-- JDEggers wrote:

I noticed from your drawing of the cowl changes that you are opening another
venturi to cool the radiator.  While this is the obvious thing to do on the
surface, would it not create another frontal restriction in the profile.
After reading Tracy's experiences with venturies, air flow etc question the
effectiveness of the radiator without channeling/baffleing and/or louvering
to direct the air flow evenly across the radiator.    I am building an RV8
and seriously considering either a 13B or 20B.   Since there no RV8 examples,
Tracy, Anderson, Atkins and powersport have to only actual experience that I
have at hand and each of them took different directions so it is hard to
judge. (I am NOT a techie engineer and don't intend to be one - however I am
an experienced practical engineer).

I have flown with Atkins so have some experience with his design which
physically resembles your design however he did not cut the cowling nor did
tracy.   He has on occasion experienced heating problems but I am convinced
it is because of the lack of directed flow on the radiator.  The Oil cooler
is well chaneled off the right air intake and seems to be very efficient.
I guess the questions I am dealing with is in the summary of the above.
     By adding a third intake port, are we adding frontal resistance.
     Should we take the direction of powersport and redesign the cowling.
     Should we take Andersons direction and baffle, baffle, baffle.

As I recall Dave is taking in air with the stock inlets and
trying to  force it down and through the rad. What I advocate 
is the opposite. Take air in below the rad and let it find its 
way up and out around the engine and out the left side of the 
cowl with the exhaust pipe. That way the air is not heated first
by the engine.
 
If the shape of the bottom of the duct is curved properly you
don't need guide vanes. Guide vanes generate aero losses all on their
own. Use a wind speed meter to check the uniform airflow through
the rad to be sure you have the right duct curve under the rad.
The duct should be bell shaped.

Check this web site for examples. http://home.earthlink.net/~rotaryeng/ 

You can close the holes up on either side of the prop if you wish.
You won't need to make a new cowl if you exit the exhaust on the
left side and use a 19 by 24 by 2 inch rad angled up under the engine.
It should fit in the stock RV cowl. Make a mockup out of foam and check.
It fits in my stock  KIS Cruiser cowl.

Paul Lamar
 
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