Kyle Boatright wrote:

Those of us who fly behind (or in front of) wooden props usually reduce RPM
significantly when entering rain. I reduce RPM to 1900 in rain, or I see
minor damage, despite the urethane leading edges. For me, 1900 rpm results
in a rotational tip speed of about 400 mph. This doesn't consider the
forward motion of the aircraft.

In WWII, more than a few combat aircraft used wooden propellers - Spitfires,
Hurricanes, and Me-109's being high profile examples. However, I have never
heard of any rain/prop issues with those aircraft. And I'm sure there were
plenty of occasions where those aircraft were flown full-out in rain. FYI,
with the Spit/merlin combination, the prop is geared to roughly half the
engine speed of 3,000 RPM. At 1500 prop rpm, a 10.75' diameter prop has a
tip speed of roughly 575 mph.

That's the kind of tip speed that will supposedly wreck a wooden prop in the
rain. So, what was different about those props? Were the blades
essentially disposable and nobody gave a second thought to trashing a set?
Did the blades incorporate some sort of technology that I've missed? (Brass
leading edges don't count - to the best of my knowledge, Spits didn't have
'em.)

Thoughts?

KB






I believe most of those old wood props had a brass leading edge cover.
That ought to protect the wood from rain erosion.

OTOH, the (metal) tail rotor on the Hughes OH6A woudld last about 5
minutes in rain.


Richard