Sand Baby (oz10531)

About this Plan

Sand Baby. Free flight glider model, designed for 'fixed towline' flying at the beach.

Quote: "Fun and games at the beach, in the park, open field or just anyplace that one can tow up a plane - flown much like a kite, this is Free Flight gliding at its very best. Sand Baby, by Tony Shennan.

The Spitfire zooms to gain height, then whips over in a screaming dive to swoop low across the beach. From the opposite direction, a Messerschmitt Bf-109 turns to meet the attack, diving out of the sun. In an instant, the pilot of the Spitfire sees his opponent and, though blinded by the sun, does the only thing possible to avoid a collision. He climbs his machine almost vertically, stalls and as the Spit falls off on one wing, allows it to gain speed in the dive to tail his opponent. A hit! The Bf-109 loses part of its tail and acknowledging defeat, makes a hurried forced landing on the beach amid a shower of fine sand.

Something out of the Battle of Britain? No, just two boys flying fixed towline semi-scale gliders on a beach in Sydney, circa 1969, 29 years after that epic battle.

The 'hit' was the sharp wing of the Spitfire cleaving the 6 ft long crepe paper streamer trailed by his opponent. To many modelers, the art of fixed tow-line flying will be a mystery but, we assure you, to learn is to take up a really enjoyable model ing pastime.

Flashback. In these days of plastics, fiberglass, styrene and hardwood, it may seem a retrograde step to look back to the days of balsawood and homemade cement made from acetone and celluloid from old car side curtains. Yet, I cannot help but think that they were more pleasant hobby days when compared to the present. Leisure meant that. Aeromodeling was a relaxation in the true sense of the word.

Ahl! Me! Well, in those early days of my aeromodeling, life, I lived at Brighton-le-Sands in Sydney. They were war years and balsa was hard to come by. Rubber was unobtainable so we built gliders.

My cousins developed a type of fixed towline glider that would fly like a kite over the sloping beaches and sandhills of Brighton. These models originally resembled rubber-powered models of the 1930s, but after experimenting with wing and tail areas and weight, it was found that models could be made and flown that would resemble full size aircraft, flying fast sweeps from side to side across the beach, actually tacking crosswind.

The cord towline was vigorously pulled to give spectacular zooms, whip stalls, dives and then let out to allow the model to 'sweep' from side to side. At the end of each sweep, the model would weathercock, hover like a hawk; then a vigorous tug would bring the model zooming across the beach in a fast climb. The more docile types for be-ginners had greater wing area and 'kited' well in a steady breeze. The general rule was: The stronger the wind, the heavier the model.

The formula for design was a rough rule of thumb:

Length A = 2.
Span B = 3.
Tail plane span = 1/4 to 1/3 x B.
Fin = 1/6 x B.

Areas followed roughly the same proportions.

Having a small son, age five, I decided to initiate him into beach flying and built him a profile all-balsa 'Tony', of about 30 inch span. l got carried away with this and added too much weight in the finish, and the result is a model that needs a stiff breeze to keep it airborne. However, on a cord line, it surely behaves like a fighter! It takes a strong arm to keep it in the air.

Obviously I had tried to teach Peter with the wrong model, so I then built a tried-and-true standard three-footer cabin model that 'kites' well in light breezes. Peter can fly this on the lightest breeze, and it is strong enough to withstand a 20 knot breeze. Many innovations are possible. For instance, because of the large dihedral angles required, (1-1/2 in per ft of semi-span, minimum) models sometimes suffer damage when flown into the deck inverted. A single hinge mechanism with elastic band springloading solved the problem on high wing monoplanes.

The accompanying plan is of a 'three-footer' (actually 38 in span) called Sand Baby, a general-purpose fun model. The model should be flown where there is a good uphill prevailing wind, and it is recommended that it be flown over sand or long grass, not hard ground. Crash landings are frequent. The wire skids under the nose are necessary. The three attachment points for cord (strong kite thread is sufficient) are for windy, moderate and calm conditions (front to rear).

Balance point is nose down slightly when the model is held at the wing tips, one-third from the TE. On windy days, always start with excess plasticene on the nose, and progressively remove until the model 'trims -out' to the breeze. If a sudden strong gust comes up, let out line..."

Sand Baby, MAN, September 1974.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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