3/4" plyform delaminates easily?

[stimulak]

I've crafted a 38 foot sharpie type hull of 3/4" plyform: single layer sides and doubled bottom. A real quick and dirty motor "sampan" of sorts, over 14 months time. Some of the scraps have been out in the NW Fla elements for all 14 months and no delam problems. Has anyone else used this ply in a similar way? Had any problems? It cost $25 a sheet and has done well so far. Recommended by R. Parker in his books. The boat was built "instant boat " fashion (a real grind when the pieces went together) with butt blocks about 18" wide. The second layer of the bottom was put on with asphalt roofing tar sealed about the edges with epoxy. External 2X4 chine. All totally sealed now, outside, with epoxy (a layer of window screening on the bottom in lieu of expensive cloth). Just discovered this forum but could use some heads up on possible problems once in the water. The plyform had only tiny voids. Only a doubled 2X6 keel on the bottom, laid flat. Any suggestions on a inexpensive lateral resistance method? Just a 60 mariner on the back for now, once launched. Best wishes>>>>> BoB G. Fla gulf coast