[templar]

500 tons is a tiny ship.

I've never understood how boats are rated. What does the '500 tons' refer to?

[deport]

I think tonnage refers to load/cargo capacity...

[LonePalm]

I've never understood how boats are rated. What does the '500 tons' refer to?

This is easy. The displacement of a ship is measured in deadweight tons. The portion of the ship below the waterline displaces a volume of water equal to the total weight of the ship and its cargo. In this case 500 tons.

Hope this helps.

Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)

[BlueDragon]

There is net tonnage, which is what it will carry.
Gross tonnage = whatever it is actually displacing.
Hauling out a 69 net ton fishing boat, some years ago
(in Ventura, CA), it was calculated that the full "lift"
was more like 130-140 tons, which would be "gross tons".
500 tons is a pretty big "boat", basically a "small" ship.
The 69 tonner I've mentioned, was 66' documented length
(measuring from rudder post to bow shear at water-line), and 75' over-all (panama measurement).

[Robert_Paulson2]

how much water they displace when they are floated.... usually... a boat will float the amount of tonnage equal to the weight of the vessel.

when it has displaced its own weight in tonnes of water, it floats at that level in the water...

that is what I was told