Rhonsperber (oz15519)

About this Plan

Rhonsperber. Simple profile glider model. Wingspan 550 mm.

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

Direct submission to Outerzone.

Note see Ente (oz15512) for article (full chapter from the book).

Quote (google-translated): "Rhönsperber. The last of the small balsa gliders is again based on a large model. It is the 'Rhönsperber', which was designed in the early 1930s by the then most famous glider designer H Jacobs (Fig. 47, see Plate V, at the end of the volume). The experience gained up to that point in the field of gliding was largely utilized in the design of this aircraft model.

The fuselage of the fullsize Rhönsperber is made of a plywood tube that tapers slightly towards the back. The vertical fin grows harmoniously out of the fuselage and forms its end with the rudder. The horizontal tail unit is self-supporting. The gull wing, typical of many gliders of the time and reminiscent of a sailing seagull, is made up of a rectangle and a trapezoid in plan and has a wingspan of 15.3 m.

Considerable performance was achieved with the 'Rhönsperber' glider. Heinemann sailed from the Wasserkuppe to Brno (504 km). The famous glider pilot Hanna Reitsch spun from a height of 2475 m to 554 m in 2 minutes and 25 seconds with 42 revolutions.

The model is again largely true to the original; only the fuselage is designed as a flat fuselage for weight reasons and because it is easier. The construction hardly differs from that of the other models. Only the wing is a little more complex. It has a real profile; that is why we use 3 mm balsa wood for its construction.

After cutting out the two wing halves, the wing profile shown in the cross-section drawings is roughly pre-worked with a balsa plane or a sharp balsa knife and only then sanded with fine sandpaper. When it is correctly profiled, ie nicely rounded at the wing nose and tapering at the wing end, it is separated at the bends. The separation points are carefully sanded at the necessary angle and glued together with UHU-hard.

For this we absolutely need a 'slipway', which we can build with a few resources from a few small boards (Fig. 48). A strip of paper about 1 cm wide under the bends prevents the glider from sticking to the slipway and strengthens the bend considerably, especially if a similar strip is glued to the top. The horizontal and vertical stabilizers are cut from 1 mm balsa wood and glued to the fuselage. This too must be done very carefully. Any mistake, e.g. an incorrect setting angle of the horizontal stabilizer, leads to a deterioration in the flight characteristics.

The center of gravity of the finished model should be 16 mm behind the wing nose. We therefore attach enough lead to the nose of the fuselage until the model is supported and exactly level at this point. Because of its slightly higher weight, this model flies a little faster than the other gliders described so far. The higher flight speed makes it less sensitive and can be flown successfully even when there is not complete calm.

Note photo of completed model [main pic] is thanks to Simon Rogers.

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