Scorpio. Radio control aerobatic slope soarer. For 2 or 3 function multi. Uses rolled plywood fuselage construction.
Quote: "Sorpio, by D Marquis.
FOR some years I have been attracted to slope soaring, one of the reasons being that I am able to take the whole family out for a day's enjoyment and indulge in flying my aeroplane at the same time in peace and quiet. I have the good fortune to live at the edge of the North Yorkshire Moors and could hardly wish for anything better in the way of good slopes.
My attraction began with a converted power model which, although it gave me the feel of soaring, was hardly satisfying and it did not really look like a glider. For that matter, neither do some of the Kippers that ably perform aerobatics, so the idea formed that it was time I built myself a model to fly and look like a sailplane but have something in hand to liven the monotony of continuous steady flight. Being a true Yorkshireman I thought about it for some time. If the basic design is sound then it will bear mulling over for a while, and if it survives this period then it must be alright. After all, thinking costs nowt.
A most important consideration in the designing of a model, of course, is in what wind strength it is to fly. For the Sunday flier it needs to be not all or nothing, but all and nothing in order to enjoy a good day out. Being beaten by a gale is one thing but it is most frustrating on a balmy afternoon having a model too heavy to fly.
These facts, together made me think about designing the impossible - the fly-in-a-gale, fully aerobatic, thermal soarer. Clearly an impossible task although not a bad thing to aim for, and as a regular flier the all-round model would allow me to dabble in a little of everything, whatever the conditions.
As I mentioned earlier, I would prefer the model to have a scale appearance. A reasonably high aspect ratio of say 12:1 would be desirable, besides looking better, the higher aspect ratio would increase the efficiency of the wing. To avoid tip stalling, that semi-mysterious term wash-out would have to be involved, but nowhere could I find a write-up to inform me just how much and why, so I let experience lend a guiding hand. More about this point later.
The wing section would be chosen for general all-round flying and simplicity of construction, and to this end a flat-bottomed section with a 12-1/2 percent thickness was utilised. The inclusion of ailerons was for two reasons. First because of the small amount of dihedral, they would be a help in steadying the model for landings and second, to be able to execute rolls without barrelling.
The tail unit, I thought, needed serious consideration. The points of interest to me evolved around three things. One, the fact that my models land on a plateau covered with heather - result, normal stabilisers are susceptible to damage. Two, if a tee-tail was employed to combat this, the stabiliser would have to be easily detachable, and three, how to set the correct angle for longitudinal dihedral. So it was that the flat plate type, all moving, knock-off stabiliser appeared on my model. This ensured the correct longitudinal alignment of wing and tail for maximum performance in flight, and also kept it out of the way when landing.
At the time the prototype was built, the price of balsa wood increased enough to make several of my colleagues and myself experiment with rolled plywood fuselages. We very soon discovered how simple, quick, and to the point, less expensive it could be. The construction was not as heavy as we had previously thought but was much tougher than conventional methods. To date, many pylon racers and 61 powered contest models in my club have been made with 1 mm. ply fuselages and flown successfully..."
Scorpio, RCM&E, May 1972.
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