DH53 Hummingbird (oz8757)

About this Plan

DH53 Hummingbird (Sylvia II). Scale model for CO2 power.

Scan from DBHL, cleanup by theshadow.

ref DBHL-6564.

Direct submission to Outerzone.

Update 28/3/2024: Added article, thanks to ilgk48. This is an extract from his full magazine scan on HPA see: hippocketaeronautics.com/hpa_plans/details.php?image_id=13234

Quote: "A real charmer and a proven flier on CO2 -how can you resist? Sylvia II. Ian Harwood's 5/6 in:1 ft DH 53.

THIS IS actually my third DH53 for CO2 power, developed over the last five years or so.

To my eye, the original Lympne prototypes with horizontal twin 750cc Douglas engine were better looking than subsequent versions for larger motors. Most of the published drawings are for various later machines but fortunately, the earliest three-view, published in Flight on the 27th September 1923, was reproduced in the book de Havillancl: the Golden Years. The same drawing, at reduced size, appeared in the October 1987 issue of Aeromodeller.

I chose to model the second machine at Lympne, named Sylvia II and numbered 12 in the competition. The other, number 8, was called Humming Bird and gave its name unofficially to the type as a whole.

Although there is nothing very complicated in the construction of the model, there are one or two slightly unusual points. To simulate the thin sheet ply fuselage skin, I used 1/80 in sheet balsa, obtainable in 15 x 2-1/2 in packs from Bollards, 54 Grosvenor Road, Tunbridge Wells, TN1 2AS. For the main structure I used 1/20 in sq balsa from SAMS, The Chapel, Roe Green, Sandon, Nr Royston, Herts, but the drawing shows 1/16 sq which should be chosen as light as possible. I find aliphatic glue best for most purposes, keeping cyano and epoxy for particular application. I also believe that card templates are the easiest way to duplicate identical shapes; and they ensure the exact placing of hole centres, such as wing dowel and undercarriage tube positions.

Fuselage: The fuselage assembly method is due to Bill Dennis and his Avro Avian Monoplane (oz2922). Pin down two lengths of 1/8 sheet along the inside edges of the longerons on the plan view and make up two sets of 1/16 spacers in between. Leave one set pinned in place and move the 1/8 jigging pieces to the outside edges of the longerons. Crack the sides at F3 and F8 and lay upside down on the plan between the jigs and the spacers. Check for squareness and glue sides to spacers. Add the second set of spacers before removing from the plan. Chamfer the sternpost uprights and join together before adding the 1/16 sq doublers aft of F8 and sanding to shape. Run in some liquid cyano along the cracks to consolidate the structure. Cover the rear curve with 1/80 in sheet, grain vertical to avoid caving-in. Fill the bottom triangular space aft of F'S with soft 1/16 sheet grain crosswise, to support the bamboo tailskid.

F1 is made from 1.5 mm ply. It is best at this stage to make up the motor mounting block with its ply facing, and drill the holes for the motor bolts at 15mm centres right through the block and Fl to ensure alignment. The four holes in F1 are for air circulation around the CO, tank, and the slot is for the feed-pipe. Before epoxying the 10 BA nuts, sand the rear face of F1 to allow the adhesive to key to the ply. Chamfer the edges of F1 to suit the fuselage outlines and epoxy in place, square and upright. Sidethrust can be better controlled with wedges later.

The 20 swg aluminium wing dowel tubes, embedded in a 1/16 balsa sandwich, aet as continuations of the spars across the fuselage. The front one also carries the undercarriage tube, which is not put in till later. Each tube lies between two lengths of 1/16 sq with a slot for the U/C tube at the bottom of the front sandwich. Epoxy each sandwich together and, when cured and trimmed to fit, set aside to harden, epoxy in place, locating with lengths of 20 swg piano wire through the holes already pierced in S2..."

Supplementary file notes

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