You are quite right about the nickname Banana Boat and I also am not sure why.
But when in the army in the 60s I and a friend used to go into the docks and work partime on the banana boats for extra cash while on leave!
One day we were in the hold of a ship and a whistle blew, next thing everybody raced out of the hold by any means possible and left us two there wondering what the heck was going on! Then someone told us to get out as there were spiders spotted among the boxes. And boy were they big, Banana Spiders and a couple of Tarantulas!
In one of the warehouses they had jars on shelves around the walls which were full of preserved spiders!
Why was she called "the Banana Boat"
The correct answer is this.
As a kid, we would see her goinig about her business, up and down the Clyde passing various points on the way.
Us weans (kids) shouting, there goes the banana boat.
In fact the was carrying raw sewage from Glasgow, to dump in the open sea.
Mums and Dads could not say, she carries S**T hence the name, The Banana Boat. Run by the Glasgow Corporation
She did also carry pensioners on a day out, "Doon the Watter". she was reported to be spotless clean. I bet she is not so clean today, as when she was a Banana Boat.
These are facts as I remember, I stand to be corrected on any points.
I also remember we had good fishing off lower reaches of the Clyde.
Gourock,Dunoon and lower. Wonder why? better then than now.
Maybe good food like Bananas
I am a Renfrew boy and Shieldhall was built in our local yard, Lobnitz & Co. I was part of a group of third year pupils at the High School and we were given a day touring Lobnitz from drawing office to the slips as part of a career programme as were due to leave school soon after. We were shown over a ship which was being readied for launch and I later learned that she was the new Shieldhall, named after the area of Glasgow where the sewage treatment plant was located. We were all very proud of Lobnitz shipbuilding history. She always gave the yard a 'toot' when she passed. Apparently, she changed the colour of the Firth of Clyde near the ***braes when she emptied her tanks!