Let's keep this thread going. I've been daydreaming about learning to sew heavy goods for a decade or more and I think it's time to commit.
Gotta take some classes first to learn what sort of machine I need though. From the posts above I realize that the methods learned from a "run-of-the-mill" sewing class might not necessarily pertain to what we (in this forum) want to do...but at this point I really don't know anything at all when it comes to sewing.
The idea of buying a 70-year-old industrial sewing machine sounds good. But I'm a techie sort of guy. Once I know what I need I'll dump a couple of grand on an appropriate, and new machine and go from there.
A heavy duty industrial machine is needed to sew heavy materials (canvas, cordura, webbing, leather, even thin plastics).
I bought a new Juki DNU-1541S with table for under $2000, with zero knowledge about how to sew, ZERO. I just knew I wanted to do it. A seamstry type sewing machine will not work, don't waste your time and money.
A sewing class will do basically nothing for you. It probably will even lead you in the wrong direction.
A industrial machine is a must, only reason to buy a used one is if you can't afford the $1500-$2000 or you think you might find out you don't have the time to dedicate to the self study required to sew heavy materials.
No one is going to teach you how to sew heavy materials, not unless you go get a part time job in a sewing factory if any still exist in your area.
Buy a Juki, Techsew, or Consew. I played around with the idea of buying a used machine but eventually realized the savings was not worth the time to find a decent used machine that didn't need work. Buy once cry once.
YouTube and Google searches are your information sources. Self study and practice practice practice are how you will learn.
Trust me I've been there, and I've done it, I can make anything now basically with one machine one thread size and one needle size, oh and a L and R zipper foot.
No one is going to teach you how to sew heavy materials.