Wood Prop Question
On Apr 5, 9:01 pm, "Kyle Boatright" wrote:
"cavelamb himself" wrote in message
link.net...
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.
I'm 99% sure that the props I'm talking about didn't have brass leading
edges. The next time you're at an airshow where a Spitfire is on display,
take a close look at the prop. On many (most?, all?) the prop is wood, and
you can't see a transition between a brass leading edge and the wood blade.
I've done this inspection several times at Osh and SnF...
KB
OTOH, the (metal) tail rotor on the Hughes OH6A woudld last about 5
minutes in rain.
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The MK XIV Spit had a five-bladed wooden prop. Ironically, the
manufacturer is now owned by a German conglomerate.
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