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Yes, a radially different concept for Prop design. I
remember when the bi-plane picked up something like a 20 MPH increase in speed
with Lipps prop - it had us all drooling to think that perhaps we could gain a
10 MPH increase with our RV aircraft. Unfortunately, in the one example I
am somewhat familiar with when put on an Rv-6 the outcome was somewhat
disappointing - I think it was a gain of only about 1-2 MPH.
Now in all fairness, Paul's admits his design approach is
dependent on somewhat untradiational accuracy in engine HP and drag of the
platform information - which may have been lacking in this first attempt.
However, since there has not been a flood of aircraft with the Lipps prop, I'm
inclined to believe that it has not yet reach the promise that first seemed
likely.
While folks can point to the 20 mph increase in the bi plane's
performance, I can't help but wonder if perhaps the original prop on the bi
plane may have been a poor choice whereupon replacing it with the Lipps (better
matched) make the performance gain seem all related to the Lipps prop rather
than replacing what may have been a poor original choice - but, just
spectulation on my part.
I really wanted to see the Lipps prop deliver all it initially
seemed to promise, but I can't find any data yet to support its initial promise
- at least on the type platforms and speeds we normally fly. It’s the
first really different approach to prop design I've seen since - well, since the
Wright brothers {:>)
If anybody has a source for information that indicates my
impression is incorrect regarding its performance on Rv type aircraft (or
similar), I would like to receive it.
Thanks
Ed
Sent: Saturday, October 09, 2010 9:53 AM
Subject: [FlyRotary] Propeller design.
I sat through a talk by Paul Lipps at Gene Nevada at the alternative engine
seminar put on by Contact Magazine several years ago.
He flew in his home built, with his propeller. Its outer blades were
the size of a 12" ruler. Imagine model sail plane wings, or bread knife blades.
He placed split tennis balls on the tips so guests did not stab themselves on
the blades.
Later, he helped a guy design new wings for a biplane racer, and those
wings looked just like his propeller
blades. It had a 4 bladed Lipps propeller as well.
Not mentioned was the low wetted area of the blades would allow greater
span with less drag. The high angle of attack at the root allowed playing card
sized cooling inlets.
In the event of failed engine his prop has less than a 3rd of the frontal
area of a conventional prop.
Not exactly full feathering, but better than anything else.
So, if the blade has less drag for each unit of lift, then you could add
span until you get close to the ground, and then add blade count until you have
accounted for all of the available HP. Then you port the rotary to get more
HP.
Warning, looking at a Lipps propeller blade may hurt your
mind......................
Lynn E. Hanover
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