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12-07-2008 | 06:56 AM

#6

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: OS91 FX

SpeedBoy,

It looks more probably that you are loosing your mind...

[&:]

If you look at any prop blade, from any make, you will see that the blade tips have a reasonably smooth shape...

The tip of the prop must promote smooth airflow, to produce good thrust, so it is shaped and if you often make 'kangaroo style' landings, which result in prop-ground clashes; the prop pulls less strongly afterward; even if you touch-up the stricken blades with a model-knife.

There are no props around, which have 'chopped' tips...

A chopped prop can be used to reduce the load on the engine, while raising the RPM... But it can be 'efficiently' used during break-in only (it will provide cooling), but never for flight.

Also, a fixed-pitch prop with a very high pitch-to-diameter ratio, will take 'ages' to build a 'vortex' and produce effective thrust...

So, with a 9x14 prop, as you suggested, a sleek plane may eventually fly very fast, but it will take it eons to reach about 65% of that high speed, for the prop to make effective thrust that would enable it to reach that speed.

This is the very reason all but the most basic aircraft, use variable pitch, or constant-speed propellers...

I believe the most 'radical' props that can be purchased are from [link=http://www.apcprop.com/cgi-bin/store/agora.cgi?maxp=400&ppinc=6a&product=+]APC[/link]... They offer a 7x10, 8x10, 9x10, 10x10 and 11x10, 11 and 12 sport props...

But even their ultra high-speed carbon fiber pylon racing props, are 7.4x8 at most...

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