Well the other day I was reading rec.crafts.metalworking, and I noticed someone had posted a URL for a page on building "Pop-Pop Boats." I didn't know what a Pop-Pop boat was, but it sounded interesting. It turns out that a Pop-Pop boat is a very simple to construct boat that is powered by steam forming in a little coil of copper tubing. It sounded so simple I went past the hardware store on my way home to pick up some 1/8 soft copper tubing and some sterno. Later that evening Mark, Kate, and I were all huddled around the bath tub watching my little boat take its first pops around our (very small) inland sea.

Wow! So simple, so fun. I'm psyched! After a few more coats of paint, and a little red striping here is the result:

To make it run I filled the copper coil with water, put a blob of sterno in a bottle cap, and slid that under the coil. The design is a little bit flawed because I used two turns of copper instead of one. I think this has the effect of making the boat go in a lazy circle.

I Later tried making this more involved pop-pop boat that uses a flat boiler with a diaphragm that pops in and out as the steam forms. I made mine using a Snapple lid to provide the diaphragm, but it didn't work at all. I would put in a blob of sterno, steam would issue from the tubes, and then finally my solder joints would melt. Apparently there's a fair amount of controversy about how these engines work, so I don't know what to optimize in order to make mine work. Oh well. I think I'll keep my eyes open for a construction article that I can follow.

I'm going to make two more of the copper tubing style boats as gifts for some children I know. I think they're going to like them. I know I do.