Defrost Fan

I used a 40mm square (approx. 1 1/2" fan opening) computer type fan, some
internally tapered PVC pipe for a reducer, and a 1 1/4" aluminum flange.
The scat tube screws on over the small rivets and a tie wrap will keep
everything in place.  We shall see if this will actually defrost.
With this setup either ambient or warm air can be used
depending on the position of the heater control.