Message-ID: <000e01c44c19$f1c528e0$2402a8c0@EDWARD>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-142007@logan.com>
Subject: Re: [FlyRotary] opinion
Date: Sun, 6 Jun 2004 18:59:38 -0400
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Steve,

    Many of us have found that 24 square inches per radiator/cooler has been
adequate, but that has been with tractor platforms.    I would assume that a
canard would need at least (if not somewhat more) as much square area inlet
as a tractor installation.  That being said, 24*3 = 72 square inches total
for radiator and oil cooler would be a minimum.  I am currently
experimenting with new ducts to see if different diffuser shapes can reduce
that inlet size, but for right now, that much area will (in most cases)
provide adequate cooling for an NA engine of  160 HP.  If you are running
boost and therefore increasing HP over that point, then you will probably
need to factor in an increase.  I would suggest that you consider increasing
your duct entrance area above 72 square inches proportional to your expected
boost power increase over 160 HP.  For example, if you think you are
producing 200HP under boost in a climb then taking your 40 HP increase over
the 160 engine, you have  40/200 =.
0.2 increase.  72 * 1.2 =  86.4 square inches inlet might be closer to what
would be needed.  That assumes that you are under boost for extended periods
over 5 minutes, if less than that then you may get through that phase before
your thermal inertia is "used " up and you start to overheat.


  I am not certain that your scoop is outside the fuselage boundary layer
which can interfere with air intake, one reason for the "extended" scoop of
the P-51 to get the inlet outside the boundary layer.  You mentioned vortex
generators which you felt addressed the boundary layer, so I am going to
assume it does.

   Your planned 73 square inches should certainly help.  It has been
sufficient for the RV series, but they do have the advantage of having the
air flow not  influenced by the aircraft body.  My last duct experiment
indicated that a tractor with streamline duct can provide adequate cooling
with as little as 56 square inches - but my coolant temp did increase 5F. So
I would continue with your current plan to expand to 73 square inches.

FWIW

Ed


Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message ----- 
From: "Steve Brooks" <steve@tsisp.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, June 06, 2004 6:10 PM
Subject: [FlyRotary] opinion


> Ed,]I wanted to get your opinion about increasing the size of my cooling
> scoop.  The existing scoop is a NACA scoop upon which I extended the scoop
> portion a little e bit to try to capture more air.  I took some
measurements
> today, and the inside of the scoop measures 1-3/4" high by 15-3/4" wide.
> Now there is an additional area that same size which is recessed that is
the
> actual NACA inlet.  I'm not sure about how to calculate the inlet size,
but
> if you exclude the NACA, it is about 27.5 SQ IN, and if you include the
NACA
> area, about 55 SQ IN.
>
> I am looking at building a scoop on the landing gear cover which extends
9"
> forward of the current scoop.  I am looking at making the width of the
scoop
> 21-3/4 inches, which is 3" wider on each side, and 1-5/8" taller (or
deeper
> depending on how you look at it).  That would make the inlet size 73.4 SQ
> IN.  There is also the actual NACA inlet along that area that tapers
toward
> the front.  I don't know what the SQ IN of the NACA is on the cover, but I
> could make some more measurements and calculate it if you think that it
> would be significant.
>
> I am interested in your feedback about the size, or from anyone else for
> that matter.   Today when flying straight and level, when I increased
> throttle, and increased speed, I also increased in oil and coolant
> temperature, which tells me that I don't have enough air flow, or
velocity,
> or pressure, or whatever the correct term is.
>
> As it turns out, I have some time to work on the scoop, especially since
> I'll be doing a little fiberglass work anyway.
>
> Thanks,
>
> Steve Brooks
>
>
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