Return-Path: Received: from [199.185.220.223] (HELO priv-edtnes28.telusplanet.net) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 856541 for flyrotary@lancaironline.net; Tue, 05 Apr 2005 21:03:44 -0400 Received-SPF: pass receiver=logan.com; client-ip=199.185.220.223; envelope-from=echolakeresort@telus.net Received: from [207.194.26.187] by priv-edtnes28.telusplanet.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050406010253.GIZH5810.priv-edtnes28.telusplanet.net@[207.194.26.187]> for ; Tue, 5 Apr 2005 19:02:54 -0600 Received: from 127.0.0.1 (AVG SMTP 7.0.308 [266.9.1]); Tue, 05 Apr 2005 18:02:47 -0700 Message-Id: <42533534.000001.02584@BOUCHER-ODDLE24> Date: Tue, 5 Apr 2005 18:02:44 -0700 (Pacific Standard Time) X-Mailer: IncrediMail (3001609) From: "Echo Lake Fishing Resort (Georges Boucher)" References: To: Subject: Re: [FlyRotary] Re: A lot to learn X-FID: FLAVOR00-NONE-0000-0000-000000000000 X-Priority: 3 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=======AVGMAIL-42533537778A=======" --=======AVGMAIL-42533537778A======= Content-Type: Multipart/Alternative; boundary="------------Boundary-00=_KW2IQL80000000000000" --------------Boundary-00=_KW2IQL80000000000000 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Hi! Guys =0D I' m showing my ignorance but you all lost me in the cooling discussion. Correct me if I'm wrong , If coolant temperature on an RV on climb out at 100mph full throttle stay within limits wouldn't a slow airplane with a t= op speed of say 125MPH be able to use the same cooling system set up? or tho= se the fact that an RV has less drag come into it?=0D Georges Boucher ( notice " No fiddly things" at the bottom of the page)=0D =0D -------Original Message-------=0D =0D From: Rotary motors in aircraft=0D Date: 04/05/05 07:34:41=0D To: Rotary motors in aircraft=0D Subject: [FlyRotary] Re: A lot to learn=0D =0D See, I told you this was the most miss-understood detail in water cooled engines! : )=0D =0D FWIW, here is my summary of the discussion so far:=0D =0D Ed, you are being way too modest. Yours has been the most coherent real world analysis so far while still tying it to the theoretical groundwork.= =20 Your brief departure into the irrelevant molecular velocity (for this discussion), was in response to someone else, not your fault.=0D =0D Jim, excellent point, we must separate the irrelevant and 'things we can'= t do anything about' from the discussion about building a actual honest to = god flying machine.=0D =0D Doug's 'rule of thumb' post was based on real physics but left out some factors that made it not universally applicable. What works for an RV wi= ll not necessarily work for a Pietenpole, even if they had the same size eng= ine And while the military must design for "Std air + 40 deg F" (100 degree= s), we have the advantage of not needing to design to that standard. On thos= e very hot days, I can accept the limitation of using a lower power setting= in climb in order to have other advantages. I'm not scrambling to intercept MiGs at 40,000 ft. But Doug's point of using rules of thumb (when accura= te and applicable), is very true. Very few builders have the time or inclination to fully absorb K & W (which he has done pretty well).=0D =0D Tracy=0D =0D Ok, Jim=0D =0D I agree that the theory part gets out of hand at times (my fault). Theor= y only counts if it works in practice {:>). However, I think these questio= n naturally arise when we start talking about some of this stuff - the old=20 how it do that". =0D =0D The only part that really counted was understanding what was necessary t= o keep air flow from separating from the walls in a diffuser. If you eliminate that problem you have done probably 90% of what you can do to achieve optimum diffuser performance (my opinion of course). So you can have otherwise adequate core surface and volume, but if you have a poor d= uct design with lots of flow separation and eddies then your system may fail = to adequately cool.