Les,
The oven is very simple. I ordered some fan heater from an electronics store a couple years back,. The were offerring 2kw heater for $15 ea. I ordered 5 of them and they sent me 10.
Each heater has 3 heating elements and a fan all wired separately.
I'm using 2 elements in each heater and the fans.
The oven is simply a box made from 33mm mdf on the top of a steel frame. (Normally used as a table.) Ply sides and a 9mm MDF botton. The are two timber rails inside to slide the foam in on.
The hot air is blown along the lower surface of the foam and then turns around and runs across the upper surface before it can exit out a slot just blow the 33mm mdf table.
A baffel is made up to help the heaters grab the already preheated air- heat it some more and it is driven back in. When the heaters are operating with out the baffel and only two elements running you get 78 deg C.
Insert the baffel and you get a bit over 100deg C - around 103 to 106.
Switch in the third element and you go over 120 dg C.
I have added some pics of the heaters used and the oven itself with others to my photo albumn.