If I designed a boat/ship what would be the formula to determine the waterline of the vessel?

I would need to calculate the empty displacement (the lowest point where the water line would be on the hull) and the loaded displacement (the highest point the waterline would be on the hull.)

For instance: The Titanic engineers designed her with internal watertight bulk heads that rose to slightly above the waterline - How did they determine the water line before they placed her in the water?

Thanks

David

You would need to use some equations relating to the shape of the specific boat, so there isn't really a general formula. A boat will displace a volume of water with the same mass as the whole boat. So what you would have to do is take the mass of the boat in kg and divide it by the density of water (1 kg/L for pure water, but it would be a little different for seawater) to get the volume (in liters). You would then have to figure out how much of the boat would have to be submerged to displace this volume... this is where the shape of the boat comes in.

quote:

---

Originally posted by methos5000:
You would need to use some equations relating to the shape of the specific boat, so there isn't really a general formula. A boat will displace a volume of water with the same mass as the whole boat. So what you would have to do is take the mass of the boat in kg and divide it by the density of water (1 kg/L for pure water, but it would be a little different for seawater) to get the volume (in liters). You would then have to figure out how much of the boat would have to be submerged to displace this volume... this is where the shape of the boat comes in.

---

Which would also have to take in account what material the boat is made of (Steel vs fibre-glass) as well I take it.

So the area of water (due to the shape of the hull) that is displaced is equal in mass as the whole vessel?

David

the only effect the material has on the waterline is its effect on the mass of the boat. of course, it effects other things such as the strength of the hull.

yes, the volume (not area) of the water displaced is equal in mass to the whole vessel.