Wobbly;
I've picked up a little knowledge here and there over the years-- it adds up over time. Some I learned by trial & error but a significant body of knowledge was learned from others... this forum, for example.
Some stuff I learned in school, some in the military (Ordnance direct support for Corporal IIB), and some in an aircraft Airframe & Powerplant course at a local community college. Much of the aircraft stuff can be found in excellent FAA handbooks that can be downloaded free on the internet. I also learned some by subscribing to Machine Design & Design News magazines. Carroll Smith's books were valuable assets on fasteners and plumbing.
Believe it or not, I learned some things by wandering through Tucson aircraft salvage yards (now extinct) and inspecting how the stuff was built. If you keep your eyes and ears open you can learn. Reading is really important.
When I was a kid there was a huge amount or WW II surplus stuff on the market for bargain-basement prices. I bought stuff and then had an opportunity to take it apart and find out what was inside. This prompted a curiosity of how it worked and why it was done that particular way. By following up on those questions, I learned about a wide variety of things.
When I worked for the National Radio Astronomy Observatory in Green Bank, WV I had an opportunity to make use of the odd collection of knowledge that I had built up and working there greatly expanded that collection. As a "Technical Specialist" I was expected to know at least something about almost everything.
Where else could I have worked with guys who had won Nobel Prizes? It was a great experience-- no money, but a great experience.
In my build diary I try to explain what I've done, how I did it, and what stuff I used. I try to be helpful to someone who may have an interest in learning how to do something similar.
One great fear some have is that they can't do something. This fear is almost always triggered by a lack of experience and knowledge. Both can be overcome. Learn and then try-- we all make mistakes but that should not paralyze us into not trying!
OK, off my soap box and back to the shop....
Regards, Neil Tucson, AZ