X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4499517 for flyrotary@lancaironline.net; Sat, 09 Oct 2010 10:56:47 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=UAZ0ep3suvkVn+xl78ZyFqEJZfCyw4fsauT9kMdOA88= c=1 sm=0 a=fStl7FSyMa0A:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=X8C6nNDgKL6hNwXO9xcA:9 a=Vn8zfn0073Jif3qscRpRd2nW150A:4 a=wPNLvfGTeEIA:10 a=kviXuzpPAAAA:8 a=Ia-xEzejAAAA:8 a=eg98aO0ybdWfcApuIM0A:9 a=CMevplyRkNhhokg7j7UA:7 a=dUNIQPcxgTb9JIHfd3nM-CAgBv4A:4 a=4vB-4DCPJfMA:10 a=EzXvWhQp4_cA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:61722] helo=EdPC) by cdptpa-oedge04.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 9E/B3-03860-A8280BC4; Sat, 09 Oct 2010 14:56:10 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Propeller design. Date: Sat, 9 Oct 2010 10:55:55 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0057_01CB67A0.8C6775D0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0057_01CB67A0.8C6775D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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=20 Sent: Saturday, October 09, 2010 11:37 AM To: Rotary motors in aircraft=20 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_0057_01CB67A0.8C6775D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Yep!, as certain seems indicated by recent = comparisons -=20 chord appears to play a significant role in prop performance, but = is one=20 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=20 started this discussion; these words from Lipps article get to the=20 point.

 

You=92ll notice = I never once=20 used the word =93pitch=94 in reference to my propeller. In my opinion, = that word=20 should be reserved for use with screws and worm gears that travel a = definite=20 linear distance per revolution. It is really an inappropriate, = nontechnical term=20 for use with props and introduces the idea that all propellers of a = certain=20 diameter and pitch are alike. It=92s as if chord and planform have no = bearing on a=20 propeller=92s characteristics; but nothing could be further from the = truth! Go buy=20 the same diameter and pitch prop from three different prop = makers=20 and you=92ll get three different performances. That is the source of = much=20 frustration for someone shopping for a prop for his plane. To properly=20 characterize a prop, the prop maker should tell you the engine = horsepower=20 required to turn the prop at a given rpm, density altitude, and speed, = as well=20 as the efficiency under those conditions. I=92d like to see you get that = information from any of them!

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