we strongly suggest that for initial test flights, the model be
balanced within the 25% to 27% CG range. At low rates, this CG
location should provide a manageable flight envelope and,
depending upon your flying abilities, might turn out to be where
you want to the fly the airplane, at least for awhile until you're
comfortable with it. As you gain experience and confidence, you
can then begin moving the CG location back, in small increments.
However, be careful when doing this. Moving the CG back can
make the airplane behave totally different in the air, so do not be
tempted to make large adjustments all at once - just sneak up
on it.
As said earlier, the further back the CG location, the more
sensitive the elevator inputs will become. Experienced R/C pilots,
used to flying high-performance giant scale aerobatic aircraft,
know that using exponential inputs to the flying surfaces (ailerons,
elevators, and rudder) of their models "dampens" these control
inputs in and around their neutral positions, producing a much
more manageable airplane when not performing the more wilder
flight maneuvers. In our opinion, exponential inputs for both the
suggested low and high rates, are virtually mandatory on the Edge
540T. As the CG is moved aft, exponential input becomes even
more critical.
The use of exponential becomes even more
important when using a 6-volt airborne battery system! This is
because a 6-volt system produces substantially quicker servo
response and without exponential, a less than experienced pilot
stands a real chance of "getting behind the curve" in terms of
control inputs.
For reference, we have been flying our own Edge 540T ARF
models with a 29% Center of Gravity. This CG location allows us
to perform virtually any maneuver imaginable, including Waterfalls,
Torque Rolls, beautiful Flat Spins, Knife Edge - normal and high
alpha types - and awesome Blenders. So for us, the 29% CG
location, along with the programmed exponential inputs we've
used, has worked very well. Whatever CG location you finally
arrive at as your own personnel optimum, will depend upon your
piloting abilities.
When establishing the CG, the airplane should be complete with
everything installed, as it would be for flight, with the fuel tank
empty. Start the process by deciding which CG location you want
to begin with. For example, let's say you want to start with a 25%
CG. As shown, this translates to 4.453", measured back from the
very front of the leading edge of either the wingtips or the wing root
ribs, next to the fuselage. Use small strips of light tack tape to
mark this measurement directly onto the two wing panels. With
another person to help, pick the airplane up off its wheels at the
wingtips with your finger directly at the tape strip. What you want
to see is the fuselage suspended perfectly level - not nose down,
not tail down - level. If it's obvious that the airplane is not level,
then the balance of the airplane, at the desired 25% CG location,
must be adjusted to achieve a level fuselage. There are a variety
of things that can be done to do this.
We routed the receiver antenna out of the fuselage and up to the
top of the fin. This positioning takes the antenna out of parallel with
the pull-pull cables and the servo extensions, providing a better
radio signal/link.
Mounting The Propeller & Spinner:
The F.P.E. 6.8 twin cylinder engine uses a six-bolt mount for the
propeller. The six bolts provided with the engine for prop mounting
are #8-32. The engine also includes a front bolt mounting plate
with the bolt pattern already drilled and with a prop hub-centering
stand-off. This means that the front bolt mount can also serve as
a drill guide for the required six holes in the hub of the propeller -
very convenient!
We used a .166" dia. drill (this is a #19 drill index bit) and a drill
press to make the six required bolt clearance holes in the hub of
our Biela 27 x 10 props. Just press the bolt hub in place and drill
one of the holes all the way through the prop. Temporarily install a
bolt through the prop hub and the prop, in the hole just drilled, and
move to the next hole. Continue in this manner until all six holes
are accurately drilled. The prop is now ready for mounting to the
engine.
Earlier in this manual we made some specific 4" diameter spinner
recommendations. Choose the spinner assembly that you wish to
use on your Edge and install it according to the manufacturer's
instructions.
Center of Gravity (CG):
Establishing the correct Center of Gravity (CG) on your Edge 540T
ARF is an extremely important issue. The fore and aft Center of
Gravity dictates how your model will react to pitch (elevator) inputs,
as well as having a direct effect on how the model flies in less than
normal attitudes, such as knife edge flight, flat spins, etc.
Obviously, the further aft the CG location, the more sensitive the
airplane becomes to elevator inputs. Moving the CG too far aft can
literally make the airplane all but unflyable and prone to every kind
stall condition imaginable.
The CG locations provided in this section are based on the Mean
Aerodynamic Cord (MAC) of the wing. In the case of the Edge
540T ARF wing, the Mean Aerodynamic Cord measures 17.8125".
This MAC measurement is the base number used for calculating
the CG locations shown in the diagram below. Because the Edge
540T planform configuration has a straight leading edge, the CG
measurements shown can be measured and used at either the
wing root location or at the wingtip location.
Because of the
model's size and weight, it may be more convenient to establish
and mark the CG at both wingtips, using another person to lift the
model at the opposite wingtip.
In terms of where you want to establish your own CG location for
your Edge, we can offer some information that will help you. First,
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