Leander, I think it is a great idea, but I wonder about your approach. Better in my opinion to just make a list of the specific things that you want to learn and then approach the people who are in a position to teach you. Example, you want to learn how to swage ? Find a rigger and tell them you are trying to learn that specific skill, or a list of rigging skills that you have made up, and offer them free labor. They could probably use an extra pair of hands and you get to work with people who do it every single day. You probably aren't going to learn something like that from a boat owner unless they just happen to need rigging done, and even then you have no idea if they know what they are doing. You can donate your time at a loft to help make sails, or any number of other things.
Edit - I'd add this too, I have found that you can learn most things with a book, tools, and time. Just take it one step at a time, learn as you go along, experiment, keep trying different things, and eventually you just figure it out. There are some really good books out there, "The Rigger's Apprentice", "The Sailmaker's Apprentice", and many others ...
Edit #2 - Good example of this is how I (and many others) have learned about engines, by getting an engine and tearing it down and then putting it back together.
There is always somebody with an old engine laying around that you can tear apart.