Forget the competition "purists". They can't agree on it at all.

Normal model airplane, "Lovers", agree . If the wings, tail parts and fuselage are made from pieces of 1 or several materials by you. It was, scratch built.
Your plan / design or someone elses does not matter a bit.


Or really simplified, NO pre made planes. ARF--ARTF-- ARTC-- etc.


BIG bobo: Pre cut kits of course are NOT part of a SCRATCH built plane.