This is something I've been wanting to build for a while, - a good old fashioned river gunboat.
Even though it's built on two hulls this is a really small gunboat and after trying to fit in a funnel and steam gubbins I gave up and decided it has one of those new-fangled Otto cycle engines and the exhaust is run up the centre of the mast (yes such things were done in reality).
Many years ago now there was a set of beta version river gunboat rules available free entitled, 'More Gunboat Diplomacy'. Fortunately I still have a printed copy of the free rules because they cost money these days. The rules weren't intended for micro model gunboats they were intended for models sized for 25-28mm wargaming figures. I always wanted to have a go, but baulked at building a suitable fleet of gunboats. Now with Lego (and certain other clone brands) my dream is made possible! Yay!