From: "Charlie England" <flyrotary@lancaironline.net>
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Date: Wed, 06 May 2015 09:34:34 -0500
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Return to Flight
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On 5/6/2015 8:01 AM, Tom Mann wrote:
> Mind you, my rotary is not flying yet and I have a Canard design but I 
> often wonder why the RV guys don’t relocate the radiator and use a 
> P-51 style scoop?
> I’ve seen many that have the radiator almost perpendicular to the 
> direction of the inflow.
> I would think that a radiator mounted just behind the seats would give 
> you the distance to properly expand the air and recover the pressure 
> more efficiently.
> Just thinking out loud ......
> T Mann

I agree, a perfect P-51 style setup would be better, but....

Ross Farnham in Canada has done it (sort of).
http://www.sdsefi.com/air9.html
http://www.sdsefi.com/rv17.htm
http://www.youtube.com/watch?v=QT8njoirTkU
http://www.youtube.com/watch?v=gPpWHvr1kJw
He won't publish hard numbers, but has vaguely hinted at a 6-8 knot 
speed gain over his old cooling system, which was pretty convoluted 
(multiple air inlets/outlets in random places for multiple random heat 
exchangers), so it was probably a net 0 gain over a well done under-cowl 
setup.

It's pretty complicated to run the plumbing, and since a complete rotary 
installation that's built with careful attention to weight can come in 
lighter than a Lyc (I put my entire FWF on a scale: 310 lbs, dry), 
moving the heat exchangers aft is likely to adversely affect the CG. 
Ross got away with it because he's running a turbo Subaru, which is 
pretty heavy.  The P-51 rad is partially submerged in the fuselage. 
Submerging the rad in the aft fuselage sounds great, but even if you can 
deal with the CG issues, with a metal fuselage you have to be very 
careful what & where you cut to get the air in & out. And the scoop 
itself is extra weight (the cowl is already there for the outside of the 
'scoop').

Water cooled engines beg for an airframe designed around them, just as 
air cooled engines have planes designed around them.

Charlie

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    <div class="moz-cite-prefix">On 5/6/2015 8:01 AM, Tom Mann wrote:<br>
    </div>
    <blockquote cite="mid:list-7675492@logan.com" type="cite">
      <div dir="ltr">
        <div style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR:
          #000000">
          <div>Mind you, my rotary is not flying yet and I have a Canard
            design but I often wonder why the RV guys don’t relocate the
            radiator and use a P-51 style scoop?</div>
          <div>I’ve seen many that have the radiator almost
            perpendicular to the direction of the inflow.</div>
          <div>I would think that a radiator mounted just behind the
            seats would give you the distance to properly expand the air
            and recover the pressure more efficiently.</div>
          <div> </div>
          <div>Just thinking out loud ......</div>
          <div> </div>
          <div>T Mann</div>
        </div>
      </div>
    </blockquote>
    <br>
    I agree, a perfect P-51 style setup would be better, but....<br>
    <br>
    Ross Farnham in Canada has done it (sort of).<br>
    <a class="moz-txt-link-freetext" href="http://www.sdsefi.com/air9.html">http://www.sdsefi.com/air9.html</a><br>
    <a class="moz-txt-link-freetext" href="http://www.sdsefi.com/rv17.htm">http://www.sdsefi.com/rv17.htm</a><br>
    <a class="moz-txt-link-freetext" href="http://www.youtube.com/watch?v=QT8njoirTkU">http://www.youtube.com/watch?v=QT8njoirTkU</a><br>
    <a class="moz-txt-link-freetext" href="http://www.youtube.com/watch?v=gPpWHvr1kJw">http://www.youtube.com/watch?v=gPpWHvr1kJw</a><br>
    He won't publish hard numbers, but has vaguely hinted at a 6-8 knot
    speed gain over his old cooling system, which was pretty convoluted
    (multiple air inlets/outlets in random places for multiple random
    heat exchangers), so it was probably a net 0 gain over a well done
    under-cowl setup. <br>
    <br>
    It's pretty complicated to run the plumbing, and since a complete
    rotary installation that's built with careful attention to weight
    can come in lighter than a Lyc (I put my entire FWF on a scale: 310
    lbs, dry), moving the heat exchangers aft is likely to adversely
    affect the CG. Ross got away with it because he's running a turbo
    Subaru, which is pretty heavy.  The P-51 rad is partially submerged
    in the fuselage. Submerging the rad in the aft fuselage sounds
    great, but even if you can deal with the CG issues, with a metal
    fuselage you have to be very careful what &amp; where you cut to get
    the air in &amp; out. And the scoop itself is extra weight (the cowl
    is already there for the outside of the 'scoop').<br>
    <br>
    Water cooled engines beg for an airframe designed around them, just
    as air cooled engines have planes designed around them.<br>
    <br>
    Charlie<br>
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