Tracy Crook wrote:

This "brick wall" at 185 mph term is being very miss-applied in these
discussions.  That was the figure on my RV-4 and would not be the same on
every plane. BTW, I was using the latest high pitch blades during my test.
The only relevant figure in these arguments is the DIFFERENCE between an
optimized comparison prop and the IVO.   Show me the data!  If the IVO was
faster, I'd be flying it instead of using it for a test club on my engine
stand.

I must point out that 210 mph is a LOUSY speed for a 180 HP Lancair.  My
very dirty RV-4 with it's fixed gear and fat, old fashioned 23013.5 airfoil
and much greater wing area will go 200 at the same altitude (5500 ft).  The
question I have to ask is:  How fast would that Lancair go with other props?

Previous comments about  the IVO (and other props) not delivering optimum
thrust near the hub is off the point as well.  I'd settle for zero thrust in
this area as long as it did not generate drag.  The IVO made lots of drag in
this area at airspeeds above 150 mph.

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

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