Electric Angle, The

Model Airplane News, Apr 2004 by Sarpolus, Dick

Easy-to-build, Speed 400 sport flyer with acrobatic performance

I built my first electric-powered aircraft 28 years ago. Technology at that time sure wasn't what it is today; there was no such thing as an ESC or BEC, the cell count needed for power was high, and I didn't even have a field charger, I have watched the progress of electric models over the years and am amazed at the new electric models' level of performance. After reading many magazine articles and Bob Aberle's book, "Getting Started in Backyard Flying," I was hooked.

I wanted to start small, keep it simple and keep the cost down. But it had to be acrobatic. A direct-drive Speed 400 motor from Graupner seemed so basic and cost so little that I decided to try that first. For the supplies, I went to Bob and Dave Peru at Balsa Products.

I'm all for traditional airplane styling, but I didn't want to go the "stick construction" route. The model is very conventional and has an almost flat-bottom airfoil and generous control surfaces. Overall, I borrowed the styling from some larger designs of mine. I kept the motor installation out in the open to permit easy power-system changes. The battery pack slides into the fuselage below the motor so the pack can quickly be replaced for charging. I use a standard 8-cell, 600mAh Ni-Cd battery pack and a 6V Speed 400 motor. A 2.3:1 geared Speed 400 motor and a Speed 480 are also possibilities. Landing gear isn't needed, and a NiMH battery may save some weight. I'm not a light builder, and the plane could have come out a bit lighter. I used miniservos, but smaller micros are available, and they'd save even more weight.

The Electric Angle gives great small-plane aerobatic fun, and you can fly it in smaller areas. As a builder, you have some choices; they depend on how much you want to spend and the performance you want. Flight-testing showed that with the direct-drive Speed 400, the plane is lively enough for some acrobatic flying. Although there was not a huge difference in performance, the geared motor and larger prop do provide some additional thrust. The direct-drive Speed 480 provides the best performance.

CONSTRUCTION

Building the Electric Angle is straightforward and doesn't involve anything tricky or difficult. I like to start with the wing, and it can be built flat on the building surface. I built my wing flat, but adding an inch or so of dihedral might be worthwhile. Pin the lower spar and bottom trailing-edge sheet to the building bench, and then glue the ribs and false ribs into place. After the glue has dried, glue the top spar, the top trailing-edge sheet and the leading edge into place. Next add the center-section sheeting, the plywood wing-mounting tab and the wingtips. The angled spar webbing between the rib locations is a bit of a pain to cut to size and glue into place, but it greatly enhances the wing's rigidity. You could glue vertical-grain-balsa shear webbing into place before you install the top spar. Build the ailerons, and then install the aileron linkage and the servo in the center of the wing.

Begin the fuselage construction by cutting the 3/32-inch balsa sides and their doublers out of 1/16-inch plywood. I cut lightening holes in the plywood doublers and in the rear of the fuselage sides. To assemble the fuselage sides, first install the three plywood bulkheads, and then pull together the fuselage sides at the rear while you're installing the rear bulkheads. Add the fuselage top sheeting next, and bevel the edges of the cockpit-area pieces so they will fit together properly. I left the rear bottom sheeting off until after I had installed the rudder and elevator pushrods. You won't need a rudder for basic flying, but I felt it was worth the weight of the additional servo for the increased maneuverability.

Assemble the tail surfaces over a flat surface, and then fit the wing to the fuselage and bolt them together. Then add the horizontal stabilizer and vertical fin and align them with the wing. After you've installed the tail surfaces, screw the rudder and elevator servos into place, install the control horns, and make the wire pushrods. I covered my model with transparent MonoKote and also used it for the hinges.

Install the 1/8-inch plywood motor-mount plate, and notch it to fit your motor. I used two nylon zip-ties to hold the motor in place. I originally made an opening in the fuselage bulkhead below the motor to allow easy battery-pack access, but because I had to move the battery pack farther aft for balance, I decided to make the pack accessible through the wing-saddle opening. A hatch on the lower forward fuselage bottom allows access to the battery connectors for charging.

I fly the plane off grass, and hand-launching it is easy. I made a removable wire landing gear that I'm sure would work fine off a very smooth surface, but I haven't yet tried it. Grass is just fine with me.

Balsa Products (732) 634-6131; balsapr.com.

Graupner; distributed by Hobby Lobby Intl. (615) 373-1444; hobbylobby.com.