For anyone has ever failed to explain to someone why kiters can move faster then the wind, problem solved. Its all about apparent wind. Read about it here.

Beat ya to it...

http://www.coastalwindsports.com/BetterBuggyBasics.html#10

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Originally posted by barnes For anyone has ever failed to explain to someone why kiters can move faster then the wind, problem solved. Its all about apparent wind. Read about it here.

The diagram in that article is all wrong. the vector diagram needs to be in scale with the velocity. For example, 10 mph needs to be 10 inches and 20 mph needs to be 20 inches (or mm or cm or whatever), then you can measure the hypotenuse of the triangle to get the apparent wind velocity.

That diagram shows 10 mph and 20 mph as the same length on each respective side of the diagram. The math for the calculation works out if you ignore that, but the diagram does not illustrate the principle.

That was a great writeup, Angus

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Originally posted by burritobandit That was a great writeup, Angus

I've read that thing 5-6 times now and I still get sucked into reading the whole thing. Some things confirm I've learned a little bit and other things are a refresher each time through.

also realize that the diagram isn't right because we can ride at more than 90 degrees to the wind. The Pythagorean Theorem Doesn't really apply because there are no right angles, you need to do some Trigonometry, not geometry.

Professor Campbell has spoken. Read it, believe it, and heed it.

well it's actually a dynamics problem, i.e. moving forces in 3 dimensions (not 2) which is not addressed by trig or geometry. Angus' sample is a good approximation and doesn't require that we return to the School of Engineering :puzzled::puzzled:

It's a good topic and always amazes me

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Originally posted by ikemiester also realize that the diagram isn't right because we can ride at more than 90 degrees to the wind. The Pythagorean Theorem Doesn't really apply because there are no right angles, you need to do some Trigonometry, not geometry.

Good point. I should edit the article to remind readers that the illustrations work during a beam reach when the wind is right off your shoulder. But it does make the point on how apparent wind shifts with buggy motion.

Once you move up or downwind, you might as well chuck the math and go flying.

actually its 4 dimensions

a 3 dimensional system moving within a fourth.

PHREE always rides with his iPod plugged in his ears. I can envision him playing Pink Floyd's "Time" while cruising the beach...

He does those jumps when "Tool" reaches the playlist though. I think those rhythmic carves might be the Floyd stuff.

BUDDHA LOUNGE

PHUTURE PRIMITIVE

they have been the flow for the blades of late

tool and as always in the mix.

hayden, baroque and Renaissance masters in there as well

i've read it (angus' article) again. every noob should read this article at least twice.
Paul

why can I "quad droople" wind speed with a 12m kite, and barely double it with a 3m kite? THAT IS THE REAL QUESTION!

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Originally posted by USA_Eli_A why can I "quad droople" wind speed with a 12m kite, and barely double it with a 3m kite? THAT IS THE REAL QUESTION!

I know what you mean. With my Reactor 10.8, I have on several occasions been able to repeat the case where I can get about 16 mph buggy velocity on steady 4 mph winds. Then I can maintain something between 10-16 mph when I look at the windsock, flagpoles and tree-tops and see that there is virtually no wind.

I believe it must be that, outside of other things like A/R, larger kites are inherently more efficient with a smaller percentage of their surface, tips and bridles creating parasitic and induced drag.

I bet it has something to do with the increasing efficiency of a large canopy in respect to air and ground resistance. The 3m in higher winds is slipping more with the same load on it from the buggy rolling. The large kite just makes better use of the wind because of the ratio of surface area to perimeter is higher. There is so much more fabric that the wind can't find a way around on the large kite except so spill it off the trailing edge giving you its power. I have noticed the same phenomenon regarding upwind angles. I've noticed with my kites that a larger kite that is well powered can take you more sharply upwind than a smaller kite well powered. I remember a day at Folly beach that my 7m Blurr was at its limit and I was going almost dead upwind, like within 10-15 degrees. Aren't kites cool?

Thanks all for the kind words. I should add that I do not consider myself an expert, but have been able to gather enough that I feel is useful considering the questions here and things that hindered me. I was also able to draw on years in the soaring/ gliding community, general aviation and some sailing. When I adapted concepts from those sources, I always tried to vet it with empirical observation on the beach in the bug to make sure it translates to our world. In some cases it either does not translate, or I have not yet developed the skills.

The article will evolve.

Another head-scratcher:

Can a Blokart ever go faster than the wind?
The sail is moving along, but it's not being sined or accelerated by the pilot.

