X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 50 [XX] (100%) SPAMTRICKS: long string of words Return-Path: Received: from smtprh01.spirittelecom.com ([165.166.0.77] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTPS id 1874363 for flyrotary@lancaironline.net; Wed, 28 Feb 2007 13:58:48 -0500 Received-SPF: pass receiver=logan.com; client-ip=165.166.0.77; envelope-from=jewen@comporium.net X-Report-Abuse-To: abuse@spirittelecom.com X-DKIM: Sendmail DKIM Filter v0.5.2 smtprh01.spirittelecom.com l1SIw0U8014963 DKIM-Signature: a=rsa-sha1; c=relaxed/simple; d=comporium.net; s=spiritmail; t=1172689083; bh=1PZR2bcOtL0rr+ybs+USpUslm54=; h=Message-ID:From:To: References:Subject:Date:MIME-Version:Content-Type:X-Priority: X-MSMail-Priority:X-Mailer:X-MIMEOLE:X-Virus-Scanned: X-Virus-Status; b=c0IlxeK6744LpvTolU1ST4Jz1LK0qyHb07kGtd0a8g/v1GWoE kIN97Ul4nNk7Vfrlm0gnnz/RX6YwiuXx3SZ/A== Received: from Engineer1 (208-104-87-198.lnhe.2wcm.comporium.net [208.104.87.198] (may be forged)) by smtprh01.spirittelecom.com (8.13.6/8.13.1) with SMTP id l1SIw0U8014963 for ; Wed, 28 Feb 2007 18:58:02 GMT Message-ID: <011c01c75b6a$5c8639f0$6b05a8c0@cooleygroup.local> From: "Joe Ewen" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl openings for water radiators Date: Wed, 28 Feb 2007 13:57:57 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0119_01C75B40.73855160" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Virus-Scanned: ClamAV 0.88/2679/Wed Feb 28 11:58:10 2007 on smtprh01.spirittelecom.com X-Virus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0119_01C75B40.73855160 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thomas, Please confirm that you want me to send it, it is a big file - 68MB. = Might bog you down a bit if you do not have a broad band connection. Joe ----- Original Message -----=20 From: Thomas y Reina Jakits=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 28, 2007 1:12 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Yes, please send me that one or post if anyone else is interested! However the real interesting thing would be to proof Ed's system as an = alternative for a clean K&N if space is at a premium. For me the whole project (still in the dream fase) is more about the = modifications, building, discussions, etc. Flying the finished product = is 2nd to everything else. I make a living (more or less) flying the most fantastic invention = ever (helicopters) in a beautiful country, so getting in the air is not = the prime factor for planning an Experimental Project... Thomas ----- Original Message -----=20 From: Joe Ewen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 28, 2007 1:04 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators I have a pdf of the K & W if you need it. I found the Excel sheet = Ed made reduced the K&W info into a manageable form. Joe ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Tuesday, February 27, 2007 7:46 AM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Thomas is right, Joe.=20 Lots of good stuff on cooling on Paul's site - if you want your = own copy of K&W they are long out of print. However, there was (may = still be there) a place in the Philippines that would make you a bound = Xerox copy of the book for somewhere around $30. Unless you like = pouring over a lot of math thought it makes for heavy reading {:>). =20 Ed ----- Original Message -----=20 From: Thomas y Reina Jakits=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 10:46 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: = cowl openings for water radiators Joe, I hate to do that, but if you need even more study stuff, go to = Paul Lamar's site and read up on the cooling chapter. He put an = impressive collection of data there and a lot of ideas - at your own = risk. There some ways that work well too (obviously, as they are = used...), but you will not find it on his site, as these ideas do not = agree with his findings. If you need something like Ed has, then you will get a lot of = info here: http://www.rotaryeng.net/cooling.html (The quoted site belongs to Paul Lamar, all info on it was = collected by him and is provid to the public by him. Where applicable = Paul Lamar holds copyrights as noted on his site...) Best Regards, Thomas Jakits, "Slim ball parasite and low life jerk" PS: Whatever one thinks about him, he does have an impressive = collection of info! ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 9:38 PM Subject: [FlyRotary] Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Actually, there is, Joe. But, you are going to be sorry you = asked {:>). I spent quite a hit of time studying a tome (Kuchuman and = Weber better know as K&W) on air cooling of liquid cooled engines = written back in the hey day of high speed mustangs lightenings, = spitfires, etc. Sort of the liquid cooling bible. Chapter 12 (the one = of most interest to us) showed a duct that reportedly had the best = pressure recovery (84% or thereabouts) around for a subsonic duct that = they had found. It was called a "StreamLine Duct" (See attached graph - = the graph a of the top graph shows the shape of the duct (or at least = 1/2 around the center line - sorry for the poor quality). =20 After quite a bit of studying and thinking about what I had = read about cooling ducts, it finally became clear to me that the perhaps = top thing that is clearly detrimental to good cooling is having flow = separation in the duct. Most of the old drawings of a cooling duct = shape followed a sinusoidal shape - rapid expansion right after the = opening. It