gonad
Well-Known Member
which one is the out of water i.e. in crane and cradle wt please? i say gross
grosss v nett tonnage
- Thread starter gonad
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Gross and net tonnage refers to volume of a vessel and the amount of cargo weight it can hold. Gross tonnage is the total volume of the vessel that could be filled with cargo. Net Tonnage is the Gross tonnage space minus the area that can not be used for cargo e.g. living quarters, engine room, bridge. The tonnage is calculated by multiplying the cubic feet by the weight of water. Basically this gives a common metric for calculating fees for all vessels.
The weight of the vessel out the water is not relevant to gross/net calculations.
The weight of the vessel out the water is not relevant to gross/net calculations.
gonad
Well-Known Member
basically trying to give crane driver a dead wt for his calcs
michael_w
Well-Known Member
Displacement is what you want. Suggest googling to get some approximation of your boat's weight. Bear in mind this can vary considerably, Different keel options, engines, etc, etc.
Oldhairy
Well-Known Member
Then the figure you want is the diplacement
charles_reed
Well-Known Member
Displacement (from the builder specs) + 40% (for all you've stowed on board).
At a guess for a GRP 41' 15-19 tonnes (unless it's a lightweight flyer). People always under-estimate their boat's weight - hence all the horror pix of tumbling cranes.
At a guess for a GRP 41' 15-19 tonnes (unless it's a lightweight flyer). People always under-estimate their boat's weight - hence all the horror pix of tumbling cranes.
jwilson
Well-Known Member
If the boat is a Carter 39 as listed in your profile it's nominal displacement is about 15,300 lbs. Add in at least 2,000 - 3,000 lbs fuel, water, and stores, and you have a displacement of about 18,000 lbs, or 9 tons. Get a crane that will lift 10 tons or more. As others have said gross and net tonnage have nothing to do with actual weight.
VicS
Well-Known Member
You need a crane rated at much more than the actual weight of the boat .... at least you do if the crane has to reach at all. If it does you may well find you need a 50 ton crane.
gonad
Well-Known Member
yes carter 39 anyway driver got afraid and so will have to find another way thanks all
KellysEye
Well-Known Member
>Net Tonnage is the Gross tonnage space minus the area that can not be used for cargo e.g. living quarters, engine room, bridge
Yes that's true which is why I'm bemused by our Part One yacht registration which has Gross tonnage but obviously has no space for cargo.
.
Yes that's true which is why I'm bemused by our Part One yacht registration which has Gross tonnage but obviously has no space for cargo.
.
Bobobolinsky
Well-Known Member
Agree with previous, you need a 50 tonne crane with a spreader frame. It's the lifting radius that will be the problem.
Refer to Post No.2; Gross Tonnage is the weight of the total volume of water which could be contained within the vessel. Your part One registered yacht can contain N x Litres of water. The portion of the vessel occupied by machinery, living space etc. is also N x Litres hence Nett Tonnage = Zero Tonnes.
VicS
Well-Known Member
KellysEye
Well-Known Member
>Refer to Post No.2; Gross Tonnage is the weight of the total volume of water which could be contained within the vessel.
I read that post and gross tonnage has nothing to do with water.
I read that post and gross tonnage has nothing to do with water.
Tranona
Well-Known Member
Refer to Post No.2; Gross Tonnage is the weight of the total volume of water which could be contained within the vessel. Your part One registered yacht can contain N x Litres of water. The portion of the vessel occupied by machinery, living space etc. is also N x Litres hence Nett Tonnage = Zero Tonnes.
Not sure where you got that idea from. The explanation that VicS gives is the correct one.
davidej
Well-Known Member
I don't think these two contradict each other
Boat-builders didn't really fill the hull with water and then weigh it - instead they developed rule-of-thumb calculations from various measurements that gave a reasonable estimate of what the water would weigh, which is described in this latest post.
Boat-builders didn't really fill the hull with water and then weigh it - instead they developed rule-of-thumb calculations from various measurements that gave a reasonable estimate of what the water would weigh, which is described in this latest post.
Daydream believer
Well-Known Member
Op has not quoted radius so your estimate may be well wrong
A 30 tonne tele will lift the boat with ease if within radius
What op should do is go to crane hire firm & get a quote for a contract lift
They will send a chap to assess the job he will want to see where crane is to stand & where boat will be when lifted & where it has to be placed
He will then give you a quote.
Any reputable hire firm will know about spreader bars etc
He should also include for a banksman in the quote
You just stick the boat by the wall or pontoon & stand clear. Do not even think about getting involved.
If the hire firm bring the wrong size crane it is down to them
Tranona
Well-Known Member
Yes, they do. Displacement is nothing to do with Registered Tonnage (see VicS post). That is the whole point of this thread. The OP was wanting the weight of his boat and asking which of the registered figures he should use. The answer is neither.
Tonnage are a calculation based on the volume of the hull, not its displacement, for use in calculating port charges, light dues etc. It is calculated gross - total volume and net after adjustments for non cargo carrying volume. It is not calculated by the builder, but by an approved surveyor who measures the boat according to the formula.
Displacement can also be calculated and will obviously vary according to the amount of equipment the boat is carrying. There is a standardised ISO method (number escapes me).
Tranona
Well-Known Member
Problem is, though, the OP is in Brazil (I think) and has already reported in another thread that the crane driver refuses to lift the boat.
VicS
Well-Known Member
Gross and net tonnages have nothing to do with weight of water.
They are the volumes of the internal spaces in cubic feet divided by 100.
1 ton is therefore equal to 100 cuft.
(100 cuft of fresh water weighs 2.79 tons, of sea water a little more.