flyrotary@lancaironline.net Mailing List Archive

"If he shaves the prop off to say, 74”, he will get a couple hundred more rpm, but will probably lose in total thrust. Diameter is a big determiner in thrust. "

Hate to drag this one out again but Diameter is a big determiner of maximum static thrust. It is not the determiner of efficiency. That is determined by mass of airflow through the prop. 2" off the prop (76 to 74") will not greatly affect this on an aircraft in the speed range of an RV. Every builder that has traded those 2" for 200 -300 engine rpm has increased both rate of climb and top speed. Obviously the thrust was more after the cut. Matching the prop to the HP curve is more important than a minor change in diameter.

Tracy

That isn't to say that Don should make that choice, especially since he is making other changes to increase power.

On Thu, Mar 25, 2010 at 12:15 AM, Bill Bradburry <bbradburry@bellsouth.net> wrote:

Those are the best numbers I have seen with anyone with a Renesis so far. In fact, I have not heard of numbers that good on any 13B. Don is getting over 200 MPH with a cruise prop and climbing at over 1400 fpm with it. The only way he is going to do better is either with an electric CS prop and/or turbo. If he shaves the prop off to say, 74”, he will get a couple hundred more rpm, but will probably lose in total thrust. Diameter is a big determiner in thrust.

I would like more pictures of Dons intake and exhaust!

Bill B

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Wednesday, March 24, 2010 3:05 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Turbo Planning

1. When I read your stats in your first paragraph, the first thought that

comes to mind is that there is too much prop.

Ditto.

Al G