X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 31 May 2010 09:44:21 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma04.mx.aol.com ([64.12.206.42] verified) by logan.com (CommuniGate Pro SMTP 5.3.7) with ESMTP id 4331338 for lml@lancaironline.net; Mon, 31 May 2010 05:49:52 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.42; envelope-from=Mquinns@aol.com Received: from imo-da03.mx.aol.com (imo-da03.mx.aol.com [205.188.169.201]) by imr-ma04.mx.aol.com (8.14.1/8.14.1) with ESMTP id o4V9nF1c003498 for ; Mon, 31 May 2010 05:49:15 -0400 Received: from Mquinns@aol.com by imo-da03.mx.aol.com (mail_out_v42.9.) id q.c84.64d063dc (37665) for ; Mon, 31 May 2010 05:49:11 -0400 (EDT) Received: from smtprly-db01.mx.aol.com (smtprly-db01.mx.aol.com [205.188.249.152]) by cia-mb07.mx.aol.com (v129.4) with ESMTP id MAILCIAMB077-5bc34c03860b34b; Mon, 31 May 2010 05:49:11 -0400 Received: from webmail-d017 (webmail-d017.sim.aol.com [205.188.181.30]) by smtprly-db01.mx.aol.com (v129.4) with ESMTP id MAILSMTPRLYDB012-5bc34c03860b34b; Mon, 31 May 2010 05:48:59 -0400 References: X-Original-To: lml@lancaironline.net Subject: Re: [LML] FW: [LML] Re: cowl flap cooling drag reduction X-Original-Date: Mon, 31 May 2010 05:48:59 -0400 X-AOL-IP: 97.104.54.191 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: mquinns@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CCCEBDA0D18E1D_1254_3C6B5_webmail-d017.sysops.aol.com" X-Mailer: AOL Webmail 31793-STANDARD Received: from 97.104.54.191 by webmail-d017.sysops.aol.com (205.188.181.30) with HTTP (WebMailUI); Mon, 31 May 2010 05:48:59 -0400 X-Original-Message-Id: <8CCCEBDA0CA69FD-1254-1BA48@webmail-d017.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: Mquinns@aol.com ----------MB_8CCCEBDA0D18E1D_1254_3C6B5_webmail-d017.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Fred, Could you send some pics? Mrak Quinn -----Original Message----- From: Frederick Moreno To: lml@lancaironline.net Sent: Sun, May 30, 2010 9:54 am Subject: [LML] FW: [LML] Re: cowl flap cooling drag reduction I put cowl flaps on my Lancair IV along with a top cooling air plenum and= I also went to fairly extreme measures to eliminate cooling leakage aroun= d the engine. Inlet area remained unchanged (6 inch diameter) although th= e inlets were raised 1.5 inches for a straight shot in and moved outboard= 1.0 inch so that I could insert a boundary layer dam between spinner and= inlets. This removes the boundary layer coming off the spinner as well= as the slower-moving separated wake flow at the shank of the propeller wh= ere it enters the spinner. I drastically cut the exit area with cowl flap= s closed compared to the stock Lancair outlets which are meant for turbo= engines at 25,000 feet. (I believe turbo engines would gain no benefit= from closable cowl flaps =E2=80=93 they need all that air flow at altitud= e.)=20 =20 Net result was that overall flat plate drag area went down (compared to= stock) perhaps 7-10% with the cowl flaps closed, and it runs cold at 65%= lean of peak, CHTs below 300F, lower than 250F at low altitudes. With co= wl flaps open (and lots of exit area) I can climb unrestricted at Vy (135= knots, best power) starting at near sea level on a 90F day. Difference= between cowl flaps closed and faired and wide open and deflected outward= about three inches is about ten knots. That does NOT mean a ten knot spe= ed improvement over stock. It means that when the cowl flaps are open, th= ey are draggy. =20 =20 I have measured pressure drop across the engine and even with cowl flaps= closed, it is too high (too much cooling air, confirming temperature data= ). So last week I made modifications to reduce the closed cowl flap exit= area another 25%. No testing yet.=20 =20 Would I do it again? Maybe. It was a lot of work. Estimate of the overa= ll speed benefit: perhaps 3.0-3.5%. It sure is nice to climb unrestricted= on a hot day. =20 =20 Fred =20 =20 Thanks, Gary. =20 Okay, so I think I would keep the L235 cowl inlet area as-is, and be gener= ous with the flappable outlet area. Actual experience is very reassuring. Terrence L235/320 N2111AL =20 =20 I also reduced the inlet area about 20%, adding a diffuser section. The= outlet area was reduced to about half of the original, depending on what= kind of bulges on the bottom are assumed to be "standard." The cooling= is marginal, but adequate - on hot days climb speeds have to be increased= and cruise is done with the flaps open. This is to keep the CHT's below= 400 and oil below 220. Closing the relatively small cowl flaps increases= the speed by 2 to 4 knots.=20 ES #157, Lycoming engine =20 =20 ----------MB_8CCCEBDA0D18E1D_1254_3C6B5_webmail-d017.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Fred,
   Could you send some pics?
 
