Bill Freeman wrote:

Vance,

A certain wood prop builder (now deceased) was building an amazingly bizarre
prop design at the end of his career.  The outer 6" had a very obvious LARGE
local pitch increase.  When asked about it, he just stated that it "helped
the prop
get a better bite, works really great".   Some of these folks are truly
blacksmiths.

One important point mentioned in one of the really early NACA prop papers is
that they tested a prop with 12% less thrust (a piece a crap, basically)
compared to
another prop and the top speed difference was only a few mph (I forget how much,
IIRC 3-4 mph).  Their comment was that top speed differences is a very poor way
to judge propellors.   Unfortunately, that is how they are judged in most
cases today.

That said, I sure hope my prop sim program has produced as good a blade in
the real world as it is on the computer screen!  ;-)   It's only zeros and
ones until
it is really tested.

Bill Freeman
Long EZ builder & pilot
BSME, MSME
EAA Technical Counselor

 
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