Flaps in the planing hulls

hi,
a question for you.
bflap=(sigma)*b where b is the beam of planing surface, sigma is flap span-beam ratio and bflap is the length of flaps. The measure of b is on the water level. Is the measure of bflap on the level water?
thanks fro the answar

 

This equation basically says that X = (X/Y)*Y .
What's the big deal?

 

Only a dafinition

There is no matter: only a definition for the measure of bflap. If bflap isn’t on the water line it exist the case of sigma>1 …. But for full-span flaps sigma=1.