Re: REFLECTOR: More on props

[Alan Shaw <wingco@iu.net>]

My hangar neighbor with a Cozy IV/Franklin has been testing 52" dia. wide cord
four bladed props of his own design and manufacture.  He has got them working
quite well for static and top end.  He explained to me that the tip does all the
work for static but the inner part is were the top end speed comes from.  I think
he is staying in the closet until he is happy with his product so that is all I
can tell you.

The science of props is not as exacting as some engineers and manufactures may
lead you to believe.  Wood props are like Martin guitars.  Two may be made and
look alike but one blows the other away.  I've seen "magic" props like that.
This tells us that it is a very imperfect science with lots of room for research
and improvement.

Al Gietzen wrote:
>From what I've gathered from various pilots of planes using IVO is that they get
good takeoff and climb performance but maybe not so good cruise.  One pilot
(Glassair II) described it to me as "hitting a wall".  Improving the performance
of his engine made no difference to his cruise speeds.  He believed that the lack
of pitch change on the inner part of the prop made that portion essentially a
"flat plate" (drag) at high speed.