X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [201.225.225.168] (HELO cwpanama.net) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1031069 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 20:52:47 -0500 Received-SPF: none receiver=logan.com; client-ip=201.225.225.168; envelope-from=rijakits@cwpanama.net Received: from [201.224.93.110] (HELO usuarioq3efog0) by frontend2.cwpanama.net (CommuniGate Pro SMTP 4.2.10) with SMTP id 61062307 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 21:11:16 -0500 Message-ID: <015001c64577$92f2d390$6e5de0c9@usuarioq3efog0> From: "rijakits" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Date: Sat, 11 Mar 2006 20:52:09 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_014C_01C6454D.A9D08050" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 This is a multi-part message in MIME format. ------=_NextPart_000_014C_01C6454D.A9D08050 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Tracy, this was one of my hang-ups with PL. I recommended to look at the drag reduction a Mustang II builder and Dave Anders with his RV-4 achieved, by using correct inlet/outlet size and using exhaust augmentation to further reduce drag. His comment was: Aircooled engine - less back pressure.... I argued: Don't believe it - at the end of the day we all have "air-cooled" engines, even rejecting about the same amount of waste heat, just a matter of transmission to the air. Whatever works for the Lycosaurus guys works for us too, just have to implement it according to our engines. Cory Bird's "Symmetry" is also a piece of cooling-art to look at!! Thomas Jakits ----- Original Message ----- From: Tracy Crook To: Rotary motors in aircraft Sent: Saturday, March 11, 2006 10:14 AM Subject: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. 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. 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 ----- From: WRJJRS@aol.com To: Rotary motors in aircraft 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 submerged and half raised scoop. NACA is a flush with the surface 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 >> Sport Aviation mag from EAA, and notice an article on cooling that >> seems to indicate that NACA's are acceptable and adequate for >> aircraft cooling needs? I have no idea regarding the authors >> credentials, and I no longer monitor PL's "newsletter".. I was >> curious more than anything else... Pauls reaction, others >> 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_014C_01C6454D.A9D08050 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Tracy,
 
this was one of my hang-ups with = PL.
I recommended to look at the drag = reduction a=20 Mustang II builder and Dave Anders with his RV-4 achieved, by using = correct=20 inlet/outlet size and using exhaust augmentation to further reduce=20 drag.
His comment was: Aircooled engine = - less back=20 pressure....
I argued: Don't believe it - at the end = of the day=20 we all have "air-cooled" engines, even rejecting about the same amount = of waste=20 heat, just a matter of transmission to the air.
 
Whatever works for the Lycosaurus guys = works for us=20 too, just have to implement it according to our engines.
Cory Bird's "Symmetry" is also a piece = of=20 cooling-art to look at!!
 
Thomas Jakits
----- Original Message -----
From:=20 Tracy = Crook
Sent: Saturday, March 11, 2006 = 10:14=20 AM
Subject: [FlyRotary] Re: = NACA's, Cooling=20 and Sport Aviation Mag..

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=20 support it and some which refutes it.  For example,  some = Lycoming=20 powered RV flyers locate a backup airspeed indicator pickup = inside the=20 cooling plenum over the cooling fins.  They report that it reads = within a=20 few MPH of the primary ASI fed from the pitot tube.  This = indicates that=20 almost full dynamic pressure is being recovered from the airstream and = that=20 pressure differential is at least as much as seen on radiator=20 installations. 
 
Bottom line is that reduced backpressure is NOT one of the = advantages of=20 an aircooled engine.  At least that is the working premise I go = on when=20 making cooling decisions on my airplane.  If I'm wrong, I'd like = to=20 know.  Anyone have data supporting/refuting this?
 
Tracy
----- Original Message -----
To: Rotary motors in = aircraft=20
Sent: Friday, March 10, 2006 = 1:25=20 AM
Subject: [FlyRotary] Re: = NACA's,=20 Cooling 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=20 inlets you will find that once enough pressure is built up they will = "flip"=20 and hardly take in any air at all. The actual NACA ducts also have = the=20 carefully designed lips, or rounded edges to train the boundry layer = into=20 the inlet. The full profile defined by the NACA is rarely used. Most = of the=20 inlets we see are some attempt at looking like a NACA inlet, without = the=20 trouble of actually BEING a NACA inlet. We used to call this = "eyeball=20 engineering." Aircooled engines do work better with NACA inlets as = there is=20 less pressure differential than with a radiator. This doesn't mean = they will=20 never work, just that the NACA didn't recomend their use with a=20 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, would you stop calling it a NACA scoop. Remove the = big=20 raised 
lip and make it flat. Than come and report to us. = Your=20 inlet is half 
submerged and half raised scoop. NACA is a = flush=20 with the surface 
SUBMERGED inlet.
Buly


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

> Dave,
> My = only=20 cooling intake is the plans Cozy IV NACA.
> Cooling has = never been a=20 problem.
> Regards,
> John
>
> David = Staten=20 wrote:
>> At the risk of invoking PL's name, anyone else = read=20 this months 
>> Sport Aviation mag from EAA, and = notice an=20 article on cooling that 
>> seems to indicate that = NACA's=20 are acceptable and adequate for 
>> aircraft = cooling needs?=20 I have no idea regarding the authors 
>> = credentials, and I=20 no longer monitor PL's "newsletter".. I was 
>> = curious=20 more than anything else... Pauls reaction, others  =
>>=20 reactions, etc.
>>
>> Translation.. yes.. I'm = stirring=20 the pot/Trolling... I figure if 
>> we are using = NACA's on=20 the Velocity, that makes us somewhat of a 
>> NACA=20 supporter..
>>
>> Dave
=
 
------=_NextPart_000_014C_01C6454D.A9D08050--