Mrak Quinn



-----Original Message-----
From: Frederick Moreno <frederickmoreno@bigpond.com>
To: lml@lancaironline.net
Sent: Sun, May 30, 2010 9:54 am
Subject: [LML] FW: [LML] Re: cowl flap cooling drag reduction

I= put cowl flaps on my Lancair  IV along with a top cooling air plenum= and I also went to fairly extreme measures to eliminate cooling leakage= around the engine.  Inlet area remained unchanged (6 inch diameter)= although the inlets were raised 1.5 inches for a straight shot in and mov= ed outboard 1.0 inch so that I could insert a boundary layer dam between= spinner and inlets.  This removes the boundary layer coming off the= spinner as well as the slower-moving separated wake flow at the shank of= the propeller where it enters the spinner.  I drastically cut the ex= it area with cowl flaps closed compared to the stock Lancair outlets which= are meant for turbo engines at 25,000 feet.  (I believe turbo engine= s would gain no benefit from closable cowl flaps =E2=80=93 they need all= that air flow at altitude.)
&nb= sp;
Net= result was that overall flat plate drag area  went down (compared to= stock) perhaps 7-10% with the cowl flaps closed, and it runs cold at 65%= lean of peak, CHTs below 300F, lower than 250F at low altitudes.  Wi= th cowl flaps open (and lots of exit area) I can climb unrestricted at Vy= (135 knots, best power) starting at near sea level on a 90F day.  Di= fference between cowl flaps closed and faired and wide open and deflected= outward about three inches is about ten knots.  That does NOT mean= a ten knot speed improvement over stock.  It means that when the cow= l flaps are open, they are draggy. 
&nb= sp;
I= have measured pressure drop across the engine and even with cowl flaps cl= osed, it is too high (too much cooling air, confirming temperature data).&= nbsp; So last week I made modifications to reduce the closed cowl flap exi= t area another 25%.  No testing yet.
&nb= sp;
Wou= ld I do it again?  Maybe.  It was a lot of work.  Estimate= of the overall speed benefit: perhaps 3.0-3.5%.  It sure is nice to= climb unrestricted on a hot day. 
&nb= sp;
Fre= d
&nb= sp;
 
Thanks, Gary.  
Okay, so I think I would keep the L235 cowl inlet= area as-is, and be generous with the flappable outlet area.
Actual experience is very reassuring.
Terrence
L235/320 N2111AL
 
 

 I also reduced the inlet area about 20%, adding a diffuser section.&= nbsp; The outlet area was reduced to about half of the original, depending= on what kind of bulges on the bottom are assumed to be "standard." = The cooling is marginal, but adequate - on hot days climb speeds have to= be increased and cruise is done with the flaps open.  This is to kee= p the CHT's below 400 and oil below 220.  Closing the relatively smal= l cowl flaps increases the speed by 2 to 4 knots. 
ES #157, Lycoming engine
 
 
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