Gross Tonnage

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for a Cranchi Smeraldo 37

The manual states:
Weight of boat with engines: 6500kg
Max displacement with full load: 8310kg

Is the latter the gross tonnage?

 

[sailorman]

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

 

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Yeah i've been reading up on that link, cheers.

Finding the cubic metres of the boat could be interesting, will try an e-mail to Cranchi

 

[sailorman]

for a Cranchi Smeraldo 37

The manual states:
Weight of boat with engines: 6500kg
Max displacement with full load: 8310kg

Is the latter the gross tonnage?

The 6500kg is the displacement " light" tanks MT
The 8310kg is the displacement with tanks full - IE displacement = weight of water displaced by the boat

 

[sailorman]

http://en.wikipedia.org/wiki/Displacement_(ship)

 

[Deleted User YDKXO]

Finding the cubic metres of the boat could be interesting, will try an e-mail to Cranchi

I doubt if they will be able to help. Gross tonnage is a measurement calculated by a qualified surveyor usually for registration purposes in the case of a pleasure boat and if thats the reason you need a Gross Tonnage figure, you will probably have to engage a surveyor to measure the boat, make the calculation and provide a certificate

 

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I doubt if they will be able to help. Gross tonnage is a measurement calculated by a qualified surveyor usually for registration purposes in the case of a pleasure boat and if thats the reason you need a Gross Tonnage figure, you will probably have to engage a surveyor to measure the boat, make the calculation and provide a certificate

Yup, a surveyor will be coming in January. However in the application form, the Gross Tonnage is asked... thought there may have been another way to find out. I'll leave that section blank on the form for now

 

[Tranona]

Yup, a surveyor will be coming in January. However in the application form, the Gross Tonnage is asked... thought there may have been another way to find out. I'll leave that section blank on the form for now

Other than a figure required for Part 1 (or equivalent) registration Gross Tonnage is meaningless. It used to be a basis for charging light dues and harbour fees but is no longer used. So, if it is required to fill a box for some other purpose an educated guess of 11 would be suitable!

If you are having it measured for registration would be interested to know how good my guess was!

 

[MYStargazer]

Gross Tonnage is a measure of useable volume, not weight. Tonnage is a corruption of 'tun' meaning a barrel (usually of wine) which was the basis of tonnage tax centuries ago, and nothing to do with tons or tonnes as a measure of weight.

 

[piratos]

for a Cranchi Smeraldo 37

The manual states:
Weight of boat with engines: 6500kg
Max displacement with full load: 8310kg

Is the latter the gross tonnage?

As said by several - GRT or nowadays GT is useless for pleasure crafts, and various tricks have been used in the past to reduce the GRT/GT - the latter is the "internation convention on Tonnage measurement of ships, 1969.
Dont remember which convention the GRT comes, but here is a comment from BIMCO :

The tonnage of ships is an important factor in their design (Tonnage Measurement No. 13), providing an expression of the ship’s relative size, weight, and capacity, depending which tonnage is employed. Their measurement is governed by an international convention so that there is an international standardisation of these important criteria.


Gross tonnage is a measurement of the total enclosed volume of the ship, and while passenger ship owners might like to boast that their ship of “X00,000 gross tonnes” is the biggest in the world, its main function is as the basis for charging various dues, such as port dues, light dues, pilotage and tug dues etc. “Paragraph ships” (Seascapes No. 58) also tend to use a certain gross tonnage as the break point after which certain additional equipment or personnel must be carried.


Port dues computed over the life of a vessel will be an enormous sum, so the designer of the ship will be anxious to minimise its gross tonnage, while, in the case of a cargo ship, maximising its cargo carrying capacity. Unfortunately, the designers’ zeal to do this may result in certain features which make the ship less seaworthy than would be the case if gross tonnage was not a consideration. Gross tonnage is computed using the “uppermost continuous deck” as one of the measurements, which immediately introduces design problems.


With containerships, for instance, there is the temptation to carry higher deck loads (which don’t count towards the gross tonnage) and reduce the freeboard - the distance between the deck and the waterline. Some smaller containerships now carry more boxes on deck than they do below, which means that they are more liable to weather damage and require a very careful watch over the stability of the ship. Of course the designers could build up the ship’s sides to enclose more of the cargo, but that would mean higher port dues, which might make the ship uncompetitive.


Similarly, the requirement to minimise gross tonnage will encourage designers to dispense with raised forecastles and poops, making it easier for the seas to board fore and aft. Some ships are built with excessive height of hatch coaming, so that it is necessary to climb a ladder to see what is in the hold! But all the cargo within the space between the coamings will not count towards the gross tonnage, so money is saved.


There is now a strong and growing movement to abolish gross tonnage for charging, perhaps using a more obvious measurement such as the vessel’s overall dimensions. Port dues would be then be computed using the “parking space” she is using as she lies alongside. This, to many people, would seem a lot more logical, and probably encourage safer designs.

 

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Thanks a lot for the replies guys, gives food for thought.

I will await feedback from the surveyor.