Here are some quick pics and descriptions of the incubator I made in 2011. I will update this page after the 2012 season is done.
Click images to see the larger version.
1) Starting with the cooler, a Coleman 120qt. I have mounted with vel-cro the Helix Basic thermostat and a Cooper thermocouple to the lid. The thermocouple rarely works because the probes are too sensitive to humidity. I believe a lab quality glass mercury thermometer would serve better as the backup thermometer.
2) When you open the lid, you can see the condensation on the underside of the plexiglass inner-lid. I had this inner lid custom made at a local plastics company to allow me to open the cooler without letting the heat escape. This lid is split so that I can remove only one side of it.
3) When you take the plexiglass away, you can see the egg box and open pan of water as well as the fan set up to blow across the open water pan. There is also an aquarium air pump pushing air through an air stone in the water pan. This increases the humidity in the main chamber, but I am not convinced it is necessary. This setup creates a LOT of condensation.
4) Taking away the egg box, and lifting the egg create diffuser I use for a spacer shelf, you can see the water bottles used for a heat sink to create the thermal mass. The larger the thermal mass, the more stable your incubator will be.
5) Below the water bottles you can see the PVC space layer along with the flex watt heat film. This is 11″ version of flex watt and a 1′ or 2′ section is sufficient for a cooler of this size. Once the thermal mass (water layer) is warmed up, the flex watt only runs at 10% or less. In this view you can also see the white probe of the Helix Basic thermostat taped to the cooler wall on the right. This is intentionally placed towards the “cool” side of the incubator away from the direct flow of the fan. This way the air in direct contact with the probe is as “ambient” as possible.