[NSRCA-discussion] Cooling/spinners

[Rcmaster199 at aol.com]

In a message dated 2/20/2006 2:04:45 PM Eastern Standard Time,  
simestd at netexpress.com writes:

If  you've ever taken a close look at the
engine installation on a high  performance piston aircraft, the cowling
is typically very tight by pattern  standards and they have nowhere near
our 3:1 outlet:intake rule of thumb  for cooling.  Instead they make
extensive use of baffling and ducting  to control the air path and make
it work for them.


It's "elementary" Thermo 101 kind of stuff with a little fluid dynamics  
thrown in for good measure. Keep the air in the turbulent regime around the  
engine to maximize cooling effectivess. To some degree, we did that in our  earlier 
designs by maintaining a slender fuse and cowling in tighter by  necessisity.
 
With the advent of the Pachyderm fuses, we copied full scale size-wise but  
with little forethought about cooling. Having a large bucket of dead air up  
front in our fatso fuses does nothing for the engine/motor. Slows the plane down 
 tho.
 
And BTW, the exit really doesn't need to have 3X the entry area to be  
effective if properly designed to draw the air out. Remember Bernoulli?? 
 
On the other hand, with so many of us having stopped building, where's the  
creativity and innovation going to come from? It saddens me to see a whole new  
generation of "modelers" who only want to fly, using ready made everything. 
It  does produce wonderful piloting skill tho.
 
Matt
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