=0D =0D Ed A=0D =0D =0D =0D Is it possible we're dismissing some important factors getting a little o= ut of our depth here? Dynamic pressure in the cores and across the cores wo= uld seem to be so highly dependent on surface friction and core density and passage size as to be impossible to estimate, much less quantify accurate= ly.=0D =0D If the purpose of the plenum is pressure recovery (converting dynamic pressure into static pressure) and it's the static pressure drop that dri= ves the mass of air through the radiator core, why not just forget about the molecular, boundary layer and core passage size considerations for the moment since we can't quantify any of that anyway. As Ed has stated so m= any times in so many ways, a good inlet/plenum design does a better job of converting dynamic pressure to static pressure than a bad one, and he's found out pretty much what he has to do to make a bad one good. =0D =0D If we measure static pressure at the forward and aft face of the radiator and we've got the pressure drop across the core. Period. We know how cl= ose we are to Ed's plenum. Then adapt the stuff that Ed has pioneered for us= to make it better An Airspeed indicator I find is handier and more accurate than a water manometer. The Pitot connection on the upwind side and the Static connection on the downwind side should give me upwards of 100, may= be 120 kias drop across the radiator at cruise. More is better. If I don't have sufficient pressure drop across the radiator, I probably need to improve my intake and plenum to get rid of the eddies Ed alludes to. Tha= t is what I've got the most influence over. If I don't get enough pressure recovery, I study Ed's findings and approach implement them better. =0D =0D I think all this molecular stuff is more appropriate to the ACRE list whe= re nothing ever really has to fly. This list (to me) is the guys who actual= ly FLY. A sound qualitative analysis of the issues involved (which we alrea= dy have) will lead me to a workable solution. That is very nice since an acceptably accurate quantitative analysis is not possible. To that end (= to coin a phrase) I don't have to know how it works or why it works, I only have to know what I have to do to MAKE it work. And I have been blessed that Ed has found out most of this.=0D =0D Are we PVORT. again? ... Jim S.=0D =0D =0D David Carter wrote:=0D =0D ----- Original Message ----- =0D From: =0D To: "Rotary motors in aircraft" =0D Sent: Monday, April 04, 2005 7:07 AM=0D Subject: [FlyRotary] Re: A lot to learn ! Re: Cooling -Learned a lot=0D =0D =0D =0D Charlie E wrote:=0D =0D At the risk of embarrassing myself with a display of misunderstanding=0D the physics of it all, should your pressure sensors be measuring dynamic=0D pressure or static? Seems like I remember Tracy's measurement pics=0D having foam chunks over the pressure sensors to remove the dynamic=0D component of the pressure measurement. I couldn't remember if your setup=0D has that (& I really don't know if it should, either).=0D =0D Charlie=0D ---------------------------------------------=0D =0D =0D =0D >> Homepage: http://www.flyrotary.com/=0D =0D >> Archive: http://lancaironline.net/lists/flyrotary/List.html=0D =20 --------------Boundary-00=_KW2IQL80000000000000 Content-Type: Text/HTML; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Hi! Guys 
I' m showing my ignorance but you all lost me in the cooling discuss= ion. Correct me if I'm wrong , If coolant temperature on an RV on climb o= ut at 100mph full throttle stay within limits wouldn't a slow airplane wi= th a top speed of say 125MPH be able to use the same cooling system set u= p? or those the fact that an RV has less drag come into it?
Georges Boucher ( notice " No fiddly things" at the bottom of the pa= ge)
 
