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
Good point, Dean. Also I would
presume the CL position on the wing could be affected by airspeed anc
could may be a factor as well - its all magic in any case {:>).
I am certain I also will never see such speeds in my 6A (at least not
intentionally), but I sure do want to taste some of that take off roll
acceleration and climb that Tracy has reported.
Ed
Ed Anderson
RV-6A N494BW Rotary
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