> Ed,  I was unable to read my messages  for a couple of days and so I
> got to read the entire discussion generated by your insightful
> analysis.  Thanks for taking the time and making the issues so clear.  
>   NASCAR is a good example of theory becoming a bug on the windshield of
> practical reality since they often cover most of  the perfectly
> designed  duct openings with tape.  Jerry
>
>
>
>
>
> On Sunday, April 3, 2005, at 06:04 PM, Ed Klepeis wrote:
>
> > Dear Ed
> >     How about a rad 16x18x2.25  with a mazda oil cooler along side
> > mounted in a sq tube frame hung under the eng mount in rubber mounts,
> > could you go for such a set up. let me know.
> >                                                                   
> > regards
> >                                                                 Ed K
> >                                                techwelding@comcast.net
> > ----- Original Message ----- From: "Ed Anderson"
> > <eanderson@carolina.rr.com>
> > To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> > Sent: Sunday, April 03, 2005 9:14 AM
> > Subject: [FlyRotary] Cooling -Learned a lot
> >
> >
> >> Too right, Jerry
> >>
> >> My  first 40 hours or so were in the marginal cooling zone. {:>).  As
> >> other
> >> things in this hobby, there are so many variables that interact, that
> >> what
> >> may appear simply at first, is almost always a bit more complex.  I
> >> say(Cooling Axiom 1) if you have enough cooling surface area and air
> >> mass
> >> flow then it WILL cool.    However, you may incur a high penalty in
> >> cooling
> >> drag - which may not be as important for draggy airframes (such as
> >> biplanes)
> >> as it is to sleeker airframes.   Also a system that adequately cools
> >> an
> >> engine producing  150 HP may not cool an engine producing 180 HP. 
> >> Picking
> >> your cooling design point is important.  Optimizing for cruise and
> >> your will
> >> be less than optimum for take and climb.  Optimize for climb and you
> >> will
> >> probably have more cooling drag than required at cruise.  Compromise,
> >> compromise - cowl flaps are sometimes used to try to have the best of
> >> both
> >> worlds.
> >>
> >> Some folks advocate a thinner, larger surface area core -which is
> >> great for
> >> slow moving automobiles stuck in traffic with low dynamic pressure
> >> potential, but I think is not the optimum for most aircraft.  Once
> >> you trip
> >> the airflow and turn it turbulent you have incurred most of the drag
> >> penalty.  Larger surface area cores disrupt a larger airstream and
> >> incur
> >> more drag.  Yes, thicker cores produce a bit more drag than the SAME
> >> frontal
> >> area thinner cores.  But, with a thicker core you can use a core with
> >> smaller frontal area.
> >>
> >>  The NASCAR radiator's average 3" thick and on the long tracks where
> >> speeds
> >> are higher some even go up to 7" thick.  My contention is their
> >> operating
> >> environment is more akin to ours than regular automobiles moving at
> >> slower
> >> speeds.  You know that the NASCAR folks will spend $$ for just a tiny
> >> advantage - so clearly they don't use thick cores because it is a
> >> disadvantage. But, some folks will continue to point to the large thin
> >> radiators designed for environments with much lower dynamic pressure
> >> as
> >> being the way to go.  Will it cool? sure it will (Cooling axiom 1
> >> above).
> >> Is it the lowest drag option for an aircraft of the RV/TailWind type,
> >> I am
> >> convinced it is not.
> >>
> >> The diffuser makes a considerable amount of difference and can made
> >> the
> >> difference between a system that cools adequately and one which does
> >> not.
> >> The biggest culprit that lessens cooling effectiveness is turbulent
> >> eddies
> >> that form inside the duct due to flow detachment from the walls. 
> >> These
> >> eddies in effect act to block effective airflow through part of the
> >> core.
> >> So keeping the airflow attached to the sides of the diffusers is
> >> crucial for
> >> good cooling from two standpoints. A good diffuser will reduce airflow
> >> velocity through the core which will reduces cooling drag.  Pressure
> >> across
> >> the core is increased which further enhances cooling.
> >>
> >> I have gone from a total of 48 sq inches opening (total) for my two
> >> GM cores
> >> and that provided marginal cooling - down to 28 sq inches (total) with
> >> adequate cooling with an engine now producing more HP.  Experimenting
> >> with
> >> the diffuser shape made the difference.
> >>
> >> The K&W book (Chapter 12) really provided the insight to how and which
> >> diffuser shapes provided the better dynamic recovery.  The Streamline
> >> duct
> >> was shown to be able to provide up to 82% recovery of the dynamic
> >> pressure.
> >> Some folks reading the chapter misinterpreted the chart to show only
> >> 42%
> >> recovery where there chart was actually only showing the pressure
> >> recovery
> >> contribution due to the duct walls and did not include the
> >> contribution due
> >> to the core.  On the same chart, an equation (which apparently gets
> >> ignored)
> >> clearly shows that the TOTAL  pressure recovery is 82%.
> >>
> >> I have taken the Streamline duct as a starting point, but since I do
> >> not
> >> have the space to provide the 12-14" for a proper Streamline duct, I
> >> did
> >> some "creative" things to try to insure that there was no separation
> >> even
> >> though my walls diverge more rapidly than the Streamline duct.  Won't
> >> claim
> >> mine are as good as a Streamline, but they clearly are much better
> >> than the
> >> previous design which basically just captured the air and forced it
> >> through
> >> the cores.
> >>
> >> FWIW
> >>
> >> Ed Anderson
> >> RV-6A N494BW 275 Rotary Hours (Plugs Up)
> >> Matthews, NC
> >> eanderson@carolina.rr.com
> >>
> >>
> >> ----- Original Message -----
> >> From: "Jerry Hey" <jerryhey@earthlink.net>
> >> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> >> Sent: Sunday, April 03, 2005 9:27 AM
> >> Subject: [FlyRotary] Re: phase I flight restrictions was:N19VX flys
> >>
> >>
> >>> It was not long ago that "cooling" was the major issue.  Now it seems
> >>> that we have learned enough to make several different configurations
> >>> work.   I can't lay my finger on what it is we have learned but my
> >>> recommendation is to use smaller radiators and EWPs.   Jerry
> >>>
> >>>
> >>>
> >>
> >>
> >>
> >>
> >>>>  Homepage:  http://www.flyrotary.com/
> >>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
> >
> >
> >>>  Homepage:  http://www.flyrotary.com/
> >>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
> >
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html