FVA 13 - Olympia Jolle

In the spring of 1938, the FVA was asked to participate in the development of a unified glider to be flown by all participants at the 1940 Olympic Games, where gliding was scheduled as an Olympic discipline for the first time. Two experimental gliders were to be built for the time being and had to be completed by January 1, 1939. Because of the strong time and performance pressure, the FVA decided to build only the FVA-13 VI in Aachen and had the V2 built in parallel by FAG Darmstadt.

Herbert Kaulbach made the general design as well as in detail the construction of the fuselage with the control organs within the scope of his diploma thesis.

The following excerpts are taken from Herbert Kaulbach’s diploma thesis, which he did under Prof. Wieselsberger and made available to the FVA archive in the original.

“General guidelines”

The task is to design a sailplane that complies with the guidelines for the Olympic standard sailplane. The following briefly summarizes these guidelines as established by the Du Vol Sans Moteur Commission in 1938. According to the decisions of the International Olympic Committee, aerobatic competitions are not permitted within the framework of the Olympic Games. Taking into account the planned tender, which envisages target distance flights of 70-100km, a glider is to be considered which could be compared in terms of performance with the well-known glider type Rhön-Bussard. The Olympic standard glider need not be a high performance machine. In spite of the fact that there are numerous gliders available which meet these conditions, the commission has decided to create a new Olympic glider according to very specific criteria. All interested nations are to construct an Olympic glider according to prescribed conditions by February 1939. These gliders are to be demonstrated in Rome in February 1939. On this occasion a commission of engineers and one of pilots will select the best machine and designate it as the future Olympic machine.

The guidelines established by the CVSM to be followed in the construction of the aircraft are as follows:

  • Wingspan: 15m
  • Uniformity of the material: steel, plywood and pine.
  • The machine should be able to maintain itself floating on the water for some time.
  • Camber brakes that limit the maximum speed in a dive to 200 km/h.
  • The pilot’s seat shall be set up assuming a height of 1.80 m.
  • Fuselage with skid without landing gear
  • Driver’s seat with back parachute
  • External width of the driver’s cabin 600 mm
  • Maximum rigging weight 160 kg
  • Payload 95 kg. If necessary, the payload must be increased to 95 kg by attaching weights. The safe attachment of payload weights must therefore be taken into account at the design stage.

The above-mentioned guidelines and the short time available for the development, design and construction of the aircraft make it seem expedient not to create anything fundamentally new, but to provide for a model based on an already existing one, which above all has good aeronautical characteristics. In a comparative flight, the decisive factor in determining whether a machine becomes an Olympic standard machine will be not so much its flight performance as its aeronautical characteristics. It therefore seems pointless to me to waste time in the design process by considering which means, choice of special airfoils, or the like will achieve the best performance. Rather, I consider it one of the basic requirements to examine an existing model with, as I said, recognized good flight characteristics from all points of view, i.e., first, to create a mathematically flawless base and, second, to find the simplest and most practical construction. Since the machine may have to be reproduced by all the nations involved, it is essential to have a perfect set of drawings with parts lists, figures, subdivision into subassemblies, etc. The price per machine should be calculated for series production. The price per machine should amount to about RM 2,500 for series production.

This price also presupposes a design based on extreme simplicity. Experience has shown that a shouldered-deck design entails considerable additional work as a result of the complicated fuselage-wing transition, where awkward creations cannot be avoided, especially since the use of Elektron or Dural light metal, which could otherwise be used to create these transitions cheaply in series production, is not permissible due to condition 2. In this case, the simplest construction method is the high-wing design, since the neck can be formed in such a way that the wing fits tightly everywhere.

Since the FVA-9 glider has the recognized good flight characteristics mentioned above, the design is based on this model with respect to wing profiles, wing outline and elevation of the control surfaces relative to each other. However, in contrast to the FVA-9, which is strutted, the new design provides for a cantilever wing suspension. Since the aircraft was to have good maneuverability above all, the performance calculations called for it to achieve at least the turning speed of the FVA-9 and, if possible, to come close to that of the FVA-10. Further construction details will follow in the design specification.

The design provides for an empty weight of 120 kg. This additional weight compared to the FVA-9 (95kg) is due to the cantilever design and the more stringent strength requirements imposed by the Commission for the Olympic standard gliders. To keep the landing speed within usual limits, 45 km/h, the wing loading was kept below 15 kg/m², and chosen to G/F = 14.8 kg/m². This results in an area of F = 14.5 m².

In order to obtain mathematically correct documentation, a model was made and measured in the wind tunnel of the Aerodynamic Institute in Aachen.

In order to be able to carry out flawless investigations with regard to workshop production, a mockup was built which makes it possible to practically determine the most favorable type of planking of the fuselage front section and to design the installation of the pilot’s seat as favorably as possible and is also of essential importance for questions of the installation of control organs, etc. The outline of the wing is to be the same as that of the already built model FVA-9.

The outline of the wing is to be largely similar to that of the already completed FVA-9. In the center section, the wing outline is rectangular and decreases in a straight line toward the outside. The depth at the fuselage is 1.22 m and remains constant up to a distance of 2.75 m. The wing is tapered from 2.75 m upwards. From 2.75 m, the depth tapers until it becomes = 0.44 m at the end of the wing. The taper ratio is therefore 0.363. This ratio was given as the most favorable in a paper by Koning and Boelen. The wing tip is then rounded off by edge arches.”

In contrast to the FVA-9, on whose design the FVA-13 was based, the design provided for a cantilevered wing suspension. For assembly reasons, it was chosen to be asymmetrical, i.e., the left wing was connected to the fuselage but still protruded beyond it, so the right wing was connected to this protruding stub outside the fuselage. This trick saved one helper during rigging.

After construction, the “Olympia-Jolle” weighed 156 kg, and the payload was exactly 95 kg. The international commission selected the “Olympia-Meise” from DFS from the three designs received from Germany, so that the two FVA-13 VI and V2 remained in the club’s possession. They were destroyed during the war, as were other aircraft.

Since the 1940 Olympics did not take place due to the outbreak of war, the “Olympia-Meise” could also no longer fulfill its original purpose. However, it was built in large numbers at home and abroad before and after the war (in France under the designation 2000).