Yeah, I know it's not a steam box, shoulda typed with more care there. I was sort of loosely planning to use insulation foam sheets to build the box, but I do have a long section of 4" PVC drain pipe in the shed, that'll probably be for the coaming stock to steam for sure. And I have plenty of scrap 1x6 from a deck project that I could use for a shorter box. It would be inefficient to try to steam the shorter ribs in the ~8' long PVC, would it not? A long and short box are in order?

Now, you've given me some very good information here. Never thought about checking drugstores for hotplates. I saw one for $30 so kind of assumed they are up there in price. I'll have to stop in a couple of thrift shops and Walgreens next week and peruse their shelves.

I did not think about the difference in hot and cold steam either, I knew that, just never thought about it in this context. That tidbit right there may prove very helpful from the start.

I do plan to steam outside, and will be careful in setting up the box and heat in a safe stable place, and I will leave pressure escapes with whatever I use for a box.

Been tempted by the coverlight would like to try that one day, but I will likely wind up using canvas duck since I can get it in town, unless I can afford nylon when the time comes.