Elfe S-3 (oz14138)

About this Plan

Elfe S-3 Soarer. Radio control scale model sailplane. Wingspan 10 ft. Scale is 1/5.

Note only two main fuselage formers are shown on the plan. Quote: "Fiberglass fuselage available from Model Plans Service, Tustin, Cal."

Direct submission to Outerzone.

Update 19/10/2022: Added 2 articles, in German, thanks to Hans Toniolo. It seems this plan appeared in several magazines.

Quote (google-translated from the German): "Elf S-3, an R/C scale glider by F Meier and B Huber.

The Elfe gliders from the workshop of A Neukom, Neuhausen, have been known in Switzerland for a long time. In professional circles, the Elfe S-3 caused a stir at the 1968 World Championships in Poland, when the three starting Elfs were represented in the top 6 places in the standard class, with the American A Smith becoming world champion in an Elfe. The relatively small distribution of these aircraft can be explained by the limited capacity of A Neukom's 2- to 3-man operation.

The Elfe S-3 is a high-performance glider with a wingspan of 15 m, built according to the OSTIV regulations (Organization scientifique et technique international du vol ä voile). It is a high-wing monoplane with a conventional tail, comparable to the Phoebus, the Libelle or the 15 m Diamant.

The construction of the Elfe differs from that of the competing aircraft insofar as it is largely a wooden construction. The wing consists of a 9 m long center section and two 3 m long outer wings. The wing shell is a plywood-balsa sandwich construction, the spar consists of a high-strength aluminum alloy. The fuselage is a shell construction in sandwich construction, with the front part being made of plastic.

The story of the model Elfe: At TELAVES we were already dealing with a predecessor of the Elfe S-3 in 1962, unfortunately the flight characteristics of this model were poor because we had chosen a wing depth that was too small and a wing loading that was too large.

Interest in the Elfe was then rekindled when the author was able to help with the static calculations for the approval of the original Elfe. However, we didn't think about a model version because the effort involved in building the fuselage seemed too great. A conventional construction is practically impossible, manufacturing the fuselage shell from plastic (GRP) is possible, but requires a lot of effort.

At this point, Franz Meier asked me about the documentation for the Elfe, and we immediately took the opportunity to build the plane in a Franz Meier/TELAVES joint effort, as this meant the risk could be shared. In addition, the development accelerated insofar as several types with different profiles and with and without ailerons and airbrakes were built at the same time.

Franz made an original [mould] out of maple for the fuselage, from which a negative was then made. The production of the fuselage shells could then be started in this negative. At the same time, the wings were constructed, namely a wing with the profile FM-1-68 without airbrakes and ailerons by Franz Meier, a wing with airbrakes and ailerons and the NACA 6412 wing profile by L Steinbrecher, the first prototype being by B Huber senior was built with the latter wing. The wing area (and also the HLW area) were slightly increased compared to the original (wing chord t approx. 10% larger), firstly so that the critical Re number range could be shifted towards lower speeds and the wing loading could be reduced. The Elfe is scaled down exactly to scale at 1:5.

Construction: The Elfe is a demanding aircraft, also in terms of construction effort, but does not pose too many problems for the average model builder..."

Supplementary file notes

Article 1 (Aero-Revue 3/1970).
Article 2 (FMT?).

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