Re: Transom Repair
Roger,<br />The only thing that may cause a problem with treated is moisture content. Epoxy will adhere fine to treated plywood, but will cause problems if it is wet. Lots of treated ply is kept outside. This is an excerpt from an APA publication on engineered wood products concerning testing conducted with epoxy and treated ply.<br /><br /><br />LAMINATING FIBERGLASS TO PLYWOOD <br /><br />Many uses of plywood in boats involve laminating fiberglass over a plywood boat component. APA recently contracted with a marine testing laboratory to study the strength of fiberglass bond using commercial resins applied to treated and untreated plywood. The objective of the study was to assess the effect of preservative treatments and panel moisture content on the strength of the laminate bond. <br /><br />The study assessed the laminating strength on treated and untreated plywood. To study the effect of moisture content, half of the panels were humidified to simulate the upper range of moisture content of what may be expected from treated panels after redrying or from panels stored at a boat manufacturer's facility.<br /><br />The treated plywood developed bond strengths similar to the untreated plywood. <br /><br />As expected, the moisture content of the plywood influenced the strength of the fiberglass bond. However, even at the highest moisture condition, the ultimate test failure mode in the vast majority of the cases was wood failure within the plywood itself, rather than at the laminate bond interface. The influence of plywood moisture content reinforces the need to specify drying after treating when using treated plywood. <br /><br />Bottom line: If using epoxy it's not neccesary as long as the wood is coated properly. Want some extra insurance, use the treated, but make sure it's good and dry.<br /><br /><br />
Roger,<br />The only thing that may cause a problem with treated is moisture content. Epoxy will adhere fine to treated plywood, but will cause problems if it is wet. Lots of treated ply is kept outside. This is an excerpt from an APA publication on engineered wood products concerning testing conducted with epoxy and treated ply.<br /><br /><br />LAMINATING FIBERGLASS TO PLYWOOD <br /><br />Many uses of plywood in boats involve laminating fiberglass over a plywood boat component. APA recently contracted with a marine testing laboratory to study the strength of fiberglass bond using commercial resins applied to treated and untreated plywood. The objective of the study was to assess the effect of preservative treatments and panel moisture content on the strength of the laminate bond. <br /><br />The study assessed the laminating strength on treated and untreated plywood. To study the effect of moisture content, half of the panels were humidified to simulate the upper range of moisture content of what may be expected from treated panels after redrying or from panels stored at a boat manufacturer's facility.<br /><br />The treated plywood developed bond strengths similar to the untreated plywood. <br /><br />As expected, the moisture content of the plywood influenced the strength of the fiberglass bond. However, even at the highest moisture condition, the ultimate test failure mode in the vast majority of the cases was wood failure within the plywood itself, rather than at the laminate bond interface. The influence of plywood moisture content reinforces the need to specify drying after treating when using treated plywood. <br /><br />Bottom line: If using epoxy it's not neccesary as long as the wood is coated properly. Want some extra insurance, use the treated, but make sure it's good and dry.<br /><br /><br />