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The designer and original manufacturer of
the Mustang II kit, Bob Bushby, is the one who published the procedure, which
is to protect the leading edge with masking tape to avoid scratches and tap on
the outer leading edge with a rubber (or other soft) mallet repeatedly until a
measurable rounding (or flattening) occurs. This is done carefully and slowly, a
little bit at a time. The wing on
the Mustang II is thin and has a fairly sharp leading edge, which makes the
onset of a stall relatively sudden, compared to a Piper or RV wing. A little rounding of the outer leading
edge will delay the separation of airflow, leading to a lower stall speed. Of course, a more rounded leading edge
has more drag and causes a slight decrease in top end speed. One must seek a careful compromise. I am willing to sacrifice a couple of
knots of speed for a plane that breaks straight ahead on stall. If I had built the wings perfectly, I am
sure that I would not have this problem.
There is probably a slight difference in the twist (washout) or dihedral
between the wings. The fix is
pretty easy, all things considered.
The wing drop was much less severe on the second flight after an initial
round of flattening. I worked on
the right outer leading edge some more this weekend and expect to see it nearly
perfect on the next flight. This is
why they call these airplanes EXPERIMENTAL.
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bob Perkinson
Sent: Tuesday, March 31, 2009 5:59
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Was; Video of
First Flight - Mustang II Now: HOW DO THER DO THAT
Bob
Not knowing how the Mustang wing is built I am curious as to how you are
changing the leading edge airfoil? Could you give a little more detail,
or post a link to an explanation of this procedure.
Curious Minds Want to Know
Bob Perkinson
Bill,
I came a little faster on my second
landing (second flight) and greased it on. I am using the fix published
by the Mustang II designer, Bob Bushby, in an early newsletter, which is to make the leading edge of the outer 1/3 of the wing that drops
- more round, i.e. not as sharp.
This allows the air to flow over the leading edge more easily at higher angles
of attack without separating from the wing and lets the wing keep flying
longer. After my initial re-work effort, the right wing drop at stall was
much less severe on the second flight and the plane more stable leading up to
the stall. The right wing still drops first, so I plan to continue
rounding the outer leading edge of my right wing per Bob Bushby’s method
until both wings stall at the same time.
The radiator and oil cooler are located
between the engine and the firewall, much like the Powersport installation http://powersportaviation.com/rv-6a_n225ps.htm
Here is a link to my engine installation
before the baffling was installed that forced all air to pass through the
radiator and oil cooler before exiting the engine compartment. http://www.eaa1246.org/big_photo.asp?id=Turbo%2Ejpg
Bob
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