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A guide to flying with floats

Model Airplane News, Sep 2000 by Onorato, Jim

Get your feet wet and start having fun on the water

One of my most memorable RC moments (second only to my first solo flight) was the first time I flew off water. The plane was a Sig clipped-wing Cub powered by an Enya .46 4-stroke and outfitted with a pair of 30-inch Balsa USA floats. To say I was nervous would be a gross understatement. Fortunately, all went well, and apprehension proved to be for naught. That was 13 years ago, and I still look forward to springtime when my boat goes back into the water and the floatplanes get dusted off for another enjoyable season on the lake. As a matter of fact, 1 don't think I've ever taken the floats off of that Cub! It's usually the first one out each spring, and the exhilaration I get from that first water liftoff never seems to fade. I hope this article will inspire other RC'ers to try this exciting aspect of our hobby.

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So just which kinds of airplanes can you put on floats?just about any, I suspect, but some are better candidates than others. My favorite is the high-wing cabin-type such as a Cub or another tail-dragger. But hey; I've even seen a DC 3 on floats! The possibilities are endless. Compared with low-- wing types, high-wing models look realistic on floats and they are much less susceptible to water getting in at the wing saddle. They are also easier to adapt to floats because their main landing gear can often serve as the front strut for the floats.

FLOAT TYPES

A variety of commercially available floats are available in several sizes, and at least four different construction materials are used in their manufacture.

These include:

Conventional wooden kits that are built with lite-ply and balsa.

Precut foam-cores that must be covered with L64-inch ply or a somewhat thicker sheet balsa.

Ready-made molded-plastic floats.

Ready-made fiberglass floats.

Wooden floats can be covered with heat-shrink film or with fiberglass cloth and resin and then painted. The ready-made plastic or fiberglass floats are usually painted but can be left as is. The choice of floats really depends on how much work you want to do and how much you want to spend on floats.

A typical balsa-and-ply float is built upside-down on the building board in much the same way as you'd build a fuselage. Lite-ply formers and stringers make up the framework that is then sheeted with balsa or thin plywood. Lite-ply doublers are usually installed at the strut mounting points. In some cases, a hardwood spine runs the length of the float and allows the strut mounts to be located anywhere along the length of the float. This really simplifies matters when it comes to "hanging" the floats on your model.

Floats may have flat bottoms or vee bottoms. Vee-bottom floats track better but are less maneuverable and also produce more spray than flat-bottom floats. Flat-bottom floats are easier to build, but they don't look nearly as good as the more scale vee types.

INSTALLATION

When outfitting a plane with floats, the biggest challenge is in the placement and attachment of the floats to the fuselage. On many planes, the forward strut is attached to the fuselage just forward of the wing's LE, and the rear strut is attached to the fuselage just aft of the wing's TE. In any event, the fuselage must be reinforced at these attachment points. A piece of '-inch aircraft plywood installed under a former and strengthened with gussets will usually be sufficient. Unless you buy a kit that comes with floats specifically designed for your plane or you buy floats designed for a specific airplane, you are pretty much on your own when it comes to attaching them. For most models, float struts have to be custom made, and on all but scale models, they are usually made with steel music wire of various sizes.

On smaller planes-up to .40 size-formed-aluminum or molded-fiberglass landing gear can be used for the struts. This works best if the bottom of the fuselage is parallel to the model's datum line so the struts are the same length. If the struts have to be different, the chance of finding the exact size for the rear strut is usually pretty slim. If you use formed gear, they will usually be rigid enough to eliminate the need for diagonal bracing. Of course, you could make the rear strut out of steel wire, but that would look a little odd.

If all this seems confusing, not to worry: there is a relatively straightforward procedure that gives good results every time. But first, I'll cover a few basics to make this a little easier to follow.

In Figure 1, the point where the front strut is attached to the fuselage is point A. Point B is where the rear strut is attached to the fuselage. Points C and D are where the front and rear struts (respectively) are attached to the floats. The wire between points A and D is the diagonal brace. The members that go between the floats at points C and D are the crossbars (Figure 2).

The struts are formed in the shape of a trapezoid with the length of the top side equal to the width of the fuselage at the attachment points and the bottom side equal to the spread between the float centerlines. The crossbars that form the bottom of the trapezoid actually extend beyond the edges of the trapezoid to provide attachment points for the floats.

A guide to flying with floats

Model Airplane News, Sep 2000 by Onorato, Jim

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