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

DENIS SMITH wrote:

Lockheed L1011 and Boeing 747-400 aircraft routinely
cruise at .85 Mach and higher.

 
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