रविवार, 19 फ़रवरी 2023

Net for Truncated Dodecahedron


Net for Truncated Dodecahedron

32 faces (20 triangles, 12 decagons), 60 vertices, 90 edges Icosahedral (2, 3, 5 fold) symmetry.


Method:


This net is made in TWO parts.


1. PART - 1. (Step -1) To draw the required decagon (ten-sided polygon), use any previous method to first draw a pentagon, or as follows (Fig.) 

Step 1


       On horizontal AB draw a circle radius OA. Arc above and below from A and B with radius AB, and connect the intersection points to find the vertical which crosses the circle at C and D. Find the midpoint of OB by drawing arcs from B with radius OB to cross the circle above and below. Join the intersection points to find point E. With compass on E and radius EC draw arc down to cross the horizontal at F. With compass on C and radius CF swing an arc to both sides to give points G and H. Walk this radius round to find the other two points of pentagon CHJKG. Draw lines from each pentagon point through the centre to the circle on the other side to find the rest of the points of the decagon CLHMJDKNGP.


2 (Step - 2) Add further decagons to alternate sides of the first decagon by first drawing arcs from each pair of points on the central decagon in turn with the same radius as that of the central circumcircles (the circle that encircles the decagon) to find the centres of the circumcircles of the surrounding decagons.


3. Then walk the side length round each circle to mark the points of each decagon (see Fig.). 



4. (Step - 3) Tune these points by drawing lines through existing and new points. A selection of checking lines only is shown here (see Fig.)


 Step 3.


5. Step - 4) Add equilateral triangles to the faces shown in (Fig 5.69. step-4).


6. (Step - 5) Add tabs and cut and fold lines as shown. The dotted arrow and tab indicates where the other part of the net joins (Fig 5.70 step-5).


7. PART - 2 (Step - 6) -is identical to the first part, except for the tabs - follow carefully (Fig 5.71 step-6).


8. When both parts are made, cut out along the solid lines: score along the dashed lines. Fold upwards along the scored lines.


9. Glue carefully and progressively (tabs inside) - one or two tabs at a time. Clean up and decorate as you wish.👍



 Illustrations of one half of the net drawn out on card and cut out (top left); the two halves assembled (top right and bottom left); and the model complete (bottom right).

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