How to cut a 3D surface in 2 parts?

 From:  boatstalker
650.1 
Hi everybody,

I need to cut a 3d surface (bottom panel of a boat) in 2 pieces. DidnĀ“t have any success with "trim". Any suggestions?

P.s. the first picture attached shows the bottom panel (yellow) separated from the side panel. The second part of developing the panels for construction is to cut the bottom panel in 2 pieces. The end result after joining the cut panels unfolding the 3D structures is supposed to look something like this (see the second picture attached).

Thanks in advance,

Boatstalker

EDITED: 3 Jun 2007 by BOATSTALKER