Originally Posted by chewy
If things weigh less in water though does that mean I don't need as much buoyancy or am I missing something.
Yes. They weight less in water as much as the volume of the material the hull (and rest of
the equipment)in the boat when fully under water. So the construction material of the boat is relevant when considering how much flotation you need. A 3 ton steel boat needs much more flotation than a sandwich GRP boat.
Can be a tricky thing to calculate and a thing to consider is also do You want the hull to be fully submerged but just floating or do you want it to stay slightly above the surface....