Just tell me what you do if you happen to have a problem where there isn't a convenient boatyard or marina to hire to fix the problem.
If you have the epoxy, fiberglass cloth, and the right skills... you can fix a lot of issues yourself.
I guess that's my point though. How many cruisers out there are carrying enough fiberglass supplies to fix anything serious? Honestly.
Furthermore, assuming the problem is serious enough to need immediate repair by said cruising sailor, can he/she really do it in the water...assuming as you say that there's not boatyard or marina to help him/her out? And if it's not that serious, can't it wait until he/she makes it to port?
Same with plumbing, electrical, and margarita machine repair.
I'm just saying that these are great skills to know (especially the margarita machine repair thing) but, jeez, aren't you setting the bar a bit high to say that one can't "effectively cruise" without these skillz?