Hello guys, I'm a n00b here, but a rather civilized one so no need to worry.

So, I'm a bit hooked on the pirate phase, and I hope to one day build a Light Schooner sailboat (I've got a book in mind and plans to tell me how to do so. Done some research, and found out it'll cost me about $3k in supplies, which is a good $20+k savings if I were to buy an already-made boat). One thing about me is I like to keep things basic. I want a basic boat that looks basically like an 18th century vessel in some way (or suggestive of it) and I want basic 18th century cannons to go on the boat as well. Firing ones, but potentially harmless firing ones. Just for show and laughs. Of course, you have to be careful around anything like this (boats and cannons alike) because they ARE potentially dangerous, but I'm a careful person who just wants to have some harmless fun and say, "I made this!"
And, of course, some of my ideas are far-fetched, but one can dream, can't they? I will, at least. So what I'm asking here is, if I were to build spud-cannons that are remeniscent of the 18th century naval cannons to put on my little boat, how would I do so (as in build the barrel and fit the technology safely and conveniently in it), and are there plans already established for this design of cannon?
Thanks a lot for your patience with a beginner, folks! I will keep pushing on with my romantic intentions. Ha!