Hi, I would like to increase the range of stability as well as I would like to take the maximum GZ after 25 degrees for a vessel with a fixed draft, depth, and beam in the lightship condition. I was thinking about the effects of shape on the vessel's stability. My vessel's CB is around 0.798. Please share your insights on how can I higher stability within such restrictions. Thank you.
Hi NA Maruf,
There are two things you can change to change the shape of your GZ curve, VCG and Hull Shape. You have a lot more control over hull shape, so that's the easiest one to alter.
The GZ is a function of the righting moment, and the righting moment is driven largely by the second moment of the waterplane area. In short, and massively simplifying things - If the waterplane area is getting narrower, then your stability (GZ) is going to get smaller.
So take a look at your model around your maximum GZ condition and see why the waterplane is getting narrower and what you would need to change to improve that. Maybe deeper chines, maybe higher deck edge.
Taking a look at the Stability Sample model, the GZ max is at 67 degrees in the arrival case. This is where the deck edge gets immersed and the waterplane area will start getting narrower.
You can use MAXSURF Stability to visualize any analysed condition from the analysis. This is a really useful tool if you are looking to refine vessels because you can visualize exactly what is happening.
Regards,
James