Introducing the Basic Ultralight Gliders by Mike Sandlin
The Goat4 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.
My airchair designs 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 none-powered ultralights, including paragliders, hang gliders, and airchairs are regulated under FAA 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 Goat4, Bug4, and some of their predecessors are free and available for downloading in CAD format (select "Drawings" from menu above). In addition, the Goat4 drawings can be viewed on the Web. My activities are non-commercial and all of the materials on my website are available for whatever purposes the user may consider worthwhile.
My gliders fly at about the same speeds as a hang glider, readily mixing with hang glider and paraglider traffic. No formal performance measurements have been made, but all are in the hang glider range and can stay up in good lift conditions. I designed, built, and flew the Bug2, Bug4, and Goats 1-4, and have soared thousands of feet above take off altitude in each of them (except Goat4, which is new as of this writing).
A Basic Ultralight Glider is not a hang glider (it has no foot launch capability) nor is it an ultralight airplane (it has no engine). Its construction is "low tech", at the hand drill and hacksaw level, for easy home building, from readily available materials (it is made mostly from aluminium tubing and steel cable with polyester fabric covering). The Basic Ultralight Gliders are best characterized by their light wing loading, which is about the same as that of a hang glider (around 1.7 lb. of gross weight for every square foot of wing area). Light wing loading results in slow flight, which is safe, comfortable, and allows soaring in small thermals (because of the ability to turn tightly). Slow flight provides the unique ability to self-launch by rolling down open slopes, usually at the same mountain launch sites used by hang gliders and paragliders. This rolling launch has become my standard procedure for local weekend soaring. The launch slope I most often use has a vertical drop of about 17 feet over a rolling distance of 72 feet (so, the rolling distance is two wing spans for the Goat). I launch here only with a headwind; a longer slope is required (by me) for calm air launching.
For further information go to the Ultralight website.