00. She will nearly hold position at 3-9:00.

http://www.youtube.com/watch?v=s3MPErZBm_0&feature=share...

just sayin'

Markite- The reason lei and paraskiflex's don't auto-zenith is because they are rigid. Arcs are floppy and the spars aren't supported very well. The tension on the front lines make the spar into a lever which is pull downward by gravity. The spar doesn't weigh much so the effect is small. A handfull of sand in one side of the kite is enough to prevent auto-zenith. The force that causes auto-zenith is probably only a a few pounds .