DH53 Hummingbird (oz15573)

About this Plan

DH53 Hummingbird. Radio control scale model, for electric power with Speed 400 motor. Wingspan 45 in.

Quote: "A conventionally built 45 in span Speed 400 powered near-scale model from the Golden Era for 4 function R/C. DH53 Hummingbird, by Duncan Barker.

Background: I first became acquainted with the full-size aircraft during a visit to Old Warden in the late seventies after having become aware of the type via the book 'de Havilland - The Golden Years'. which provided the design information. First thoughts at that time were around a model spanning about 1.8 metres for a .40 4-stroke. However, due to interest in various other projects it did not materialise.

More recently, largely due to the water logged state of our club site in the autumn and winter months making flying IC powered models unpleasant if not impossible, I decided to enter the low cost end of electric flight.

Having got a feel for electric via two electric gliders. a 400 powered sports model, and reading relevant magazine articles. I felt ready to attempt designing a small electric scale model. The Hummingbird was already in mind, I had sufficient information to hand, and so far as I am aware, it is a type not previously modelled.

Description: The model is designed at 12.5% scale. At this size it fits fully rigged into most family cars. Construction is based on the full-size with concessions to practical modelability where appropriate. Wings are separate panels located to the fuselage by short pegs and a rubber band. The compression struts are functional, taking the flying loads and setting the dihedral.

Hitec HS81 servos fit into each wing. Closed loops are used for rudder and elevator. Access to rudder and elevator servos, receiver and battery is via a hatch in the fuselage bottom.

The Graupner Speed 400/FG 2.33:1 turns a 10 x 6 folding propeller. A fixed blade propeller is more scale like, but the first landing resulted in a fractured gearbox casing. A Schulze 25A speed controller fits behind the motor, its BEC output provides sufficient current to drive the four H581 servos and a 7 channel Micron receiver. Air enters the engine/controller compartment via holes in the cowl and dummy cylinders, passes through former FL exiting through the cockpit opening. The top cowling detaches providing access to the motor and speed controller.

Tail Pieces: Build the tail surfaces over the plan and sand to shape. Make elevator and rudder horns and epoxy in place. Elevator and rudder are hinged with Mylar.

Wings: Mark the rib positions on the main spars and dry fit the ribs. Pin down trailing edge, 1/8 square lower rear spar, lower aileron spar, and main spar with ribs dry fitted packing up the main spar with scrap 1/8 sheet. Line everything up and glue. Add wing tips, upper rear spar, upper aileron spar and leading edge. Remove from the board and cut out the ailerons. Face the front of the aileron with 0.4 mm ply. The rear wing spars after removal of the ailerons are not faced, the covering material is brought over from top to bottom.

Make the aileron horns and epoxy them in place. Fit the aileron servos, temporarily hinge the ailerons with masking tape, and make up the control linkages. Ailerons are hinged with the covering material. Aileron servos are finally fitted prior to covering.

Fuselage: Initial assembly is done with the sides pinned upside down over the plan. Threading a piece of piano wire of similar diameter to the wing pegs through the front peg holes helps with alignment. Dry fit F1 and F2. When everything is square, add cyano. Bring the rear fuselage together at F5, glue this former in place, then bring together the rear end making sure the sides extend beyond the last uprights to provide a slot for the fin post..."

DH53 Hummingbird from R/C Model World, December 2001.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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