Perry Mick wrote:

Think I might have got that backwards.  On page 108 of Hollman's
book, it says "leading edge" on the curved side, the trailing edge
is straight.

Goto
http://www.hartzellprop.com/top_prop/index_topprop.htm

Here is a similar prop on a Cessna
http://www.hartzellprop.com/top_prop/images/cessna_182_2.jpg

Sure looks like the trailing edge is straight, not the leading edge.
--
Perry Mick
perrym@teleport.com
Duckt N7XR
http://www.mickaircraft.com/duckt.htm

I think you are right Perry but I assume it will not be much loss if
the leading edge is made straight. On the other hand people could use
the urethane rain resistant trick Bill mentioned for the curved leading edge.

Paul Lamar

NACA says that planform is unimportant, and I believe it.  The only
case where it is important is for a quasi-constant speed flex-prop.
In this case you need the tip behind the root to get the proper
flex.  Might make your pitch motor work harder with some
planforms, too.

Otherwise, any planform is fine.  There MIGHT be a bit of drag
reduction with the now-fashionable sheared tips.

Bill

I would think swept back tips would act somewhat like swept back wings
delaying compressibility effects. I have heard that this causes high
stress in the thin trailing edge due to centrifugal forces and is 
this is the reason it is not done to a greater extent. The blade wants
to straighten itself out and this cause high bending loads.

Paul Lamar
 
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