Thermal test chamber for edge of space testing.

Step 3 Prep the cooler

We found this rather large budwiser compliant cooler at a local grocery store. It claims to keep 10 cases of beer cold for 10 days. It was selected due to the ease at which the lid was removed, and the size of the internal volume. Due to the size of the coil and circulation fan, much space is needed. Make sure your cooler is dry and clean. Having water or moisture in the cooler is bad.

Start by removing the lid on your ice chest/cooler by whatever means required. In our case, it was 5 screws. We will be building a replacement lid for the cooler, which we can then drill holes into. You could, in theory, use the stock lid and drill holes in it. This reduces it's effectiveness for cooling beer later, unless you like your beer at -70c.

Next, cut and form your pink insulative foam to fit the recess left by the removed lid. Cutting and shaping foam is messy prospect; the chips get stuck everywhere, have a shopvac handy. Cutting foam can be done with a skillsaw, handsaw, or even a table saw. If you happen to have a hotknife made out of nichrome wire, it cuts foam rather effectively. For final shaping, simple 100 grit sandpaper works best. The goal is to create a new lid which needs to be 'press fit' into the cooler. It should compress slightly when it's properly installed on the top of the cooler. This will create a very effective seal.

Finally, install your circulation fan. We used a duct fan from a hardware store. It fit nicely inside of our cooler. Somehow, the specifications on the fan do not list the lowest temp it will operate at. There is some risk that the oil used on the fan will freeze; keeping the fan running should allow the heat from friction to keep the bearings at a happen temp. In practice, this has shown to be true.

When you are done, you should have something which looks like the below photos..