Flying Boat (oz16950)

About this Plan

Flying Boat. Free flight sport model. Wingspan 36 in.

Direct submission to Outerzone.

Quote: "Unknown. Air Model Design Competition. Flying Boats."

Update 20/8/2026: Added article, thanks to Normand Bisson.

Quote: "Air Model Design Competition. Flying Boats.

Have you tried your hand at designing a 'dream' ship? Com'on, it's easy, join the fun, enter now.

Ever watch someone hand-launch a Flying Boat when your main interest was in a water take-off? Disappointing, wasn't it? The other extreme is when the Flying Boat refuses to become airborne and scoots around and around on the water.

These examples point up the major problem with a Flying Boat, which is water taxiing stability. A standard ROG model practically jumps off. But a Flying Boat has a gradual build-up of speed. This means that the ROG model offsets the torque of the engine by the action of the wing, almost from the start. A Flying Boat depends on its flotation gear to take care of the torque at the start of the flight. Therefore, to achieve water taxiing stability we must control the torque with the flotation gear we use.

Torque effect depresses the left wing float much deeper than the right. This means that when the model begins to move the greater drag of the left float will produce a left taxiing circle.

The effect of taxiing to the left will be to expose the dihedral of the right wing to the airflow; producing greater lift on the right side. To counteract this increase of lift on the right side, the left float will have to carry a still greater load, which means that the left float will have to ride deeper in the water. This automatically increases its drag and tightens the turning radius. Under such circumstances the model has a poor chance to take off.

Knowing what happens if we let the model develop a left turn while taxiing, we should design the model so that it will tend to move in a straight course. It is not as easy as it sounds since we are working in two mediums, air and water. There may be many different solutions which will prove satisfactory, but we confine our discussions to the design on page 41.

The most important reason for this design is the layout of the flotation system: main float in front, and two small ones on the stabilizer. This arrangement has proven itself on ROW models even though we may not see it on big-size Flying Boats because it provides torque control with the needed fore and aft stability. During the take-off period, while the model is gradually lifting off the water, the rear floats still provide torque control. If the floats were in front, they would lift off the water before the wing started to provide torque control. Fore-and-aft stability is essential during the take-off because the model should hold a horizontal position. If it bobs and tips, it may build up too much drag and retard the take-off.

Another factor to consider in designing Flying Boats or ROW models is the vertical position of the CG. A boat is designed with the CG below the center of bouyancy. This provides automatic water stability..."

Supplementary file notes

Article.
Page 41, drawing, enlarged.

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