Fairing Model: Tool Materials
Dateline: 04/07/99With all of the materials--well, at least most of them--on hand, it was time to start building the tool. The first step was to cut the major components: the bulkheads and the foam.
Bulkheads
The bulkheads are made from medium-density particle board. This isn't like the low density board where you can easily see individual particles. Medium density board has a very fine grain; it almost looks like a monolithic material. It is also stronger and has a higher mass density than low density board. We have even been able to use it for low-cycle autoclave tools.
Because of the board's high density, it is extremely difficult to cut. Hand tools would be very slow, and not too accurate, so a band saw was the obvious choice.
We set up an extension arm on the saw table with pins located from the saw blade at the radii of the bulkheads. By drilling a hole in the center of the bulkhead and rotating around the pin, we were able to cut reasonably accurate circles.
The largest diameter of the part was just over 60 inches. Particle board comes in standard 4'x8' sheets, so the largest bulkheads couldn't be cut from a single sheet. To cut these pieces, we first had to splice together smaller pieces.
Foam
It wasn't until we got the foam pieces cut and stacked in one place that we realized how big this tool was going to be. Knowing the dimensions is one thing, but actually seeing the volume of materials required puts it in perspective.
The individual pieces weren't simple blocks cut to length. To fit around the cylindrical sections, they needed to have a trapezoidal cross-section--narrower towards the inside, wider towards the outside.
The blue foam cuts very nicely on the bandsaw. Thus, these cuts were simple to make by tilting the band saw table to the appropriate angle. The blocks for the conical sections also had to be tapered lengthwise, requiring a few extra cuts.
Finally, each piece needed a "step" or "shelf" for resting on the inner bulkheads. These features had to be cut by hand. A simple hand saw or scroll saw worked fine in this case.
Next article, we start assembling the tool.
