Saturday, July 7, 2007

Steam Bending

I decided that the chassis of my wings needed some curved components. I considered making these with some home made glulam components, but ultimately chose to steam bend the parts.
Having never done this before, I started by knocking together a crude steam box out of some scrap pine. This box is enhanced with a plug on one end, a candy thermometer, a hinged door with a magnetic clasp n the other, and a series of copper wires inside to keep the pieces off the floor of the box. There is a copper pipe sticking out the bottom which is hooked up to an old kettle sitting on a hotplate. I find I can get about 2.5 hours of steam out of the kettle so it works well for me.
I made this setup originally thinking that it was just going to be temporary because I was unsure as to the odds of success, but as it turns out it works just fine, although the box has corkscrewed itself about 2 inches of twist, I think next time I am going to be looking for exterior plywood.
The first step in the process is to first soak the parts for 24 hours in a tub of water, I tried to omit this step and found the the results were mixed to put it mildly.
The steam box is preheated before the parts go in, from looking at the gauge it seems to top out at 95°C which I suppose is partly due to the altitude here. Once it is up to tempature I toss the parst in and steam them for 15-20 minutes depending on thickness.
Once steamed the parts are bent by hand for greater control of the bending, however I find that I burst way too many capillaries in my thumbs doing this. Then they are placed on a peg board so they don't spring back as they cool.

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