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Until recently switching to composite, GW had been using Greenwood XL in place of marine plywood since the late 90's. There have been fewer reports of rotted transoms since then. Here is an interesting post from THT where a builder describes what Greenwood is:
https://www.thehulltruth.com/boatin...-whites-view-greenwood-forestry-products.html
Greenwood Forest Products made Greenwood XL Panel for the marine industry from approximately 1994 through 2014. Less and less boatbuilders using plywood as reinforcement in transoms and stringers led them to discontinue selling the product in 2014 or so. They sold the rights to one of their distributors who planned to continue with the product, presumably having it private label manufactured for them by Greenwood. Whether that continued or actually happened I do not know, but that is why if you try to look it up on their website, you won't find any info about it. Greenwood offered a limited lifetime warranty against any kind of rot fungal decay or delamination of the plywood itself-not delamination from fiberglass/resin bonded to the greenwood xl product. I personally used the product from 1995 through 2010 and never once had a claim against their product in roughly 2000 boats built over that period. We used it for all transoms, stringers deck reinforcements, core reinforcement, bulkheads, etc. I continued to use it for a couple of years until it changed hands because the price shot up 30%. At that time, I switched to the only competitor they had, which was Aqua Ply. Same basic product, same lifetime warranty, more options for higher grade panels-pre sanded panels, etc.
I still today use and sell the Aqua Ply product in my shop. Both Greenwood and Aqua Ply are whats called a CCA treated wood. You probably heard of it years back when there were a bunch of studies about outside playground units made from similarly treated wood that had to be removed. Reason being is that the "A" in CCA stands for Arsenic, which can be absorbed through the skin. CCA products were banned for exposed surface use, but can still be used for non exposed applications such as when they are encapsulated with fiberglass/resin in boats/marine applications. The reason it was used in boats in the first place is that normal treated plywood (which uses creosote or some other petroleum based treatment) does not work with polyester/vinylester resins, or typical contact adhesives used for carpet installs such as non molded floors on small runabouts or on most pontoon boats. The resin may initially bond, but it will easily delaminate the first time any kind of moisture gets to it, or even just due to vibration/impacts. Greenwood and Aqua-ply both are the upper end of the plywood spectrum. There are basically 4 levels-regular plywood which even if encapsulated is not a good idea for boats as it will rot/delaminate when it absorbs water. Marine grade plywood, which is better because it uses waterproof glue to hold the panels together so it will not delaminate just from water absorption, it also cannot have any voids in the plys if it is designated "marine grade". Treated plywood, which is again a bad choice for reasons already stated. Then you have marine grade treated, which is what Greenwood/Aqua Ply are. It is "marine grade" that is then CCA treated so it will not rot.
https://www.thehulltruth.com/boatin...-whites-view-greenwood-forestry-products.html
Greenwood Forest Products made Greenwood XL Panel for the marine industry from approximately 1994 through 2014. Less and less boatbuilders using plywood as reinforcement in transoms and stringers led them to discontinue selling the product in 2014 or so. They sold the rights to one of their distributors who planned to continue with the product, presumably having it private label manufactured for them by Greenwood. Whether that continued or actually happened I do not know, but that is why if you try to look it up on their website, you won't find any info about it. Greenwood offered a limited lifetime warranty against any kind of rot fungal decay or delamination of the plywood itself-not delamination from fiberglass/resin bonded to the greenwood xl product. I personally used the product from 1995 through 2010 and never once had a claim against their product in roughly 2000 boats built over that period. We used it for all transoms, stringers deck reinforcements, core reinforcement, bulkheads, etc. I continued to use it for a couple of years until it changed hands because the price shot up 30%. At that time, I switched to the only competitor they had, which was Aqua Ply. Same basic product, same lifetime warranty, more options for higher grade panels-pre sanded panels, etc.
I still today use and sell the Aqua Ply product in my shop. Both Greenwood and Aqua Ply are whats called a CCA treated wood. You probably heard of it years back when there were a bunch of studies about outside playground units made from similarly treated wood that had to be removed. Reason being is that the "A" in CCA stands for Arsenic, which can be absorbed through the skin. CCA products were banned for exposed surface use, but can still be used for non exposed applications such as when they are encapsulated with fiberglass/resin in boats/marine applications. The reason it was used in boats in the first place is that normal treated plywood (which uses creosote or some other petroleum based treatment) does not work with polyester/vinylester resins, or typical contact adhesives used for carpet installs such as non molded floors on small runabouts or on most pontoon boats. The resin may initially bond, but it will easily delaminate the first time any kind of moisture gets to it, or even just due to vibration/impacts. Greenwood and Aqua-ply both are the upper end of the plywood spectrum. There are basically 4 levels-regular plywood which even if encapsulated is not a good idea for boats as it will rot/delaminate when it absorbs water. Marine grade plywood, which is better because it uses waterproof glue to hold the panels together so it will not delaminate just from water absorption, it also cannot have any voids in the plys if it is designated "marine grade". Treated plywood, which is again a bad choice for reasons already stated. Then you have marine grade treated, which is what Greenwood/Aqua Ply are. It is "marine grade" that is then CCA treated so it will not rot.
