Donald (oz9615)

About this Plan

Donald. Radio control floatplane sport model. For .19 to .35 power with 3 functions.

Quote: "ALL full-size seaplanes, and by lack of imagination, all our models have a V-shaped hull and often a complex design rather difficult to build (Fig. 1). Before copying the full-scale shape, one has to ask why this shape? Is it only an effort to represent the full-size navy type boat hull ... stability? What stability? Perhaps for a hull type of sea boat, but surely not necessary for a twin float seaplane, sitting firmly on her two floats? Why not a simple, flat-bottomed hull, that would slide nicely on the water like a water ski? The only reason for this intricate shape is to soften the landing on the water. The hull comes in contact with the water in a progressive manner, first the edge of the V, then the sides and this acts like a shock absorber. With a flat bottom, a full-size seaplane would not survive a normal water touch down. Structural damage would take place at every landing (actually it is the same with a full-size land plane which could not land without shock absorbers).

Happily, our models are much, much stronger than full-size airplanes. They can survive severe punishment, cartwheeling, and so on, that would bend a full-size plane. It is the same with a model seaplane which can undergo a severe 'splash' without damage - so why bother with a V-shaped hull, let us try a flat-bottomed one - many advantages:
1. Building is so, so much easier.
2. Such a hull is much more efficient on the water. It will slide on the water with very little drag while a normal V-type hull will painfully plough its way through the water.

Of course, there are other reasons for a V-hull. It will have a better directional stability, and will be less prone to bounce and ricochet. We will be obliged to add small fins on our hull, and to prevent bouncing; we have only to come for landing without excessive speed, flaring gently.

Floats are easy to build in conventional structure but it is much better to cut them in styrofoam, since waterproofing is not a problem. Such flat bottom floats are very easy to build (see 'Donald' plan) they are cut in a block of styro-foam with two pairs of templates (Fig. 2). A first pair of templates are used for the side view but it is difficult to cut the step with a hot wire, it is better to cut it after with a sharp metal blade. Keeping the two parts of the styrofoam block, a second cut is made with the two other templates..."

Donald, RCM&E, July 1970.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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