The original segment here asked “How hard can it be to make a dodecahedron? Well the answer seems to be pretty easy….. but there are lots of ways to make it harder. When I first assembled the MDF pieces off the saw I thought that the fitting part was going to be the easy bit and that the dying and marquetry would be the sticky parts. That remained my belief until the final assembly time arrived and I realized that with the allowable tolerances it was going to be an interesting fitting job after all. It turns out that all the little operations associated with veneering, trimming, wetting, drying, warping and unwarping had each taken a small toll on the initial accuracy. The sum of these little discrepancies was enough to require a certain amount of “fitting”.
This is the setup I used to “fine tune” the fits. It wasn’t the angles that were out as much as the dimensions. Nothing was out much but any small mismatch in length on adjacent pieces would show as a gap in one of the joints, so the fine tuning began. The sanding disc now stays put and the jig slides the piece across it. It allowed me to take off very small amounts and by applying more pressure to one or the other end, I could take a little more off one end if I wished.
This photo shows the two critical areas that had to match perfectly for length, the joints between the sides and the bottom and the joints between sides. Herte they’re getting pretty close to good.
At last it’s time to summon up some courage and glue up the bottom. The bottom was done first for the obvious reason, to practice before gluing up the top. The pieces have been assembled outside up, taped to exactly match at the corners, turned over and glue has been applied to the mating faces. The stick was a piece of scrap I had that approximated the open angle well enough to make a good glue spreader. In the background you can see the clamping system parts I came up with.
And here are the parts in the photo above in service clamping the sides of the bottom together. The pieces of cloroplast have vee notches cut in them that hook on the pentagons’ tops to keep the wedges from slipping down under pressure. It worked really well.
The fact that all the angles are the same should guarantee a symetrical glue up but I didn’t trust what could easily be uneven pressure exerted by the bungee cord so just to be sure, I made a fitted pentagon to check the inside. It actually did need a little persuasion but once it was right it stayed that way nicely. The corners of the pentagon were removed to avoid getting it stuck in there.
When the sides were glued up I did a last fine tuning of the bottom and glued it in with masking tape. After a quick sand up to remove unwanted glue this was the resulting bottom all glued up. I must have gone through half a roll of packing tape assembling, disassembling, tuning and reassembling and then repeating. Between the top and the bottom I’ll bet I pre-assembled these things twenty times or more before finally gluing them.
Here’s the top glued up. For reasons that would take too long to explain I couldn’t use the same tape up / glue up sequence with it and as a result the top was glued up with the sides all at once. This was of course the scary one because of the marquetry.
With most of the panic over and the glue ups successful this is pretty much where it stands today. This part has taken a lot more time than I expected but I’ve learned lots of interesting things about the various processes involved.
Thanks for dropping in. I hope you’re still enjoying this as much as I am.
As always comments, critiques and questions will all be acceped and appreciated.
-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/