Return-Path: <13brv3@bellsouth.net> Received: from imf19aec.mail.bellsouth.net ([205.152.59.67] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 3100423 for flyrotary@lancaironline.net; Thu, 18 Mar 2004 11:23:40 -0500 Received: from rad ([68.221.170.60]) by imf19aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040318162335.TCDB12770.imf19aec.mail.bellsouth.net@rad> for ; Thu, 18 Mar 2004 11:23:35 -0500 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Rev-2 Runs! Date: Thu, 18 Mar 2004 10:21:37 -0600 Message-ID: <013301c40d05$1685edd0$6001a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0134_01C40CD2.CBEB7DD0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0134_01C40CD2.CBEB7DD0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable > FWIW, the CAFE Foundation's research has shown that using a cooling > exit shape very similar to Finn's cheek exits might be the most > efficient way to get air out of the cowl. > > Charlie Interesting, but what about cooling drag? Right now I have way more cooling than I need. I was hoping to reduce cooling drag by closing off those exits - potentially with the few inches of the cone removable for hot summer days. Finn This is all very interesting. On the rev-1 version, I was planning to = try to use the cheek extension area as the only air exit, because it looked = to me to be the lowest pressure area. Traditionally, the bottom of the = cowl is used, but I can't believe that's a low pressure area. The top of the fuselage would get into high pressure due to the front of the canopy, = not to mention the ramifications of an oil or water leak. To me, the sides of = the fuselage seem to be the natural choice for air exit. =20 This did work, but only to a point. I found that I had too much cooling with the bottom, and cheeks open, so I blocked off the bottom opening. = That would have been much better in cruise, but was too little for climb. = The new cheek exits are noticeably smaller than the old ones, so I'm sure it wouldn't work as the only exit. Of course I also have a muffler coming = out the bottom now, so I don't have the option to close that off anyway. = It would have been easy to block off the cheeks on the old cowl, since I already had those bulkheads, but for some reason, I never tried it. =20 I'm also interested in the drag penalty for leaving the cowl cheeks = open. I don't mind the look of the open cheeks (hold the proctologist jokes) = and they do allow for easy inspection of most of the engine. For now, I'll = be happy to leave them open for the extra cooling, and inspections ability, = but once I start cleaning up the airframe, they'll have to get closed and = faired if they're causing me any significant drag. =20 Do we have any aerodynamics folks who could comment on this (in plain English ) ? Thanks, Rusty=20 ------=_NextPart_000_0134_01C40CD2.CBEB7DD0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message

> FWIW, the CAFE Foundation's research has shown = that using a=20 cooling
> exit shape very similar to Finn's cheek exits might be = the=20 most
> efficient way to get air out of the cowl.
>
>=20 Charlie

Interesting, but what about cooling drag? Right now I = have way=20 more
cooling than I need. I was hoping to reduce cooling drag by = closing=20 off
those exits - potentially with the few inches of the cone = removable=20 for
hot summer days.

Finn

This is all very interesting.  On the = rev-1 version, I=20 was planning to try to use the cheek extension area as the only air = exit,=20 because it looked to me to be the lowest pressure area.  = Traditionally, the=20 bottom of the cowl is used, but I can't believe that's a low pressure=20 area.  The top of the fuselage would get into high pressure due to = the=20 front of the canopy, not to mention the ramifications of an oil or water = leak.  To me, the sides of the fuselage seem to be the natural = choice for=20 air exit. 

This did = work, but only to=20 a point.  I found that I had too much cooling with the bottom, and=20 cheeks open, so I blocked off the bottom opening.  That would = have=20 been much better in cruise, but was too little for climb.   = The new=20 cheek exits are noticeably smaller than the old ones, so I'm sure it = wouldn't=20 work as the only exit.   Of course I also have a muffler = coming=20 out the bottom now, so I don't have the option to close that off=20 anyway.   It would have been easy to block off the cheeks = on the=20 old cowl, since I already had those bulkheads, but for some reason, I=20 never tried it.   

I'm also = interested in the=20 drag penalty for leaving the cowl cheeks open.  I don't mind the = look of=20 the open cheeks (hold the proctologist jokes)  and they = do allow=20 for easy inspection of most of the engine.  For now, I'll be happy = to leave=20 them open for the extra cooling, and inspections ability, but once I = start=20 cleaning up the airframe, they'll have to get closed and faired if = they're=20 causing me any significant drag.  

Do we = have any=20 aerodynamics folks who could comment on this (in plain English = <g>)=20 ?

Thanks,
Rusty 
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