The platform that Avigator is based on is a Sig Kadet Senior. It was selected
for it's large wing area (allowing large payload), it's forgiving flying characteristics
(large, slow, stable trainer), and because several others have succesfully electrified
this model.
A helicopter platform was briefly considered, but was deemed unsuitable for this task. A
fixed wing platform provides greater payload-range, has simpler controls, and uses a
cheaper radio system.
A word of warning to those who may follow - this is not a kit for beginners. It requires
much more shaping and cutting of parts than other kits, and the assembly instructions are
poor.
Mounting the motor/gearbox proved challenging. Attempts were first made to bolt the gearbox directly to the firewall, since it has bolt holes for this. Prop clearance was a problem. In the end a wood crossmember was bolted between the ends of the supplied motor mounts, and the gearbox was bolted to this piece, with the motor above the motor mounts.
The motor controller resides in the first compartment, where the fuel tank would usually go. There is a small hole in the bottom of the second compartment to pass the wires to the motor battery, and to let cooling air pass out. The edges of this hole were reinforced with spruce crossmembers, since the battery will pull the wires in a crash. Holes were cut in the firewall to let cooling air in.
Two dowels were attached to the lower fuselage, similar to the wing dowels, so that the motor battery can be mounted on the belly of the plane with rubber bands. This arrangement will hopefully allow the batteries to exit the plane gracefully in the event of a crash. This will also allow the batteries to receive plenty of cooling air.
To reduce weight, the fuselage sides and top were sheeted with 1/16" balsa instead of 3/32". The 5/32" firewall was replaced with a 1/8" one, and the large triangular supports behind the firewall were replaced with 1/4" squares.
The rudder and elevator servos were mounted at the very rear of the payload compartment, and a separate nosewheel servo was mounted at the very front, in order to keep the pushrods out of the payload compartment. Crossbraces were added to the tail boom to support the pushrods.
Several hardwood cross-braces were added to the payload compartment for mounting of electronics. The rear servos, computers, comm board, compass, and multiplexing board are all mounted in the upper part of the compartment, with access through the wing saddle. The nosegear servo, batteries, receiver, power supply board, and tilt sensor are mounted in the lower part of the compartment, with access through two hatches in the bottom. A plywood frame joins the hard drive and 386 board into one assembly, which then screws to the fuselage.
A third row of windows was added, so that the payload is easier to see from outside. The new window frame was cut from 1/16" balsa.
Several of the modified components were cut from plywood or balsa using our T-Tech router. The AutoCAD drawings of these parts will be available on this page at a later date.
Back to Avigator
Revised 5/27/99