Lightship Calculation

Hi all,

I am trying to calculate the Lightship of my Panamax Tanker. I've got confused with which methods I should use.

I tried with Watson method but it is not clear how to apply it.

Any suggestions please?

Thx, Alaa

 

as far as i know, weight of lightship is summary of weights of hull, machinery complex, equipment (cranes and similiar things) and project reserve (about 100 - 200 metric tonnes)

 

The only method available is to add up all the weights that should be included in the Lightship. You can do it with a hand calculator, an Excel spreadsheet, or some software ready to add the weights you specify.
Another issue, that does not seem to be bothering you, is to know the weights that should be included in the Lightship, which are, in short, what kruklindete indicates.

 

Thanks kruklindete & TANSL,

I forgot to mention that I just have the main parameters of my ship. I do not have any details about the weights.

So I am asking about an empirical method to estimate the lightship depending on the main parameters of the ship.

Regards, Alaa

 

The Watson method does require that you know a little something about the proposed arrangement of your vessel.

There are several similar methods which can be used. I did a google search for "watson method for lightship weight" and found not only Watson's original paper, but several other similar methods.

I have a copy of the Watson paper. If you have some specific questions, I would be glad to try to answer them.

 

Thanks for answering,

In fact I do not have the original paper for Watson. I have the Practical Ship Design.
Can u please send the paper? I am not sure if it has more details than the book.

Thx, Alaa

 

You can find the paper here:

http://www.akademi.itu.edu.tr/helvaci/DosyaGetir/57571/PAPER-2-1.pdf

It is quite large; about 18 Mbytes scanned, so be prepared to wait for it to download.

 

Abalkees,

If you have only main particulars, you need to use a reference ship to estimate your lightship. I advise you to check for publications like Significant Ships from RINA where you will find a lot of useful data for a conceptual design. If you don't find the exact same dimension, you need to correct the lightship weight.

Since you have the Practical Ship Design, check the section 1.3 Ship Design Data that emphasizes the need for a naval architect to collect data from reference ships.

For your specific need, I would say that a Panamax containership will be around 20,000 MT (rough estimation that needs to be refine as your design progress). It depends of the percentage of high-tensile steel you will use, your GA, Owner's specific requirements and so on.

Good luck