turns out that "traditional" shape is probably one of the = worst shapes for a cooling duct (the story why is too long to get into = here). Anyhow, Flow separation leads to eddies and turbulence which = casts a "shadow" of turbulent air on the cooling core. Like a shadow, = the further away from the core the separation occurs (like near the = entrance of the duct) the larger the shadow it casts on the core area. = This "shadow" adversely interferes with the flow of air through the = core and reduces the effectiveness of the core. What causes this separation is that as pressure is recovered = by the expansion of the duct, the build up of the very pressure recover = we want - starts to hinder the boundary layer flow near the wall of the = duct. It slows it down and causes it to lose energy and attachment to = the duct wall. At a certain point the flow separates and starts to = tumble/rotate and depending where (near the duct entrance or near the = core) the flow separates, determines how much of the core area is = adversely affected. So if the boundary layer's energy level (air speed = of its molecules) is maintained at a high level separation is less = likely. So ideally, you would like to prevent any separation during = pressure recovery. The Streamline Duct is the so called "Trumpet" duct = or "Bell" duct . After the opening, there is a long section of = non-expanding duct followed by a rapid expansion into the "bell" shape = just before the core. The long non-expanding part of the duct maintains = the energy (air flow) of the boundary layer and separation does not = occur until well into the "bell" shape expansion.=20 In fact, it happens way up in the corner of the bell/core = interface and affects a very small area of the core. For full effectiveness the "Streamline duct" from K&W needs a = length of 12-17". Well, that's way more distance than I had. So I got = to thinking that if keeping the speed of the air molecules near the duct = wall helps prevent boundary layer separation and the cooling killing = eddy of turbulent air - what could I do with my short 3 - 6" (no jokes = you guys). We all know from Bernoulli that if an area is squeezed down = that the velocity of the air flow increases - right? =20 So I decided to try to maintain or increase the energy of the = air by pitching down the neck just before it goes into the bell shape = expansions in hopes that the increased energy will help the boundary = layer stay adhered to the duct wall until well into the corner of the = bell shape. So that's the story of the pinched ducts. There is no = question in my mind that this is not as effective as if I could have had = the 16" to build the duct - but, in this hobby, you work with what = you've got - right? Does it work? Who knows - but I seem to fly with less opening = area than most folks and have no cooling problems. So that's my 0.02 on = the topic - see told you, you would regret asking {:>). Ed ----- Original Message -----=20 From: John Downing=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 8:53 PM Subject: [FlyRotary] Re: cowl openings for water radiators Ed, is there some particular reason that you necked the = inlet down small, then enlarged it again. Thankyou for the pictures. = JohnD ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 3:39 PM Subject: [FlyRotary] Re: cowl openings for water radiators John, don't know if these photos will help. But, like you = I only have between 3 and 6" of duct distance on the radiators. You = should do Ok with 20 sq inch on each opening with a good diffuser/duct. = Attached are some photos of my current ducts. The openings are 18 sq = inches each. I have had one opening down to as little as 10 square = inches - but that was a bit marginal - so opened it back up. I have a = generous exit area for the hot air including a larger 4" x 12" bottom = opening as well as louvers on each side of the cowl. So you mileage = could vary - but Tracy has essentially the same size opening as well as = several others. Ed ----- Original Message -----=20 From: John Downing=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 12:12 PM Subject: [FlyRotary] cowl openings for water radiators What size openings do I need for the water radiators? = The Wittman Tailwind cowl I have has postal slots of 3' x 7 3/4" , which = is approx. 22 1/4 sq in. on each side. Sam James for the 160 Lycoming = is using 4 3/4' round holes which are 17.6 sq. inches on each side. My = radiators are quite close to the opening and I plan on making the = diffusers trumpet shaped, will the openings be large enough if I can = stay over 20 sq. inches on each side with a decent trumpet shape. JohnD = hushpowere II on order - hope to start in 2 weeks if weather = cooperates. ---------------------------------------------------------------- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ ------------------------------------------------------------------ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ ---------------------------------------------------------------------- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ ------=_NextPart_000_0119_01C75B40.73855160 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thomas,
Please confirm that you want me to send = it, it is a=20 big file - 68MB.  Might bog you down a bit if you do not have a = broad band=20 connection.
Joe
----- Original Message -----
From:=20 Thomas y=20 Reina Jakits
Sent: Wednesday, February 28, = 2007 1:12=20 PM
Subject: [FlyRotary] Re: = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

