charles.harbert wrote:

Jim you wrote:
"I have been doing some prop test flying, last week I mounted Neil's 3 blade
Ivo prop, very smooth, climbes like hell but unwinds around 180 mph., not
the answer to flexible."

Awhile back on the PL rotary line, I posted a thought that perhaps the reason
that the IVO 3 blade prop was inefficient above 180-200 mph was because it was a
compromise of a 60" prop. You're effectively twisting an avg 60" (30"-90")prop
which is a lot less efficient than rotating the entire blade ala constant spd
prop. I've recently switched to an avg 80" (50"-110") deep pitch IVO and had it
up to 200 mph (in the patern) just for a short period.

It still has great t/o capability, and I think it will produce much higher spds
than my old normal pitch IVO blades. I talked to a Lancair IV owner who was
using an IVO and their spd was in excess of 200 kts. IOW, you might consider
getting the deep pitch IVO blades and try them before you give up. IVO is pretty
good about these things and may give you a good deal on them to try out. You
might want to give him a call to discuss.

Chuck, quite some time ago, as I recall it was at the first Golden State
Flyin over a year ago, Don Bates analyzed the IVO and found that the
roots of the blades were going into a negative angle of attack around 180 MPH.
Tracy tried one and confirmed this. Now Jim has tried it and also
confirmed this. I think it has nothing to do with the pitch.

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

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