Originally Posted by
evilroy
Where do you actually start?
I don't have a intelligent answer for you, but I know of a couple helicopter models that started as 2 saw-horses with 2 "unbreakable" ventilation ducts laid across them, from which they built the entire aircraft around those ducts. It's only my opinion, however, when those "unbreakable" ducts eventually do break, it seems like you have to disassemble the entire aircraft to replace them.