What is the benefit of using wood in the nozzle design?

I’m just curious as to why wood was used in this design.

Wood is somewhat of a termal insulator. Aluminum would have transferred heat to the wires. That and wood is inexpensive and easy to have shaped to specifications. You could probably have gone with aluminum and a thermal break there, or a machined stack instead of the compression stack that exists, but it works pretty well and i’ve not seen one catch on fire so far.