[NSRCA-discussion] Cooling/spinners

[Thomas D. Simes]

On Mon, 20 Feb 2006 11:41:14 -0600
"Nat Penton" <natpenton at centurytel.net> wrote:

> As Matt mentioned, the only way to use the spinner as an effective air
> mover is as a cetrifugal blower. This would call for an open nose, and
> the need for  properly shaped vanes (as a third part ?).

Quite a few full scale propeller aircraft have the spinner listed on
their master minimum equipment list.  In other words, the FAA doesn't
consider the aircraft to be airworthy without the spinner.  This used to
be the topic of a favorite check ride "gotcha" question when I was
getting my ratings.  The student was asked whether the airplane was
airworthy without the spinner - and naturally they had a 50% chance at
that one.  But the follow on question of "why" revealed whether they
understood the regs or were guessing.  On the general aviation aircraft
I've flown where the spinner was required, it was listed as part of the
cooling system for the engine.  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.  I would submit that there are likely more gains to be
had by concentrating on the path that airflow takes once it enters the
cowl rather than by trying to turn the spinner into a fan.  In general,
increasing the efficiency with which air transits the cowl will also
decrease drag a bit and increase the flow rate which increases cooling
(presuming the air is appropriately directed).  In other words it's
nearly a freebie - the only costs are the weight and expense of the
baffling material and some time spent in experimentation.

Not to discourage innovation though, I have been experimenting in the
fan direction and have applied for a patent on a Pressure Redirection
(of) Outside (air) Particles device.  I'm working on a commercial brand
name for it, but for now I'm just referring to it by the working acronym
P.R.O.P. ;-)


Tom
 
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   "Z-80 system stack overflow.  Shut 'er down Scotty, the system's
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Thomas D. Simes                                 simestd at netexpress.com 
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