X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-wy0-f180.google.com ([74.125.82.180] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTPS id 4963542 for flyrotary@lancaironline.net; Sun, 01 May 2011 18:06:46 -0400 Received-SPF: pass receiver=logan.com; client-ip=74.125.82.180; envelope-from=rwstracy@gmail.com Received: by wyj26 with SMTP id 26so3955354wyj.25 for ; Sun, 01 May 2011 15:06:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=/hhvoBqie9WR6hn6QpRqv5KjUSPVTLc/yMB17eCDjPo=; b=vFGWRmJlcbCWK8vIK7MHKm/XytwTSng5PxU7g8CeiywGwi/zL6ZS3wN6hxFWbvyo70 rt5JdRqsc77VHrKiwuKFPe4jfGdoWzVjLF6xOB42gzslcvcevyTz9Z9ydVHBkkHoHljl n4GfJ8B9qrqZx+4VNFaOR0AHLlIFJVwaKxhH8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=g6IzCJGfE+myyVQJilMsL9GaVUvuEk/wm4rN2+jqO0U0eBDb9+uU+YcltPTSN26V5U ovvRC+DY4s2YCKJpcfJopMg6taVoVSIP7q3sqW+ir1wg+bLVCvQ6JcethqY5A10zezF9 eUEncsD1zSRa7lK10L05JV8+3Mp+tOBibOhJk= MIME-Version: 1.0 Received: by 10.216.79.11 with SMTP id h11mr2165461wee.77.1304287570236; Sun, 01 May 2011 15:06:10 -0700 (PDT) Received: by 10.216.190.132 with HTTP; Sun, 1 May 2011 15:06:10 -0700 (PDT) In-Reply-To: References: Date: Sun, 1 May 2011 18:06:10 -0400 Message-ID: Subject: Re: [FlyRotary] Re: Cooling Inlets From: Tracy To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=000e0ce0d1204f15c504a23e1df3 --000e0ce0d1204f15c504a23e1df3 Content-Type: text/plain; charset=ISO-8859-1 I may have read it wrong, but it seems the NACA study that Tracy was referencing said that the cooling drag for the Aztec they were testing was about 5% to 7% of total drag. I've read before that cooling drag is more like 30% of total drag. Big difference there it seems. E I have heard the 30% of total drag as cooling drag but it applied to CLEAN airplanes. The Aztec is no biplane but does not qualify as 'clean' . 5 - 7% still sounds low however. T On Sat, Apr 30, 2011 at 11:10 AM, Ernest Christley wrote: > Ed Anderson wrote: > > For a high speed cruise environment, I would think cooling drag might be >> of more importance than say perhaps a few pounds of additional weight, on >> the other hand if you are flying an already draggy biplane for example, >> cooling drag is probably a very small part of your over all drag, but >> getting cooling with low airspeed might be the system driver. >> Its all about compromises - space, weight, flow, drag, etc. - oh, yes! - >> and cooling of course {:>) all matched to your constraints and operating >> environment. >> >> > > > I may have read it wrong, but it seems the NACA study that Tracy was > referencing said that the cooling drag for the Aztec they were testing was > about 5% to 7% of total drag. I've read before that cooling drag is more > like 30% of total drag. Big difference there it seems. > > Does anyone have any better insight, or is this just an apples vs oranges > thing? We've spent a LOT of time discussing cooling drag on this list. Is > it even worth worrying over? Is it worth stressing over an engine > overheating to go 196MPH instead of 192MPH? > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > --000e0ce0d1204f15c504a23e1df3 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable I may have read it wrong, but it seems the NACA study that Tracy was=20 referencing said that the cooling drag for the Aztec they were testing=20 was about 5% to 7% of total drag. =A0I've read before that cooling drag= is more like 30% of total drag. =A0Big difference there it seems.

E
I have heard the 30% of total drag as cooling drag but it applied to C= LEAN airplanes.=A0 The Aztec is no biplane but does not qualify as 'cle= an' .=A0 5 - 7% still sounds low however.

T



On Sat, Apr 30, 2011 at 11:= 10 AM, Ernest Christley <echristley@att.net> wrote:
Ed Anderson wrote:

For a high speed cruise environment, I would think cooling drag might be of= more importance than say perhaps a few pounds of additional weight, on the= other hand if you are flying an already draggy biplane for example, coolin= g drag is probably a very small part of your over all drag, but getting coo= ling with low airspeed might be the system driver.
=A0Its all about compromises - space, weight, flow, drag, etc. - oh, yes! -= and cooling of course {:>) =A0all matched to your constraints and opera= ting environment.
=A0


I may have read it wrong, but it seems the NACA study that Tracy was refere= ncing said that the cooling drag for the Aztec they were testing was about = 5% to 7% of total drag. =A0I've read before that cooling drag is more l= ike 30% of total drag. =A0Big difference there it seems.

Does anyone have any better insight, or is this just an apples vs oranges t= hing? =A0We've spent a LOT of time discussing cooling drag on this list= . =A0Is it even worth worrying over? =A0Is it worth stressing over an engin= e overheating to go 196MPH instead of 192MPH?

--
Homepage: =A0http:/= /www.flyrotary.com/
Archive and UnSub: =A0 http://mail.lancaironline.net:81/lists= /flyrotary/List.html

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