AIRCO DH2

Model Airplane News, Jul 2005 by Johnson, David

A CLASSIC WW I PUSHER BIPLANE

IN LATE 1915, A YOUNG BRITISH DESIGNER NAMED GEOFFREY DE HAVILLAND developed a worthy adversary for the Fokker E.lll Eindecker that was wreaking havoc on the Allied air services. Although somewhat slow, the Airco DH2 was extremely maneuverable. Because the RAF had not yet perfected a synchronized machine-gun system that could fire between the propeller blades, he chose a pusher configuration for the DH2 so the guns could be fired straight ahead. The DH2 brought the "Fokker scourge" to an end. My model has the, same maneuverability as the original and will certainly provide great slow-flying action! Let's get started on the model.

CONSTRUCTION

All of the tail surfaces have laminated outer edges made of four strips of 1/32x 1/8-inch balsa. I soaked them in water and wrapped them around lite-ply forms. Coat each strip with yellow wood glue and create a strip four layers deep. Pull the lamination around a plywood form, and hold it firmly in place with pins. After a couple of days, remove the laminations from the forms, and trim the forms to length. Place them over the plans, and add the inner ribs. The control horns should be installed after the surfaces have been covered and painted.

The wings are straightforward, and all of the wing panels are essentially the same. Cut the ribs to shape, and glue them to the leading and trailing edges. Cut the spars a little over length and install them in the rib notches. The one-piece wingtips are formed by laminating two layers of 1/32-inch balsa to form a bow shape that matches the ribs. Cut them to shape and install them after the wings have been assembled. To build the ailerons, I cut the ribs off behind the spar and then cut the aileron rib sections to length after they had been removed from the wing.

The upper and lower wings are built in the same way, but the lower panels' spars extend 1/8-inch out from the root rib and are plugged into the fuselage sides. Glue the upper panels securely to the center section with ¾-inch dihedral under each tip. Don't add the aileron horns until after the parts have been covered and painted. Glue small triangular pads to the wing spars for attachment points for the wing struts. Small pinholes in the pads accept the alignment pins that protrude from the ends of the wing struts.

BUILDING THE FUSELAGE

Build each side frame over the plans; then assemble the sides with the crosspieces placed in between them. Glue the top formers into place, and then add the 1/32-inch balsa rear decking. Cut small openings in the sheeting for the front cabane struts.

I made the nose piece by carving a Styrofoam block and then covering it with two layers of 1-ounce fiberglass cloth and epoxy resin. Cut out the cockpit opening, and trim the nose piece to fit the fuselage. Once you're satisfied with the fit, remove the foam. Glue the outer shell into place after the model has been painted.

Use very hard, 1/8-inch-square balsa to make the tail booms. You can also make them out of 1/8-inch dowels if you sand them down a bit. Before you cover the model, install the motor mounts.

POWER SYSTEM AND RADIO GEAR

The power system is uncomplicated and provides plenty of power for the DH2.1 used a Graupner Speed 280 Race motor and a 4:1 gearbox to turn an 11x4.7 APC Slow Flyer propeller. To power the motor, 1 used a GWS 10A ESC and a Kokam 2-cell, 74OmAh battery pack. I used three GWS Pico servos and a Futaba receiver and transmitter.

FINAL ASSEMBLY

I covered my model with Peck-Polymers Japanese tissue and shrunk out the wrinkles with water sprayed with an atomizer. I then applied three coats of Sig Lite-Cote dope. I cut openings for the servos and glued them into place. I applied a very light coat of Sig Olive Drab dope to all of the green areas and the exposed portions of the servos. Once the dope has dried, install the battery tray, and glue on the nose piece.

Cut out four sets of front and rear interI plane struts; then cut out a pair of front and rear cabane struts. Sand them all to shape, and stain or paint them as you like. Insert the alignment pins into each end of the interplane struts and into the tops of the cabane struts so that only Me inch protrudes.

Epoxy the cabane struts to the fuselage as shown on the side view; they should be vertical when seen from the front. Place the top wing on top of the cabane struts, and push the lower wing panels into position. If everything is square and the wings are aligned, glue the upper wing to the cabane struts. To glue the lower wing panels into place, apply glue only to the strut stubs that key into the fuselage. Install the interplane struts in pairs working outboard, and use only a small drop of CA to attach the ends.

It's easiest to rig the wings before you install the tail booms. In an X-pattern, attach the cross-bracing threads between the center pairs of interplane struts. Start at the rear lower wing root spar, and pull the thread in between the root rib and the fuselage; then glue it to the wing's underside. Cross up to the top of the middle strut, and continue until you get back to the top of the cabane struts where you will tie off the thread. Now repeat the process, starting at the lower leading edge.