X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [65.54.250.80] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1030641 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 11:33:56 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.250.80; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sat, 11 Mar 2006 08:33:11 -0800 Message-ID: Received: from 4.171.150.140 by BAY115-DAV8.phx.gbl with DAV; Sat, 11 Mar 2006 16:33:08 +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 11:33:00 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0386_01C644FF.8D2A32A0" 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 11:33:00 -0500 X-OriginalArrivalTime: 11 Mar 2006 16:33:11.0115 (UTC) FILETIME=[7C7C89B0:01C64529] This is a multi-part message in MIME format. ------=_NextPart_000_0386_01C644FF.8D2A32A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable My fault for not defining the 'probe'. It was more or less a static = port at the rear of the plenum, not a pitot probe. A pitot type probe = was placed in the inlet as an experiment in one case and it measured = around 100 mph at cruise speeds (~180?).=20 Tracy ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Saturday, March 11, 2006 11:00 AM Subject: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Tracy, I'm not certain what the airspeed probe in the cowling is = really telling you , except that the velocity (dynamic pressure) of the = air stream as measured by the probe is near that of the outside air.=20 It would seem to me that it depends on how the airspeed indicator is = oriented. If it is pointing into the airstream coming through the cowl = duct then the airspeed probe itself is a stagnation point (regardless of = what's happening around it). If on the other hand, if the airspeed = probe is oriented perpendicular to the airflow and is being used more as = a static port then I would agree that indicates the pressure build up is = close to that of a radiator core stagnation. If we look at Q =3D Mv(Th-Ta)*cp. We know we have higher temp = cylinder heads with a Lycoming than with our core. That being the = case, it would seem that you might not need the same mass flow to = conduct away the same Q. However, while the cylinder head temps are = higher, the$64 question is whether the heated departing air temp = increased any more (or less) than it would through a core. It seems = pretty clear that regardless of whether cylinder head or core that = slowing the air down (within limits) provides more time for heat = transfer to the air and should result in better cooling in either case. = But, it may be that given the higher temps of the cylinder head that = you may not require as much pressure recovery to cool as with a core. = Just some speculative thinking. New Hangar is due to arrive tomorrow! Ed ----- Original Message -----=20 From: Tracy Crook=20 To: Rotary motors in aircraft=20 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.=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 =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 = >> 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 =20 >> we are using NACA's on the Velocity, that makes us somewhat = of a =20 >> NACA supporter.. >> >> Dave ------=_NextPart_000_0386_01C644FF.8D2A32A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
My fault for not defining the 'probe'.  It was more or = less a=20 static port at the rear of the plenum, not a pitot probe.  A pitot = type=20 probe was placed in the inlet as an experiment in one case and = it=20 measured around 100 mph at cruise speeds (~180?). 
 
Tracy
----- Original Message -----
From: Ed Anderson
To: Rotary motors in = aircraft
Sent: Saturday, March 11, 2006 = 11:00=20 AM
Subject: [FlyRotary] Re: = NACA's, Cooling=20 and Sport Aviation Mag..

 Tracy, I'm not certain what the = airspeed=20 probe in the cowling is really telling you , except that the velocity = (dynamic=20 pressure) of the air stream as measured by the probe is near = that of=20 the outside air. 
 
 It would seem to me that = it  depends=20 on how the airspeed indicator is oriented.  If it is pointing = into the=20 airstream coming through the cowl duct then the airspeed probe itself = is a=20 stagnation point (regardless of what's happening around it).  If = on the=20 other hand, if the airspeed probe is oriented perpendicular to the = airflow and=20 is being used more as a static port then I would agree that indicates = the=20 pressure build up is close to that of a radiator core = stagnation.
 
If we look at Q =3D = Mv(Th-Ta)*cp.  We know we=20 have  higher temp cylinder heads with  a Lycoming than = with our=20 core.  That being the case, it would seem that you might not = need=20 the same mass flow to conduct away the same Q.  However, = while the=20 cylinder head temps are higher, the$64 question is whether = the=20 heated departing air temp increased any more (or less) than it would = through a=20 core.  It seems pretty clear that regardless of whether cylinder = head or=20 core that slowing the air down (within limits) provides more time for = heat=20 transfer to the air and should result in better cooling in either = case. =20  But, it may be that given the higher temps of the cylinder head = that you=20 may not require as much pressure recovery to cool as with a = core.  Just=20 some speculative thinking.
 
New Hangar is due to arrive=20 tomorrow!
 
Ed
 
 
 
 
 
 
 
----- Original Message -----
From:=20 Tracy Crook=20
To: Rotary motors in = aircraft=20
Sent: Saturday, March 11, = 2006 10:14=20 AM
Subject: [FlyRotary] Re: = NACA's,=20 Cooling and Sport Aviation Mag..

Just a comment on one often repeated point:  "There is = less=20 pressure differential [on an aircooled engine] than with a=20 radiator".   This factor is a major one in the = decisions/arguments=20 made regarding cooling 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=20 a few MPH of the primary ASI fed from the pitot tube.  This = indicates=20 that almost full dynamic pressure is being recovered from the = airstream and=20 that 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=20 of an aircooled engine.  At least that is the working premise I = go on=20 when making cooling decisions on my airplane.  If I'm wrong, = I'd like=20 to 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=20 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=20 that submerged inlets don't work well with RADIATORS. The comments = PL has=20 been making are only to re-publish the data. If you do a smoke = tunnel test=20 on submerged inlets you will find that once enough pressure is = built up=20 they will "flip" and hardly take in any air at all. The actual = NACA ducts=20 also have the carefully designed lips, or rounded edges to train = the=20 boundry layer into the inlet. The full profile defined by the NACA = is=20 rarely used. Most of the inlets we see are some attempt at looking = like a=20 NACA inlet, without the trouble of actually BEING a NACA inlet. We = used to=20 call this "eyeball engineering." Aircooled engines do work better = with=20 NACA inlets as there is less pressure differential than with a = radiator.=20 This doesn't mean they will never work, just that the NACA didn't = recomend=20 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,=20 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=20 half 
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=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=20 an article on cooling that 
>> seems to indicate = that=20 NACA's are acceptable and adequate for 
>> = aircraft=20 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,=20 others 
>> reactions, = etc.
>>
>>=20 Translation.. yes.. I'm stirring the pot/Trolling... I figure = if =20
>> we are using NACA's on the Velocity, that makes us = somewhat=20 of a 
>> NACA supporter..
>>
>> = Dave
=
 
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