This post comes to us via a email posted to the Scout-L mailing list by Jay Thal. I would like to thank him for letting me repost his email and the photos he took while making his solar oven.
Back on Dec. 30, 2009, I referenced an article "Hearth Surgery" which appeared in the New Yorker magazine about the designing and building of environmentally and culturally appropriate stoves for peoples and nations on the edge. It's still worthwhile reading so hunt it up at your local library.
Now I'm building a Parabolic Solar Oven. These are fun projects for myself (one last summer was a stereoscopic digital camera I first tested at Jambo) but I share them with the Scouts so that they can consider the abnormal in their everyday lives.
"There is no use trying," said Alice: "one can't believe impossible things."
"I dare say you haven't had much practice," said the Queen. "When I was your age, I always did it for half an hour a day. Why, sometimes I've believed as many as six impossible things before breakfast". -- Lewis Carroll
Well, Solar Ovens aren't exactly impossible but they can teach more than lighting up a Coleman.
One of the other hats I wear is that of an "Election Judge" and I've long been appalled by the post-election waste of the signage -- particularly the non-biodegradable waterproof plastic corrugated variety that wind up in the waste dump. So I've asked some of the campaigns to save some of those for me. (recycling is cheaper, too, than buying the material at an art supply store.) So, today, I've been cutting up some of those 18" x 24" / 61cm x 45.7 cm lawn signs with my trusty X-acto. Believe me, using metrics also makes this easier.
As a model I'm relying upon: http://images3.wikia.nocookie.net/__cb20090702202754/solarcooking/images/b/b6/Collapsible_Parabolic_Cooker_plans_English.pdf
with some modifications -- using the plastic corrugation material instead of cardboard; using silvered mylar instead of aluminum foil; and using some pipe/plumbing pieces to make the pot support. Silvered Mylar is available in art supply stores, or on-line in 55"wide x 25' long rolls (enough to make many cookers and/or funhouse mirrors).
This design offers two options: an accordion folding model, see too: http://solarcooking.wikia.com/wiki/Collapsible_Parabolic_Cooker or a non-collapsible model. It's Argentinean, and adds to my appreciation of not just their grass-fed beef, wines, and Iguazu Falls.
It'll take about six lawn signs to make the small parabolic oven (0.6 m2), and about eight to make the large parabolic oven (0.8 m2)) The wire stands used to stick them into the lawn, bent to 30 degrees, can stabilize the segments (or for your garden plants) if I choose a third option: four stackable 90 degree segments.
Many other sites exist, among them these two:
Guess I'm stlll living in the days when Scouts made some of their equipment rather than go to an outfitter.