That link you found Bert was a real gem. Fascinating reading. As a nipper, I was taken by my parents on a few trips to Llandudno/Menai Bridge on the St. Tudno. The many photos in the link highlight what a sleek, beautiful vessel she was. The "sleek" bit was touched on insomuch as she had a narrow beam. My stomach well remembers her rolling like a pig! The wonderful (I thought so anyway) smells of hot oil and steam wafting up from the engine room, clanging of the telegraph AND folk throwing up over the side remains in the memory. I don't remember the cardboard "sick pots" though!
The passage through "The Swillies" was always gripping. If the tide was right, the water was almost boiling - or so it seemed, due to the very narrow channel and the unseen rocks lurking below. Would the top of the masts clatter the underside of the bridges ? Plenty of clearance of course, but when you were knee-high to a grasshopper things seemed different.
Thanks futurepast for ringing "Full Ahead Together" on the subject.