[ Most recent update: 28 September 2012. ]
Making a Dodecahedron, Part 3
The final four cuts are similar to the previous ones in that the layout lines simply run from the centerline of the circle on one surface to the tangent point on the circle on the adjacent surface, as shown in the photo, above. Similar layout lines are made on the bottom of the block.
As you can see in the photo, the cut line must ‘ bend ‘ around a corner on its way from the center line on the upper surface, then go to the point at which the tangent line met the circumference of the circle on the adjacent surface.
Unfortunately, the circle no longer exists on two of the edges (the vertical edges in the photo) because it was cut away when previous cuts were made.
Fortunately, the length of the edges of each of the twelve pentagons (the length of the diameter of the layout circle on the ‘master’ surface of the cube you started with) was captured in Part 1 of this series. Aren’t you glad you captured that length now that it is useful for finding exactly where the cut line must terminate?
Simply divide the diameter in half to find the midpoint, then place the midpoint of the diameter at the midpoint of the long edge on the right hand side of the photo, then mark the ends of the diameter. This locates the tangent points for the new layout lines.
Distortion in the photo makes it appear that the edges of the pentagons are not equal, but they are.
I use a very thin and flexible strip of teflon plastic straightedge to serve as a guide which bends around the ‘corner’ to connect the two points, then draw the layout line from the end of the center line on top of the block to the tangent points.
If you don’t have a suitable straightedge for bending around the ‘corner’, here is an alternate method – –
Use that circle’s diameter (whatever it is for YOUR dodecahedron) then:
 place one end at the end of the center line on top of the block
 slide the other end along the edge until it just reached the point where the ‘ bend ‘ must be made.
 draw a layout line from the end of the center line at the top of the block to the ‘bend’ point, then . . .
 draw another layout line from the ‘bend’ point to the tangent point on the ‘long edge’
Repeat the steps outlined above for the remaining layout lines, and you are ready to do the final cuts.
BUT . . . before you apply saw to wood, I suggest you check the lengths of the edges for the pentagons to be sure they are identical to the diameter of the layout circle you first drew in Part 1.
Make any correction(s) required before you actually do the cuts.
After doing the final four cuts, you will probably have a bit of touch-up to do before applying varnish or whatever you decide to use for the finished surface. I usually apply three or more coats of high quality marine grade spar varnish, followed by a couple coats of paste floor wax as the finish for my wooden dodecahedrons.
– End of Making a dodecahedron –