Back to the damper van - last time the model had received front and back extensions filled with polystyrene foam. I hoped this would provide enough buoyancy to keep it above the water.
Back in the test tank (basin) my hopes were dashed. While the van floated OK, the bow was just under water. Admittedly I had added a set of AA batteries but there is still a receiver and speed control to be fitted so this boat isn't going to get any lighter !
Water also found its way in through the grille. This isn't a big problem as I've not sealed this up yet, but you don't really want water anywhere inside a boat. On the plus side, it didn't sink, and the water ingress wasn't huge so the project is still worth pursuing.
So, the next move is to find some lighter batteries. Obviously 4 AA's are too heavy so a smaller pack will be required. There's a lot of choice here, I just need to find one. If all else fails a set of AAA's won't weigh as much. Power requirements won't be huge as this isn't a fast boat. I'm only after 6 volts as the electronic require a certain amount to work.