Yes, please send me that one or post = if anyone=20 else is interested!
However the real interesting thing = would be to=20 proof Ed's system as an alternative for a clean K&N if space is at = a=20 premium.
 
For me the whole project (still in = the dream=20 fase) is more about the modifications, building, discussions, etc. = Flying the=20 finished product is 2nd to everything else.
I make a living (more or less) flying = the most=20 fantastic invention ever (helicopters) in a beautiful country, so = getting=20 in the air is not the prime factor for planning an Experimental=20 Project...
 
Thomas
----- Original Message -----
From:=20 Joe Ewen=20
To: Rotary motors in = aircraft=20
Sent: Wednesday, February 28, = 2007 1:04=20 PM
Subject: [FlyRotary] Re: = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

I have a pdf of the K & W if = you need=20 it.  I found the Excel sheet Ed made reduced the K&W info = into a=20 manageable form.
Joe
 
 
----- Original Message -----
From:=20 Ed Anderson
To: Rotary motors in = aircraft=20
Sent: Tuesday, February 27, = 2007 7:46=20 AM
Subject: [FlyRotary] Re: = Pinched=20 ducts was : [FlyRotary] Re: cowl openings for water = radiators

Thomas is right, Joe. 
 
 Lots of good stuff on cooling on = Paul's site -=20 if you want your own copy of K&W they are long out of = print. =20 However, there was (may still be there) a place in the Philippines = that=20 would make you a bound Xerox copy of the book for somewhere around = $30.  Unless you like pouring over a lot of math = thought it=20 makes for heavy reading {:>). 
 
Ed
----- Original Message ----- =
From:=20 Thomas y Reina Jakits =
To: Rotary motors in = aircraft=20
Sent: Monday, February = 26, 2007=20 10:46 PM
Subject: [FlyRotary] Re: = Pinched=20 ducts was : [FlyRotary] Re: cowl openings for water = radiators

Joe,
 
I hate to do that, but if you = need even=20 more study stuff, go to Paul Lamar's site and read up on the = cooling=20 chapter. He put an impressive collection of data there and a lot = of=20 ideas - at your own risk. There some ways that work well too = (obviously,=20 as they are used...), but you will not find it on his site, as = these=20 ideas do not agree with his findings.
If you need something like Ed = has, then you=20 will get a lot of info here: http://www.rotaryeng.net/c= ooling.html
 
(The quoted site belongs to = Paul Lamar, all=20 info on it was collected by him and is provid to the public by = him.=20 Where applicable Paul Lamar holds copyrights as noted on his=20 site...)
 
Best Regards,
Thomas Jakits,
"Slim ball parasite and low = life=20 jerk"
 
PS: Whatever one thinks about = him, he=20 does have an impressive collection of=20 info!
 
 
----- Original Message ----- =
From:=20 Ed Anderson =
To: Rotary motors in=20 aircraft
Sent: Monday, February = 26, 2007=20 9:38 PM
Subject: [FlyRotary] = Pinched=20 ducts was : [FlyRotary] Re: cowl openings for water = radiators

Actually, there is, Joe.  But, = you are=20 going to be sorry you asked {:>).
 
  I spent quite a hit of time = studying a=20 tome (Kuchuman and Weber better know as K&W)  on air = cooling=20 of liquid cooled engines written back in the hey day of high = speed=20 mustangs lightenings, spitfires, etc. Sort of the liquid = cooling=20 bible.   Chapter 12 (the one of most interest to us) = showed=20 a duct that reportedly had the best pressure recovery (84% or=20 thereabouts) around for a subsonic duct that they had = found.  It=20 was called a "StreamLine Duct" (See attached graph - the graph = a of=20 the top graph shows the shape of the duct (or at least 1/2 = around the=20 center line - sorry for the poor = quality).  
 
 After quite a bit of studying = and thinking=20 about what I had read about cooling ducts, it finally became = clear to=20 me that the perhaps top thing that is clearly detrimental to = good=20 cooling is having flow separation in the duct.   = Most of the=20 old drawings of a cooling duct shape followed a sinusoidal = shape -=20 rapid expansion right after the opening.  It turns out = that=20 "traditional" shape is probably one of the worst shapes for a = cooling=20 duct (the story why is too long to get into = here).
 
