sea chest

[N.A.M.E]

Easy really if it's approximately rectangular. Height x length x width in metres x1000, result is volume in litres.

corrected.

I need to determine the length, width, and height. that's my question

 

[N.A.M.E]

Fill it with water. Then drain off the water whilst measuring the volume of water thus drained

I’m supposed to determine the dimensions, as the sea chest is yet to be made.

 

[N.A.M.E]

A vessel of c. 30m is unlikely to have many true sea chests, which are usually found in commercial shipping as in Awol's helpful diagram. It therefore seems wise to assume that NAME's mother tongue is not English (though he is undoubtedly competent), and possibly that his question relates to larger vessels being built overseas without support from a formally qualified naval architect familiar with the calculations that OP seeks . The most likely (single) "sea chest" that springs to mind in context of the OP's question as needing "inputs" is that of the whole hull, and 'displacement' or 'displacement tonnage' is probably the commonest metric used in creating stability programs and hydrostatic curves.

Perhaps the OP could add more information ?

The vessel is under construction ( crew boat 30m) , with the hull completed and the auxiliary system determined.
We are currently working on the piping system calculations.

 

[awol]

David Dunning and Justin Kruger come to mind. I do not think that an internet forum populated by small boat sailors is going to be helpful in, what could be if you get it very wrong, a critical design area of a 30m ship. Having been involved in projects where management demanded material progress before specifications and design were determined I wish you luck! This isn't a CMAL project by any chance?

 

[Daydream believer]

I need to determine the length, width, and height. that's my question

Then you must know the maximum space that the item will fit in to. Plus these days one would assume(Assumptions?) there are CAD sections of the hull. So take a number of cross sections. CAD will give you the area of these sections. The shape is irrelevant, Cad can calculate areas. Apply these to various lengths until you have the volume that you are looking for. If the space you have available does not give the required volume then one needs to go back to the drawing board. If you achieve the required volume with space to spare, then all you need to do is move the design fore & aft to get it in the optimum position. Once again a decent CAD program will calculate the CofG. Pipe volume is a piece of cake with CAD. But you have to decide how much of the associated pipe work volume is contributed to the chest volume & how much to other works ie pumping etc.

 

[jbweston]

Surely if this a real ship construction project, the calculation ought to be made by a professional who's properly qualified, briefed and insured, not by a group of well-meaning anonymous third parties sitting on virtual bar stools?

 

[RunAgroundHard]

The sea chest area is determined from the pipe area that engineers calculate based on the pressure loss calculations for services. If there is more than one service drawing from the sea chest, then you need to add these areas.

Next establish the free flowing area of the grill that will be fitted over the sea chest. The free flowing area has to be larger than the total area of the service pipes. This will give you a dimension for the outlet premier of the sea chest.

Next establish the structural strengthening, baffles between inlet pipes and anodes, adjust adjust the surface area to make sure that it is still above the pipe inlet areas.

You now have a perimeter based on the grillage, likely a depth based on the anodes, stiffeners and baffles if more than one pipe. You can calculate volume.

However, you need to also take into account pressure loss across the mouth of the sea chest due to velocity of the ship, that is the same calculations for parasitic pressure loss in pipes but using the combined velocities. This is a check that the sea chest grill is not too restrictive. If the pressure drop is large, it could cause marginally sized pumps to stall on start up.

If the hull is double skinned, or there are structural members that would get in the way of pipe flanges and isolation valves, then you need to extend the sea chest to clear the obstructions.

 

[MontyMariner]

Where's Refueler when you need him, he should know something about this sort of thing.

 

[fredrussell]

I wonder if OP has considered which anchor to use on this vessel?

 

[Muddy32]

My boss likes 36Bs

 

[Daydream believer]

My boss likes 36Bs

Fredrussel said anchors- Not his girlfriends cup size

 

[N.A.M.E]

David Dunning and Justin Kruger come to mind. I do not think that an internet forum populated by small boat sailors is going to be helpful in, what could be if you get it very wrong, a critical design area of a 30m ship. Having been involved in projects where management demanded material progress before specifications and design were determined I wish you luck! This isn't a CMAL project by any chance?

no it's not

 

[N.A.M.E]

Then you must know the maximum space that the item will fit in to. Plus these days one would assume(Assumptions?) there are CAD sections of the hull. So take a number of cross sections. CAD will give you the area of these sections. The shape is irrelevant, Cad can calculate areas. Apply these to various lengths until you have the volume that you are looking for. If the space you have available does not give the required volume then one needs to go back to the drawing board. If you achieve the required volume with space to spare, then all you need to do is move the design fore & aft to get it in the optimum position. Once again a decent CAD program will calculate the CofG. Pipe volume is a piece of cake with CAD. But you have to decide how much of the associated pipe work volume is contributed to the chest volume & how much to other works ie pumping etc.

thank you very much

 

[N.A.M.E]

The sea chest area is determined from the pipe area that engineers calculate based on the pressure loss calculations for services. If there is more than one service drawing from the sea chest, then you need to add these areas.

Next establish the free flowing area of the grill that will be fitted over the sea chest. The free flowing area has to be larger than the total area of the service pipes. This will give you a dimension for the outlet premier of the sea chest.

Next establish the structural strengthening, baffles between inlet pipes and anodes, adjust adjust the surface area to make sure that it is still above the pipe inlet areas.

You now have a perimeter based on the grillage, likely a depth based on the anodes, stiffeners and baffles if more than one pipe. You can calculate volume.

However, you need to also take into account pressure loss across the mouth of the sea chest due to velocity of the ship, that is the same calculations for parasitic pressure loss in pipes but using the combined velocities. This is a check that the sea chest grill is not too restrictive. If the pressure drop is large, it could cause marginally sized pumps to stall on start up.

If the hull is double skinned, or there are structural members that would get in the way of pipe flanges and isolation valves, then you need to extend the sea chest to clear the obstructions.

I will take this into consideration, thank you very much.