X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [65.54.250.79] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1031835 for flyrotary@lancaironline.net; Sun, 12 Mar 2006 23:02:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.250.79; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sun, 12 Mar 2006 19:58:01 -0800 Message-ID: Received: from 4.171.150.25 by BAY115-DAV7.phx.gbl with DAV; Mon, 13 Mar 2006 03:57:58 +0000 X-Originating-IP: [4.171.150.25] 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: Sun, 12 Mar 2006 22:57:49 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B1_01C64628.62EE5320" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Sun, 12 Mar 2006 22:57:49 -0500 X-OriginalArrivalTime: 13 Mar 2006 03:58:01.0702 (UTC) FILETIME=[52CC4860:01C64652] This is a multi-part message in MIME format. ------=_NextPart_000_00B1_01C64628.62EE5320 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Yes, it tells you the pressure above the cooling fins of the engine = (almost full dynamic pressure). Yes I am making the assumption that the = pressure below the engine (other side of the cooling fins) is the same = as the backside of the radiator. Is that not reasonable? The cooling = exit is the same in both examples. Note that the pressure above the = engine was almost full dynamic pressure WITHOUT the exit being blocked. = Therefore my conclusion that the pressure differential is NOT lower on = the aircooled engine. Am I missing your point Al? Tracy ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Saturday, March 11, 2006 8:15 PM Subject: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. I guess I'm missing something here; but I don't see that the ASI = reading inside the cowling tells you about the pressure recovery, or the = pressure drop across the cooling fins of the airplane. If I blocked the = exit from the cowl, and the inlet is facing into the airstream, I'd = expect the ASI would read (essentially) the same as that from the pitot = tube. IOW, if the flow is being significantly affected by exit = conditions (area, exit ducting, or the pressure at the exit) then it = tells you neither about potential pressure recovery of the inlet, nor = the relative pressure drop of radiator vs. cooling fins. What it tells = you is. . ; well, the pressure inside the cowling above the engine. No? Al 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.=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 =20 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 = 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 = >> curious more than anything else... Pauls reaction, others =20 >> reactions, etc. >> >> Translation.. yes.. I'm stirring the pot/Trolling... I figure = if =20 >> we are using NACA's on the Velocity, that makes us somewhat of = a =20 >> NACA supporter.. >> >> Dave ------=_NextPart_000_00B1_01C64628.62EE5320 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Yes, it tells you the pressure above the cooling fins of the engine = (almost=20 full dynamic pressure).  Yes I am making the assumption that the = pressure=20 below the engine (other side of the cooling fins) is the same as the = backside of=20 the radiator.  Is that not reasonable?   The cooling = exit is=20 the same in both examples.    Note that the pressure = above the=20 engine was almost full dynamic pressure WITHOUT the exit being = blocked. =20 Therefore my conclusion that the pressure differential is NOT lower on = the=20 aircooled engine.
 
Am I missing your point Al?
 
Tracy
----- Original Message -----
From: Al Gietzen
To: Rotary motors in = aircraft
Sent: Saturday, March 11, 2006 = 8:15=20 PM
Subject: [FlyRotary] Re: = NACA's, Cooling=20 and Sport Aviation Mag..

I guess = I=92m missing=20 something here; but I don=92t see that the ASI reading inside the = cowling tells=20 you about the pressure recovery, or the pressure drop across the = cooling fins=20 of the airplane.  If I blocked the exit from the cowl, and the = inlet is=20 facing into the airstream, I=92d expect the ASI would read = (essentially) the=20 same as that from the pitot tube.  IOW, if the flow is being=20 significantly affected by exit conditions (area, exit ducting, or the = pressure=20 at the exit) then it tells you neither about potential pressure = recovery of=20 the inlet, nor the relative pressure drop of radiator vs. cooling = fins. =20 What it tells you is. . ; well, the pressure inside the cowling above = the=20 engine.

 

No?

 

Al

 

 

 

Subject:=20 [FlyRotary] Re: NACA's, Cooling and Sport Aviation = Mag..

 

Just a=20 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=20 problem is that I have seen absolutely no empirical evidence to = support it and=20 some which refutes it.  For example,  some Lycoming powered = RV=20 flyers locate a backup airspeed indicator pickup inside the = cooling=20 plenum over the cooling fins.  They report that it reads within a = few MPH=20 of the primary ASI fed from the pitot tube.  This indicates that = almost=20 full dynamic pressure is being recovered from the airstream and that = pressure=20 differential is at least as much as seen on radiator=20 installations. 

 

Bottom=20 line is that reduced backpressure is NOT one of the advantages of an = aircooled=20 engine.  At least that is the working premise I go on when making = cooling=20 decisions on my airplane.  If I'm wrong, I'd like to know.  = Anyone=20 have data supporting/refuting this?

 

Tracy

-----=20 Original Message -----

From: WRJJRS@aol.com=20

To: Rotary motors in = aircraft=20

Sent: Friday, = March 10,=20 2006 1:25 AM

Subject: = [FlyRotary] Re:=20 NACA's, Cooling and Sport Aviation Mag..

 

Group,

The=20 problem with submerged inlets, and Buly is correct to mention that = means=20 flush with the surface, is that they do not handle back pressure = well. Ed A=20 posted the original NACA data and their conclusion was that = submerged inlets=20 don't work well with RADIATORS. The comments PL has been making are = only to=20 re-publish the data. If you do a smoke tunnel test on submerged = inlets you=20 will find that once enough pressure is built up they will "flip" and = hardly=20 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.=20 The full profile defined by the NACA is rarely used. Most of the = inlets we=20 see are some attempt at looking like a NACA inlet, without the = trouble of=20 actually BEING a NACA inlet. We used to call this "eyeball = engineering."=20 Aircooled engines do work better with NACA inlets as there is less = pressure=20 differential than with a radiator. This doesn't mean they will never = work,=20 just that the NACA didn't recomend their use with a radiator/heat=20 exchanger.

Bill=20 Jepson

 

 

In a=20 message dated 3/9/2006 8:24:30 PM Pacific Standard Time,=20 atlasyts@bellsouth.net writes:

John, = would you=20 stop calling it a NACA scoop. Remove the big raised 
lip = and make=20 it flat. Than come and report to us. Your inlet is half =20
submerged and half raised scoop. NACA is a flush with the=20 surface 
SUBMERGED inlet.
Buly


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

> Dave,
> My only = cooling=20 intake is the plans Cozy IV NACA.
> Cooling has never been a = 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..
>>
>>=20 Dave

 

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