Gross Tonage

[daiquiri]

The precision depends only on the number of iterations, so it is your decision.
Cheers!

[Guillermo]

I have not checked daiquiri's spreadsehet, but we de a similar process to get the new GTs when altering volumes over deck in commercial fishing and other working vessels.

[KRL]

Is the gross tonnage subtractable?

If I know the volume of space removed, I can find K and the GT of part removed. Can I then subtract the GT removed from the vessel's GT to obtain the new GT?

I used this method as a check to the iterative process and value is quite similar however I was wondering whether it is a correct method for the future as it is a pretty straight forward method.

[daiquiri]

Strictly speaking, GT's cannot be summed or subtracted directly because they are not linear functions of volume. But I've done few calcs and saw that the error obtained by doing so will generally be small, around 1.0-2.0% for a wide range of volumes.
So, imho, you should see what is the accuracy of your volume measurements and decide which way to go.
Cheers!

[Guillermo]

That can work for an approximative process only, but not to submit for approval. Directly adding or substracting GTs is also not good at all when calculating GTs for a FV,as minor variations can bring heavy consequences for the licensing of the vessels.

[Bassoom]

Dear All,
I have to say that the conversation here was very rich.
I have done the same method before to get the new GT after an addition to the super structures, but knowing that what i have done is correct is really encourging.
thanks to all of you.