Alan Tolle wrote:

Let me try this from another direction.  I  suggested  using the shortest
possible gear box (11 inches sounds just fine and I don't care who makes it
as long as it can carry the power load and turns the standard direction) on
an RV-4 or -6 aircraft (for example) for a very good reason.  When you get
around to calculating weight and balance you will discover that you need all
of the weight you can get as far forward in the cowling as you can get it.
It is either that or lead ballast.  There is nothing any more dangerous than
an aft CG -4  or -6, and I had a number of friends who are now non-living
proof of this statement.  The fact that the short gear box leaves enough
room between the engine and the firewall for large enough cooling cores is a
bonus which will greatly simplify the overall installation.

No question that there is a scientific way to determine needed cooling core
size.  There is a formula for anything and everything.    But I also know
that a lot of problems like cooling core size have required solution by cut
and try.  Currently there are too many variables in the aircraft
installations which have flown.  Study them --- no two are even close to
being alike in core size, placement, air inflow and outflow, ambient
temperature conditions, etc.  Instrumentation is weak or lacking.  I don't
think there is any way of calculating a required radiator size.

At this very early experimentation stage the simple solution would seem to
be install the largest radiator and oil cooler you have space for and add an
effective cowl flap to control the air flow through the cooling cores to
raise (by closing) or lower (by opening) the temperature as required.
Opening and closing the flap on the belly scoop was the way the P-51 worked.
Granted the airflow story was lot more exotic..

I have noted before that I come to this forum as a builder, not as a
technical type.  .  Over my 20 years of home building  (three RV-3s, one
each -4, -6, and -6A)  the best solution has nearly always been the simplest
one.  Complexity usually means more time and money building and more  to go
wrong flying.   There is ample time for refinement in the future.  The first
task is to get rotary conversions into the air that work.  Maybe not
perfectly optimized, but that work.

It is like the ongoing discussion of oil metering.   I think everyone who
has flown dumps oil (usually 2 cycle) into the gas.  It is the simplest, and
the safest, and going to add about a dime to the cost of your gallon of gas.
Any metering system adds just one more thing to go wrong.  BTW the rotary
engine oiled via the gas looks exactly as recently described --- a dead
ringer for a two cycle tear down.  Everything is clean, oiled, and very.
very little carbon is present.

Thanks Allan I really appreciate all you have done for the rotary
engine in airplane cause. 

Paul Lamar

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