X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 24 Jan 2008 17:34:57 -0500 Message-ID: X-Original-Return-Path: Received: from smtp124.sbc.mail.sp1.yahoo.com ([69.147.64.97] verified) by logan.com (CommuniGate Pro SMTP 5.2c4) with SMTP id 2691962 for lml@lancaironline.net; Thu, 24 Jan 2008 14:14:12 -0500 Received-SPF: none receiver=logan.com; client-ip=69.147.64.97; envelope-from=elippse@sbcglobal.net Received: (qmail 53466 invoked from network); 24 Jan 2008 19:13:34 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=sbcglobal.net; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=ZJEbpw5qd5k2j11HHeWu9WscK6cLNYg0W+/jEGqjSbYhYT/+bQgP2w3ldhuRyc/NA/Nmqg4nbucEUF+qCEwsRZBlZAsoH+DWAhOw0ZN9WcDe6tQYDuSuoOeA30l8QLYAKeltTS3fEQXRdYsF7Vb0sPPfNyLInRzm8vy5WzFxAZY= ; Received: from unknown (HELO Computerroom) (elippse@sbcglobal.net@75.15.152.6 with login) by smtp124.sbc.mail.sp1.yahoo.com with SMTP; 24 Jan 2008 19:13:34 -0000 X-YMail-OSG: DB6UnMcVM1mHh98ekTOpkBAxIRykgaJEkITAIAEoD3.D5Zlm.md4lE9BTTqqD6Wyf9Z0EuS8xQ-- X-Yahoo-Newman-Property: ymail-3 X-Original-Message-ID: <006701c85ebd$44166f50$469b0f4b@Computerroom> From: "Paul Lipps" X-Original-To: "Marv Kaye" Subject: prop performance X-Original-Date: Thu, 24 Jan 2008 11:13:53 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0064_01C85E7A.3488C9E0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_0064_01C85E7A.3488C9E0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable I modified the prop tips on my friend Oscar's Lancair 235/320. It was a = Great American two-blade fixed-pitch prop, and we got 214 mph-215 mph = TAS at 8500' dalt at 2600 rpm, totally stock O-320. I made the tips into = a slashed tip, with the tip shape sorta' elliptical in plan-form from = the LE to the TE, but with no change in diameter at the TE. The lower = surface of the tip was slanted up to the top surface to form a sharp = edge all along it. The top speed increased from 214-215 mph TAS to = 219-220 mph mph TAS at 2660 rpm, the rpm increase due to the increased = thrust from the prop giving higher speed and rpm, not from increased = power. Since horsepower is roughly a cubic function of speed ratio, = going from 214 at 2600 to 219 at 2660 is an efficiency (horsepower) = increase of (219/214)^3 x 2600/2660 =3D 4.8%; this from some simple tip = shaping. BTW, these speed numbers were carefully arrived at from GPS, = not IAS! My three-blade ELIPPSE prop on my 235 with a 125 HP O-235 gets = me off the ground in 1000' at 1350 lb, 500' dalt according to the tower = personnel. I typically climb at 110 mph IAS, 2410 rpm, and get a ROC of = 1400-1550 fpm at 1000' dalt. I've modified several props by increasing = the root chord and pitch with fiberglass and modifying the tip shape and = have gotten more speed with less rpm. The tip shape is the biggest = contributor to prop in-efficiency, with the other being the poor helix = angle and the un-aerodynamic shape of the root airfoil. ------=_NextPart_000_0064_01C85E7A.3488C9E0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
I modified the prop tips on my friend = Oscar's Lancair=20 235/320. It was a Great American two-blade fixed-pitch prop, and we got = 214=20 mph-215 mph TAS at 8500' dalt at 2600 rpm, totally stock O-320. I made = the tips=20 into a slashed tip, with the tip shape sorta' elliptical in plan-form = from the=20 LE to the TE, but with no change in diameter at the TE. The lower = surface of the=20 tip was slanted up to the top surface to form a sharp edge all along it. = The top=20 speed increased from 214-215 mph TAS to 219-220 mph mph TAS at 2660 = rpm,=20 the rpm increase due to the increased thrust from the prop giving higher = speed=20 and rpm, not from increased power. Since horsepower is roughly a cubic = function=20 of speed ratio, going from 214 at 2600 to 219 at 2660 is an efficiency=20 (horsepower) increase of (219/214)^3 x 2600/2660 =3D 4.8%; this from = some simple=20 tip shaping. BTW, these speed numbers were carefully arrived at from = GPS, not=20 IAS! My three-blade ELIPPSE prop on my 235 with a 125 HP O-235 gets me = off the=20 ground in 1000' at 1350 lb, 500' dalt according to the tower personnel. = I=20 typically climb at 110 mph IAS, 2410 rpm, and get a ROC of 1400-1550 fpm = at=20 1000' dalt. I've modified several props by increasing the root chord and = pitch=20 with fiberglass and modifying the tip shape and have gotten more speed = with less=20 rpm. The tip shape is  the biggest contributor to prop = in-efficiency, with=20 the other being the poor helix angle and the un-aerodynamic shape = of the=20 root airfoil.
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