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Hi Rusty,
Saw where you are about to start
your radiator ducts. Here is some food for thought. I am convinced
based on my research, some e mail exchanges with the person who wrote the recent
cooling article in KITPLANE and my own experimentation that probably the best
diffuser approach practical for our aircraft type is a truncation of the K&W
Streamlined Diffuser duct.
The expert and I agreed that provided you truncate
the streamline diffuser from the inlet end that you should lose very little
efficiency so long as the rapidly divergence in the "Bell Shaped" area right
before the core is maintained. As you are probably aware I reduced
my left radiator inlet duct from 24 in^2 to 10 in^2 for a total radiator inlet
area (both inlets) reduction of 33%. My coolant temp did increase by
5 F but I am convinced that duct is much more efficient at flowing air than
before and generates less drag. Now when I do both ducts, I will probably
set the inlet area around 15 in^2 rather than 10 in^2 to provide a little
pad for those very hot days. But whatever opening area you decide on, your
airflow should benefit from the use of the streamline duct approach.
Since the cores are not symmetrical, you will need
to enter the width or height separately and generate a coordinate plot from each
view. I would lay the top and side coordinates out on cardboard first and
then transfer them to a block of foam and use them to shape the foam to the
streamline duct shape. Then fiberglass over that would give you your
duct.
I have attached some photos and my streamline duct
coordinator generator if you are interested. While ideally your
coordinate system should be based on the ratio between your inlet area and core
area - any ratio that gives you close to your desired inlet and core area should
be a large improvement. So what I'm saying not to get hung up on exact
match - close enough will provide considerable benefit if not
perfection.
As I have stated, with sufficient air mass flow and
surface area you will cool! However, unless you optimize to the extend
possible, you may also incur considerable cooling drag.
I know you have a lot to get done and may decided
to put this off until the next revision, but thought I would throw it out
at this time - so I wouldn't hear later "Why didn't Ed tell me?"
{{:>)
Best Regards
Ed
Ed Anderson
RV-6A N494BW Rotary
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Matthews, NC
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