As I mentioned in my last blog, making the 1/4-scale model for my wooden sculpture stand was very straightforward. In general, one of the values of building an accurate model, other than enabling you to see the project in three dimensions instead of two, is that you can get an indication of the steps involved in the actual construction of your project. This is definitely the case with a full-scale mock-up. With a scale model, however, it's really important to stay aware of the fact that some critical operations may be affected when moving up to full size. This was precisely what I encountered with my project.
I had built my model out of some 5/4 Douglas fir that was at hand in my shop, cutting four rectangular blanks with 45° bevels on the long sides, and simply glued the four pieces together, after which I transferred the 2-D pattern onto two adjoining faces and cut out the shape at the bandsaw. From my drawing, you can see that at its widest, the finished shape is 14-3/4".
At its narrowest (where the base meets the top), it is 9". That means that my curve needs to go through a thickness of almost 3" on each side. I also wanted to maintain a minimum thickness of 1" in the walls of the base. To do that I would need to start off with sides that are roughly 4" thick. It also means that a 45° bevel cut would be going through over 5-1/2" of material! Not something I could manage on my 10" tablesaw. And that doesn't even consider the enormous amount of 8/4 mahogany (and dollars!) it would take to make up that blank.
At this point I started looking at other options. One idea, suggested by a couple of friends, was to create a framework over which I would put two laminations of 1/4" bending plywood, followed by a skin of veneer in my material of choice—mahogany. The construction would look something like this:
While this approach had things to recommend it, particularly its economy of materials, I was concerned about how to manage those four long curved edges—even if I could make the skeletal framework, I worried about making those seams where sheets of bending ply come together on a compound curve look crisp and clean. So I rejected that method.
A second alternative—the one I eventually decided on—was suggested by another friend who pointed out that if I ultimately laid a finish veneer on the surface, then I could build up the form in an inexpensive solid wood (hollow center with thick walls, as originally imagined when I made my scale model), but I wouldn't have to deal with cutting those thick beveled edges. I would still have to saw the curves through 15" of material, but I had access to a few different bandsaws with that capacity. I also felt more comfortable cleaning up those curved edges in solid wood rather than bending plywood. I decided to go for that approach.
So I bought 50 BF of 8/4 poplar, milled and glued up my various planks, and proceeded to build up my form with a succession of glue-ups:
My first glue-up was the bottom and two sides, followed by gluing on the other two sides.
I then added another pair to achieve final thickness on two sides. You can never have enough clamps!
Last, the final thickness was added to the other two sides. After each glue-up I did a small amount of scraping and hand planing to remove glue squeeze-out and flatten the faces. A total of four glue-ups in all, and my form was now ready. Next step: Making a full-size template for the curves. Coming soon in my next post.