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Old 10-17-2002, 04:22 AM
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Ollie
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Join Date: Dec 2001
Location: Punta Gorda, FL
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Default question for ollie

I'm skeptical by nature. The only numbers I trust are those that are carefully measured with due consideration given to instrument calibration and error analysis. Eyeballed estimates can be way, way off. No measurement is complete without a probable error attached.

Back about 1980 some very talented Austrian machinists put together a plane called the Dassel, set up the required 150 meter course that the FAI required for a world record and proceeded to fly the glider through the course at about 250 KPH (~150 MPH) in both directions. At that speed it only took about two and a quarter seconds to fly the course. If one used human timers and stopwatches, how accurate would the measurements be if the reaction time of the human timers varied between 1/3 and 1/2 second? At any rate, the FAI at first recognized the world record but later had to withdraw their recognition when an error analysis was made. Very embarrasing to all concerned.

I've never seen a Diamond Dust fly. I believe they are very, very fast but I would not consider any claim of 240 MPH more than advertising hype until I knew all the details of how the measurements were made. What were the measuring instruments? How had they been calibrated? What was the wind speed and direction relative to the course? How was the course measured? Were passes through the course made in both directions? How free of parallax were the instruments' set up? Etc, etc, etc.

The pictures I have seen of the Diamond Dust show a plane that is loaded with parasitc drag. It's my intuition that the top speed of the Diamon Dust is limited by the RPM of the engine and the pitch of the prop in addition to the very, very high parasitic drag.