I think the usual deal with water in Airex composites is water between the
fglas and the Airex. Problem is freezing leading to further loss of bond
and it goes downhill from there. I was told by a surveyor that every rudder
he ever tested showed water infiltration (solid layups). How does the water
get in? Probably at fittings or at places where the glass has been abraded
by grounding.
DAve