Talk:Tonnage

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A long ton measures weight. Its value is 2,240 pounds. (The common ton in use in the Imperial and U.S. systems of measurements is the short ton of 2,000 pounds.)

I don't know where the 'Imperial' in the bracketed part of the above came from but the reverse is true - the short ton is almost never used in the UK, 'ton' (and 'Imperial ton') almost always meaning the 'long' ton of 2,240lb.

A measurement ton measures space. Its value is 100 cubic feet.

This is the Registered Ton as used in shipping, which is why ocean liners like the Titanic and the two Queens used to be measured in Gross registered tonnage (GRT), which has nothing to do with the weight of the ship (displacement) but is the amount of space the ship has for carrying cargo, in units of 100 cubic feet. The 'registered' part of the name comes from the amount of cargo space the ship was registered at Lloyds to safely use.

Warships are measured in displacement tonnage, which is why a liner like the Queen Mary appeared to weigh more than most battleships, which of course wasn't true, as what was being measured in the liner was space not weight. :) —The preceding unsigned comment was added by 82.111.113.204 (talk • contribs).

Actually RMS Queen Mary did displace nearly 80,000 tons (and also measured about 81,000 tons gross). And she therefore was heavier than the Yamato class battleships, the heaviest ever built. But the point is correct; displacement and gross tonnage measure two different things. And in recent years shallow draft cruise ships with large superstructures boast enormous gross tonnages on relatively modest displacements. Kablammo 03:35, 19 May 2006 (UTC)

Contents 1 Definitions of "ton" 2 More on Tonnage 3 I think we're getting there ! 4 Displacement Tonnage Calculation Error

[edit] Definitions of "ton"

I've removed the following material, because for now I can't see how it fits in (the article certainly doesn't explain):

• A measurement ton measures space. Its value is 100 cubic feet (2.832 cubic meters).
• A freight ton also measures space. Its value is 40 cubic feet (1.133 cubic meter).
• A long ton measures weight. Its value is 2,240 pounds (1,016.05 kg). (This is the common ton in use in Imperial measurements; the ton of the U.S. system of measurements is the short ton of 2,000 pounds (907.18 kg).)
• A metric ton (commonly written tonne and abbreviated t) equals 1,000 kilograms.

How should this be re-introduced (if at all)? For example, I think "measurement ton" belongs under gross/net tonnage, because one ton = 100 cubic feet in those systems (as far as I know). So where does "freight ton" come in? I think the definitions of "long ton" and "tonne" should simply be left to the long ton and tonne articles.

As for the paragraph "Gross Tonnage ... is often expressed in gross tons, measurement tons, or cubic meters." Quite apart from being absurdly circular, isn't this just totally wrong? Isn't one gross ton equal to 100 cu ft? — Johantheghost 19:27, 1 January 2006 (UTC)

I've found some references, and had a go at re-doing all the above. I think freight ton belongs in ton. — Johantheghost 21:03, 1 January 2006 (UTC)

[edit] More on Tonnage

Tonnage in the modern sense is solely a measure of volume. Weight measures (such as displacement) are no longer referred to as 'tonnage'. (See Society of Naval Architects and Marine Engineers text books). What is required is a definition of Lightship, Deadweight and Displacement. Once I figure out how to do that I will add definitions. Currently Lightship refers you to the wrong definition - that is a ship with a navigation light on it). The weight terms lightship and deadweight are sub-parts of displacement. Lightship is the weight of the ship and deadweight is the weight of everything it carries (ex: fuel, cargo, crew, provisions, etc.).

I rather like the idea of Wiki and hope it gets used in a constructive manner. What is required is a greater effort to reference accepted text of specific subjects to ensure Wikipedia is collecting facts and not just a lot of opinions. Jmvolc 00:51, 10 May 2006 (UTC)

Hi, a couple of points:

• "Tonnage in the modern sense is solely a measure of volume": how many times in how many different contexts have I seen the term "displacement tonnage"? I can't even count them. The Society of Naval Architects and Marine Engineers may well have its own definition of "tonnage", but even that society can't be considered definitive if the term "tonnage" is very widely used in a different way. Wikipedia has to reflect how the world uses a word, not just one society, however learned.
• When you deleted displacement, did you click on "what links here" (on the left) to check the articles that reference this one? I have a feeling that a number of other articles use this one to provide a definition of displacement.
• So, at the very least, I believe that the tonnage article should mention displacement. Not because it's necessarily "correct", but because this is where people will come looking for it. There are two ways we can do this:
  1. By creating an article for "displacement", and linking to it from here. See Golden Globe, and how the article refers to the movie awards, but provides a redirect to the yacht race. If we do this, we need to check every reference to tonnage to see if it needs to be redirected.
  2. By including displacement here, noting that this is not a strictly correct usage of "tonnage".

