Hi there,
I was wondering how ship designers would calculate things such as draft and different coefficients of form (such as block coefficient) during the design stage, before the ship would be set in the water. Does anyone know what formulas would be used?
Thanks.
thanks for this. After determining the internal volume and weight of the ship, how would the draft then be calculated?
Thanks for the input. Would the block coefficient come into play with checking for the correct weight and if so how would that be calculated?
Hold on, you have to have some requirements ( a SoR...Statement of Requirements) in order to begin the design process. For draft as an example, a 1950's trans-Atlantic liner has twice the draft of a modern cruise liner, even though they superficially appear to have the same size, shape, and function. It is because the weather and route requirements are different.
Start with a volume (displacement) to length curve for the speed-length ratio you want/are given (these can be looked up in a good NA text). This gives a the station areas and a midship section within beam and draft restrictions based upon standard types (cargo, combatant, passenger, speedboat, sail boat, etc.). You seem to have some of these already, so work them all up.
The LWL to speed places the midship location, then put in a few waterlines, diagonals (and or bilge radii) and a profile to cover the "cargo" block buildup (ie container hold stacks, cargo holds, staterooms, weapons, engine room and machinery spaces, etc.).
Then the cross-checking of stations/waterlines/diagonals to the displacement-length curve goes through a few cycles as you put in some control points (design waterline, deck edge, turn of the bilge, etc) for each station and begin your weights. Cycle and repeat until structure, decks, weights, powering, and prime mover are pretty settled. Then finalize the shell and do a clean lines plan. After the lines plan is finished and all the limits (tonnage, length, beam, etc) are met, then pull the offsets off.
Of course, a lot of that work today depends on how you are developing the drawing, by hand to be digitized or directly on the computer. Sometimes you need to work with (or around) any drafting program you are using. FWIW, I have not yet found a CAD program I like for developing a lines plan from scratch.
