Second only to the duct tape, polyurethane foam becomes my preferred tool and material, by far besting chewing gum so widely used as an improvised …everything, actually.
But surely, I will have to quit ready-made one, in pressurised containers. Great, if you spend the whole can at once, they tend to clog with dried foam and sometimes you can only trash the half-full can, still worth few Euros — or hack it seriously, with a bit of a personal risk.
Yesterday, seeing the spring really coming, N. gave me her approval to convert the Valentine Box into a fully fledged solar cooker.
Everything was ready. The glazing with cutting edges secured by way of tarp scraps and duct tape (yes, one cannot just ditch the duct tape, it holds the world together), wrapped in the mylar silver foil (as a separation layer), to be put on top of the box, squeezing out the excess of foam sprayed along the top edge, creating a perfect gasket.
Only, the foam didn’t cooperate.
I’ve been shakin’ and tweakin, nickin’ and pickin’ and even blowin’ a bit — to no avail at all. A half-full can of top-shelf low-expansion PU foam was totally oblivious to my efforts. Heck, I have no money for such extravaganza!
So I decided to give it a hack. With my old faithful multitool in a rubber-gloved hand, I kept cutting and drilling the valve, until a wave of bubbles erupted unstoppably.
Hastily, I spread the foam as planned, putting still-erupting container on a patch of foil, where it ended its shelf life, transformed from a foaming cornucopia into an (absolutely #NSFW and adult-only) objet d’art you may see here.
Meanwhile, I was following the plan. Glass put on top of the foam, left through the night.
The last part was easy. Our last mylar blanket provided a silver lining. Thermometer (no engineering without measurement!) found its place. And off, to the balcony, we go![su_slider source=”media: 3424,3426,3425,3450,3444,3446,3439,3449,3448,3451″ limit=”31″ link=”image” target=”blank” responsive”yes”]
At the first try we easily crossed 80*C limit, even if the early spring sun was still a bit veiled and low.
For now, it is absolutely legitimate solar-assisted haybox. Just for the sake of learning, I am going to make a foam cover to replace glass in sunless conditions.
Post-coital reflections (aka lessons learned)
- Two-component PU foam, stupid! A bit less convenient, but we do not need more #NSFW art, do we.
- Spreading mylar foil and stapling it to the foam is only fun at the beginning. For serious use and production we need pre-cut panels of foam, laminated silver from one side, thin plywood at the other. Modular build for the win!
- Also, if we are not (everybody) geeky hacking types, we like things look nice, do we. So some paint on the plywood side and maybe some masking corners for you, picky aesthetes.
- Foam no more, in fact. Thin layer PU glue (or two-sided foam tape) and rubber foam window seals will do the job nicely. And look better.
- Double wall polycarbonate glazing with nicely finished edges, hinges and a handle — all details making it fun to use.
- Oven thermometer, external reflectors, assembly/user guide. You will love it.
Now there is time to do some testing and after that, expect more goodies from Freelab.
Meanwhile, support your friendly tinkerer — this is all for the liberatory technology development!