I finally got the required building to produce these, so I made a couple (that's the cap it appears) and together with a few other ships, went out to see what they can do.
The first problem I came across was making them fire when I wanted to. In Empire/Napoleon, it's always possible to see exactly when your guns are completely reloaded - as the aiming cone turns bright red - whereupon the ship fires. In this game with cannon bunes, it either takes ages for it to turn bright red again, or doesn't actually bother firing when it does - even if you've turned off 'fire by will' and are doing the firing manually. In Empire when firing manually, I always got a broadside off exactly when I wanted to.
Another thing, I don't get what 'faster reloading' does. I know what it should do: reload the cannons faster, but it doesn't appear to do that to me.
Finally, how many broadsides of four cannon should you need to put a heavy bune out of action? Are they that solidly made that they can shrug off cannon fire like they do? Are cannon ships a poor choice against the bigger Japanese ships - I have to say I think so after my experience.
I have to say also, I was very underwhelmed with the cannon ships. I ended up losing the battle, because the enemy's heavy bunes refused to surrender - they kept routing and then coming back - so time ran out. If I'd had a full stack of firebomb ships, or fire arrow ships I would've won that battle because of their ability to set things on fire - nothing makes a glorified giant rowing boat surrender better than a bit of fire. I mean, surely if you more or less moor a cannon bune right alongside another ship and fire broadsides, the cannon balls should smash one side of the ship, kill a load of people within and exit on the other side? As I said, instead of that, the heavy bunes seem to shrug cannonfire off.
I usually love Shogun 2's naval battles, but I have to say that this one bored me. I imagine FoTS's battles are more fun because they have proper 'modern' cannon ships?
So, has anyone got some tips for me?