Tetrahedral Kite:
The typlical tetrahedral kite is a multicelled rigid box kite composed of tetrahedrally shaped cells. The cells are usually arranged in such a way that the entire kite is also a regular tetrahedron. The kite can be described as a compound dihedral kite as well.
The cells are all oriented exactly the same toward the wind such that only one of the edges is nearest to the bottom. This edge points and is inclined somewhat toward the flier. The top edge is perpendicular to the flier and level. This is in contrast to the resting position of a tetrahedron on a level surface, where three edges are on the bottom. Each cell is covered on the two sides lowest to the ground. The kite is bridled toward (or at) the front point and flown single line, without a tail.
Spar joints are numerous and complex for a kite, with many joints requiring connection of 6 (or more) spars. This makes the kite more difficult to assemble on the field. However, the kite also takes up a lot of volume in relation to wing area. The volume is triangular and pointy and doesn't match the rectangular interior of vehicles well. This makes the kite more difficult to transport fully assembled.
Variations on this design theme include an increased dihedral angle between the wing faces, use of nonequilateral face triangles, and assembly of cells into other overall shapes.
Performance
The assembled multicell structure is very rigid and very strong. Increasing the number of cells improves the lift/weight ratio. Because of these features, very large tetrahedral kites have been built. As every single edge contains a spar, the kites are generally heavy and require good winds.
Once aloft, they present a very stable flight characteristic and generally seem to sit at a single (but not especially high) point in the air. Because of the regular cell shape, flight orientation, and stillness in flight, perfectly regular versions of the kite can appear somewhat like an isometric illusion while aloft.
History:
The kite was developed by Alexander Graham Bell in the early 20th century. Bell built a number of models, including the Cygnet II, with 3393 cells that carried a man aloft behind a ship.