I think he has way less power than you do Perry. I am sure your stock
Mazda tuned intake EFI system is way better than his log manifold with

a two

barrel carb. I think your fan tips are up against the mach # brick wall.

I calculate a vector sum of 909 fps with 5300 rpm and 160 knots in the
fan.
Doesn't seem like the brick wall should start that early.  Maybe it
does.
Isn't mach one around 1100 fps?

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

Depends on a lot of things such as temp and air density not the
least of which is the airfoil used. What are your tip airfoils
now a days?

I know you know that but for others that might not.
BTW 600 MPH is 880 fps. 700 MPH is 1027 fps. You are up there.

Paul Lamar

Perry,

The issue is that the airfoil accelerates the air as it passes over the
top (DUH), which increases the velocity enough to generate a
local shock when freestream is .7 to .8 Mach.  Notice that no aircraft
cruise above about .82 Mach, for the same reason (I mean subsonic A/C,
of course).  Special airfoils (like NACA 16 series) delay the onset of this
shocking, which is what I have been looking at for the CS prop, esp at
the tips.  At the lower Mach numbers the Clark Y is a good airfoil
for a fixed pitch prop, not as good for a wing.  A high max C sub L and
a wide range of useable alpha are important for a fixed pitch prop,
and low drag is not as important (@ low Mach).  For a wing, the drag
is bad, but a Cub with enough HP can do some impressive STOL,
but Cubs are very slow in cruise - both due to the Clark Y wing.

Bill
Long EZ builder & pilot
mechanical engineer

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