Sure, same as a kite. A kite does not need to be sined to go faster than the wind, it just adds a boost more power from the added airspeed.

The the sail of the Blokart (or and iceboat or whatever) generates lift (like the kite's sail does) as the air accelerates around the back of the airfoil shape the sail creates. The faster the blokart goes, the more apparent wind, the more lift (pull) and so forth until the equilibrium is reached.

via some new info I've heard from designers, the kite lines can cause up to 5 times the drag of the wing.

I don't know exactly what that means, but I'm heading in that direction.

I can believe that easily. When lines "sing" they are vibrating and effectively increasing their diameter, and thus drag. The Q-powerline people use a special coating on the lines they make for the military that acts as boundary layer control, keeping them quiet with minimal drag. Fast and quiet =Stealth.

So, theoretically, a sail on a Blokart is more efficient than comparably-sized kite on a buggy? (Greenbird vs. Xxtreme Apexx) :wow:

Interesting if true, as Blokarts also *seem* to offer the ultimate "chilled out" flying session compared to most buggy experiences.

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Originally posted by lad So, theoretically, a sail on a Blokart is more efficient than comparably-sized kite on a buggy? (Greenbird vs. Xxtreme Apexx) :wow: Interesting if true, as Blokarts also *seem* to offer the ultimate "chilled out" flying session compared to most buggy experiences.

actually the xxtreme apexx has a long long long way to go before it's as refined as the Green Bird.

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Originally posted by acampbell I can believe that easily. When lines "sing" they are vibrating and effectively increasing their diameter, and thus drag. The Q-powerline people use a special coating on the lines they make for the military that acts as boundary layer control, keeping them quiet with minimal drag. Fast and quiet =Stealth.

Actually, you are part right part wrong.

Q-Powerline does use an outer linear wrap around the spectra core of their lines that allow the wind to flow across the lines smoother than unwrapped lines - thus causing much less parasitic drag than other kite lines.

But -
Q-Power line sings quite loudly compared to other lines.
As you mentioned, the sine wave caused by the vibration of the lines is what causes the most drag. Your lines aren't just restricting wind from the diameter of the line but more from the entire sine wave the line is creating. The more the line vibrates, the larger the sine wave - thus the more restriction (and disruption of air flow) the lines will create. This is the same reason that a single strand of wire will cause more wind resistance than a 6" diameter pipe. The air flows smoothly over the pipe (kind of the same way it flows over your kite) but gets very disrupted and distorted from the vibrations caused by the wire.

All lines vibrate.

The frequency that those lines vibrate will determine just how much resistance the lines will give. Lower frequencies are much larger and more disruptive than higher frequencies. Even though you can't hear any audible vibrations from your lines - they are still vibrating. This vibration is in the sub-sonic frequency range and causes tremendous line drag and resistance. As the power of the kite increases, the frequency that the lines are vibrating at also increases causing your lines to start singing when they are stretched very tightly.

Q-Powerlines are designed to load up the braid of the lines faster which means that your Q-Powerlines will start singing at a very high pitch very quickly in lower winds. This high pitch vibration is a much higher frequency than what is obtainable by other lines and allows Q-Powerline to have much less resistance and parasitic drag than any other line on the market. Q-Powerline is the only known company that has actually wind tunnel tested their lines against hundreds of other lines and proven that their lines have less parasitic drag (military contract requirements).

Q-Powerline can be quite noisy and will sing much louder and start to sing quicker than other line. Some people take this as adding more drag or reaching the breaking strain of the line faster but that is very far from the truth. It actually gives much much less drag as explained above but, because the line is vibrating at a much higher frequency, it actually helps maintain the rated breaking strain of the lines more than a line that is vibrating at a much lower frequency (think of a line that is constantly being pounded on by huge whipping yanks compared to a line that is only being tugged on in very small inputs).

So, Q-power is more audible than other lines but has less parasitic drag overall and higher strength when under load.

Sorry to drag on about this.... (pun intended) Just some useless information for everyone to share next time your sitting around with your buddies waiting for the wind to blow. I need to get out of this office and fly!!!!!!

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Originally posted by lad So, theoretically, a sail on a Blokart is more efficient than comparably-sized kite on a buggy? (Greenbird vs. Xxtreme Apexx) :wow:

I'm not sure. A buggy with a racekite can do what, 4-5X speed of wind? I read that iceboats can do 6-7X. I don't know what the number is for a Blokart.

