Super Star 40 - Modifications
24 Apr 98
I carried out 2 main modifications to my Super Star 40 (SS40) during its life being tail drag u/c and to a biplane:
The first modification was to allow conversion to tail drag u/c. I decided that it must be possible to swap between tail drag and tricycle u/c as required and in a reasonable time. I fitted an additional mount plate using the same main u/c legs as for tricycle. I also fitted a removal tail wheel and steering linkage.
To convert from tricycle to tail drag the nose leg linkage is disconnected at the servo and the linkage and leg removed together. This is the only fiddly bit as the nose leg has to be rotated to allow enough play in the linkage to allow the leg to drop out of its bearings. The main u/c legs moved to the new forward position and the tail wheel assembly fitted. This takes about 5 minutes. The reverse process is followed to return to tricycle u/c. I frequently used to fly with one u/c configuration and then swap it at the field.
I was looking in my garage one day and thought that I must be able to do something with the wing of Mirage 550 (the only bit salvageable from the crash). I decided to attempt a biplane conversion to my SS40. This would have to be done with the SS40 in tail drag configuration or I would have a 4" stagger in the wings or put a big hole in the lower wing. I made a cradle to support the new low wing such that the bottoms of the two wings were parallel. I added a dowel behind the lower wing trailing edge and banded on the wing. It looked good and also flew well. The aileron response was slightly slower but still retained excellent authority. The only problem being a tendency for the lower wing to shift on aileron input and touch the upper wing. This didn't seem to affect the handling of the model it just worried me.
To counter the wings hitting each other I made some very simple interplane struts. The Mirage wing has solid tip blocks so I drilled a hole, at the thickest section, and glued in a piece of brass tube (sliding fit over 12 swg rod). A piece of 12 swg rod was cut approx 3/4" longer than the gap between the wings. I didn't want to modify the SS40 wing so the strut could only press against it. I solder a 3/4" washer to each rod flush with the end of the rod and as the SS40 wing is film covered I added a 3" diameter ply disc (to spread the load and prevent damage to the film). This also meant that part of the ply disc was under the spar of the SS40 wing. a collet was fitted to the rod and set so that it the rod was effectively slightly longer than the wing gap. This cured the problem and removed the doubt when flying in this configuration.
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