Date: Sun, 19 Feb 1995 17:12:32 -1000 From: mgraves@leadingedg.win.net (Michael Graves) Message-Id: <1659@leadingedg.win.net> Subject: Kiting to record altitudes - a revision Richard Synery, author of "Kiting to record altitudes", has asked me to post to rec.kites a revision to the first printing of his book. It would appear that Richard made a mistake in calculating his table of constant lift, as set out on page 47. The revised table follows. I have also uploaded it to the archives as altitude.tif. this file is in TIFF-F format, since Richard faxed it to me, and was concerned that those who bought the book have access to the revision with all page formating in tact. We can thank Dr Gordon Schmidt of North Canton, Ohio for catching the error, which is a significant one indeed. Dr Schmidt will likely be asked to proof things for Richard in future. Richard Synery is not on-line, but can be reached by phone at (416) 923-7800 in the evenings. He is currently building kites for his next record attempt. Michael Graves -------------------------------------- Table of Constant Lift Lift varies directly with the number of molecules per second that flow past your kite's wings. Air density is a measure of the number of molecules in a cubic foot of air. If a cubic foot of air at sea level contains 6 million molecules, and a cubic foot of air at 21,900 feet contains only 3 million molecules, then the wind at 21,900 feet must blow twice as fast as the wind at sea-level to provide the same amount of lift. The following chart shows the wind speed needed at various altitudes to equal a 10 mph wind at sea level. Altitude Wind mph Altitude Wind mph Mean Sea Level 10 42,000 21.20 2,000 10.29 44,000 22.23 4,000 10.61 46,000 23.33 6,000 10.94 48,000 24.47 8,000 11.28 50,000 25.67 10,000 11.64 52,000 26.76 12,000 12.01 54,000 27.85 14,000 12.41 56,000 28.94 16,000 12.82 58,000 30.76 18,000 13.25 60,000 32.58 20,000 13.70 62,000 34.34 22,000 14.18 64,000 36.09 24,000 14.68 66,000 37.85 26,000 15.21 68,000 39.60 28,000 15.76 70,000 41.36 30,000 16.36 72,000 43.60 32,000 16.97 74,000 45.85 34,000 17.63 76,000 48.10 36,000 18.38 80,000 52.58 38,000 19.29 90,000 66.98 40,000 20.21 99,999 84.89 Note: If the wind at all altitudes blows at the same speed, and the kite flies well at sea level with a wing area of 10 square feet, then the numbers under "wind mph", (times 2) show the wing area needed to produce the same lift as that generated at sea level. Note: 47 Values not on this list can be calculated by ratio. For example: If you have an 18 mph wind at sea level, what is the equivalent wnd speed, in miles per hour, at 6,000feet ? The ratio is: 1 0 is to 18 as 10.94 is to _____? (1 8 X 10.94) / 1 0 = 19.69 mph. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =