These things have been around for a while.

Aeromodeller published an article by Charles W. McCutchen in July 1954 for his Charybdis.  It was for .5 to .8cc engines.  Its motor boom was 24", the rotor blade was 36" by 2", the stabilizer blade was 18" by 1.5" and the balance boom was 20".  I do not have the 54 Aeromodeller article, but Aeromodeller printed a small drawing of it in the early 70's (my copy of that page is not dated).

A scaled down version for an .010 by H.D Sherrard was published in the October 72 issue of American Aircraft Modeler.  It was call the Charybdis.   Sherrard gave credit to the Aeromodeller design. 

Ken Willard had one called the Rotoriser  for an .049 in the March 1984 issue of Model Builder.  It was the size and configuration as the Aeromodeller design and Willard gave credit to that design. The magazine explained it was a free flight, single rotor blade helicopter.

By all accounts, these are easy to trim and fly.  In the mid 70's, I tried one scaled down for an .020.  After a bit of fidgeting with the stabilizer blade, it worked very well.  I lost it to the forest near our house in Maryland.

If anyone is interested, I will scan one of these articles, but it what I have will not scan well or show very well on this forum.  Plans for the American Aircraft Modeler design are available from the AMA plans service.

Keith