X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 73 [XX] (60%) SPAMTRICKS: long string of words (40%) RECEIVED: IP not found on home country list Return-Path: Received: from [201.225.225.168] (HELO cwpanama.net) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1874469 for flyrotary@lancaironline.net; Wed, 28 Feb 2007 14:17:06 -0500 Received-SPF: none receiver=logan.com; client-ip=201.225.225.168; envelope-from=rijakits@cwpanama.net Received: from [201.224.94.164] (HELO usuario5ebe209) by frontend2.cwpanama.net (CommuniGate Pro SMTP 4.2.10) with SMTP id 103151297 for flyrotary@lancaironline.net; Wed, 28 Feb 2007 14:41:02 -0500 Message-ID: <017001c75b6c$d5c399f0$a45ee0c9@usuario5ebe209> From: "Thomas y Reina Jakits" 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 14:15:38 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_016D_01C75B42.EC0AFA20" 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 This is a multi-part message in MIME format. ------=_NextPart_000_016D_01C75B42.EC0AFA20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable JOe, please send it to=20 thjakits@gmail.com If you need a hugh maibox, let me know and I send you an invite for = gmail 2800+ MB Thomas ----- Original Message -----=20 From: Joe Ewen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 28, 2007 1:57 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators 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_016D_01C75B42.EC0AFA20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
JOe,
 
please send it to
 
thjakits@gmail.com
 
If you need a hugh maibox, let me know = and I send=20 you an invite for gmail  2800+ MB
 
Thomas
----- Original Message -----
From:=20 Joe = Ewen=20
Sent: Wednesday, February 28, = 2007 1:57=20 PM
Subject: [FlyRotary] Re: = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

Thomas,
Please confirm that you want me to = send it, it is=20 a big file - 68MB.  Might bog you down a bit if you do not have a = broad=20 band connection.
Joe
----- Original Message -----
From:=20 Thomas y=20 Reina Jakits
To: Rotary motors in = aircraft=20
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=20 the 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=20 getting in the air is not the prime factor for planning an = Experimental=20 Project...
 
Thomas
----- Original Message ----- =
From:=20 Joe=20 Ewen
To: Rotary motors in = aircraft=20
Sent: Wednesday, February = 28, 2007=20 1:04 PM
Subject: [FlyRotary] Re: = Pinched=20 ducts 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=20 7:46 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=20 $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=20 aircraft
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=20 (obviously, as they are used...), but you will not find it on = his=20 site, as these ideas do not agree with his = findings.
If you need something like Ed = has, then=20 you will get a lot of info here: http://www.rotaryeng.net/c= ooling.html
 
(The quoted site belongs to = Paul Lamar,=20 all info on it was collected by him and is provid to the = public by=20 him. 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 = 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=20 cooling of liquid cooled engines written back in the hey day = of high=20 speed mustangs lightenings, spitfires, etc. Sort of the = liquid=20 cooling bible.   Chapter 12 (the one of most = interest to=20 us) showed a duct that reportedly had the best pressure = recovery=20 (84% or thereabouts) around for a subsonic duct that they = had=20 found.  It was called a "StreamLine Duct" (See attached = graph -=20 the graph a of the top graph shows the shape of the duct (or = at=20 least 1/2 around the center line - sorry for the poor=20 quality).  
 
 After quite a bit of studying = and=20 thinking about what I had read about cooling ducts, it = finally=20 became clear to me that the perhaps top thing that is = clearly=20 detrimental to good cooling is having flow separation in the = duct.   Most of the old drawings of a cooling duct = shape=20 followed a sinusoidal shape - rapid expansion right after = the=20 opening.  It turns out that "traditional" shape is = probably one=20 of the worst shapes for a cooling duct (the story why is too = long to=20 get into here).
 
Anyhow,  Flow separation leads = to eddies=20 and turbulence which casts a "shadow" of turbulent air on = the=20 cooling core.  Like a shadow, the further away from the = core=20 the separation occurs (like near the entrance of the duct) = the=20 larger the shadow it casts on the core area.  This=20 "shadow"  adversely interferes with the flow of = air=20 through the core and reduces the effectiveness of the=20 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=20 boundary layer flow near the wall of the duct.  It = slows it=20 down and causes it to lose energy and attachment to the duct = wall.  At a certain point the flow separates and starts = to=20 tumble/rotate and depending where (near the duct entrance or = near=20 the core) the flow separates, determines how much of the = core area=20 is adversely affected.  So if the boundary layer's = energy level=20 (air speed of its molecules) is maintained at a high level=20 separation is less likely.
 
So ideally, you would like to = prevent any=20 separation during pressure recovery.  The Streamline = Duct is=20 the so called "Trumpet" duct or "Bell" duct .  After = the=20 opening, there is a long section of non-expanding duct = followed by a=20 rapid expansion into the "bell" shape just before the = core. =20 The long non-expanding part of the duct maintains the energy = (air=20 flow) of the boundary layer and separation does not occur = until well=20 into the "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=20 guys).  We all know from Bernoulli that if an area is = squeezed=20 down that the velocity of the air flow increases - = right? =20
 
So I decided to try to maintain or = increase=20 the energy of the air by pitching down the neck just before = it goes=20 into the bell shape expansions in hopes that the increased = energy=20 will help the boundary layer stay adhered to the duct wall = until=20 well into the corner of the bell shape.  So that's the = story of=20 the pinched ducts.  There is no question in my mind = that this=20 is not as effective as if I could have had the 16" to build = the duct=20 - but, in this hobby, you work with what you've got -=20 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=20 aircraft
Sent: Monday, = February 26,=20 2007 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=20 again.  Thankyou for the pictures.  = JohnD
----- Original Message = -----=20
From:=20 Ed = Anderson
To: Rotary = motors in=20 aircraft
Sent: Monday, = February 26,=20 2007 3:39 PM
Subject: = [FlyRotary] Re:=20 cowl 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=20 inch on each opening with a good diffuser/duct.  = Attached=20 are some photos of my current ducts.  The openings = are 18=20 sq inches each.  I have had one opening down to as = little=20 as 10 square inches - but that was a bit marginal - so = opened it=20 back up.  I have a generous exit area for the hot = air=20 including a larger 4" x 12" bottom opening as well as = louvers on=20 each side of the cowl.  So you mileage could vary - = but=20 Tracy has essentially the same size opening as well as = several=20 others.
 
Ed
----- Original Message = -----=20
From:=20 John = Downing
To: Rotary = motors in=20 aircraft
Sent: Monday, = February=20 26, 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=20 160 Lycoming is using 4 3/4' round holes which are = 17.6 sq.=20 inches on each side.  My radiators are quite = close to the=20 opening and I plan on making the diffusers trumpet = shaped,=20 will the openings be large enough if I can stay over = 20 sq.=20 inches on each side with a decent trumpet shape.  = JohnD       = hushpowere II=20 on order - hope to start in 2 weeks if weather=20 cooperates.

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