I prefer the latter course, at least for now, because they really are very closely related at least. I don't think "displacement" (or "deadweight" for that matter) are large enough subjects to justify their own articles. And it's noted under "Origins" that they have common origins.

So, I've done (2) for now. All comments welcome.

Other points:

• The way to handle "lightship" is to put a note at the start of the lightship article pointing to the article that discusses the ship weight -- currently this article. I've done this.
• Your point about "reference accepted text of specific subjects" is absolutely right, and that's why it's a cornerstone of Wikipedia policy -- see Wikipedia:Verifiability. So, if you could add references for the informaton you added, that would be great.

Cheers, — Johan the Ghost _seance 11:49, 10 May 2006 (UTC)

Here is a source for various definitions, including gross tonnage, displacement, and block coefficient (used for determining displacement): http://www.foreship.com/pdf/naterms.pdf Would this be helpful? Kablammo 03:43, 19 May 2006 (UTC)

[edit] I think we're getting there !

A few points of clarification (I hope) ...

• I am very new to this media so please excuse my first coarse attempts at contribution
• Tonnage is not a term used exclusively in the marine industry but that is all that is described here ... is there some way of pointing out that other industries use this term as well?
• In the marine context, using 'tonnage' in reference to any weight or mass item is incorrect and should be noted as such. Would it not make more sense to move the section discussing the weight terms to their own entry and refer to them from here?
• I am still too much of a neophyte to appropriate references but hopefull Johantheghost can help???

Jmvolc 01:28, 16 May 2006 (UTC)

OK, to respond:

• No apologies are required for any genuine contributions, coarse or otherwise! The whole nature of any Wiki, and Wikipedia in particular, is that it's better to have people slam in changes so that other people can tidy them up, than to spend forever agonising over what is "right".
• Non-marine uses of "tonnage": I'm not aware of any such uses, so maybe the way to start is to write a sentence or two about them, either here or in the article, and we can discuss the best way to handle them. Probably at first the way is to split this article into sections like "Maritime", "Dental", whatever... if the sections get huge, then they can be split into articles.
• Displacement as "tonnage": the term tonnage is so frequently used to refer to weight that I really believe that this article needs to mention it. Given that "tonnage" originally did mean weight ("the eventual decision to assess dues based on a ship's deadweight..."), I think there's ample reason to include displacement in this article. We just need to note that in modern usage, "tonnage" is strictly volumetric, and I think we've about got that covered. An article on "displacement" would be too small to be worthwhile, I think.
• References: if you provide references in whatever format you like, I'll be happy to tidy them up. Just stick the publication info and page numbers in the text, or whatever.

Cheers, — Johan the Ghost _seance 15:13, 16 May 2006 (UTC)

[edit] Displacement Tonnage Calculation Error

I believe there is a math error in the article below: In the last sentence of the second paragraph; dividing by 64 results in a very small number. Multiplying seems to result in a more reasonable answer. (Dividing by 35 to get long tons seems right) 70.137.56.237 03:00, 18 May 2006 (UTC)Bobthenewbie.

Weight measurements While not "tonnage" in the proper sense, the following methods of ship measurement are often incorrectly referred to as such:

Displacement is the actual total weight of the vessel. It is often expressed in long tons or in metric tons, and is calculated simply by multiplying the volume of the hull below the waterline (ie. the volume of water it is displacing) by the density of the water. (Note that the density will depend on whether the vessel is in fresh or salt water, or is in the tropics, where water is warmer and hence less dense.) For example, in sea water, first determine the volume of the submerged portion of the hull as follows: Multiply its length by its breadth and the draft, all in feet. Then multiply the product thereby obtained by the block coefficient of the hull to get the hull volume in cubic feet. Then divide this figure by 64 (the weight of one cubic foot of seawater) to get the weight of the ship in pounds; or divide by 35 to calculate the weight in long tons.

Sorry ... its :

W = rho g V where:

W = weight or displacement

rho = density

g = gravity

V = volume

So .. with 64 lb/ft³ and 35.0 ft³/L.Ton for Sea Water ...

This means that if V is in ft³, displacement (W) is:

W_{(in long tons)} = V / 35.0

W_{(in pounds)} = V x 64

I have changed the article appropriately.

Thanks, Jmvolc 01:48, 19 May 2006 (UTC)

Excellent, it's looking good! — Johan the Ghost _seance 14:19, 19 May 2006 (UTC)