Not sure if anyone would be able to help me… I’m taking a Transport Canada Stability and Ship Construction 3 exam soon and have just been self studying to prepare.

I have a copy of an old exam that I’ve been working on, and one question has given me fits. Looking through a couple different stability books, I can’t seem to figure out how to answer it. The question reads :

The motor tug “Sept Iles” is floating in normal operating condition 50% consumables SW. If its FP tank is pumped full with SW, calculate the new metacentric height (GM) corrected for free surfaces (FS) and the vessel’s new longitudinal center of gravity (LCG).

I have the ship stability book available to me, well online http://www.scribd.com/doc/175729282/Sept-Iles-Stability-Book

I’m assuming they want to know GM transverse, although I could be wrong. I’ve used GM L = L / t xGG 1 and can get the longitudinal GM.

For 50% consumables the GM solid is 1.16, GM fluid is 1.12. Would using the GM fluid be all I need to do to “correct for free surfaces”? The FP tank is on the centerline, and they also say it is pumped full, so I can’t see it affecting free surfaces any more. The stability book gives me a Free surface inertia of 36 for the forepeak tank… I cannot find what this means anywhere.

The stability book give me lots of information, I just don’t know how to use it to find the new metacentric height.

I’ve found the LCG just by using the moment of the full forepeak tank, that is fairly easy.

Thanks for any help… figuring out stability is giving me grey hairs…

-Sean