-------Original Message-------
 
Date: 04/05/05 07:= 34:41
Subject: [FlyRotar= y] Re: A lot to learn
 
See, I told you this was the most miss-understood detail in water co= oled engines!  : )
 
FWIW, here is my summary of the discussion so far:
 
Ed, you are being way too modest.  Yours has been the most cohe= rent real world analysis so far while still tying it to the theoretical g= roundwork.  Your brief departure into the irrelevant molecular = velocity (for this discussion), was in response to someone else, not= your fault.
 
Jim, excellent point, we must separate the irrelevant and 'things we= can't do anything about' from the discussion about building a actual hon= est to god flying machine.
 
Doug's 'rule of thumb' post was based on real physics but left out s= ome factors that made it not universally applicable.  What works for= an RV will not necessarily work for a Pietenpole, even if they had the s= ame size engine.  And while the military must design for "Std air + = 40 deg F" (100 degrees), we have the advantage of not needing to design t= o that standard.  On those very hot days, I can accept the limitatio= n of using a lower power setting in climb in order to have other advantag= es.  I'm not scrambling to intercept MiGs at 40,000 ft.  But Do= ug's point of using rules of thumb (when accurate and applicable), is ver= y true.  Very few builders have the time or inclination to fully abs= orb K & W (which he has done pretty well).
 
Tracy
Ok, Jim
 
I agree that the theory part gets out of= hand at times (my fault).  Theory only counts if it works in practi= ce {:>).  However, I think these question naturally arise when we= start talking about some of this stuff - the old "how it do that". =
 
The only part  that really counted = was understanding what was necessary to keep air flow from separating fro= m the walls in a diffuser.  If you eliminate that problem you have d= one probably 90% of what you can do to achieve optimum diffuser performan= ce (my opinion of course).  So you can have otherwise adequate core = surface and volume, but if you have a poor duct design with lots of flow = separation and eddies then your system may fail to adequately cool.
 
Ed A
 

Is it possible we're dismissing some important factors get= ting a little out of our depth here?  Dynamic pressure in the cores = and across the cores would seem to be so highly dependent on surface fric= tion and core density and passage size as to be impossible to estimate, m= uch less quantify accurately.

If the purpose of the plenum is pres= sure recovery (converting dynamic pressure into static pressure) and it's= the static pressure drop that drives the mass of air through the radiato= r core, why not just forget about the molecular, boundary layer and core = passage size considerations for the moment since we can't quantify any of= that anyway.  As Ed has stated so many times in so many ways, a goo= d inlet/plenum design does a better job of converting dynamic pressure to= static pressure than a bad one, and he's found out pretty much what he h= as to do to make a bad one good. 

If we measure static press= ure at the forward and aft face of the radiator and we've got the pressur= e drop across the core.  Period.  We know how close we are to E= d's plenum.  Then adapt the stuff that Ed has pioneered for us to ma= ke it better  An Airspeed indicator I find is handier and more accur= ate than a water manometer.  The Pitot connection on the upwind side= and the Static connection on the downwind side should give me upwards of= 100, maybe 120 kias drop across the radiator at cruise.  More is be= tter.  If I don't have sufficient pressure drop across the radiator,= I probably need to improve my intake and plenum to get rid of the eddies= Ed alludes to.  That is what I've got the most influence over. = ; If I don't get enough pressure recovery, I study Ed's findings and appr= oach implement them better. 

I think all this molecular stuf= f is more appropriate to the ACRE list where nothing ever really has to f= ly.  This list (to me) is the guys who actually FLY.  A sound <= I>qualitative analysis of the issues involved (which we already have)= will lead me to a workable solution.  That is very nice since an ac= ceptably accurate quantitative analysis is not possible.  To = that end (to coin a phrase) I don't have to know how it works or why it w= orks, I only have to know what I have to do to MAKE it work.  And I = have been blessed that Ed has found out most of this.

Are we PVORT= =2E again? ... Jim S.


David Carter wrote:
-----=
 Original Message -----=20
From: <jbker@juno.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, April 04, 2005 7:07 AM
Subject: [FlyRotary] Re: A lot to learn ! Re: Cooling -Learned a lot


  
Charlie E wrote:

At the risk of embarrassing myself with a display of misunderstanding
the physics of it all, should your pressure sensors be measuring dynamic
pressure or static? Seems like I remember Tracy's measurement pics
having foam chunks over the pressure sensors to remove the dynamic
component of the pressure measurement. I couldn't remember if your setup
has that (& I really don't know if it should, either).

Charlie
---------------------------------------------

    
  

>>  Homepage:  http://www.flyrotary.com/

>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
 
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