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
Our reluctance has been that we have already finished this part prior to getting involved with the rotary engine. Even our fuel sump low point is in a well formed by the low material on either side of the NACA scoop. We would have been more likely to fill the scoop in than shave the bottom off to the roof of the scoop. I will have to look more closely at the construction so far to determine whether to fill or to shave.
Shaving the 3" off would amount to some significant intrusion into the structure both on the outside and the inside. If the 3" wedge of foam were removed then the P-51 scoop would not be dangling down quite so obstrusively. Much to consider.
...Chrissi
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