X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [65.54.250.78] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1030583 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 10:15:21 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.250.78; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sat, 11 Mar 2006 07:14:35 -0800 Message-ID: Received: from 4.171.150.140 by BAY115-DAV6.phx.gbl with DAV; Sat, 11 Mar 2006 15:14:33 +0000 X-Originating-IP: [4.171.150.140] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Date: Sat, 11 Mar 2006 10:14:27 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0226_01C644F4.93E9F450" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Sat, 11 Mar 2006 10:14:27 -0500 X-OriginalArrivalTime: 11 Mar 2006 15:14:35.0839 (UTC) FILETIME=[81F684F0:01C6451E] This is a multi-part message in MIME format. ------=_NextPart_000_0226_01C644F4.93E9F450 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Just a comment on one often repeated point: "There is less pressure = differential [on an aircooled engine] than with a radiator". This = factor is a major one in the decisions/arguments made regarding cooling = of aircraft engines. The problem is that I have seen absolutely no empirical evidence to = support it and some which refutes it. For example, some Lycoming = powered RV flyers locate a backup airspeed indicator pickup inside the = cooling plenum over the cooling fins. They report that it reads within = a few MPH of the primary ASI fed from the pitot tube. This indicates = that almost full dynamic pressure is being recovered from the airstream = and that pressure differential is at least as much as seen on radiator = installations.=20 Bottom line is that reduced backpressure is NOT one of the advantages of = an aircooled engine. At least that is the working premise I go on when = making cooling decisions on my airplane. If I'm wrong, I'd like to = know. Anyone have data supporting/refuting this? Tracy ----- Original Message -----=20 From: WRJJRS@aol.com=20 To: Rotary motors in aircraft=20 Sent: Friday, March 10, 2006 1:25 AM Subject: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Group, The problem with submerged inlets, and Buly is correct to mention that = means flush with the surface, is that they do not handle back pressure = well. Ed A posted the original NACA data and their conclusion was that = submerged inlets don't work well with RADIATORS. The comments PL has = been making are only to re-publish the data. If you do a smoke tunnel = test on submerged inlets you will find that once enough pressure is = built up they will "flip" and hardly take in any air at all. The actual = NACA ducts also have the carefully designed lips, or rounded edges to = train the boundry layer into the inlet. The full profile defined by the = NACA is rarely used. Most of the inlets we see are some attempt at = looking like a NACA inlet, without the trouble of actually BEING a NACA = inlet. We used to call this "eyeball engineering." Aircooled engines do = work better with NACA inlets as there is less pressure differential than = with a radiator. This doesn't mean they will never work, just that the = NACA didn't recomend their use with a radiator/heat exchanger. Bill Jepson In a message dated 3/9/2006 8:24:30 PM Pacific Standard Time, = atlasyts@bellsouth.net writes: John, would you stop calling it a NACA scoop. Remove the big raised = lip and make it flat. Than come and report to us. Your inlet is half = =20 submerged and half raised scoop. NACA is a flush with the surface =20 SUBMERGED inlet. Buly On Mar 9, 2006, at 10:44 PM, John Slade wrote: > Dave, > My only cooling intake is the plans Cozy IV NACA. > Cooling has never been a problem. > Regards, > John > > David Staten wrote: >> At the risk of invoking PL's name, anyone else read this months =20 >> Sport Aviation mag from EAA, and notice an article on cooling = that =20 >> seems to indicate that NACA's are acceptable and adequate for =20 >> aircraft cooling needs? I have no idea regarding the authors =20 >> credentials, and I no longer monitor PL's "newsletter".. I was =20 >> curious more than anything else... Pauls reaction, others =20 >> reactions, etc. >> >> Translation.. yes.. I'm stirring the pot/Trolling... I figure if = >> we are using NACA's on the Velocity, that makes us somewhat of a = >> NACA supporter.. >> >> Dave ------=_NextPart_000_0226_01C644F4.93E9F450 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Just a comment on one often repeated point:  "There is less = pressure=20 differential [on an aircooled engine] than with a radiator".   = This=20 factor is a major one in the decisions/arguments made regarding cooling=20 of aircraft engines.
 
The problem is that I have seen absolutely no empirical evidence to = support=20 it and some which refutes it.  For example,  some Lycoming = powered RV=20 flyers locate a backup airspeed indicator pickup inside the cooling = plenum=20 over the cooling fins.  They report that it reads within a few MPH = of the=20 primary ASI fed from the pitot tube.  This indicates that almost = full=20 dynamic pressure is being recovered from the airstream and that pressure = differential is at least as much as seen on radiator = installations. 
 
Bottom line is that reduced backpressure is NOT one of the = advantages of an=20 aircooled engine.  At least that is the working premise I go on = when making=20 cooling decisions on my airplane.  If I'm wrong, I'd like to = know. =20 Anyone have data supporting/refuting this?
 
Tracy
----- Original Message -----
To: Rotary motors in = aircraft
Sent: Friday, March 10, 2006 = 1:25=20 AM
Subject: [FlyRotary] Re: = NACA's, Cooling=20 and Sport Aviation Mag..

Group,
The problem with submerged inlets, and Buly is correct to mention = that=20 means flush with the surface, is that they do not handle back pressure = well.=20 Ed A posted the original NACA data and their conclusion was that = submerged=20 inlets don't work well with RADIATORS. The comments PL has been making = are=20 only to re-publish the data. If you do a smoke tunnel test on = submerged inlets=20 you will find that once enough pressure is built up they will "flip" = and=20 hardly take in any air at all. The actual NACA ducts also have the = carefully=20 designed lips, or rounded edges to train the boundry layer into the = inlet. The=20 full profile defined by the NACA is rarely used. Most of the inlets we = see are=20 some attempt at looking like a NACA inlet, without the trouble of = actually=20 BEING a NACA inlet. We used to call this "eyeball engineering." = Aircooled=20 engines do work better with NACA inlets as there is less pressure = differential=20 than with a radiator. This doesn't mean they will never work, just = that the=20 NACA didn't recomend their use with a radiator/heat exchanger.
Bill Jepson
 
 
In a message dated 3/9/2006 8:24:30 PM Pacific Standard Time,=20 atlasyts@bellsouth.net writes:
John,=20 would you stop calling it a NACA scoop. Remove the big raised  =
lip=20 and make it flat. Than come and report to us. Your inlet is = half =20
submerged and half raised scoop. NACA is a flush with the = surface =20
SUBMERGED inlet.
Buly


On Mar 9, 2006, at 10:44 PM, = John=20 Slade wrote:

> Dave,
> My only cooling intake is the = plans=20 Cozy IV NACA.
> Cooling has never been a problem.
>=20 Regards,
> John
>
> David Staten = wrote:
>> At the=20 risk of invoking PL's name, anyone else read this months  =
>>=20 Sport Aviation mag from EAA, and notice an article on cooling = that =20
>> seems to indicate that NACA's are acceptable and = adequate=20 for 
>> aircraft cooling needs? I have no idea = regarding the=20 authors 
>> credentials, and I no longer monitor PL's = "newsletter".. I was 
>> curious more than anything = else...=20 Pauls reaction, others 
>> reactions,=20 etc.
>>
>> Translation.. yes.. I'm stirring the=20 pot/Trolling... I figure if 
>> we are using NACA's = on the=20 Velocity, that makes us somewhat of a 
>> NACA=20 supporter..
>>
>> Dave
 
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