P-51 style should look pretty cool with a bent canard...And no I don't

have any drawings, hell all I got is a wing.

tc

Well Todd, we have the bend canard too :) now all I have to figure out

is..what the heck is a P-51 type scoop with boundary layer air bleed? Does
anyone have some good pictures, formulas, data etc for configuring these
things?

...Chrissi

Surely you have seen pictures of a P51 Chrissi?
Don't copy the duct however. It is wrong! You will need an opening
at least 20% of the rad area and a very large opening at
the rear of the airplane to let the air out. Twice the inlet area
at least.

I would guess the boundary layer to be at least an inch
thick at the back of a canard. What say you Al Gietzen?

About 1.5" thick 10 ft back from the nose at 160 kts.

Big outlet area causes drag.  You'd like to have the air exit at a velocity
close to the speed that it came in.   Typically figure for the expansion due
to heating plus a little margin gives you 1.6 to 1.8 times inlet.  Make sure
the exits are in low pressure areas; like at the back of the cowling in a
pusher.

BTW, on the Velocity, the pressure recovery near the back of the airplane -
say about the firewall - is quite high; making attempts at having air come
out the side of the cowling ineffective.  NACA scoops have been shown to be
effective inlets at the engine, but likely would not have the pressure of a
ram scoop.

Al

Adjustable cowl flaps are called for as the dynamic pressure is four
times higher at 200 MPH than it is at 100 MPH. 100 MPH is the critical
design point as that is closer to the speed people takeoff and climb out at.

An air cooled engine I suspect has a lower pressure loss across it than a rad
and that is why NACA said NACA scoops are not suitable for rads and
oil coolers. I just down loaded that pertinent  12 meg PDF file from:
http://naca.larc.nasa.gov/reports/1945/naca-acr-5i20/

Paul Lamar

Chrissi:

You might want to look at early Long-EZs that had the P-51 type scoop.
The big belly NACA wasn't even a Rutan original.  Someone else did that
later and it was widely copied.  Puffer incorporated it into the Cozy IV
plans.  The bottom of the Long-EZ fuselage starts curving upward as you
move back toward the firewall, and the NACA that made the bottom flat
to the firewall was just an aftermarket add-on. So you could reshape the
bottom of the Cozy IV to follow the "ceiling" of the NACA duct.

--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

If you want a bit of evidence that canard people are giving up on it Dick Rutan
has a set of water cooled cylinders for his Long Ez engine. He is using
the P51 style duct to feed air to the rad. If you do try the NACA
duct please down load the pdf file because some of the design features are critical
as to how well it works.

http://naca.larc.nasa.gov/reports/1945/naca-acr-5i20/

I also know Klause used a boat tail to get the bottom flat for the NACA
duct on his Variez. A boat tail I suspect will also work to reduce
the drag of the P51 style scoop.

Paul Lamar
 
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