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Interesting if true, as Blokarts also *seem* to offer the ultimate "chilled out" flying session compared to most buggy experiences.

At NABX last year I came across a Blokart tipped on its side with both carbon axles snapped off like toothpicks. The driver was hanging upside down unable to free himself from his harness and had a broken collarbone (well something was poking under his skin where it should not have been). He was not chilled. :o

The kite would be more efficient per size than the blowkart. Most land sailers use a sail that is appx. 50-70 square feet in area. The Greenbird has a sail that is (I'm estimating here) 30' high and 4-5 foot wide. This would equate to a sail area of appx. 135 sq.ft. Speed comparisons - the Greenbird hit speeds of 127 mph in winds averaging 45-65 mph - very rough estimate of 2.2 times the wind speed - using a sail of appx. 135 sq.ft.

Ozzy hit speeds of 77 mph using a sail of appx. 35.5 sq. ft. in winds averaging 40-50 mph. - very rough estimate of 1.9 times the wind speed but with a sail area of nearly 1/4 the size.

We are comparing apples to string beans here..... but sail size to sail size, it would appear that kites are more efficient for a given wind range.

Peter Lynn has a new 'personal' website with some good articles on kite physics and kite traction.

The following link is to an article on kites vs sails for boats, and pretty much applies to the kite buggy vs. landsailor question:

http://www.peterlynnhimself.com/Kites_For_Yachts.php

krumly

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Originally posted by awindofchange The kite would be more efficient per size than the blowkart. Most land sailers use a sail that is appx. 50-70 square feet in area. The Greenbird has a sail that is (I'm estimating here) 30' high and 4-5 foot wide. This would equate to a sail area of appx. 135 sq.ft. Speed comparisons - the Greenbird hit speeds of 127 mph in winds averaging 45-65 mph - very rough estimate of 2.2 times the wind speed - using a sail of appx. 135 sq.ft. Ozzy hit speeds of 77 mph using a sail of appx. 35.5 sq. ft. in winds averaging 40-50 mph. - very rough estimate of 1.9 times the wind speed but with a sail area of nearly 1/4 the size. We are comparing apples to string beans here..... but sail size to sail size, it would appear that kites are more efficient for a given wind range.

Argen Hit 77mph

More efficients or More stable. Stable was the key I think, unstable broke all my lines.

It'll be tough for novice-intermediates not to compare apples to string beans, but if it's learning you are seeking then it's all good.

Remember. the GreenBird is a Landsailor. We ride ParaKarts with long string with Drag and our wings work so much differently.

If you need a dose of speed and want to learn, grab some walkey talkies and hit the lake with Kent, he'll teach you a thing or two about speed. Particularly how to slow down with all that juice in your hands.

Note the emergency braking procedure near 50mph at the end of the first song.
http://www.vimeo.com/4082803

Nice vid Eli and great music choice. You need to fly down here soon and we will take off to my dry lake in Texas and bring the World Speed Record back home to a US rider where it belongs.

Big John

PS nice use of the Flinstones Breaks LOL:wee:

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Originally posted by USA_Eli_A Quote: Originally posted by awindofchange The kite would be more efficient per size than the blowkart. Most land sailers use a sail that is appx. 50-70 square feet in area. The Greenbird has a sail that is (I'm estimating here) 30' high and 4-5 foot wide. This would equate to a sail area of appx. 135 sq.ft. Speed comparisons - the Greenbird hit speeds of 127 mph in winds averaging 45-65 mph - very rough estimate of 2.2 times the wind speed - using a sail of appx. 135 sq.ft. Ozzy hit speeds of 77 mph using a sail of appx. 35.5 sq. ft. in winds averaging 40-50 mph. - very rough estimate of 1.9 times the wind speed but with a sail area of nearly 1/4 the size. We are comparing apples to string beans here..... but sail size to sail size, it would appear that kites are more efficient for a given wind range. Argen Hit 77mph More efficients or More stable. Stable was the key I think, unstable broke all my lines. It'll be tough for novice-intermediates not to compare apples to string beans, but if it's learning you are seeking then it's all good. Remember. the GreenBird is a Landsailor. We ride ParaKarts with long string with Drag and our wings work so much differently. If you need a dose of speed and want to learn, grab some walkey talkies and hit the lake with Kent, he'll teach you a thing or two about speed. Particularly how to slow down with all that juice in your hands. Note the emergency braking procedure near 50mph at the end of the first song. http://www.vimeo.com/4082803