So it turns out that the build should be relatively straight forward. We calculated that a boiler (system) of about 25 to 30 KW should suffice and a twin feed tank. However, I was surprised to hear of course that a fire with a back boiler should feed the second coil in the hot water tank but would could not be controlled. What this means is that there is no way to switch off the back boiler when the hot water in the tank reaches temperature. It will switch off the gas boiler but no secondary controls. This is an interesting risk to have. It means that the back boiler on the fire may ultimately boiler the hot water tank. I will need to think through that. I also find that hard to believe and will look into it.
The second coil in the tank is designed to be fed by solar power. So in theory that would never be able to heat the tank to a dangerous temperature. But someone must have cracked this problem. I will look into it.
I can also put my radiators in zones with controllers to have them independently run. I am yet to decide if this is useful. I am not sure why I would only want to hear part of the ship and then let the rest freeze.
The rest of the day was spent sorting the deck. Yawn. Not much to tell there other than the amount of scrap metal is far more than I thought.