Dodecahedron Light Fixture

I saw this light fixture online and instantly knew I wanted it. Problem was it was over 500 dollars! So I went to the Internet to begin learning about dodecahedrons and if anybody has done this project before.
2 or 3 people had, but their explanations and plans were less than helpful. After some serious math and a lot of wrong ideas, I finally cracked the code and made my own dodecahedron, and now I'm sharing it with you!

To Calculate how much wood you need for this project, you need to know how big you want the light fixture to be. I used this website, https://rechneronline.de/pi/dodecahedron.php and figured I needed my pentagon sides to be 7 inches. So for the amount I took 7" per piece x 5 pieces per pentagon x 12 pentagons per dodecahedron= 420" or 35 feet of wood. I used 2x2 because I wanted my light to remain thin but still have a sturdy look. These boards usually come in bundles at 42" per board, so I could cut 5 pieces and have a 6th thats just a tad too short. I went ahead and bought extra wood because this was the first time doing this project and I figured I'd botch a board or two.

Now that I knew I needed 7" pieces, I set the fence on my table saw to 7" plus a blade width (which varies depending on your blade) so that I had exactly 7" of wood. I would cut a whole board down and mark the five pieces so that I kept the pieces together in a group. This proved useful because of the differing sizes of the boards. After cutting several boards down to groups of 5, I turned my guide to 54 degrees and reset my fence so that the corner of the wood was directly on the blade. I also made sure that the boards were cut laying on the same side, otherwise pieces would be taller than others. I cut 1 side of all 5 pieces, and then flipped them over and cut the other sides as to make sure I cut the angles correctly. After this step I had 60 pieces of approx. 7" pieces of wood with 54 degree cut on both sides.

To build my jig I found the most accurate group of 5 pieces and taped them into a pentagon. I then took a 2"x4' and cut it down to 6" pieces,(I used 6" so that the overlap wouldn't disrupt the corners of the pentagon, like you can see in the pictures.) I screwed the jigs down with screws long enough to go through the 2"x4' and the base board I worked off of as to not scratch the countertop. I made sure not to screw the screws down all the way so they could be removed easily for when I changed pentagons after gluing. Eventually I made a second jig so I could glue twice as many pentagons at once.

The 2nd to last picture is a glued pentagon, and the last picture is 8/12 finished (not sure why I didn't take a picture of all of them glued.)

The last angle to cut for the dodecahedron is the dihedral angle. This is the angle that connects one plane to another, and for a dodecahedron, the angle is 116.6 degrees. To cut this angle I subtract 90 (what a blade sits at) and get 26.6 degrees. I used a chop saw to cut this angle, but highly suggest using a table saw, as it is safer and has a lesser chance of breaking the pentagons. The miter is set at 54 degrees to line the blade up properly with the side of the pentagon. I started the blade at the top corner and cut down. After 60 cuts, I had my 12 pentagons ready to be glued.

To make my life easier when gluing, I decided to glue the pentagons into pairs and then into a half. I matched up pentagons that had identical sides, glued them, and used clamps to keep them together.

After making 3 pairs (6 pentagons) I glued them together to make half of the dodecahedron.

Once I had the half made, I went one pair at a time and glued them to the half until I had once place left for a pair.

As you can see in the last picture, the pentagon pair didn't fit because of the inexactness of my cuts and saw. To make up for this, I recut 10 8" pieces and used the table saw to shave them down at 54 degrees until they fit the sides of the dodecahedron where they were to be glued.

To save yourself this trouble, ensure your accuracy at the beginning of this project by making sure all your pentagon pieces are the same and your angles/di-hedral angle is exact.

Now that I had finished gluing and had an entire dodecahedron, I needed to smooth out all the corners and edges. I bought a tub of lightweight spackle and went to town on the 30 edges and 20 vertices. I overpacked the edges and vertices to make sure that when I sanded them down it would be flush to the wood.

After spackling all the sides and corners, I began sanding the dodecahedron down. I started with 100 grit because the spackle was light and wood was fairly smooth to start off with. I continued using higher numbers until I got to 400 grit. I had to hand sand the dodecahedron because the angles were too tight and small for a power hand sander.

Oddly enough, my painting room turns out to be an old shower in our house we don't use. To minimize contact and maximize the area I could paint at once I used twine and hung the dodecahedron by two points within my shower. I would paint a coat with black spray point, let it try with a fan, and in between coats i would rotate what corner the twine sat on. Four coats later (with 400 grit soft sanding in between to keep it smooth) and I was done.

To mount the light, I got a 1/4" thick piece of plexi-glass that was slightly larger than a face of one of the pentagons and cut it down to be slightly smaller than a pentagon. I predrilled holes for the screws and for the socket to sit in, right in the middle of the glass. I screwed in down with somewhat short screws to ensure I didn't go all the way through the the wood. I used a larger bit to widen the whole and then fit the simple light socket and cable through it so that the smaller top part of the socket (along with a washer to distribute the weight) fit through enough for a nut to pinch down from the other side.

For the actual light fixture, I cut down a 1" pipe and used a circular simple ceiling mount.

Any questions? Not enough details? Troubles/problems with a step? Email me at : raleighdavisup@gmail.com