X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 50 [XX] Return-Path: Received: from elasmtp-galgo.atl.sa.earthlink.net ([209.86.89.61] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2024139 for flyrotary@lancaironline.net; Thu, 03 May 2007 16:16:57 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.61; envelope-from=jerryhey@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=Yeq1jondvGoO5gwN8iYf8+3MCRBqAUCcGBdYP8mfXj3CP932IfZCZODZWz2YVBFp; h=Received:Mime-Version:In-Reply-To:References:Content-Type:Message-Id:From:Subject:Date:To:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [71.49.146.183] (helo=[192.168.0.101]) by elasmtp-galgo.atl.sa.earthlink.net with asmtp (Exim 4.34) id 1Hjhif-0003BL-Cu for flyrotary@lancaironline.net; Thu, 03 May 2007 16:16:06 -0400 Mime-Version: 1.0 (Apple Message framework v752.3) In-Reply-To: References: Content-Type: multipart/alternative; boundary=Apple-Mail-1-200184780 Message-Id: <7140729D-897E-4131-A2B3-8E61D3568BA1@earthlink.net> From: Jerry Hey Subject: Re: [FlyRotary] Re: Cooling area drag Date: Thu, 3 May 2007 16:16:03 -0400 To: "Rotary motors in aircraft" X-Mailer: Apple Mail (2.752.3) X-ELNK-Trace: 8104856d7830ec6b1aa676d7e74259b7b3291a7d08dfec7928606bc79d94b96213d500ec32bec962350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 71.49.146.183 --Apple-Mail-1-200184780 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Bob, have you considered putting the intake above the rad. You could get rid of the deflectors and the air would follow a simple path down through the rad and out. Jerry On May 3, 2007, at 4:00 PM, bmears9413@aol.com wrote: > Ed, > Give me some pointers on my cooling system before I get started. > You surely will save me some mistakes. My air intake will be below > and behind my radiator. I imagined just building some deflectors to > "s" the air up to the radiator. Aft of the radiator the air will > exit out the back half of the air scoop. the radiator will be > laying flat, under the motormount. the oil coolers are under each > wing...as it should be in s spitfire. > Thanks, > Bob Mears > Supermarine Spitfire > > > > > > > -----Original Message----- > From: eanderson@carolina.rr.com > To: flyrotary@lancaironline.net > Sent: Thu, 3 May 2007 11:49 AM > Subject: [FlyRotary] Re: Cooling area drag > > Actually, Mark, I started pulling together what I believed to be > the major factors without getting too down in the weeds about > rotary cooling, a couple of years ago with the intention of > publishing an e book (pamphlet more likely) . Then I ran into the > problem that the seemingly best diffuser (Streamline duct) was > simply too long (in its optimum configuration) for most of our > needs. Yes, you can shorten it but then you incur more drag. So I > scratched my head about that for a while until the light bulb came on. > > After experimenting with a number of duct shapes and reading more, > I came to the conclusion that if my understanding about what killed > effective cooling was correct then I should be able to achieve my > cooling/drag goals with the "Pinched" duct. But, what I wanted to > do and never took the time to do was to go back with Mr. Bernoulli > and calculate the air velocity along each segment of the streamline > duct and then do the same for my "pinched" duct to see if there was > any similarity. Also, I have not paid much attention to the > exiting duct - simply because I don't have room for one. I tired > one back almost 8 years ago and decided the zigs and zags it had to > avoid engine/motormount, etc impeded airflow more than helped it. > > > But, alas, just as I was recently about to go to publication, the > new "bible" of cooling was published - so how could I possibly > compete {:>). I may still do it as if it passes the gauntlet of > folks on this list (or errors if any {:>)) are corrected,as it may > be useful to some. > > Ed > > > ----- Original Message ----- > From: Mark Steitle > To: Rotary motors in aircraft > Sent: Thursday, May 03, 2007 12:34 PM > Subject: [FlyRotary] Re: Cooling area drag > > ED, > > So, tell us, when is your book on cooling going to be available? > > Mark > > > On 5/3/07, Ed Anderson wrote: > Less we forget how important drag is in our hobby, I took a formula > for calculating drag at different airspeeds and the Hp required to > push the given frontal area along at the stated airspeed. > > This is for two of our traditional GM evaporator cores using their > combined frontal area of 180 sq inch or 1.25 sq feet. This > assumes that airspeed shown represents the velocity through the > cooling core (which is not really likely to reach speeds above 80 > mph if you have any sort of ducting), but that is an assumption on > my part since as Bill keeps reminding me I have not instrumented my > ducts {:>) > > Air Speed (MPH) > HP > 40 > 0.533333 > 60 > 1.80 > 80 > 4.27 > 120 > 14.40 > 140 > 22.87 > 160 > 34.13 > 180 > 48.60 > 200 > 66.67 > > > Clearly the faster your cruise speed the more important it is to > minimize cooling drag. Of course the airspeed the core sees should > normally not be over 10% of your cruise speed or 30% of your climb > speed (According to Horners rule of thumb). So slowing down your > cooling airflow to lessen drag is one reason for paying some > attention to your ducting. However, cooling again depends on many > other variables, for instance accepting a high velocity airflow > through your core may permit you to use a smaller frontal area > core thereby offsetting to some extent the higher drag. In fact, > space constraints may force you to his configuration regardless. > > Another factor to consider is trade off between frontal area drag > and thermal transfer efficiency. A large thin radiator is > theoretical the most efficient due to that factor. However, it > disturbs a larger segment of air (resulting in higher drag) - not > really important in an auto at 60 mph but very important in a Cozy > at 200+ MPH. > > A thicker core with smaller frontal area disturbs less air and > while it has more skin drag that is small compared to the frontal > area drag. Tracy refers to the approach of thicker cores as "... > getting the most cooling possible for the smallest column of air > disturbed". So while theoretically the thicker core is less > thermodynamic efficient - it turns out with sufficient dynamic > pressure available it provides definite benefits in our > application. The average thickness of NASCAR radiators is 3" and > up to 7" for the longer high speed tracts. Since they operate in > speed regimes close to what most of us fly - they just might know > what they are doing given the $$ they will spend for even a slight > speed advantage. > > Ok, back to creating a company - boy, a lot to learn > > Ed > > > > > > > Ed Anderson > Rv-6A N494BW Rotary Powered > Matthews, NC > eanderson@carolina.rr.com > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > http://www.dmack.net/mazda/index.html > > AOL now offers free email to everyone. Find out more about what's > free from AOL at AOL.com. > --Apple-Mail-1-200184780 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1 Bob, =A0have =A0you considered = putting the intake above the rad.=A0 You could get rid of the deflectors = and the air would follow a simple path down through the rad and out.=A0 = Jerry


