I probably am
overpropped at static and low speed. I told Clark Lydick to build me
a speed prop. I figured that being overpropped on take-off doesnt matter
if you have lots of HP and can get off the ground in 1200 ft and climb
like a banshee anyway. I'll be sending the prop back for adjustment once I
get solid numbers, but I don't think I'll want him to cut it back
much.
john Slade
What sort of top speed, and cruise
speed do you expect? What would be common for an
O-360 powered
plane?
Cheers,
Rusty (wishing the RV airfoil wasn't
so draggy over 220
mph)
I used to think the same thing (draggy
airfoil) but I think the problem with RVs over 220 is related to
wing / tail / fuselage incidence. At 220 I get the
visual impression that I am in a dive during level
flight.
The early Citation jets used the same airfoil as
the lowly RV.
Tracy
Tracy,
As you known, the airflow over the
horizontal tail is such as to exert down force on the tail (Nose up) to
overcome the forward pitching movement of the CL of the wing
airfoil. I suspect that at the higher airspeeds the airflow over the
wing could be changed sufficiently that the tail surface might be
providing less downforce (nose up ) than required.
In otherwords the downforce on the horizontal stab is
sufficiently lessened that the nose lowers until the horizontal stab finds
a new equilibrium point at your higher airspeed. As nose goes down,
more of the upper surface of the horiz stab is exposed to the airflow
causing more down force/nose up until the new equilibrium is
reached. Just a
thought.
Ed
Ed
Not questioning anything you just
stated. Keep in mind also, that with the dynamic pressure increasing
as the square of the speed, the required angle of attack of the wing is
reduced and the nose goes down from that alone. I am not sure what
the CL shift is as the AOA decreases with increase in speed. Tracy
is seeing AS numbers that I will never see on my 9A.
Dean Van Winkle
RV-9A
13B