Return-Path: Received: from mallard.mail.pas.earthlink.net ([207.217.120.48] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2638064 for flyrotary@lancaironline.net; Wed, 15 Oct 2003 14:10:15 -0400 Received: from h-68-166-182-146.sfldmidn.covad.net ([68.166.182.146] helo=richard) by mallard.mail.pas.earthlink.net with smtp (Exim 3.33 #1) id 1A9q6A-0004iI-00 for flyrotary@lancaironline.net; Wed, 15 Oct 2003 11:10:14 -0700 Message-ID: <00eb01c39349$4ba8b870$6901a8c0@richard> From: "Eric Ruttan" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: rooster-tail drag Date: Wed, 15 Oct 2003 14:22:29 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00E8_01C39327.C4123100" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_00E8_01C39327.C4123100 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I have never seen a NACA scoop used to vent air FROM the aircraft BACK = into airstreams. I have reviewed all the NACA papers on scoops and have never seen this = effect described. Please point us to any reference on the subject. Respectfully, Eric ----- Original Message -----=20 From: JJ JOHNSON=20 To: Rotary motors in aircraft=20 Sent: Wednesday, October 15, 2003 11:04 AM Subject: [FlyRotary] Re: rooster-tail drag What is roster tail drag? how and where does it get created? Is there = anything about that written up on the net?I'd like to know since I'm in = the process of figuring out where to put my radiators in the Long = EZ.ThanksMarko Marko, Think of rooster tail drag as drag that's created when air = leaves the cowl at steep angle. The air, instead of turning and moving = along the side of the cowl like you'd think it would, shoots straight = out from the cowl for a small distance [ 6" may seem small but it will = create a huge drag penalty!] Another way to think of it is when your = driving and you throw that apple core out the window, notice how it goes = straight out for a little bit and then the on-coming air slows it down = and it 'appears' to go back.. Air leaving the cowl of your plane will = follow basically the same sort of path. So if we smooth this exit we'll = find that we reduce drag. Its one of the reasons that NACA ducts are = soooo popular, they create a very smooth exit [ the air is coming out = parallel to the side of the cowl and then as the duct narrows it is = accelerated and gradually pushed out into the normal airstream. So = simple yet it took years to understand it all. My 2 cents Jarrett Johnson --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.525 / Virus Database: 322 - Release Date: 10/9/2003 ------=_NextPart_000_00E8_01C39327.C4123100 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I have never seen a NACA scoop used to = vent air=20 FROM the aircraft BACK into airstreams.
I have reviewed all the NACA papers on = scoops and=20 have never seen this effect described.  Please point us to any = reference on=20 the subject.
 
Respectfully,
Eric
----- Original Message -----
From:=20 JJ=20 JOHNSON
Sent: Wednesday, October 15, = 2003 11:04=20 AM
Subject: [FlyRotary] Re: = rooster-tail=20 drag

 What is roster tail drag? how and = where does it=20 get created? Is there anything about that written up on the=20 net?I'd like to know = since I'm in the=20 process of figuring out where to put my radiators in the Long=20 EZ.ThanksMarko
 
 
Marko, Think of rooster tail drag as drag that's created when = air=20 leaves the cowl at steep angle. The air, instead of turning and moving = along=20 the side of the cowl like you'd think it would, shoots straight out = from the=20 cowl for a small distance [ 6"  may seem small but it will create = a huge=20 drag penalty!] Another way to think of it is when your driving and you = throw=20 that apple core out the window, notice how it goes straight out for a = little=20 bit and then the on-coming air slows it down and it 'appears' to go = back.. Air=20 leaving the cowl of your plane will follow basically the same sort of = path. So=20 if we smooth this exit we'll find that we reduce drag. Its one of the = reasons=20 that NACA ducts are soooo  popular, they create a very smooth = exit [ the=20 air is coming out parallel to the side of the cowl and then as = the duct=20 narrows it is accelerated and gradually pushed out into the normal = airstream.=20 So simple yet it took years to understand it all.
 
My 2=20 cents
Jarrett Johnson
 
 

---
Outgoing mail is certified Virus Free.
Checked = by AVG=20 anti-virus system (http://www.grisoft.com).
Version: = 6.0.525=20 / Virus Database: 322 - Release Date:=20 10/9/2003
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