Akaflieg Stuttgart F-1 Fledermaus rudderless competition glider

[Avimimus]

I'm trying to figure out the control arrangement for this design. The F.1 Fledermaus was a pretty efficient sailplane design in 1933. As originally built it had only a horizontal tail-plane, with the vertical control surfaces moved out to the wingtips (which might also allow them to act as fences)? It seems like a pretty innovative design, and the provision of a conventional tail was apparently done only to please the judges in gliding competitions.

So far as I could gather, these wing tip stabilisers were all-moving and one source seemed to suggest they had some control over roll as well (although I have doubts about this due to the provision of conventional ailerons).

Unfortunately, I'm not a native German speaker and most of the references are in German.

Some info:
http://www.uni-stuttgart.de/akaflieg/projekte/die-flugzeuge/f-1-fledermaus/

P.S. By the way, it appears there aren't any 3-views of this design.

 

[Jemiba]

Re: Akaflieg Stuttgart F-1 Fledermaus control system?

From the linked site about the control system:
- Control around the vertical axis was accomplished by the wing end plates,
releasing the fuselage from torsion loads.
- The differential aileron control was completely buried (in the wing ?)
- For landing, the wing end plates could be moved outward simultaneously.

Interesting side note: For bailing out in the case of an emergency, the complete nose
could be jettisoned.

 

[Avimimus]

Re: Akaflieg Stuttgart F-1 Fledermaus control system?

Thanks - that helps a bit!

I wonder how the end-plates worked... being so far out on the wing tips one might expect them to perform more like drag-rudders than conventional rudders.

 

[Avimimus]

Re: Akaflieg Stuttgart F-1 Fledermaus control system?

Apparently the lack of a vertical stabiliser meant that fuselage weight could be reduced to about 25 kg (21 kg in some sources)... the additional vertical stabiliser may also have been added after a difficult landing (instead of only added at the request of competition judges).

Some more info:

"In order not to load the auxiliary spar, the ailerons (each 1.3 m2) are attached to the main spar. This has not increased their effectiveness, yet the steering forces have remained small. The hinging axis lies in the wing upper skin; the rudders are being activated by hidden pusher rods with differential action. The vertical disks at the wing tips (Endscheiben) consist of a fin and a rudder. Foot pedals activate the rudders; left/right pedal for directional steering and both pedals together for air braking."

From Willy Fiedler's biography: https://ritstaalman.files.wordpress.com/2014/09/willy-fiedler.pdf

This source (a history of Akaflieg Stuttgart in the original German) might be a bit clearer:
http://www.scalesoaring.co.uk/VINTAGE/Books/50-Jahre-Akaflieg%20Stuttgart_s.pdf

It seems to have information from about page 38 to page 72, along with a nice variety of photos showing the internal contruction. However, I can't read it.