Complex sentence: It had a two-part wing had a rectangular plan apart from rounded tips, fabric covered wooden structures with a main spar at about mid-chord and two auxiliary spars, one of them forming the leading edge.
Split into simpler sentences: It had a two-part wing of rectangular plan apart from rounded tips. Each half-wing was a fabric covered wooden structure with a main spar at about mid-chord and two auxiliary spars, one of them forming the leading edge.