On Dec 16, 4:16 am, Stealth Pilot
wrote:
a well made newbie prop can deliver exactly the same performance as a
professionally carved prop. after all they were newbies once themselves.

I'd be willing to bet that the prop I have--a Colin Walker
unit, uncertified, built by a guy who probably got his start building
one for himself, is MORE efficient than, say, a Sensenich. The builder
of my prop used a more cambered airfoil that pulls better than a
Sensenich, he milled off the leading edge and built it up with hard
urethane and shaped it so that it's a seamless, lightweight abrasion
protection much better than Sensenich's crude riveted-on brass leading
edge that disrupts airflow and can harbor moisture under it, and so
on.

here is a trick for sizing the prop. make it an inch overlength.
in straight and level flight you should not be able to hit redline
with full throttle.
trim 5mm from each end and rebalance and refinish.
fly it again and the top rpm will be slightly higher.
when the revs come just up to redline rpm with full throttle your prop
is the correct size.

I shortened mine from 76" to 72" to get more RPM on takeoff,
and lost performance in all regimes. I wish I could put those tips
back on. It used to cruise at a speed and RPM that indicated zero or
slightly negative slip, believe it or not. Not anymore. Now it slips a
little. Don Downie, an old homebuilder of note, said that long props
would do that.

Dan