Mixes
The essence of all
spectacular and tight maneuvering lies in
mixing. Naturally a programmable radio is
required for this kind of functionality.
Below are a couple:
Elevator
- Flap mixing
Probably the most popular mix is elevator
- flap mixing for those 6 foot loops and
tight cornering maneuvers. The actual
setting up of this type of functionality
depends on the make of radio used, so
consult your computer radio's manual or
your local hobbyshop for more information
on this.
The basic
theory behind this is that when you pull
up elevator the elevator goes up, hence
less lift from the tail surface than from
the wing, meaning that the tail sinks
below the wing. Now similarly, when your
flaps go down, this causes more lift
created by the wing than from the tail,
hence the wing lifts above the tail.
Combine these two and the elevator sinks
while the flaps lift and voila, a much
tighter loop. However, this also adds a
certain amount of drag, meaning more
throttle is required to keep the speed up.
Most often
elevator - flap mixing is acheived by
having two seperate aileron servos,
meaning that the ailerons can function as
flaps as well, called flaperons, so
technically in this case it's called
elevator - flaperon mixing.
Spoileron
mixing (AKA Fall out the sky button)
Spoilers generally act as air-brakes and
are used to lose height or speed without
picking up speed. Spoilerons are simply a
two servo aileron setup using the
ailerons as flaps as well, except that
the flaps go up instead of down. The up-going
ailerons cause less lift to be created by
the wing as well as adding more drag,
slowing the model down and making it lose
height quickly.
Spoilerons
are often used on funfliers to lose
height or speed quickly, on landing to
prevent bouncing or in spot-landing to
suddenly lose height and land when over
the spot. In 3D flight spoilerons can be
used to alter the aerodynamic properties
of a wing, resulting in all kinds of
outrageous maneuvers.
Power
curve
This is some essential
theory on extreme aerodynamics where the
wing has essentially stalled, and the
model is simply in the air utilising a
kite effect and thrust from the engine.
Fox Models XTC Control setup:
Elevator: Minimum 50mm either way
Elevator-flap mixing optional, 30 - 40% Exponential
Rudder: Minimum 50mm either way
No mixing, 30 - 40% Exponential
Ailerons: Minimum 50mm either way
Elevator-flap mixing optional, 30 - 40% Exponential
To experiment with this is
relatively simple: at a safe height, with
the engine on idle, slow the model down
to a stall attitude and add a little
power, the model should simply continue
forward with a slightly nose-high
attitude. The wing has started to stall
but the line of thrust is pushing the
model upward and forward, but with little
lift coming from the wing the model
simply continues forward.
This is a very critical
attitude for a model to be in, it can
easily go wrong and the model could stall,
however with practise one can learn to
fly the model at this speed, resulting in
those ultra-slow nose-high landings and
even in the slightest breeze it is
possible to hover in the same place.
Be very careful when flying
on the power-curve, it is easy to push
the model beyond it's stall with too
little power on and take the model home
in kit form again.
Harrier
The Harrier is an extreme
version of the power-curve flight in
which the model flies in a straight line
at an angle of 45 degrees to the
direction of flight.
Fox Models XTC Control setup:
Elevator: Minimum 50mm either way
No mixing, 30 - 40% Exponential
Rudder: Minimum 50mm either way
No mixing, 30 - 40% Exponential
Ailerons: Minimum 50mm either way
30 - 40% Exponential
Spoilerons on a switch, both ailerons up 40mm
This mode of flight utilises
spoilerons. Spoilerons are essentially
the ailerons of the model set up as flaps
but both ailerons going up when the
spoilerons are activated.
Start by slowing the model
down (at a safe height), engine on idle,
then a quick input of up elevator to an
angle of 45 degrees, throttle open to
about half-throttle and flip the
spoileron switch. The model should start
to float along in this mode. Using the
elevator, try to keep it at an angle of
about 45 degrees while using the rudder
to steer it around. Also learn to use the
throttle to gain or lose height while
flying on this mode. If you get
into trouble open the throttle and switch
off the spoilerons!
With practise it is possible
to steer the model around quite
accurately. Do a few circuits in this
mode and become aquainted with what
happens when it all goes wrong before
practising the Harrier lower down.
The Harrier looks most
spectacular as a low pass at walking
speed and it might even be possible to
land the model from this mode (with
practice).
Prophang
The Prophang is one of the
more difficult maneuvers to master, but
once you get it right it is probably one
of the most spectacular. The trick is to
fly along slowly then pull to vertical,
let the speed bleed off and open the
throttle to keep the model in a
stationary vertical position.
Keeping the model in a
vertical position requires a lot of work
with throttle, rudder and elevator and a
little aileron, the torque from the motor
tends to make the model start torque
rolling. Practice this at a safe height
and once you can hold your model in a
stable prophang and be able to fly out of
the prophang without losing any height,
you can slowly start practicing at a
lower and lower height.
[Insert image]
A good prophang requires
enough power to prophang at about two-thirds
throttle, allowing enough power to be
able to climb vertical out of a prophang.
Ideally, equip your Fox Models XTC with a
reliable engine such as the OS .46 FX and
a tuned pipe of your preference.
Torque
roll
The torque
roll is simply an extention of the
prophang. Once you've mastered the
prophang and can do a stable and
controlled prophang, you can move on to
the torque-roll. This is probably one of
the most difficult maneuvers to master
and requires a lot of practice at a safe
height.
Generally,
when in a prohang a certain amount of
aileron input is required, this is due to
the torque of the engine causing the
model to start rolling to the left. First
try letting the torque of the engine
start the roll, add some left aileron if
necessary to get the model slowly rolling
to the left while in a stationary
vertical position. It will still be
necessary to keep the model in the
vertical using inputs of rudder and
elevator.
Once the
model has rolled and the bottom of the
model is towards you, things get a little
more difficult, with the rudder being
reversed. A simple rule here is to give
left rudder if the left wing(wing to your
left) drops or right rudder if the right
wing drops (simply put, rudder toward the
wing that drops).
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