Because the Alexander Graham Bell tetrahedral kite is completely modular, you can change the shape every time you put one together. That's what makes it such a fascinating kite.
Six years ago I talked with two Germans, Til Krapp and the late Peter Malinski, who had co-designed high-tech plastic connectors for tetras. They wouldn't sell any but they agreed to trade for them and I had to sew 100 two-foot sails to swap for enough of the connectors to make my own large tetra. By the time I finished making all those ripstop sails, I was pretty sick of the whole thing and didn't get around to making my own tetrahedral kite until last winter. The winter is really bad in Monument, Colorado, where I live, and it provides ample motivation to stay indoors and build kites.
Seeing Til Krapp fly his own tetra again last year humbled me into thinking I should finish my own, and a projected seminar on Bell at Fano, Denmark, this year added a further incentive. Beyond that, every serious kitemaker sooner or later has to face up to the challenges posed by Bell, as he does to Cody, certainly, and to Jalbert and Rogallo. He has to see for himself exactly what their achievements were by building reproductions of their innovative kites. With the year 2000 months away, another factor in my decision to build was the increased worldwide interest in the 1900 millenium, when Bell himself was working on aeronautical projects.