I have Cliff Charlesworth's book Scale Model Gliders. I bought it from Traplet Publications. Chapter 3 is on Motor Gliders. There are Three-Views for the following motor gliders:
Schleicher ASK-16
SF 25E Super-Falke
SF 28A Falke
Fournier RF-9
Schleicher ASK-14
Scheibe SF-33
Sportavia RF-5B Sperber
There are photographs of the following:
Model T61 in flight
Full size SF28-A Tandem Falke
Model construction pictures of an SF28-A motor glider
GROB109-B
ASK-14
Top view and side view plans are shown for a model of the T61 Falke fuselage
Years ago I ordered the quarter scale plans of the Reiher II from Charlesworth at this address:
C.H. Charlesworth, 41 Spring Road, Frome, Somerset. BA11 2JN England
Payment was awkward. Payment years ago "must be via international money order in pounds sterling - obtainable at many banks."
My old list of his plans did not include any motor gliders but his book shows some that he built so there are probably plans of motor gliders now. You will have to contact him or Traplet Publications or both.
Bob Harold

