X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost04.isp.att.net ([207.115.11.54] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4499581 for flyrotary@lancaironline.net; Sat, 09 Oct 2010 11:50:44 -0400 Received-SPF: none receiver=logan.com; client-ip=207.115.11.54; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-85-148-241.mco.bellsouth.net[98.85.148.241]) by isp.att.net (frfwmhc04) with SMTP id <20101009155006H0400oce51e>; Sat, 9 Oct 2010 15:50:06 +0000 X-Originating-IP: [98.85.148.241] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: Propeller design. Date: Sat, 9 Oct 2010 11:50:06 -0400 Message-ID: <3D04D24511DE42A3925D481719421732@Desktop> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01CB67A8.1E9C2F70" X-Mailer: Microsoft Office Outlook 11 Thread-Index: ActnwjMrvqQe/s2cRwy4ZWKIafgMXgABw8tA X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 This is a multi-part message in MIME format. ------=_NextPart_000_0006_01CB67A8.1E9C2F70 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 Ed From: Al Gietzen Sent: Saturday, October 09, 2010 11:37 AM To: Rotary motors in aircraft 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! ------=_NextPart_000_0006_01CB67A8.1E9C2F70 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

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

 

Ed

 

From: Al = Gietzen

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!

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