That book is quite a find. I first saw a copy back in the 1970's in the Enid, Oklahoma public library. We were in town for the Tri-State Music Festival. Being a nerdy kid I gravitated to the library where I found that book. It was quite inspiring. I have a set of Lulla-Bi plans in my build something half-a pile. I don't have a copy of the Laumer book but I do have a copy of "Building and Flying Model Aircraft" by Paul Garber dated 1928. I guess it was capitalizing on the boom in aviation interest that followed the Lindberg flight. The airplanes are mostly gliders or rubber power along with diversions into kites and boomerangs. Going along with the quote above the book goes into detail on how to make practically everything as there were few prefabricated parts to be had.