The other factor is rad
thickness. Rad thickness must be kept to two inches or less to insure

Al Gietzen wrote:

Whoops.  I think B does not follow A.  The computed pressure drop through

my

3" thick core (2 rows of 1 1/4 tubes) is 2.6 inches of water; about 0.1

psi.

This is for a flow velocity through the core of about 25 ft/sec; which I
think is about what you would get for your 80% efficient duct at 100 mph

if

your radiator area to intake area ratio is 4.5 - 5 to 1

 I don't think

there is any reason not to use a thicker radiator to get the heat

transfer

area you need; and (perhaps) taking a small drag penalty.  And this
particular wing installation allows for fairly optimum inlet AND exit
diffusers

Well lets say we go up to 3 inches thick. The length required for 600 cubic
inches would then be 600/(7*3) or 28 inches long. Or two rads 14 inches

long.

It will be very hard to bypass the boundary layer with a duct that wide
under the wing.

Yes, I certainly agree that pesky boundary layer is a problem.  Mostly I was
suggesting that it isn't true the rads "must be kept to 2 inches or less".
I was wondering if some small VG's forward of the under wing inlet could
help with the boundary layer problem; or would it just make things worse.

below. As I recall the owner of this V6 powered airplane complained about
the drag.

Gee, I don't think so.  I think Dan is quite happy with it.  I don't like it
because of turbulence it generates for the prop; and the possible effects on
prop efficiency.  I know that his airplane is quite heavy and the
performance isn't the greatest.

IMHO the best place for an intake duct with a wing mounted
rad is in the leading edge as many World War II airplanes had. The best

place

for the outlet duct is sort of a split flap trailing edge.

No doubt about that.  I'd love to be able to have an inlet at the leading
edge; but as you say, it is difficult.  In my case with the Velocity, it is
impossible; the fuel tanks and the retract gear wells are just forward of
the spar.

Well, you know what they say; an airplane is large number of compromises
flying in close formation.

Al

There is also the issue of cooling on the ground. There is no doubt in my
mind two inches is better for that than three inches. I also want my airplane to
cool while climbing at max angle. Read lower speeds. I frequently run into 
situations where climbing at max angle is important.

Paul Lamar
 
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