Fred (oz4253)

About this Plan

Fred. Rubber scale model.

Quote: "A 33 in span rubber powered flying scale model designed for the Arden power unit.

FRED'S EXISTENCE WAS revealed long ago via the pages of the Aeromodeller annual 1968-69. A 1/72nd scale drawing of the Flying Runabout Experimental Design by Messrs Clutton and Sherry showed a delightfully pugnacious-looking light plane with a low aspect-ratio/constant chord wing using an undercambered Gottingen section, a largeish tailplane rather too close to the wing TE for (model) comfort, and a simple 'boxy' fuselage with semi-circular top decks front and rear.

I decided to build to a scale which would produce a model of about 36 in span, as the trim adjustments would not be too taxing for my limited skills in that direction. The only other scale model I'd ever built was an own-design S-4 Kania (oz2548) of some 2/3 this size, and this had shown that a reasonable size models could survive my rough handling, a much greater threat to my models than their return to terra firma.

Because of the short moment arm, a decision was made to produce movable control surfaces which could, in theory, provide washout in the mode of a crude flying wing via the ailerons, and a powerful stab section, (i.e. highly cambered), by means of the elevators. As the stabiliser angle was only to be settled after testing. I thought it likely that the variables of camber and incidence would give me considerable latitude when this stage was reached, and, if stability was still suspect, then as much up-aileron (on both sides) as was required would solve the problem.

Gears: Sharp eyed readers will probably note that a number of changes in the structure are visible. These were the result of correspondence with the designers of the full size FRED, and their great help concerning details. For one thing, thrust-lines on FRED replicas tended to vary a bit according to the power plants employed. As I'm very keen on the use of gear-boxes for scale models because they help to avoid excessively large props, two gear-boxes were built from old clock gears; then a casual visit to the local hobby store revealed the existence of a nicely made, pre-packaged unit with nice gears, prop and an instruction sheet which demonstrated that the manufacturer had more than a rubbing contact with model aircraft. This unit, (the Arden), had a 5:1 ratio gear. In other words, for one revolution of the rubber motor, the prop turned five times. It also offered the possibility of using other prop sizes, but data did state that it was suitable for models up to 26in. span. FRED's 33in. did seem rather reminiscent of my local council's rate increase by comparison with the Arden's recommend-ation, but the soundness of the unit's fabrication encouraged me to take the risk. After all, two other more conventional gear units had been produced and could be employed if required.

A 9-1/2 in dia plastic prop was bought as an alternative to the 7 in job in the Arden pack simply as an insurance against under-propping, a considerable snag with rubber scale as past experience had indicated. (Prop-swaps are easy on the Arden unit, by the way.)

I discovered that the Arden unit would fit very neatly into the nose block of the model; (a smaller FRED wouldn't have provided the required clearance), but the design now meant that the original intention of building a radial engine version wasn't feasible. The nose was modified to suit, and the motor-peg moved forward in anticipation of a reduced nose weight with the abandon-ment of the heavy brass gears.

Construction: Wings. These are three-piece, consisting of outboard panels and a centre section. It would be easier and lighter to make them as a single unit, but my intention was to allow for variations in dihedral by alternative wing-joiners with altered geometry. A knock-off system was planned, but a conventional 'banded-on' system can be used with slight alterations to the cabane unit.

Sliced ribs are employed as being more economical with balsa, and are much closer to scale. The original rib spacing is followed, but half-ribs are used rather than a sheeted leading edge to minimise weight.

Sliced ribs are very easy to cut. The sheet must be accurately marked to give constant depth, and a smooth template prepared. I always use a nose gusset at the leading edge for greater gluing area, and core template which, together with profile templates, allows the made-up ribs to be sanded as a block in the conventional manner.

Spars must be very accurately marked and cut as they act as an assembly jig into which the ribs are slotted. Main and rear spars should be matched for congruence by comparing the slots. With the three-piece wing, the wing-joiner boxes must now be built. They can be a loose fit front to rear on the joiners, but should be only 'easy' top to bottom..."

Quote: "Staying with the 1980s and the December 1981 edition of AEROMODELLER... there is one very nice scale rubber plan to post. This is TREVOR FAULKNER'S 'FRED'. The full size FRED 'Flying Runabout Experimental Design' by Messrs Clutton and Sherry appeared towards the end of the 1960s. Trevor' design uses the ARDEN pre packaged rubber power unit than on the market but I think no longer available. It had a 5:1 gear box and a tube into which the rubber motor was loaded. Winding was by a crank. But it would be very simple to adapt to the normal rubber setup. I suggest a propeller of about 11 inches and moving the rear rubber peg back one or two bays Raise it slightly to match up with the prop shaft. The plan for the 33 inch span model is to 1/5th scale and a very full construction article gives all the building and flying details."

Supplementary file notes

Article pages, text and pics.

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