Koechlin 1909 (oz14972)

About this Plan

Koechlin 1909. Free flight scale model for rubber power. Peanut scale.

Note for full article, see Santos Dumont 19 bis (oz14886)

Quote (google-translated from the German): "Construction of the Koechlin 1909 model: This model has very favorable dimensions for a peanut model. The plan is also very suitable as a template for larger model aircraft (RC) with combustion engines or other types of propulsion. The number of ribs on the surface is correctly maintained.

First, suitable material must be obtained for building the model. Good solid balsa wood, not too heavy, all thicknesses specified, especially solid wood for the 4 torso straps. Grass cane, the long thin beige stalks that grow on the edge of the forest, approx 1 mm dia, approx 60 cm long, is required for the landing gear and rudder frame.

For the pilot and rudder we need insulation or foam, ideally 'light blue, goofmate', possibly also Styrofoam, both of which have to be hollowed out. For steel wire we need the dia 0.2 0.3 0.5 and 0.8 mm. The thinnest silver-grey silk threads are needed for bracing, nylon and polyamide are also suitable. Some silver-grey paper is still missing for the engine cover and aluminum pipe dia 2 and 3 mm for the exhaust and cooling line.

The fuselage is usually started with the 2 side ladders. This is best done on a copy of the plan, which is mounted on a softwood base. The steel pins, preferably with heads, are easy to press into. Once the crossbars have been glued in, using UHU-hard as for all balsa bonds, the hull is carefully sanded smooth and flush with a sanding block.

We wrap the fuselage in both directions with thin silk thread, which is stapled in the corners with a little UHU-hart. The hull, which has now become very torsionally stiff, is now covered with brown 12 g/m2 Japanese paper (use Glutofix). After drying, the hull should be moistened. A day later, the hull can be painted twice with 50% diluted stretch varnish. If you only have white paper, you can water the paper with a water-soluble stain (eg mahogany).

If you can, buy the beautiful spoked wheels (see appendix for source) or try to make them yourself. The spoke wheels from old master E. Fillon, France, only weigh 0.05 g each! Steel wire with balsa wood or grass cane must be glued with UHU-plus for 5 minutes.

The ribs of the wings are made in the rib block between the largest and smallest template (liner plate) and two 0.8 mm steel wires. The rib package is cut all around with a sharp razor blade down to the sheet metal template, then cut off roughly flush with the balsa knife and sanded completely with the sanding block. All other details can be found in the plan.

The end of the fuselage and the tailplane should be guided particularly easily. You can sand the cross sections thinner or use light balsa wood for the horizontal stabilizer. It is clear that a precision scale must be there, perhaps you have to make it yourself, because it is needed to check the weight of the model or to check the specific weight of balsa boards. The tail unit should only be carefully sprayed lightly on both sides with water mist (do not use tension varnish).

Now we prepare the rubber strand. The cross section of the rubber depends on the weight of the model. For example, if it weighs 8 g, 4 mm2 (4 threads 1 x 1) may be sufficient; with a cell weight of around 12 g, up to 6 mm2 is required..."

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