I'm afraid it's a complex thing...
It's some sort of measure of how long the surrounding water in which the
hull floats feels the hull itself.
Hull performances are afected a lot by its lenght and actually by its
apparent lenght, as it is the hydrodynamic measure involved in Froude and
Reynolds numbers estimation.
The difficult thing is to measure this lenght, as it changes upon many
conditions (speed and waves the most important) and to control it during the
design!
An example of its importance is the shape of sailboats' bows in last two
American Cup races: last time all the boats had that sort of "knee" (or
hunch) instead of traditional faired lines: this bump slows down water at
its "entrance" in the hull area thus lenghtening the volume of water moved
by the hull and then the hull's apparent lenght!

Bye
Marco


"Pablo" ha scritto nel messaggio
. ..
Hi,

Can somebody tell what is the difference between the apparent length
and
the length of the hull. From what I understand depending on the
longitudinal
shape of the hull the apparent length can be change. Is the apparent
length
the girth of the hull? Can someone give me some examples. Thanks for your
help.

Pablo,