Mike Sandlin designed and built what he calls “airchair” basic ultralight gliders. The Pig1, Goats1 & 4, and Bug4, are home built, basic ultralight gliders. Technically these aircraft are ultralight sailplanes, but they are best described as "airchairs", which are simple, slow flying gliders with the pilot sitting out in the open air rather than inside a fuselage.
The airchair dersigns are intended to provide open air soaring, forgiving flight characteristics, convenient transport, simple "garage technology" construction, and a high level of crash safety. In the United States, all unpowered ultralights, including paragliders, hang gliders, and airchairs are regulated under FAR Part 103, which allows gliders to be built and flown with no direct official oversight as long as they weigh less than 155 lbs.
The complete descriptive drawings of the Pig1, Goat4, Bug4, and some of their predecessors are free and available for downloading in CAD format. In addition, the the Goat4 drawings can be viewed on his Web. His activities are noncommercial and all of the materials on his website are available for whatever purposes the user may consider worthwhile.