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05-27-2009 | 12:07 PM

#47

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: os 61sf

Quote:

ORIGINAL: tony0707

I am sure if I went to a smaller prop (11/5)and was turning 13,600 with my .61SF, my horsepower will exceed your numbers - I have no need to run 1,000 RPM more - as the speed and power of this engine in this plane is a true handful. The Kaos airframe is an extremely efficient airframe. Horsepower number are not the do all - end all in an airplane set up.
The best possible vertical is my criterion for performance; and every engine needs to be propped differently, for a given airframe.

Hi, Tony.

In fact, horsepower IS everything...
Not rated, claimed, or advertised HP; but actual calculated HP.

HP, as it is calculated by the [link=http://mvvs.nl/prop-power-calculator.xls]PropPower[/link] calculator, will determine the thrust that your engine is capable of putting out, at every flight speed.

Read your high-school physics textbook again please...

With things as they are now; had you removed your piped OS.61SF with the 12x6 APC and instead installed and rebalanced the mini-piped MVVS .49 with the Bolly 11.5x6 (not 11x5...) prop, your Kaos would have flown better and faster, climbed better and accelerated faster too.

Your mistake is the setup!
The SF is OS' first long-stroke series engine and in the interest of preserving flying sites; it was designed to be at its best, at lower RPM - 10,500-11,000, with a longer tuned-pipe (to make its noise less buzzy to sensitive ears).
In this guise it would produce about 1.8-1.85 HP actual HP, spinning a 12x10, or a 13x8 in this RPM range...

'Letting it go' as you did, with the 12x6, just puts it on the over-run... More RPM - but significantly less HP; which necessarily means less performance.

I believe you 'ain't seen nothing yet', of what your Kaos is capable of...

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