X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao103.cox.net ([68.230.241.43] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4499489 for flyrotary@lancaironline.net; Sat, 09 Oct 2010 10:36:53 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.43; envelope-from=alventures@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao103.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20101009143619.JDBY23084.fed1rmmtao103.cox.net@fed1rmimpo03.cox.net> for ; Sat, 9 Oct 2010 10:36:19 -0400 Received: from BigAl ([72.199.216.236]) by fed1rmimpo03.cox.net with bizsmtp id GecH1f00A56cS2o04ecHsR; Sat, 09 Oct 2010 10:36:17 -0400 X-VR-Score: 0.00 X-Authority-Analysis: v=1.1 cv=ZQ6Y7pMpbf3IjBwcEMB58TnwUaYQ/k9O+va7hVMiiyI= c=1 sm=1 a=RQi-rca4OukA:10 a=lN8H/RjlhkCyIsyuOn2r7w==:17 a=tcCYrvVNY1oF8dMVM7oA:9 a=9A2YRCd-xjVrYjMBZrgyMJpjToMA:4 a=CjuIK1q_8ugA:10 a=37erTl9Rn2hGQsrVDZcA:9 a=4xIqhMmxhPtS9kEJ_9UA:7 a=vppCtyCMAc4NLdEKMOs-at8nMbAA:4 a=lN8H/RjlhkCyIsyuOn2r7w==:117 X-CM-Score: 0.00 Authentication-Results: cox.net; none From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Propeller design. Date: Sat, 9 Oct 2010 07:37:09 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01CB6784.C8038910" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6863 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 Importance: Normal Thread-Index: ActnuW+mdeQFkvSCTmWCHNcvWmE+zwADdfUg In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0008_01CB6784.C8038910 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Baking up to the issue that started this discussion; these words from = Lipps article get to the point. =20 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_0008_01CB6784.C8038910 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

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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