Perry Mick wrote:

Paul wrote:

If you do change the prop (fan) grind off a little thickness on
the ends of the blades and slather on some carbon fiber
cloth. I think you are getting some internal compressability
effects which is limiting your RPM to 4400. My gut feeling
is the engine should be turning up more.

If you look at the HP vs. RPM plot on my webpage, you'll see
I'm operating about right where that plot shows, 4400 RPM at
60 knots, and 110 HP.  This is using the program from the
Hollman book "Modern Prop and Duct Design."  This program has
proven to be right on every time.

The only way I can increase RPM is to increase HP or change
the prop in some way.  My blades may be overly thick, about
1 inch thick at the root, about 3/8 inch thick at the tip.
Going to 2 blades would immediately give me a big increase
in RPM, I ran the numbers awhile back, but haven't looked
at it in awhile.

Perhaps you can go beyond the computer predictions with thinner
blades at the tips. The airliner turbofan data certainly suggests
that. High tip drag will most certainly suck up some HP.
You might not need to go to fewer blades or your two blade
will rev higher with thinner tips.

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org