X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao101.cox.net ([68.230.241.45] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2211787 for flyrotary@lancaironline.net; Sun, 29 Jul 2007 15:28:36 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao101.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20070729192756.HRCN1349.fed1rmmtao101.cox.net@fed1rmimpo01.cox.net> for ; Sun, 29 Jul 2007 15:27:56 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo01.cox.net with bizsmtp id VXTw1X00H1xAn3c0000000; Sun, 29 Jul 2007 15:27:57 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Inlet Scoops Date: Sun, 29 Jul 2007 12:29:55 -0800 Message-ID: <000001c7d21f$3a089a90$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7D1DC.2BE55A90" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7D1DC.2BE55A90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Are there any guidelines / rules of thumb for the entrance area of inlet scoops. I am referring to the leading edge of the scoop. Is a narrow (1/8") frontal area OK or should it be larger and radiused? If larger, = how large? =20 Joe Good question, Joe. I would like further information on that as well. I = can tell you what I think I know. It depends somewhat on the function of = the scoop. =20 An induction air scoop that is sized for good ram pressure recovery at speed, and minimal drag, should have a fairly large radius edge. At low speed and high engine rpm that scoop is pulling air in around that = corner, and will be less restrictive with a larger radius. How large? I don=92t = know exactly how that should be determined. Mine has about =BC - 5/16=94 = radius =96 seems to work fine. =20 Air inlets for cooling, etc. should also have a radius, and somewhat of = an airfoil shape on the outside. A radius should give a bit of local = external diffusion, and give smoother, attached flow over the surface. I used a fairly small radius, about 3/32 =96 1/8=94 on the main coolant rad scoop = which seems to work very well. =20 I=92m thinking my underwing inlet for the oil cooler could benefit from = a larger radius, but there are other problems there. =20 Al ------=_NextPart_000_0001_01C7D1DC.2BE55A90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Are there any guidelines / = rules of thumb for the entrance area of inlet scoops. I am referring to the leading edge of the scoop. Is a narrow (1/8") frontal area OK = or should it be larger and radiused? If larger, how = large?

Joe

Good question, Joe.=A0 I would = like further information on that as well. I can tell you what I think I = know.=A0 It depends somewhat on the function of the scoop.

An induction air scoop that is = sized for good ram pressure recovery at speed, and minimal drag, should have a = fairly large radius edge. =A0At low speed and high engine rpm that scoop is = pulling air in around that corner, and will be less restrictive with a larger = radius. How large? I don’t know exactly how that should be determined.=A0 Mine = has about =BC - 5/16” radius – seems to work = fine.

Air inlets for cooling, etc. = should also have a radius, and somewhat of an airfoil shape on the outside. A radius = should give a bit of local external diffusion, and give smoother, attached flow = over the surface.=A0 I used a fairly small radius, about 3/32 – = 1/8” on the main coolant rad scoop which seems to work very = well.

I’m thinking my underwing = inlet for the oil cooler could benefit from a larger radius, but there are = other problems there.

Al

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