Air Conditioning discussion;

Asbestos suit is on---- let er rip!!!

When I first started debated recommending the Airflow system, a major detracting statement I always heard was, "I like the system, but I can't stand all the drag from that scoop". I said it too!  I insisted that Bill Genevro put the scoop into a wind tunnel and test it. He did, and it resulted in a much lower profile scoop. I like the results so I installed it, and it's been absolutely great! Talk to anyone who has one.  

 I began the testing and I reported the airspeed loss was less than five knots. I was comparing data from a prop tested several years ago to a post air conditioning installation test.  There were few altitudes where was zero knots lost.  The highest I recorded was three knots.

The case could be made for the scoop in the Airflow system, that it could provide a thermal boost. Air comes in cold and goes out hot.  I think that the P-51 boasted about a boost.  But I think that's a stretch. But in any case, it may be less than the Aero Cool system.

Regarding Aero Cool, It is a mistake to think that holes in the fuselage, blowing a large stream of hot air, provide no drag.  They do!  Then, think about structure-- and the fact that we have a stressed skin in a true monocoque* structure.  A detailed stress analysis was accomplished by Martin Holman when the airplane was initially developed. To cut holes in the fuselage without redoing the stress analysis means you're taking the "experimental" label literally. Has anyone looked at the load path from the landing gear box/wing attach points to the horizontal /vertical stabilizer?

The Aero Cool system needs a large fan to cool the condenser.  Consider the electrical load--heavy wiring--heavy switches-- stress on alternator and other components.

The reason the system needs a fan is because NACA scoops do not work where the fuselage area is reducing. Many builders have had a difficult time locating the static ports at a +/- zero location. Too far forward reads low--Too far aft reads high. Why??

The original NACA scoop for ventilation was on the leading edge of the vertical stabilizer where the area is increasing. It could not be located anywhere else, because the area was reducing. 

 If you put tufts on the NACA leading edge inside the scoops and fly the airplane you will notice that air is coming out-- not going in. Therefore fans must be used to counter this effect.  Why are we working against Mother nature here?

So in summary, I would say;

The Aero Cool the system is heavier. (Extra equipment-fan. Heavier wiring-fan.  Heavier hoses- to run further aft.) 

The Aero Cool system has drag by cutting holes in the fuselage and blowing out hot air. Perhaps more drag than a scoop.

      (Questions arise as to structural strength. *)

The Aero Cool system requires much more electrical service.

The Aero Cool system is much more complex to install.
The Aero Cool system can take valuable baggage space. 

The Aero Cool system moves the center of gravity aft. Will you be able to carry backseat passengers in that rare event they're needed? 

The Aero Cool system cost more to purchase--costs more to install.

The Airflow systems unit needs no fan for the condenser. 

It works well on the ground (the propeller provides the cooling airflow over the condenser.)

Therefore, it's lighter.

Condenser can be smaller because of the adequate Airflow in all régimes.

Condenser is located outside the hull, and the heat associated in a closed contained environment, therefore requiring less Airflow to cool the condensate.

Small loss in airspeed, that perhaps, may be the same as, or less than the Aero Cool system, due to less weight, and no holes in the fuselage providing turbulent Airflow over the fuselage and tail surfaces. 

No sacrifice of space in the aft baggage compartment. 

Much less cost. 

Much simpler installation.

And besides--doesn't that P-51 scoop looked neat!!!! 

KISS

Charlie Kohler