Lightship Estimation

Please suggest the method of preliminary estimation of lightship weight (all components) of aluminum hulled high speed patrol craft

 

It is a simple addition of everything. You separate all the components and measure or calculate their individual weights. For example, you can get the weight per square meter of the plating from the manufacturer, and multiply it by the surface area of the hull, deck, bulkheads, etc. Other items, like engines, generators, winches, etc. usually have their weight published by the manufacturers too. Software may offer some shortcuts by calculating area of plating, or total length of stiffeners.

 

Welcome to the forums Adithyan.

What gonzo said, or you could do it the other way. Say that your requirement is something similar a 34m ISLAND class USCG cutter. You start with a full load displacement of ~170 LT and then you start removing your fuel (from you range requirement), stores (from you endurance requirement), crew, ammo, and SAR loadout. What you are left with is the lightship. From here you can then subtract engines, generators, electronics, weapons, potable water, etc. and end up with a bare hull weight...now you can determine if you can actually build a hull to hold all the stuff you took out.

Or you could just look at a complete 3 digit SWBS weight report from a similar craft. Here is what you would see if you were designing a 10K LT training vessels for maritime academies.
https://www.maritime.dot.gov/sites/...erations/rrf/2611/lightship-weight-report.pdf

 

There are other methods of getting estimates on light ship weights from people that have reference of many boats of the same criteria they'll have quick reference about the boats with no fluids for these kind of boats

 

I don't quite understand the reference to fluids for estimating lightship. Engine fluids must be taken into account in lightship, but some fluids and other heavy fluids should not be taken into account.

Edited 21/09/2024 . My sentence should say : "Engine fluids must be taken into account in lightship, but some fluids and other heavy weights should not be taken into account."

 

It's just reference to start you can then add the fluid weights of the capacity of water and fuel
There is good reference of what exist was the main point is all I was suggesting to zoom in on for a starting point.

 

I have corrected my previous post.
I don't know if the concept of lightship is sufficiently clear, but between that weight and the displacement at full load there are many important weights that should be pointed out. The fluids (I would rather speak of liquids) are not usually the most important part to deduct from the full load.

 

I have not doubt you have a clear view

 

Yes, you are correct. Thanks.