hydrostatics calculation

In freeship, I tried to find the hydrostatics by entering the
start draft=0m
end draft=1.7m
step draft=0.010m
trim=0.377m (which is the default value when i opened "hydrostatics" under calculation tab.
I got the result in .txt format which shows the calculation only till draft of 0.280m. I tried varying draft step and tried other combinations as well but unable to calculate hydrostatics till the actual draft of 0.377.

1) What is the reason for this?
2) When i click on "hydrostatics", i get a window where the trim is default at 0.377m WHY?
3) In "design hydrostatics" midship draft =0.377m. Is trim = midshift draft. I think Trim=draft forward-draft aft.
I hope i'm not completely mistaken. Please help!

 

My guess is that the calculation stops at 0.28 m because on the next step the program finds a leak point, a hull opening, an open transom or similar. In simple words, you have a point in your hull through which water can enter. In mathematical wording, at some draft the underwater surface which describes your hull is no more simply connected, which appears to be a necessity for Freeship in order to work properly.

How about posting your .fbm model here, so that we can check it out and try to find the leak point?

Cheers

 

hydrostatics

thanks for the help

 

I have performed the calculation with no problems. However, I have set the trim to 0.

A trim of 0.377 is equal to boat's design draft, which means that the ship is so inclined that very soon the transom would get submerged during the calculations. That is probably the reason for the premature end of calcs.

Cheers

 

A note about your model: it has awfully lots of control points!

It must have been a real mess to create a fair surface with such a huge number of control points. They also slow down and eat the memory of the computer, because with so many points the hull surface becomes mathematically too complex.

My advice is to keep the number of control points to a minimum required to give the hull a shape which you need. In this case a net of 15x10 control points should have been enough.

Cheers

 

thanks a lot for the help, after changing trim to zero, i got hydrostatics till draft of 0.450
evn if end draft is 1.7m. and the reason is leak point at/after 0.450m of draft
i increased control points thinking it may give accurate values as meshing increases.
but actually, trim is not equal to zero. because by running design hydrostatics (in "design hydrostatics.txt"), angle of trim=2.001dgr

Part of the text file is as follows
Parameters of ship sinkage:
Difference of midship draft : 0.000 m
Midship draft : 0.377 m
Initial transverse metacentric height ho : 2.653 m
Initial longitudinal metacentric height Ho : 21.125 m
Angle of heel Psi : 0.000 degr
Angle of trim : 2.001 degr