Anderson Greenwood AG 14 (oz15307)

About this Plan

Anderson Greenwood Model 14. Radio control scale model, for electric power. Twin-boom pusher layout.

Quote: "A semi scale, 51 inch model designed for direct drive 500 Buggy motor or a modified Mini Olympus gearbox and two 400 motors. Anderson Greenwood 14, by Robin Fowler.

I came across the Anderson Greenwood Model 14 in a book of Paul Matt drawings, lent to me by a fellow club member and I had an instant liking. I was soon cutting another piece from my roll of tracing paper and pinning it to the drawing board. As l scaled off the dimensions and translated them onto paper at a suitable size I admired the lines of this small aircraft. The pusher configuration with the engine nestled into the space at the rear of the fuselage pod appealed, as did the twin boom and tricycle undercarriage. Here was a nice little package of model potential.

The original had a span of 34 ft 7, a length overall of 22 ft and a wing chord of only 42.5 in, This would have to be 'adjusted' in the interests of a viable model and the flaps, which took up the first 55 in of the control surfaces outboard of the booms, which would be added in to the available aileron length, thus reducing the aileron throws required. These were the only deviations I proposed to make at the outset, but in the event, a mis-measurement of my own drawing resulted in my bending up the main undercarriage legs so that they were too long by about an inch, thus increasing ground clearance.

I decided this was no had thing, apart froin the slight added weight, as I was not sure what power I would be using. I had drawn the AG14 up to use a 500 bum motor on six cells, but I had recently taken two 400s linked to a single Mini Olympus gearbox out of a.nother model and this would fit into the airframe ideally. The downside of this installation however, would be that I may have to use a larger than scale prop, but now that I had the added ground clearance, this ought not to present an insurmountable obstacle.

One further modification from scale arose early on. The wing section, which should have been NACA 4418, would be translated into a flat-bottomed section of similar thickness for ease of building.

Structure: The main concern I had was for torsional rigidity for the wing root areas that would have to carry stresses from elevator control movements delivered to them by the booms. The booms themselves could be made very strong by using Cyparis for top and bottom with sixteenth ply sides. A little heavy perhaps. but the booms were of small cross sectional area and I doubted if even solid balsa (with grooves cut out to take elevator snake and aerial conduit), could stand up to the loads - especially in landing.

The wing roots would be fully skinned with medium hard balsa with Cyparis for top and bottom spars webbed on both sides with 1/32 ply. An early decision was to have the model basically of one piece, but to have wings outboard of the booms removable. This then required building in brass flat rods positioned vertically for rigidity in the outer ends of the root section locating into a tube in the corrresponding ends of the outer wing sections.

The fuselage pod would be hung from the wing by liteply sides and a liteply floor provided to carry the battery pack, servos and receiver. I would clad this with ordinary builder's foam to sand to the shape required; which would be tricky to achieve by balsa sheet. Balsa sheeting is never a process I relish as my efforts normally land up showing every longitudinal joint. Maybe I should use more sandpaper and a different wood glue, but then why bother? The foam solution's only drawbacks lie in its ability to spread itself thinly over a wide area in the event of a sudden impact with something hard, and disappear altogether on contact with cellulose thinners. Since this model was going to be finished in silver Solarfilm I would just have to make sure I didn't apply too much heat with the iron or I would undo any good I managed to do with the sanding block.

Building: First to get attention was the fuselage pod and the four bits of liteply, which interlock to create the basis for further construction. These were soon glued together and setting while I bent up the undercarriage wire. Every time I set to with wire firmly in the vice and vigorous application of the iron persuader, the racket broadcasts the fact that I still haven't bought myself the wire bender I tell myself would really be a good idea for the next model. Such are promises!

The saddle clamps were quite easily made from some scraps of brass sheet cut to shape, then laid across the vice with a gap between the jaws about half as wide again as the wire to be clamped. A bit of said wire is then laid across and hammered down into the gap and in seconds the clamp is ready for drilling..."

Direct submission to Outerzone.

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