HighPlains
Posts: 2729
Joined: 3/2/2003
From: Over da rainbow,
KS, USA
Status: online
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Speedboy,
This is one of the best looking models I have ever seen on RCU, especially the wing graphics. I'll bet it will inspire many copies, and I can assure you of at least one.
As to the radar speed - yes if one takes the ground rpm and the prop pitch you come up very short of 170 mph. But there is a lot more to it than such a simple calculation.
First, all engines unload when they get into the air. Since your pipe may be slightly short and sized for a 7.5 cc engine, it may allow the engine to unload even more than normal. It would be nice to have a recording analysed to see what it is getting up to. While 18K would not surprise me too much, I doubt it is reaching 24K.
Second, the prop's true pitch may be slightly more than marked. Many props pitch are reference to the backside of the blades airfoil, while the true zero lift line of the prop's airfoil is several degrees more. Net result is higher speed.
Third, your best speed may have wind assist. The gradiant between ground airspeed and the speed of air higher up can be fairly large.
Fourth and most important, assuming your dive was at 45 degrees, and the model weighs around 6 pounds, gravity was adding two additional horsepower to the 2+ hp that the engine should be putting out. With this happening, I expect the pipe on the engine was actually holding down the diving speed.
< Message edited by HighPlains -- 12/1/2007 6:19:58 AM >
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All Forums >> RC Airplanes >> Extreme Speed Prop Planes >> PATRIOT AT 170 MPH !!!!!!! 
PATRIOT AT 170 MPH !!!!!!! - 
