Flaps and formulas

In the process of studying the effects of the application of flaps under the hull I found this formula that I think is missing something.
Does it look familiar?

LCG = [LCGe * (D-Pn)+(Pn*Bfl)]/D

Where D is supposed to be static displacement...??? or another kind of displacement?
Can you explain this formula please?

 

LCG usually means longitudinal centre of gravity, this will remain the same with the flaps at any angle (I assume you're talking about trim tabs at the stern). This is because the tabs may be considered light relative to the rest of the boat and the invidual C.G.s don't move for'd or aft. If they are particularly large tabs this may not be the case.

There may be a difference in the effective LCB. where did this formula come from? can you post some more info on your project to help us solve this?

cheers,

Tim B.

 

Hi Tim thanks for replying, this is not about a project but about some formulas I'm studying for the course I'm taking.
this formula come from one of the textbooks I'm studying on.
The formula itself comes from savitsky papers (I guess) and it's about finding "movements" of LCG due to trim tabs application.