Brief Description: Installed heater box on firewall
I decided to mount my cabin heater control box on the starboard side of the firewall. The two inch duct tube will then run inside the lower part of the forward baggage compartment close to the inboard panel. The control cable will be routed between and just above the duct where it will exit through a hole in the firewall. It will loop around and under the box to a bracket just below the butterfly arm on the vent box. I haven't fabricated the bracket yet but it will probably be made from some scrap aluminum angle. There will either be a doubler with platenuts on the back for a couple mounting screws.
The trickiest part of this task was deciding how to cut the 2" hole in the stainless steel firewall. After some reading and discussion with another builder I decided to try a good quality bi-metal hole saw. I ruled out the fly-cutter due to its difficulty to control in a hand drill. I also wasn't sure how the cutter would stand up to the stainless. In the end I purchased a Lennox 2" bi-metal hole saw with an arbor at Lowes. Using a very slow rpm on my hand drill and some Boelube I was able to cut a nice clean hole. I fabricated a double with platenuts for the aft side of the firewall.
