Boat Weight

[seashaw]

On cert of registry, I have two weights gross tonnage and register tonnage, what is the difference between these and how much does my boat actually weigh

Mark

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[Robin]

Neither of those figures which are both volume measurements! Displacement is the weight figure you want & it is not on the registration docs.

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[milltech]

Would it be true to say then that most weights are assessed by computer since travel lifts don't measure weight? How else might it be done?

<hr width=100% size=1>John
<A target="_blank" HREF=http://www.allgadgets.co.uk>http://www.allgadgets.co.uk</A>

 

[qsiv]

The only accurate way is to hang the boat of a single point lift with a loadcell above the diamond spans. Smaller race boats can sometimes be lifted from a strop attached to the keel mountings, coming up through the companionway or cockpit.

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[richardandtracy]

Most jib cranes have a good load cell on them - by law they must have a device fitted which rings a bell when there's a danger of the jib being overloaded, and in most cases (ie cranes less than 40 years old) it's an electronic load cell. This will give you a total lifted weight. To get the boat weight, simply deduct the sling weight.

If the crane load cell isn't accurate enough, hire a load cell when lifting the boat. They're usually £20 - 40 per day from a lifting equipment hire place. Try to get one with a flying lead handset - reading the numbers when they're 20ft in the air is difficult.

As a last resort, accurately measure the boat in all 3 dimensions, note the waterline height and ..
No, you don't want to calculate it from the actual displacement do you?

Regards

Richard


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[milltech]

Yes the swimming bath test might be a bit over dramatic!


<hr width=100% size=1>John
<A target="_blank" HREF=http://www.allgadgets.co.uk>http://www.allgadgets.co.uk</A>

 

[qsiv]

The RORC certainly charge £20 for the use of one of their calibrated loadcells - and they wont allow those integrated with cranes - as I understand they are prone to inaccuracies when being used for really accurate measurements. Certainly those integrated in travellifts are noted for their inaccuracy.

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[snowleopard]

gross/registered tonnage

are volume measurements. gross is the whole lot, registered is that less the parts not available for carrying cargo eg 'chart space' is the nav station. i don't know how many cubic metres make a 'ton'. commercial harbour dues are levied on registered tonnage which excludes deck cargo. this is why container ships carry their cargo above decks, the bastards.

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[seashaw]

Is it possible to work out a rough idea of the weight from the gross tonnage as I need to know what size crane to hire. by the way the gross tonnage is 40 ton.

mark

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