Copyright © Thomas Fetter
My first curing oven was the design published by Shadow Composites that was made from foam insulation and used a mechanical switch to control the heating lamps. Eventually, it was time to replace the oven with something more durable, and one where I could control the temperature. There were plenty of good examples on the Internet, but all the designs used heat lamps and fans in a single chamber. I found that the heat distribution with this design was not very even from one end to the other, even with the fans. So I decided to add a duct to circulate the air and maintain a more even heat distribution.
I use the curing oven mostly for fiberglassing tubes. I use Dunstone heat shrink tape over a layer of peel-ply. The heat tape needs 160 deg F to trigger the tape to shrink, so a curing oven is required. I also find that epoxy, even after a 24 hour cure is still a little soft, and, when sanding, clogs the sandpaper very quickly. An hour in the curing oven completes the cure, and the epoxy then sands very cleanly.
Here is the oven. It is made from 1/4" plywood with a 1x4 external frame. It is lined with 1" foam insulation.
To get an even heat distribution, I added an internal partition. The fans blow the air from the heating camber at the far end down the duct and our the holes at the near end. The air then returns through the main curing chamber. The thermal-couple can bee seen mounted to the top of the partition at the far end. The design works quite well.
This is a large oven, so I use three 150 watt heat lamps to ramp it up to temperature quickly. It takes approximately 25 minutes to ramp to 160 deg F.