Fopul^r Science Monthly 



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Fig. 25 



Fi'. 27 



it looks like '-"ig. 25. Opened out flat, 

 it appears as shown in Fig. 26. 



Now if we fold this on line X and 

 connect point? K by a brace exactly as 

 long as one side of the triangle, we have 

 a tetrahedral cell. Tie a bridle to it as 

 shown. This kite has small surface for 

 its weight, but it can be expanded by 

 adding cells until it will carr>- almost 

 an\- reasonable weight. 



A large and complex tetrahedral is 

 shown at the top of this page. Each cross 

 represents one of the elements 

 shown above, but now the 

 frame work is composed of 

 horizontal bars only. The 

 trans\"erse bars are shown be- 

 tween the rows of cells, and 

 are so marked. The longi- 

 tudinal bars are shown by the 

 circles. 0\er this frame when 

 tied together, \- e r 3- fine 

 wires are stretched at the 

 tetrahedral angle, and the cell 

 surfaces are cemented to these. ,' 

 The surfaces in the kite here 

 shown ma>- be made of verj- 

 Chinese rice paper. With the vertical 

 supports shown, this makes a ver\- 

 light and rigid flying-frame. It is 

 a good plan to start with a few cells 

 and gradually increase the number as 

 you build successive frames and be- 

 come more expert. The cells can be 

 arranged in any regular or fantastic 



tough 



figure as long as they are symmetrical 

 about the keel. 



The other 5 sticks should be of the same 

 length, but made of stout bamboo, 

 split about 5< in. wide. Whittle them 

 till they balance nicely when hung 

 inverted from the bottom stick. N'o 

 other way of fastening can be used 

 except lashing the intersections with 

 fine copper wire or strong cord ; braided 

 fish line is good. Make it measure 3 ft. 

 exactly. Ever>' angle in the frame will 

 now be exacth' 60 degrees. 

 Di%"ide each stick into 3 equal 

 parts, each one foot long. 

 Take some fine copper wire 

 (No. 28), and stretch it smooth 

 between these di%ision points. 

 When it crosses, tie it with 

 sewing silk or cotton thread 

 lashing. This ^*-ill make 9 

 di\isions on any face. Set it 

 so you look along the bottom 

 stick, and cover e\"er\- alter- 

 nate triangle of wire that 

 shows edge on to the front 

 look at it in this position. 



Fig. 29 



when you 



with strong paper pasted on the wire. 

 Tissue paper is good if strong enough 

 to stand the strain. You should now 

 have ten httle paper V'§, 3 on the 

 bottom row, i behind the other, 4 in the 

 center rows two and two, and 3 on the 

 top, side by side. Looking down on 

 the late, it looks like Fig. 28. 



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Fig. 28 



