Here’s a photo of my Catto
3-blade, circa 2007. Not much chord there. 66” dia, 80 pitch.
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Saturday, October 09, 2010
7:50 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Propeller
design.
It seems to me that Catto
might be trying to incorporate that wider chord into his recent props. I
don’t remember Tracy’s and others earlier props having that wide a
chord?? I also wonder if it would work if the tip didn’t thin out
like Lipps props do.
Bill B
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Saturday, October 09, 2010
10:56 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Propeller
design.
Yep!, as certain seems indicated by
recent comparisons - chord appears to play a significant role in prop
performance, but is one Prop parameter that is seldom specified in prop specs
Sent: Saturday, October 09, 2010 11:37 AM
Subject: [FlyRotary] Re: Propeller design.
Baking up
to the issue that started this discussion; these words from Lipps article get
to the point.
You’ll notice I never once used the word
“pitch” in reference to my propeller. In my opinion, that word
should be reserved for use with screws and worm gears that travel a definite
linear distance per revolution. It is really an inappropriate, nontechnical
term for use with props and introduces the idea that all propellers of a
certain diameter and pitch are alike. It’s as if chord and planform have
no bearing on a propeller’s characteristics; but nothing could be further
from the truth! Go buy the same diameter and pitch prop from three different
prop makers and you’ll get three different performances. That is the
source of much frustration for someone shopping for a prop for his plane. To properly
characterize a prop, the prop maker should tell you the engine horsepower
required to turn the prop at a given rpm, density altitude, and speed, as well
as the efficiency under those conditions. I’d like to see you get that
information from any of them!