How heavy is the average cruise liner?

Question

How does the weight affect the draft of a cruise liner (how much teh ship goes underwater)?

Answer 1

It's not necessarily the weight but the capability of the engines that determine speed.

There are ships out there at 10,000 GT (gross ton) and up to 160,000 GT (RCL Freedom class). One of the fastest (possible if at full speed ahead) is the QM2 at 150,000 GT.

But also GT refers to the actual passenger space not just weight. How heavy are the ships? Very heavy <grin>

What is underwater is relative to the height of the ship probably more than just weight for balance.

I'm not an engineer so don't know the technical details on any of this. I can only say the Poseiden Adventure isn't going to happen.

Answer 2

Some of the luxury cruise liners are only a couple thousand in tonnage where as the biggest is over 160,000 (Freedom of the Seas)....i went on Norwegian spiril which was 76,000 and next year am going on RC Explorer of the Seas which is (138,000)...ive also been on the smaller 30,000 tonnage ships so it varies....most of the ships now a days are bigger so the norm is over 50,000 by now approaching 75 i think

Answer 3

Cruise ships are rated in Gross Registered Tons (GRT).  Despite its name, this is actually a space rating.  One GRT is 100 cubic feet ...

http://cruises.about.com/od/cruiseglossa...

Definition: Measurement used on a cruise ship. Each gross registered ton equals 100 cubic feet of enclosed revenue-earning space within the ship.

Examples: Most cruise ship ports use the amount of gross registered tons (GRT) to determine harbor and port fees.

The typical cruise ship is between 45,000 and 120,000 GRT (some are bigger, some are smaller, but you asked what is typical).

If you want to know how much a cruise ship weighs, then you want to know how much water it displaces.  

http://cruises.about.com/od/cruiseglossa...

Definition: The weight of the volume of water that is displaced by the ship's hull is equal to the ship's weight. The unit of measurement for displacement is the long ton. One long ton equals 2,240 pounds.

Examples: The displacement of a ship is equal to the weight of both the ship and the weight of the water that it displaces. In order to be buoyant, a ship must weigh less than the water it displaces.

It is easy to find the GRT for a cruise ship.  It is much harder to find the displacement of a cruise ship.  However, we can get this information for a few ships.  For example ...

The QM2 displaces 76,000 tons and is rated at 148,528 GRT

The Voyager of the Seas displaces 64,000 tons and is rated at 137,276 GRT

The Sea Diamond (sunk April 2007) displaced 11,700 tons and was rated at 22,412 GRT.

So it appears that the displacement of a cruise ship is about one half of its GRT rating.  So, if a typical cruise ship is 45,000 to 120,000 GRT, then a typical cruise ship displaces (weighs) 22,500 to 60,000 tons.

How does this effect draft?  For any given hull, the more the ship weighs, the greater its draft will be.  However, the design of the hull will also affect the ship's draft.  Two ships, each with the same displacement will have different drafts if the hull designs are different.