I am in the process of building a parabolic solar cooker using a base of thin plywood and a final coating of cob to finetune the shape.
The project has gone really well so far and is currently drying in my back yard. I made up a special scribe to indicate the height that the cob should be around the concave bowl of the parabola. Please look at how the scribe works to make the parabola! It is wonderful!
The little device was used to form the curve of the entire parabolic bowl.
This shows the cooker in action
You can find my progress so far at http://www.youtube.com/watch?v=06V1uLgPWyY and there will be more video taken very soon (30 august 2007) Brian