Weight?

[Guest]

Hi, still confused about the difference between reg. tonnage, gross weight and displacement. Buying a 53ft steel ketch, a Bay Class, and all three methods of measuring are given in the specs. So really would like to know - how much she actually weighs...

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[qsiv]

According to Archimedes Displacement = Gross weight.

Registered tonage is a simple calculation based on length, beam and mulded depth, and bears no explicit relationship to displacement - rather it is a measure (inaccurate for yachts) of the carrying capacity of the vessel.

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[snowleopard]

Gross Registered Tonnage is a measure of internal volume of the hull. Gross refers to the fact that it includes spaces which are excluded from the final registered tonnage (e.g. chart space). it was probably intended to be roughly the same as the weight for the type of vessel in common use at the time it was devised but bears little resemblance for a modern yacht.

Displacement is the actual weight. If you want to measure it you could hoist it on a crane and the driver would be able to tell you. the other way is to calculate the displaced volume of water from the hull lines, for a boat floating in salt water 1 cu metre = 1.1 tonnes.

the method of measurement of volume uses simpson's rule which is explained in any yacht design book. it's tedious, especially if you have to take the measurements from the hull but it gives pretty accurate results.

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[Guest]

Hi thanks guys for your answers. You have confirmed my belief that the Bayclass 53 has a dispacement of 25 tons ie she weighs 25 tons. Gross tons was listed as 36.61 and reg tons 24.92. Having paid the deposit, subject to test sail, I was worried about her performance as the broker insisted she was - another weight - 35 tons.
Thanks again

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