Physics: Why we can go faster then the wind.

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.

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

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?

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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!!!!!!