X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1030620 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 10:59:05 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-04-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k2BFwI0u024749 for ; Sat, 11 Mar 2006 10:58:20 -0500 (EST) Message-ID: <001f01c64524$ed7ae030$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Date: Sat, 11 Mar 2006 11:00:32 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01C644FB.046202D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_001C_01C644FB.046202D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 = 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_001C_01C644FB.046202D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 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 on=20 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=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 the=20 same mass flow to conduct away the same Q.  However, while the = cylinder head temps are higher, the$64 question is whether the = heated=20 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 = tomorrow!
 
Ed
 
 
 
 
 
 
 
----- 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=20 you stop calling it a NACA scoop. Remove the big raised  =
lip and=20 make it flat. Than come and report to us. Your inlet is 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 = 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
=
 
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