# Stability Problems

DELFTship forum Hydrostatics and stability Stability Problems

• Author
Posts
• #38154
Luiz Fuchs
Participant

Hello,

I’m facing a problem with the stability of my “system” (see the picture)

The “system” is composed by two retangular vessels (10x20x3m) that are carrying a metallic structure (60×7.5×7.5m). They will be used to transport the structure to the construction point.

I assumed there’s no relevant pitch movement and the main problem is the roll movement.

Assuming the software gives the righting arm based on the roll movement, why when I increased the transversal length (from 20 to 30 m) the stability presents worse results and when I decreased the transversal length (from 20 to 10 m) presents better results (bigger righting arm)?

• #38155
Maarten
Keymaster

Hi,
Can you share your model so we can have a look?
thanks

• #38158
Jesus Cruz
Participant

It doesn´t make much sense what you are saying?, can you share an image showing the coordinates system?

If you share the file I will run some calculations, and give you my thougths about it

Regards

• #38202
Luiz Fuchs
Participant

Sorry for the delay,

Here is the File.

• #38204
Jesus Cruz
Participant

Can you send it in 6.35 versión please, I can´t open newer versions….

Thanks

• #38205
Luiz Fuchs
Participant

Hello!

I can’t save in an older version, i don’t have access to the pro version anymore. :dry:

thanks for the support!

• #38206
Jesus Cruz
Participant

Send me the drawing and data to cruzmayora@hotmail.com so I can reproduce your file in my 6.35 versión software and check the problema.

Regards

• #38214
Sharat Jami
Participant

Hello Ifuchs,

I hope this shall give you an idea about how the righting arm curve of a beamy hull and an narrow hull looks like

you can also see the comparision for different kind of hullforms

So in your case the hull is pontoon, i.e it has high initial stability, but it shall last for only upto 10 – 15 deg, after that there is a consistent, decrease in GZ value and it vanishes around 40-45 deg i.e you, so these kind of vessels will be best suited for coastal water operations.

the more wider you make the more stiff the vessel will become. so your max GZ value will increase at same lesser angle
,
I have simulated your case kindly refer the GZ curve comparisions i have found.
CASE-1: Width 30 m

CASE-2: Width 20 m

CASE-3: Width 10 m

I hope i must have clarified.

• #38226
Luiz Fuchs
Participant

mail sent.

• #38229
Luiz Fuchs
Participant

“jsharatchand” thank you for helping with your great report on this forum
and
“cruzmayora” for helping by e-mail (really, it helped a lot) :laugh:

thank you guys!!1 😛