Inclining Experiment

[mbhanoo]

Hello Everybody,

In the inclining experiment calculations, why free surface effect is added to the GM value. Since the value is too small, instead of neglecting it, why it is added to the GM. Please clarify.

[Ad Hoc]

You've written that slightly incorrect.

GZ =GMsin(angle), so for small angles the shift of centre of gravity from the free surface is ineffect to "raise" the CoG. This rise in CoG creates the loss of GM, when you draw out the geometery of vectors.

[mbhanoo]

Yes sir, I fully agree with you. For small angles of heel, there will be negligible raise in KG hence no loss in GM. But I have seen in so many inclining reports, free surface correction GG0 is added to the GM value, even if it is too small. I request you to clarify that.

[Ad Hoc]

mbhanoo

You misunderstand me. The formula and procedure IS for small angles and there IS an effective rise in CoG, for small angles, hence the reduction. So you're incorrect in assuming a "negligible raise in KG".

For large angles the reduction is:

(density -liquid/density-sea) x Inetria of tank/ Volume of ship

see attached.