Wednesday, October 19, 2011
Some recent events have prompted me to issue a cautionary note about flying kites and Aeropods. I highly recommend avoid flying the 9 ft kite when ground wind speeds are above 12 mph. Though the 9 ft kites are rated 3 - 18 mph, this is a bit deceptive. The problem is that we are measuring our wind speed at ground level (AGL). Typically you can add 5 to 10 mph for winds aloft, and if it's gusty even more. The spreader on the 9 foot seems particularly ill suited to absorbing the stress produced by gusts above 20mph. If you are flying kites at wind speeds above 12 mph AGL, there is a very good chance you are at the functional limit of the kite when aloft. We have now seen four of these kites fail under similar circumstances.
We are trying out a slightly more robust spreader to see if that helps, (this is the carbon rod that stretches across the kite between the wing spars). We have to be careful not to rely on this too much though. These delta kites have maximized surface area in order to lift in light winds. This can become a problem as winds increase and become gusty. There is a point at which strengthening the spreader will just pass the failure to another stress point on the kite.
For what it's worth, I have found that the 7 ft kite does better under those conditions, and if you have sustained winds in the 6 - 12 mph range, it can handle the MonoCam easily, and probably the TwinCam at the higher end. As always, be sure to do a test flight without a camera to get a sense of what is happening aloft. Attaching a tail to the kite during the test flight can help to determine wind direction and speed aloft. You can use the Beaufort Scale to help judge the winds form the ground. The Beaufort Scale is available on our site at: <sites.google.com/site/iccarspro…> Look in the documents at the bottom of the page. There is also an abbreviated version is the little kite flying handbook from Into the Wind that you received at the summer workshop.
Another good reason to avoid flying Aeropods when ground winds are above 12 mph is that it becomes increasingly difficult to capture good images as the wind overcomes the Aeropods stabilizing mechanisms in the higher winds aloft.
Remember, the more practice you have with the kites, the better you will understand how they behave in different wind conditions, and what you can do to mitigated things like sudden gusts or fall-offs in wind speed. Practicing with your Monocam will help you prepare for successful flights with the TwinCam and other more valuable sensors down the road.