Avro 534 Baby (oz7503)

About this Plan

Avro 534 Baby. Scale model for radio control. For 20-30 size engines and 4 function RC. Scale is 1/7.

Quote: "A 1/7th scale, 44 in wing span, three function model of the World Record beating baby biplane. Designed by Don Luck.

Roy Chadwick might have had the modeller In mind when he designed the full-size Avro runabout. Ideal for an upright model engine - Don Luck made the best use of the quiet running of an unsilenced O.S. 20 four-stroke - simple but pleasant lines and a colour scheme that reverses the Henry Ford dictum, what more could you wish for?

Specification
AVRO 534 ''BABY" G-AUCQ (G-EACQ)
Scale 1/7th - 14.3%
Wing Span - 44ins
Weight - 3lbs
Engine - 0.19 - 0.26cu.ins. (0S20FS in prototype)
Propeller - 11 x 4ins
Radio - Fleet XP/FM Micro Fix, 270MAh battery and three Heel FPS 18 servos (There is room for standard servos)

Don Luck starts his article: If you have built a conventional WWI biplane, or similar, go straight to 'Flying' and 'Notes'. In other words, the construction is traditional and shouldn't hold any surprises to the reasonably experienced scale modeller. For those of you who prefer a few comments, here are Don's building notes.

Fuselage: Cut out and pre-assemble 1/8 in plywood engine mount/firewall F2. Glue left and right 1/4 in balsa doublers to 0.8mm ply fuselage sides.

Build fuselage (1/4 in sq longerons) crutch over plan view - steam or 'crease inside' to achieve severe curvage at tail and firewall. Fit formers F5, F9a and 1/4in sq cross pieces. Fit pre-assembled F2/engine mount plus F1a.

Add left and right fuselage sides, rear longerons, all cross pieces and side pieces - fit ply formers UC1 and UC2. When completely dry. remove from building board and complete fuselage top with rear formers, stringers and 0.4mm ply cockpit coaming. (Fit only the F1 ply component at this stage.)

Install 12swg cabane and 10swg piano wire undercarriage, stitch to ply supports with button thread, then soak with glue. Solder the three tin plate top wing fixings in place. Fit 0.4mm ply coaming between F2 and F4. Fit 3/32 in fuel tank platform across fuselage on 1/4 in sq supports positioned to suit tank used (4ozs SLEC tank on prototype). NB Tank is positioned on starboard side thus leaving space for RX on port. Build removable engine cowling from 0.8mm ply formers, 1/4in sq balsa frame and 0.4mm ply skin. Fit radiator wire mesh with soldered tinplate crankshaft surround, trim to fit within F1 cut-out, glue to Fla. Fit 0.4mm ply cover (same shape as Fl but slightly smaller inside cut-out).

Top wing: 1/8 in Lite ply centre, on 1.5mm ply, (with lightening holes) pinned down as a guide for spars - do not glue to ribs yet and do not pre-drill wing bolt holes yet.

Lay down spars, fit ribs etc., build the outer wing panels to dihedral break only. When dry prop up wing tips 1-1/4 in, glue in dihedral braces and centre section ply plate into one unit adding remaining ribs.

Position wing in place, measuring and centring before drilling the three 6BA clearance wing bolt holes. Drill 1/16 in dia into wing strut blocks and glue in 1/16 in split pins (underneath!) - see note on struts on alternative methods of fixing.

Bottom wing: Build as per top wing, noting centre section variation (NB Split pins strut fixings on top). Add fuselage sub ribs to undersurface centre section.

Wing struts. Set up and fit wings, check both are warp free and cut hard balsa struts to length and glue in 1/16 in split pins, either fore and aft, with one piece wire fixing, or tap 10BA one of a pair of split pins and bolt on.

Tailplane/rudder: Normal construction - cover before fitting horns and installation. Note grain direction to avoid possible warping - as the 'all flying' rudder hinge area is limited use heavy duty hinges ('Beckey' large scale nylon with No12 ally knitting needle as hinge used on prototype) or use large 'Kavan' type. Remove hinge pins - interleave hinges and use one piece 20swg wire hinge pin and push up into fin.

Covering: As preferred, but keep as light as possible e.g. white 'Fibafilm' is very good but colour is not 'solid' - prototype is a compromise by Fibafilm on undersurfaces and Solarfilm on top surfaces. Lettering with Solartrim. Nose and cowlings, tissue, dope and painted back to windscreen.

Flying: Take off is typical of a narrow track early biplane with non-steerable tail skid - direct into wind and steady increase in engine revs, holding in up and not over-controlling the swing - lift off occurs when elevator is levelled - throttled back to just under half power. The flight pattern is quite predictable, rudder is powerful and rates should be adjusted to 1 in each way - (full rate is required for low speed landing and ground handling) elevator is also sensitive and 1/2in each way is adequate although at tickover landing speed full up trim (or switching out rates) is required to flare and three-point without 'arriving'.

Notes: The target weight of 3 lbs or less, giving up to 11 oz/ sq ft wing loading, is easily achieved despite generous wood sizes and scale number of ribs (56!) no extra nose weight was necessary with the O.S. 2OFS engine to balance within calculated CG, rudder and elevator are closed loop control as per full size. A pilot is a prerequisite, he fills the cockpit and lends scale realism - cockpit instrumentation is black scratch board with dials scored in. The engine exhaust was extended to exit on the 'scale' side and three more dummy aluminium stubs were bolted to the removable cowl - a remote glow socket is also installed to simplify start-up and choke/needle valve and fuel fill are accessible outside - (the cowl is rather small and fiddly to fit with the engine running!) working vents/louvres (bent card) ensure adequate cooling.

Scale outline is accurate according to documentation and photos from Queensland Museum where this Bert Hinkler record breaker is displayed. (The 1977 Aeroplane three view was wrong! which George Cull subsequently confirmed when he visited Oz). .."

Direct submission to Outerzone.

Update 02/06/2016: article pages, text & pics added, thanks to RFJ.

Supplementary file notes

Article.

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