# gross tonnage vs. net tonnage



## ambianceack (Aug 27, 2006)

What is the difference between gross tonnage and net tonnage. On my certificate of documentation it lists both. 


Is net tonnage when there is really nothing on the boat (except mast, rigging, and motor etc) and gross tonnage (all the gear, water, fuel, provisions, etc.) the maximum (i.e, the difference between the two) I can put on the boat?


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## hphoen (Apr 3, 2003)

More than you want to know...

http://en.wikipedia.org/wiki/Tonnage


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## nolatom (Jun 29, 2005)

there are all kinds of tricks to convert gross tonnage to net tonnage, i.e. "temporary" closures of "weather decks", so that a fairly large ferry can still measure in at under 100 gross tons net.

In general, sailing vessels, designed without regard to how much cargo (who cares?) they can carry, tend to have more gross tonnage than the motor craft which *are* designed to minimize gross tonnage or net tonnage. Really, some sailboats try to be over 5 gross tons, because then you're eligible for U.S. documentation, as I recall.

Honeslty, you really don't want to know. It's a weird system that's been way over-tweaked over the years...


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## lawriegubb (Jul 17, 2006)

Whilst looking at tonnage....Ais is required to be carried by ships over 300 tons. I'm finding it hard to visualise vessel that size. any one got a representative example of about 300 tons?
Lawrie


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## knuterikt (Aug 7, 2006)

Hi
You will be having problems finding a wessel of exactly 300 gross ton (GRT), since this is a "magic" limit. Most vessels will be either bellow 300 (like 299) or a good jump above 300.
Found a wessel on the net with GRT=297
http://www.tdi-bi.com/vessels/powell.htm

Length: 142.33 ft (43.38 m)
Breadth: 35.0 ft (10.67 m)
Draft: 10.042 ft (3.06 m)


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## nolatom (Jun 29, 2005)

lawriegubb said:


> Whilst looking at tonnage....Ais is required to be carried by ships over 300 tons. I'm finding it hard to visualise vessel that size. any one got a representative example of about 300 tons?
> Lawrie


Picture a good-sized offshore tug or offshore oilfield supply vessel. Around 140 to maybe 180 feet overall. If you're thinking of a conventional freight ship or tanker, you won't really find any under 300GT, because of the way tonnage is measured (as closed-in, as opposed to on-deck, cargo-carrying capacity), they'd be just too small to be practical.


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