On May 3, = 2007, at 4:00 PM, bmears9413@aol.com = wrote:

Ed,
Give me some = pointers on my cooling system before I get started. You will save me = some mistakes. My air intake will be below and behind my = radiator. I imagined just building some deflectors to "s" the air = up to the radiator. Aft of the radiator the air will exit out the back = half of the air scoop. the radiator will be laying flat, under the = motormount. the oil coolers are under each wing...as it should be in s = spitfire.
Thanks,
Bob Mears
Supermarine = Spitfire
=A0
=A0
=A0
-----Original = Message-----
From: eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent: Thu, 3 May 2007 11:49 AM
Subject: [FlyRotary] Re: Cooling area drag

Actually, Mark, =A0I started pulling = together what I believed to be the major factors without getting too = down in the weeds about rotary cooling, a couple of years ago with the = intention of publishing an e book (pamphlet more likely) .=A0 Then I ran = into the problem that the seemingly best diffuser (Streamline duct) was = simply too long (in its optimum configuration) for most of our needs.=A0 = Yes, you can shorten it but then you incur more drag.=A0 So I scratched = my head about that for a while until the light bulb came = on.
After experimenting = with a number of duct shapes and reading more, I came to the conclusion = that if my understanding about what killed effective cooling was correct = then I should be able to achieve my cooling/drag goals with the = "Pinched" duct.=A0 But, what I wanted to do and never took the time to = do was to go back with Mr. Bernoulli and calculate the air velocity = along each segment of the streamline duct and then do the same for my = "pinched" duct to see if there was any similarity.=A0=A0 Also, I have = not paid much attention to the exiting duct - simply because I don't = have room for one.=A0 I tired one back almost 8 years ago and decided = the zigs and zags it had to = avoid engine/motormount, etc impeded = airflow more than helped it.
=A0
=A0
But, alas, just as I was recently about to go to = publication, the new "bible" of cooling was published - so how could I = possibly compete {:>).=A0 I may still do it as if it passes the = gauntlet of folks on this list (or errors if any {:>)) are = corrected,as it may be useful to some.
----- Original Message -----
Sent: Thursday, May 03, 2007 12:34 PM
Subject: [FlyRotary] Re: Cooling area drag

ED,
So, tell us, when is your book on = cooling going to be available?=A0
Mark

On 5/3/07, = <> = wrote:
Less we forget how = important drag is in our hobby, I took a formula for calculating drag at = different airspeeds and the Hp required to push = the given frontal area along at the stated airspeed.
This is for two of = our traditional GM evaporator cores using their = combined frontal area of=A0 180 sq inch or 1.25 = feet.=A0 This assumes that airspeed = shown=A0represents the velocity through the cooling core (which is not = really likely to reach speeds above 80 mph if you have any = sort of ducting), but that is an assumption on my part since as Bill = keeps reminding me I have not instrumented my ducts = {:>)
=A0
=A0
Clearly the faster your cruise speed the more important it = is to minimize cooling drag.=A0 Of course the airspeed the core sees = should normally not be over 10% of your cruise speed or 30% of your = climb speed (According to Horners rule of thumb).=A0 = So slowing down your cooling airflow to lessen drag is one reason for = paying some attention to your ducting.=A0 However, cooling again depends = on many other variables, for instance accepting a high velocity airflow = through your core may permit you to use a smaller frontal area =A0core = thereby offsetting to some extent the higher drag.=A0 In fact, space = constraints may force you to his configuration = regardless.
=A0
Another factor to consider is trade off between frontal = area drag and thermal transfer efficiency.=A0 A large thin radiator is = theoretical the most efficient due to that factor.=A0 However, it = disturbs a larger segment of air (resulting in higher drag) - not really = important in an auto at 60 mph but very important = in a Cozy at 200+ MPH.=A0=A0
=A0
A=A0thicker core with smaller frontal area disturbs less = air and while it has more skin drag that is small compared to the = frontal area drag.=A0 Tracy refers to the approach of thicker cores as = "...=A0getting the most cooling possible for the smallest column of air = disturbed".=A0 So while theoretically the thicker core is less = thermodynamic efficient - it turns out with sufficient dynamic pressure = available it provides definite benefits in our application.=A0=A0 The = average thickness of NASCAR radiators is 3" = and up to 7" for the longer high speed tracts.=A0 Since they operate in = speed regimes close to what most of us fly - they just might know what = they are doing given the $$ they will spend for even a slight speed = advantage.
=A0
Ok, back to creating = a company - boy, a lot to learn
=A0
=A0
Ed Anderson
Rv-6A Rotary = Powered
Matthews, NC
#N494BW
http://www.dmack.net/mazda/index.html

AOL now offers free email to everyone. Find out = more about what's free from AOL at .


= --Apple-Mail-1-200184780--