note of warning was posted from an RCU member about a problem
with the CG location given in the instructions. The published
CG is at 36% of mean aerodynamic chord and he found the aircraft
was unmanageable. If 36% corresponds to the 3-3/4" back
from the top wing LE center line, as per the manual, then we
wanted to investigate what went wrong.
can get squirrelly if the CG is too far aft or if the incidences
are wrong. It sounded like we should start out with a CG forward
of the manufacturer's recommendation. It appeared that our calculations
were correct, assuming the dimensions are correct, and, we wanted
it balanced at 25% average mean cord. Many skilled pilots will
fly a ship balanced at 33% to 35% AMC, but, it can be a real
surprise at times, especially if the plane has a heavy wing
loading. This CG is not recommended for initial test flights.
to our findings, we now feel that the correct starting point
for the CG for test flying is 2-7/8" (not 3-3/4) back from
the LE of the top wing. The 3-3/4" CG in the manual appears
to be for extreme performance once you are familiar with the
bipe and have advanced flying skills. We brought this to the
attention of the U.S. distributor for World Models, Airborne
Fai Chan from AirBorne Models reported the following:
checked with the factory on their flying test record, they did
have the prototype tested at 3 3/4 in. CG. Not sure if the test
pilot had very skillful hands or they have added some off record
nose weight. I went through the calculations and I agreed that
the CG is too far back. I think 3 in. from leading edge of top
wing is about right. Please try this and let me know if it works."
Battery and Safe Balanced Charging:
For the ultimate in Lithium safety and longevity, I'll be using
a BalancePro HD Lithium system from FMA Direct. The BalancePro
HD 3200mAh R/C Aircraft Pack and BalancePro HD 6s Discharge
Protection Module provide discharge protection for each cell
during flight. You simply cannot over-discharge the pack and
the Discharge Protection Module provides an early warning by
pulsing the motor so you have sufficient time to land without
a dead stick.
charging, the BalancePro HD 6s 10amp LiPo Charger not only balances
each cell on every charge but can charge at a 3C rate for a
quick 20 minute charge!
will be recharging my Lithium pack in the plane. For these smaller
glow conversions, especially Bipes, it is often easiest to install
the battery at the beginning of the flying day, recharge it
in the plane, and fly it several times during the day at the
field or at an event.
the past, this was a dangerous scenario when using a Lithium
pack and I would not recommend it. The BalancePro HD system
eliminates this danger because it cannot over-charge a pack
and it cannot get the wrong cell count! The BalancePro HD product
line completely protects every cell in the pack.
Above is a typical interconnect diagram of the BalancePro HD
Lithium Power Solution. The ESC control line is routed through
the DPM so it can pulse the motor for an early warning of pack
depletion to aid in a proper landing before cutting off the
motor power. Note that the On/Off switch assembly would go in-line
with the UBEC output to the receiver.
is a layout diagram in both block and picture form. It shows
the component inter-connections except for the On/Off switch
assembly that is inserted between the Rx. pack (or UBEC) and
the spare receiver channel.
can mount the components using either Velcro or servo tape.
I typically mount my On/Off switch so that ON faces the front
toward the motor. The left area where the UBEC resides will
be covered by the servo tray. The flight pack will side by the
receiver up front behind the firewall.
M5 v2 receiver using a white antenna wire so I routed it through
the bottom of the fuselage and taped it back to the tail. Sometimes,
if the fuselage is sufficiently long, you can run the wire through
a plastic tube and keep it inside the fuselage.
first rough tested the CG by laying the pack on the outside
of the fuselage. It looked near perfect to where the 6-cell
BalancePro HD pack would only fit inside without modifications.
This was a good start. I removed the bottom wing which required
unscrewing 3 screws.
lining the top of the fuselage inside with IMPAD foam from FMA
Direct, I was able to insert the BalancePro HD 6s 3200mAh pack
into position. It was almost secure without any additional foam
blocks to hold it.
I decided to move the BalancePro HD 6s DPM to the other side
next to the ESC to make routing the wires easier. It also allowed
me to create an access hatch so I can connect the BalancePro
HD pack to the DPM from outside the plane when the lower wing
pack can then be recharged inside the plane by disconnecting
the DPM and using the 12" BalancePro HD Extension Cable
to the charger.
can also easily connect the Dean's Ultra plugs from the DPM
to the ESC to arm the plane once I am at the flying station.
This access may not be needed but I decided to try it. The optional
LED/Spkr Module was mounted outside the plane so that I can
hear the DPM warning for pack depletion in addition to feeling
the motor pulsing. In other applications, I have been able to
hear the audible alert from a considerable distance.
My hatch was created with scrap plywood and a toothpick. I sealed
some of the cut covering with clear tape.
the wings was even easier than I had expected it to be. The
incidence templates and well fitting ARF parts made the assembly
a snap. This is usually a time intensive task of measuring incidences.
first step was to mount the bottom wing using a single screw
and washer into a pre-mounted t-nut. Next, the upper wing braces
are mounted and then the wing is positioned in place and held
by the incidence templates. Since the proper position is revealed
against the fuselage, it was an easy process to drill four holes
and screw the upper wing braces to the fuselage sides. The last
step is to attach the outer wing cabane on each side. I drilled
the holes through both the cabane and wing holder while the
incidence template was in place. I then removed the template
to secure the cabane with the supplied screws, washers, and
nuts. The other side was assembled in a similar fashion.
had two spare metal braces left over that I couldn't figure
out where they were needed. I saw no reference to them in the
manual but I had the tiny screws and nuts in my kit to mount
the braces. Another RCU member building the same ARF had a newer
manual and showed me where to mount the braces. I'll have to
assume that it was a modification and it took a while for the
manual to catch up.
upper to lower aileron linkages were supplied in the kit and
the ailerons have pre-positioned pin holes for perfect alignment
of the control horns.