How dense are boats?

[PTTG]

I'm working on an expansion for Spaceships that will work with various hull types, shapes, and TLs. To do this, I need to know what a reasonable volume-per-tonnage rating is for most ships.

Before anyone posts "well, obviously, less dense than water," true, but I'd like to know some more details, particularly the ratio of loaded weight to unloaded weight.

As you might have gathered, this is a slightly more granular approach to Spaceships.

I imagine that ships of varying materials have differing ratios of capacity and dry mass. My current system assumes that ships can be made of generic wood (representing any timber fine enough for shipbuilding), Iron sheets, and steel, or can be made of some combination of wood and metal for high strength and lightness.

I'm not too concerned about TL, but given the variety of materials available, it's late TL 5.

EDIT: I got a very helpful PM which answers my basic question adequately.

Originally Posted by Agemegos

The density of a ship turns out to be its displacement divided by its gross register tonnage divided by 2.83168. (Because 100 cubic feet of volume will hold 2.83168 tonnes of water).