freakingfast

My Feedback: (3)

Have you ever wondered what speed your prop would need to turn to make Mach 1?
That is of course if the prop stays intact.

Air temperature 82*
Prop diameters @ rpm for Mach 1 tip speed. This is static, forward velocity of the plane will raise the tip speed.
7.4@35,000
7.8@33,200
8”@ 32,700
8.8@ 29,700
9” @ 29,050
10” @ 26,150
11” @ 23,750

Over 92% mach the airflow begins to detach from the propeller which decreases efficiency and dramatically increases noise.
Example:
(11”) 23,750 x .92 = 21,850

See for yourself, a cool calculator tool.
http://www.pponk.com/HTML%20PAGES/propcalc.html

Mike Connor

My Feedback: (5)

The "helical" tip speed in flight Vtip is obtained by adding the airspeed V to the rotation tip speed Vr using the rule of vector addition.

Vtip = SQR( Vr ^ 2 + V ^ 2 )

freakingfast

My Feedback: (3)

Mike's a sharp guy to have around for the right answers, always thinking. Sometimes this tech jargon goes over my head faster than my planes.[X(]
But this time I got it.

Mike Connor

My Feedback: (5)

I didn't figure out these equations but persistent in finding them.