Sean Plummer's 2.3m Extra 330 Build Thread - Page 2
Install a steerable tailwheel, assembly. A tailwheel is not supplied with the kit. I chose a Graphtech http://www.graphtechrc.com/ all carbon assembly, it is very light weight. The fuselage already has the plywood mount installed. Simply drill through the skin into the plywood and use the supplied wood screws to secure the assembly. Connect the steering springs to the Pull-Pull rudder horn.
The stabs are next. This model uses plug in elevators with
dual servos, the tube and anti-rotation pin is already installed. Check
alignment as per the instructions. The Elevator servos are designed to be
installed inside each stab half. The installed servo mounts are designed for
standard servos, I have decided to use the New
Futaba Digital S9451 servo
http://www.futaba-rc.com/servos/futm0211.html. This
servo weighs 1.98oz. and has 120oz torque.
The openings in the stab root rib need to be opened up a little to install the
servos. I used a file wrapped with adhesive backed sand paper to accomplish
this. Check the fit of the servo into the servo mount, adjust as necessary.
Remove the servo and drill a hole into the "Servo Rib" so the servo lead can exit. Using string and a wheel collar thread the string through the rib and back out.
Tie the string to the servo connector and pull through the rib.
Mount the servo into the servo mount using
servo screws. I used
DuBro heavy duty servo arms for the elevators. Note:
Turn the servo arm sideways as shown while installing the servo.
The supplied elevator control horns are now glued into position as per the instructions. Alignment jigs are fabricated from scrap plywood and insure precise and equal control horn placement. This step is critical to produce a perfect tracking model. Secure jig/horn into position with masking tape while the epoxy cures. Note: Use slow cure epoxy, and clean all parts with alcohol prior to gluing.
The elevators are pre-hinged and simply need to installed using the steel wire as per the instructions. Install 4-40 pushrod/clevis hardware and check that elevators operate properly with NO Binding through the entire throw range. Note: Binding can cause very large current from the receiver battery resulting in a crash due to a dead receiver battery. The removable elevator halves are connected to the model using allen cap screws, drill through the stab into the aluminium joiner and use a Tap to thread the tube as per the instructions. Repeat on the other elevator half.
Next the Aileron servos, The wings use a removable "hatch"
for the aileron servos. The model can use 1 or 2 servos per aileron, the kit
includes servo mounts for standard size servos.
I have decided to use a single New
Futaba Digital S9152 servo
http://www.futaba-rc.com/servos/futm0211.html for each
Aileron. This servo weighs 2.6oz. and has 277oz torque. Using this single High
Power servo will reduce weight and provide ample power for the ailerons.
The aileron servo horn is mounted like the elevators, and an alignment jig is
fabricated to ensure equal aileron throw. I fabricated the servo mount using
hardwood and plywood, use Slow Cure epoxy to glue the parts together. The large
futaba servo arm provided with the servo, is perfect for this application.
Screw the servo plate to the wing as per the
instructions.
With all basic components completed it is now time to fit
the motor battery tray. Assemble the model and mark the C/G position on the
wing. Place the motor battery into the model and move until the proper C/G is
achieved. Try to position the battery as close to the centerine of the model as
possible to reduce potential coupling issues. In the case of the 2.3m Extra, the
batteries ended up protrudng in to the Motor dome and across the Wing tube. In
this case the battery tray is positioned so the batteries cross the centerline
of the model from front to back.
Fabricate a strong battery tray from, 1/4" "lite ply". This is a really
important step as the batteries will represent about 20% of the models weight. A
very strong battery tray will ensure the batteries will not shift during flight
and also "Protect" them in the event of a crash. I have seen batteries ejected
and destroyed from crash impact. If the batteries are properly mounted they
often sustain no damage, as the airframe absorbs the impact in the event of a
crash. Here are the first pics:
The battery tray is now finished by adding velcro straps
prior to gluing. Use a scroll saw or razor saw to cut slots for the velcro
straps. Be sure to smooth any sharp edges that may cut the velcro over time.
Note: 2 holes are drilled directly over the landing gear to acces the landing
gear mounting
screws
The tray is glued to the "Wing Tube" and the landing gear formers. Prepare gussets using balsa, use the aluminium wing tube as a sanding block by applying adhesive sand paper directly to the wing tube. carefully rough-up the wing tube and landing gear formers prior to gluing. Use Slow epoxy to glue the Battery Tray and gussets into position. Note: Install the wing joiner into the tube while the tray is glued to ensure a strong and proper shaped bond.
Install vecro to floor of the battery tray. Also install the primary battery
straps so they wrap around the wing tube and over the Batteries totally securing
them to the airframe as shown in the pics. Also install velcro to both the top
and bottom of the batteries allowing the velcro to "Grip" from the tray and the
straps.
