Fournier RF-1 (oz15509)

About this Plan

Fournier RF-1. Simple rubber profile scale model. Wingspan 470 mm.

This plan appeared in the book "Flugmodelle Bauen und Einfliegen" by Werner Thies & Willi Rolf, 1975.

Direct submission to Outerzone.

Quote (google-translated): "Rubber motor model 'Fournier RF-1': We have now made a series of hand-held gliders from paper, cardboard and balsa and now want to build a motor model powered by rubber threads. For this purpose, a semi-lifelike replica of the well-known Fournier RF-1 motor glider was selected.

First, we transfer the components to the balsa boards using carbon paper or tracing paper (Fig. 70, see Plate VI, at the end of the volume). This small rubber motor model follows the concept known from the all-balsa gliders. As here, there is a flat fuselage, which in this case has an elongated recess to accommodate the rubber threads. This design of a rubber motor model is the simplest option. The wings and tail unit will also pose little difficulty in making them. However, it must be ensured that the profile curvature of both wing halves is even and that the attachment to the fuselage is clean and flawless. For this purpose we use the angle template shown (under no circumstances should these corners be glued!).

Now, first of all, something should be said about the drive. The most important thing here is the propeller, which was made from balsa in the original model. A suitably cut block was then worked on to create an attractively shaped propeller. It is easier for a beginner to look for a suitable plastic propeller in model shops, preferably with the corresponding propeller bearing. This saves some effort and avoids complications.

In any case, however, it is important to ensure that the propeller's pull direction is directed slightly downwards, also known as the 'dive'. This ensures that the model does not stall in powered flight, ie it does not climb too steeply upwards and then immediately tips over again. A little celluloid at the front and back of the propeller bearing, or thin aluminum sheet if necessary, together with a glass bead ensure a durable and at the same time smooth bearing. The fuselage head is reinforced somewhat by pieces of balsa glued to the sides.

Bending the steel wire, as is necessary for making the main landing gear and the tail (which also serves as a support for the rubber strand), is certainly difficult during construction. But it can be done with a small pair of flat-nose pliers that have a good grip! You also need side cutters or sharp pliers to cut the wire.

Wheels from an old toy can be used as wheels, as long as they are not too heavy. Once the wheels are attached, they are secured against falling off by applying a little synthetic resin glue (only this type sticks to steel wire). The wire is attached to the fuselage in the same way. Now you can paint the model as usual and add the contours of the tail units and ailerons, as well as the landing flaps. The usual colored decorations and a cleanly outlined cabin shape also increase the joy of a well-built model.

Four threads with a cross-section of 1 x 1 mm or two with a cross-section of 1 x 2 mm serve as the rubber motor. As can be seen in Fig. 70, they are attached to the propeller bearing and the other to the rear vertical wire. To prevent the rubber from constricting too much and possibly tearing, a piece of insulating tubing is pulled over it. The rubber threads can only be knotted together to the correct length once they have been placed around the rear bearing. If this is not done, the knot must be untied again!

With the rubber motor attached, the model's center of gravity is now supported and balanced. This may result in tail-heavy behavior. We then know that lead still has to be attached to the top of the fuselage until the flight position is achieved. A little trick with our model (although this means that the model loses some of its naturalness) is to move the position of the main impeller forward by bending the strut. If necessary, a heavier wheel must also be attached in addition to this measure! This then acts like a trim attached to the front.

Like all motor models, the RF-1 is first flown in a gliding flight like a glider model. All measures for achieving a smooth gliding flight, as known from the previous explanations and not least from personal experience, apply. It should be remembered that the high resistance of the stationary propeller means that the gliding flight is relatively steep. Only when the gliding flight is OK should you give the propeller around 50 turns. Then you start the model with the fuselage tilted slightly upwards, because in this direction it is most likely to climb away.

The propeller should of course be turned in such a way that it pulls as it runs down. As obvious as this may sound, you often see beginners turning it in the wrong direction. They are very shocked when, after releasing the propeller at takeoff, the model comes shooting backwards towards them with strange flight behavior, but does not make a usable flight. Gradually, if everything is OK, you can increase the number of revolutions up to 250. However, the rubber threads must be well rubbed with a special lubricant, as described in the 'Rubber Motor' chapter.

A complete success is when the RF-1 model performs flights of up to 15 seconds."

Supplementary file notes

Article.

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