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Re: Air Scoops

The factory has gone to "down draft cooling" by using a plenum that
attaches to the entire upper surface of the engine. The plenum is then
fed through two 4" ducts that have been attached to and routed from the
original "armpit" scoops.

1) Both the Lycoming and Franklin engines were designed with down draft
cooling in mind. The original design of updraft cooling on the Velocity
was based on simplicity so that the average non-aviation mechanic /
engineer builder could easily build the plane without having to make his
/ her own plenum arrangement. (Am I right, Alan?)

2) That big rear opening on the original airframe, and the three rear
ports on the XL, are both at a point where the pressure is just about as
low on the entire fuselage as it is going to get. Yea, though the air
floweth through the labyrinth of 90 degree bends  and fins to get "out", 
it is being suckth through those bends and fins as much as being blownth
through. (Sorry, don't know what broughteth that on!?) 

3) With regards to the approach on engine cooling  that it "should be
approached carefully and with some good forethought, drawings, planning,
etc...", I say if you don't like what is tried and true, then do it
differently. "Try it, then fly it". If it works better, try to improve
it, If it don't, try something else or do it like the rest and figure out
why your system is not responding like everyone else's. It doesn't take
but less than 10 minutes to figure out your engine is being cooled
reasonably well, or not at all.	

Engine cooling, as long as it is approached reasonably, is one of the
areas in which the "Experimental Builder" can experiment. If temps stay
low on the ground, and during climb out, chances are you might be onto
something. If you can't taxi to the first intersecting taxiway without
excessive temps. then go back to square one.

Just my two cents worth :>)

Safe and Speedy Construction


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