I finally got Chiquita, my Venture Newport cutter, in the water and on her mooring so I turned my attention to my 1979 M17 Amorita. The transom hull deck joint was cracked all around and there are several other cracks as well. I attacked the cracks with a grinder and belt sander, trying to bevel the cracks so I could lay in new fiberglass and epoxy. I ground through lots of filler/puitty and other evidence that the transom had been repaired before. I think it may have been in an accident of some sort. There is a 3/4" plywood core between the inner and outer transom skins. It looks like they attempted to bond the plywood in place but it had come loose. The plywood goes completely across the transom and extends from the top to just below the middle rudder gudgeon. There is a wide notch in the bottom of the plywood where it goes around the glassed-in gudgeon baqcking board. Anyway, I discovered that the lateral crack in the fiberglass extended all the way across the transom. A bit of tugging and the top half of the fiberglass skin came completely off in my hands. I plan on removing the 3/4" plywood "core" and replacing it with new plywood or something else recommended by you guys. I'll bond it to the inner fiberglass with thickened epoxy. Then I will glass over the outside of the core and build it up to the original thickness. Does that sound like it will work? Other questions: The plywood appears to have been added during a previous repair. Was there any type of "core" between the inner and outer transom as built? The plywood is fairly heavy. What other core material could I use? Balsa, Foam? Can I re-use the outer fiberglass panel that I had pulled off as part of the repair (for bulk) or should I just go with all new glass cloth, roving, and mat? Can I mix carbon fiber tape and regular fiberglass cloth in the laminate? Click on the link in my signature and go to the album "M17 Transom Repair" for pictures. I'll be copying this post to the Trailer Sailers Montgomery forum so I can post some pictures directly. Thanks in advance for your suggestions and tips. -- Henry https://picasaweb.google.com/heinzir