I've just done a hull repair on my Tornado. The core was compressed over a region about the size of my hand and the outer layer of glass had a crack. It was in a non-critical load area (below water line and just in front of main beam). After stripping away the paint & primer (no GelCoat on Marstroms), you could clearly see the Nomex core honeycombs beneath the translucent glass layer. Lots of the cells were visibly darker than the surrounding cells. I thought it was excess resin. My repair consisted of drilling 1/8" holes through the outer skin spaced evenly over the compressed area. These would later be injected with thickened epoxy via syringe. Before injecting, I cleaned up the area with alcohol followed by acetone, including using a sprayer to squirt it up into the holes to flush out drill debris and/or sanding dust. While using a heat gun on lowest setting to dry it all out, I notice a fair bit of liquid seeping and then dripping out of the holes. Kept at the heat expecting the excess acetone to quickly evap away, but the liquid kept coming. Eventually it became a nearly constant trickle. Realized then it was actually sea water, not acetone. The dark cells of the core were actually holding water, not resin. The heat was causing these to boil & steam and the water would find it's way to the holes and escape. Took more than 1 hour of this gentle heating to get to a point where no more water was coming out and for the cells to become light in appearance.

The crack in the outer skin did not in anyway cross all the affected cells...so either the compression had damaged the cell walls enough to allow water through or water got in there from normal absorption processes. The latter would mean most of the boat would have similar quantities in the cells!! <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />