I don=E2=80=99t consider cooling drag a significant issue on an = airplane making=20 barely 100MPH. The heat under the cowl is certainly something to be=20 considered.

Thanks!!

Richard=20 Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

From: CozyGirrrl@aol.com

Sent: Monday, July 09, 2012 11:48 AM

To: Rotary motors in = aircraft

Subject: [FlyRotary] Re: First lift off with single=20 rotor

Congratulations Richard, it's a great start.

Big "general rule of thumb" is give your exit (in a low pressure = area) 150%=20 of air inlet area. Think of the impact heat has on air in a hot air = balloon plus=20 the under cowl turbulence and slowing the air way down in there it is = easy to=20 see back pressure building up.

It is a good starting point and you can always begin blocking off = bits of=20 both inlet and outlet once it all looks like it is cooling then you can = begin=20 working on lessening the cooling drag.

Chrissi &=20 Randi

www.CozyGirrrl.com
Clic= kBonds=20 10/$7.50
CG Products, Custom Aircraft Hardware
Chairwomen, = Sun-N-Fun=20 Engine Workshop

In a message dated 7/9/2012 10:50:15 A.M. Central Daylight Time,=20 res12@fairpoint.net writes:

Cleared the ground for a brief period today. As far as the = airplane is=20 concerned, everything is good. CG seems to be right on the spot. Much = better=20 as it was 12 years ago at the first flight with the SOOB.

Here is the reason why it was not a flight. A few days ago when I = started=20 high speed taxi, as soon as it picked up air speed, the engine started = to=20 sputter and almost cut out totally. This was at the same RPM as at a = run up,=20 where it does not do that. With a wiggly tail dragger as the Avid is, = there=20 was no way reading enough instrument for making a preliminary = analysis. I=20 recorded the instrument panel with a GoPro at 2sec intervals.

Looking at the first pictures, the answer came up right away, = increasing=20 pressure under the cowl where the intake for the engine is located. = Like the=20 EGT shot up over 1600 just before the sputtering started. Since my = radiator=20 air is going to the outside of the cowling, there was no impact on = cooling.=20 Btw cooling is really good. At an OAT of 95F, oil and water stayed at = around=20 170F no matter what I did.

For todays runs, I taped the inlet around the prop hub shut. Sure = enough,=20 the sputtering occurred at higher airspeed, and was not as total, = however, EGT=20 was still going to around 1600.

The conclusion is, I have to open the cowling exits a lot.

Richard=20 = Sohn
N2071U

http://www.fairpoint.net/~res12/home.html