hydrostatic calculation test

[maricpdm]

Version: free
test: box: L=10m, B=6;m T=3m mean shell thickness=0.01m
calculated by hands:
moulded volume=180m³
total displ. vol = 10.02×6.02×3.01 = 181.56m²
wetted surface area = 10x3x2 + 3x6x2 + 10×6 = 156m²

delftship free result:
total displ.vol=182.16
wetted surface area = 216

I suspect that the result by delftship is not right.

Attachments:

• 10.jpg

[maricpdm]

nobody explain this difference?

[Maarten]

Hi Fengjun,

The most likely explanation for this descrepancy is that you placed this box with one side on the center line (the SB side of the box), but did not remove this side plane of the box. Then, when calculations are done, the SB side is mirrored (including this extra side): now there are two planes at the center line touching, but wetted. To get correct results remove the offending surface.

To understand what happened, move the box away from the center- you’ll see the calculations are correct.

I hope this explains the confusion.

[maricpdm]

thank you very much.
I understand.

[maricpdm]

about block coefficient in delftship

In this sample, why the block coefficient is more than 1.
Cb is calucated with displaced volume in delftship?

[Marven]

CB is calculated using the displaced volume and the length and beam from the project settings. So either the displacement is calculated incorrectly (perhaps by using the wrong shell thickness or appendage coefficient) or the length and beam from the project settings are incorrect.

[Lewis Ardron]

My calculations for the volume of your “test piece” agree with Delftship.

With your calculations for whetted area you are not taking into account the skin thickness you specified. Delftship adds the skin to the outside of the lines plan.

[Markku Lindholm]

For wetted surface You shold take accout allso the bottomplate area, 6×10 =60.

[Author]

Posts