David Leonard
The Rotary Roster:
http://members.aol.com/_ht_a/rotaryroster/index.html
>
> Tracy wrote:
>  D@*x!, lost another 2 hour message to the blue screen of death.

That does it, I can't debate the issue any more.  Your time is far too
important to spend this much time debating what is really a minor point.
In the range of the possible radiator designs your thick vs. my thin are
really very close to the same thing.  IMHO, this is all just minor
theory points..

> Tracy replies:
>
>  OK here is the guts of what I blathered on for two hours about:
>
> You are correct about the importance of the velocity of air in the
drag
> equation.  But the air velocity through the rad is of no (or very
minor)
> importance.
>
> The velocity that matters is the velocity of the air at it's *source*.
> That, of course, is the speed of the air rushing past the airplane
that we
> snagged to run through our cooling system.  Since this speed is the
same
> regardless of what radiator is sitting inside the cowl, the *only*
factor
> that makes any difference is how much of that air we used.  More air =
> more
> energy = more drag.
>
> Tracy
>

Yes, except.  The forward energy used to slow down that incoming air is
offset by any thrust you may be able to obtain from the exiting air (or,
if you prefer, there is also significant drag at the exit point, this
drag is inversely proportional to the speed of the exiting air).  Like
in a jet engine, what matters is the difference between the intake and
exhaust velocity.  And this is where I disagree with your first point,
the rad is the main determinant of this difference in velocity between
intake and exhaust (given optimum ducting- which I'll admit is darn near
impossible).  The more energy you loose passing air through the rad, the
less you will be able to speed it for smooth exit.  And it is velocity
through the rad (because of its cubed effect) that is the primary
determinant of energy loss there.

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