Had a new submarine come in for a 6 month checkup, and the skipper had a small complaint. At low speed, the boat would tend to turn left, and he had to hold a couple of degrees of right rudder to keep the boat going straight. Ring on a couple of bells and all was well, straight course with zero rudder. But at full or flank, the boat would go the other way. Needed a couple of degrees left rudder to hold a straight course. Somehow I was assigned the task of investigating this.
Turns out a) the hull wasn't dead straight. When you're welding all these pieces of big pipe together, tolerances add up. This hull apparently ended up with a slight stbd kink - just enough to make it want to turn left on its own. b) The upper rudder wasn't symmetrical. You'd think these things would be made to templates and this wouldn't happen, but you could actually see it if you ran the periscope up all the way and looked down on the rudder - it had a camber in it. I think at low speed, the hull took control, while at high speed the rudder had enough lift to overpower the hull.
I can see that with any boat, there'll be some differences between the way things 'should be' and 'the way they are'. The trick is in identifying the differences and figuring out what can be corrected and what must just be lived with. Kinda applies to a spouse, too. The Admiral has certainly learned to live with lot of my 'quirks'.