Three Stage Beach Cabin (no architect listed)
Two Stage Expandable vacationer, by Walter Wiedmeyer
These images came from a promotional booklet from the Douglas Fir Plywood Association for 18 holiday houses built with fir plywood by various modern architects.
I love the illustrations as well as the designs. Ah.. I wish I could present drawings like these to my architecture clients! They are so much more beautiful and expressive than any flashy 3D CAD perspective I've seen!