Anyhow,  Flow separation leads to = eddies=20 and turbulence which casts a "shadow" of turbulent air on the = cooling=20 core.  Like a shadow, the further away from the core the=20 separation occurs (like near the entrance of the duct) the = larger the=20 shadow it casts on the core area.  This=20 "shadow"  adversely interferes with the flow of air = through=20 the core and reduces the effectiveness of the = core.
 
  What causes this separation is = that as=20 pressure is recovered by the expansion of the duct, the build = up of=20 the very pressure recover we want -  starts to hinder the = boundary layer flow near the wall of the duct.  It slows = it down=20 and causes it to lose energy and attachment to the duct = wall.  At=20 a certain point the flow separates and starts to tumble/rotate = and=20 depending where (near the duct entrance or near the core) the = flow=20 separates, determines how much of the core area is adversely=20 affected.  So if the boundary layer's energy level (air = speed of=20 its molecules) is maintained at a high level separation is = less=20 likely.
 
So ideally, you would like to prevent = any=20 separation during pressure recovery.  The Streamline Duct = is the=20 so called "Trumpet" duct or "Bell" duct .  After the = opening,=20 there is a long section of non-expanding duct followed by a = rapid=20 expansion into the "bell" shape just before the core.  = The long=20 non-expanding part of the duct maintains the energy (air flow) = of the=20 boundary layer and separation does not occur until well into = the=20 "bell" shape expansion. 
 
 In fact, it happens way up in = the corner=20 of the bell/core interface and affects a very small area of = the=20 core.
For full effectiveness the "Streamline = duct"=20 from K&W needs a length of 12-17".  Well, that's way = more=20 distance than I had.  So I got to thinking that if = keeping the=20 speed of the air molecules near the duct wall helps prevent = boundary=20 layer separation and the cooling killing eddy of turbulent air = -=20  what could I do with my short 3 - 6" (no jokes you = guys). =20 We all know from Bernoulli that if an area is squeezed down = that the=20 velocity of the air flow increases - right?  =
 
So I decided to try to maintain or = increase the=20 energy of the air by pitching down the neck just before it = goes into=20 the bell shape expansions in hopes that the increased energy = will help=20 the boundary layer stay adhered to the duct wall until well = into the=20 corner of the bell shape.  So that's the story of the = pinched=20 ducts.  There is no question in my mind that this is not = as=20 effective as if I could have had the 16" to build the duct - = but, in=20 this hobby, you work with what you've got - = right?
 
Does it work?  Who knows - but I = seem to=20 fly with less opening area than most folks and have no = cooling=20 problems.  So that's my 0.02 on the topic - see told you, = you=20 would regret asking {:>).
 
Ed
 
 
----- Original Message ----- =
From:=20 John Downing =
To: Rotary motors in = aircraft
Sent: Monday, = February 26, 2007=20 8:53 PM
Subject: [FlyRotary] = Re: cowl=20 openings for water radiators

Ed, is there some = particular reason=20 that you necked the inlet down small, then enlarged it = again. =20 Thankyou for the pictures.  JohnD
----- Original Message = -----
From:=20 Ed Anderson =
To: Rotary motors = in=20 aircraft
Sent: Monday, = February 26,=20 2007 3:39 PM
Subject: = [FlyRotary] Re: cowl=20 openings for water radiators

John, don't know if these photos = will=20 help.  But, like you I only have between 3 and 6" of = duct=20 distance on the radiators.  You should do Ok with 20 = sq inch=20 on each opening with a good diffuser/duct.  Attached = are some=20 photos of my current ducts.  The openings are 18 sq = inches=20 each.  I have had one opening down to as little as 10 = square=20 inches - but that was a bit marginal - so opened it back = up. =20 I have a generous exit area for the hot air including a = larger 4"=20 x 12" bottom opening as well as louvers on each side of = the=20 cowl.  So you mileage could vary - but Tracy has = essentially=20 the same size opening as well as several = others.
 
Ed
----- Original Message = -----=20
From:=20 John Downing =
To: Rotary = motors in=20 aircraft
Sent: Monday, = February 26,=20 2007 12:12 PM
Subject: = [FlyRotary] cowl=20 openings for water radiators

What size openings do I = need for=20 the water radiators?   The Wittman Tailwind = cowl I=20 have has postal slots of 3' x 7 3/4" , which = is  =20 approx. 22 1/4 sq in. on each side.  Sam James for = the 160=20 Lycoming is using 4 3/4' round holes which are 17.6 sq. = inches=20 on each side.  My radiators are quite close to the = opening=20 and I plan on making the diffusers trumpet shaped, will = the=20 openings be large enough if I can stay over 20 sq. = inches on=20 each side with a decent trumpet shape. =20 JohnD       = hushpowere II on=20 order - hope to start in 2 weeks if weather=20 cooperates.

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