I took the prototype hull to the pond. With the 1700kv brushless motor installed I only had to add an extra 120g of lead to trim the hull. Which means I'm in trouble.
Overall it went pretty well. But the hull is obviously too heavy. I need to make the walls and bottom thinner. I may also widen the hull a little bit to get extra internal volume (= buyoancy). Superstructure and everything above deck will have to be very light.
With little freeboard and no deck (just some tape at the front to prevent splashes from getting into the hull) what was bound to happen happened : it sank. At some point I increasedspeed and looked elsewhere for a second. I turn my head back and see the white hull 3 or 4 centimeters underwater. Oops ! I quickly headed back with the ABS hull sinking deeper and deeper.
Our pond isn't really a blue lagoon and you can't see past 40cm. And there are submerged tree branches and stuff. But I managed to pull the hull to the surface and salvage it.
Anyway, back to the computer to fix the hull. And I'm waiting for electronics (RX, ESC).