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Message
I believe Tracey felt the reduced airfoil
shape and/or reduced pitch change of the prop root contributed to his
lower top end performance. I was hoping Tracy would jump into this
discussion and refresh my memory.
Tracy was planning to to to the RV fly-in in Lakeland
this weekend, so you won't hear from him right away.
If the
prop root profile was the cause for his lower performance, I am estimating this
may not have an effect on my application since I am a pusher and thrust
contribution from the root area is likely to be small. The only adverse
effect this should have is on ground cooling, but I am planning on exhaust
augmenters to assist cooling.
I believe the
issue is the root area as you recalled. The IVO is just a flat bar at that
point, and creates a bunch of drag. I believe Tracy wanted to try it
again, but with some sort of cuffs added to the spinner to improve the
shape. FWIW, this problem also exists to some extent with our monster
props, since the center is also pretty flat. Tracy did in fact make a
funky looking cuff that smoothes out the root area of his new prop, and he
felt like it did make a measurable difference. I haven't done it, and I
don't think Ed has either.
I had also
speculated previously that pushers wouldn't be effected as much, because
the fuselage blocks much of the effected area. Al will be
disappointed to hear that I have absolutely no engineering studies to back
that up :-)
Cheers,
Rusty (parts
needed)
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