I settled on the design for a panel cooker from Cooking with Sunshine by Lorraine Anderson and Rick Palkovic. It calls for a piece of cardboard that is 4 foot by 3 foot, some heavy duty aluminium foil, and a little Elmer's glue. It took a little scouting to locate a piece of cardboard that size, but with the help of family and friends, I was finally able to come up with one. Mine was actually a little bit too big, so I cut it down to size.
Unfortunately, I didn't notice until after I had done my measuring and cutting, that the yard stick I was using had four inches cut off of it (that's what comes from trying to work through a project with six little helpers, and a good dose of cold medicine). Thinking of all the work involved in finding the cardboard, I scaled down the pattern from the book by four inches, and continued. You can find patterns for making panel ovens all over the Web, but if you can get your hands on Cooking with Sunshine, their pattern is very simple and straight forward. I'm pretty sure even a middle school aged child could build one of these on their own.
Just draw out the grid lines according to the measurements given. Use the grid lines to mark off the sections that need to be cut out. Then, using heavy scissors or a box knife, cut out the marked sections.
Again, use the grid lines to mark score lines and slots. Score the lines and cut out the tabs using a box knife or scissor edge. Fold the box on the score lines, making sure the corners will fit into the slots.
Unfold the box, and lay the cardboard out flat. Tear off two sheets of heavy duty tinfoil, long enough to cover cardboard. Set these aside and prepare the glue, by diluting it half and half with water. Cover half the cardboard with glue (I found the easiest way was to dump it on, and spread it with my hands). You need to work quickly so the glue won't dry. Place one sheet of foil over the glue, dull side up. Smooth it out.
Repeat with the second half of the box. Tuck the extra foil around the back of the cardboard, and glue it in place.
Finally, refold the box, breaking through the foil at the slots. Your ready to cook! You want to set the cooker in the sun, and place a black pot on an insulator (like a brick or a piece of wood - I used a black cake pan placed upside down), and inside a turkey bag or under a glass bowl, in the middle of the cooker.
It was 3:00 in the afternoon when I finished my oven, which is a little late for good sun here, but I wanted to try it out. I went with s'mores, because that's the easiest solar test food I know. I also placed an oven thermometer in the pan. The temperature reached 250 degrees Fahrenheit within 15 minutes, and the s'mores were melty and delicious within the a half an hour. I can't wait to let the kids try it out in the full sun of the middle of day.
It's great to be a homeschooler!