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smhamilt

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18 ft aluminum starcraft. usi

18 ft aluminum starcraft. using 2 pieces of 3/4 in treated plywood. I plan to bond these together with 3M 5200. Any comments before I do this? Thanks
 
"Sounds like an excellent choi

"Sounds like an excellent choice for a waterproof permanent job. I would use the slow dry 5200 it gives you plenty of time to work, about 5 to 7 days. The fast dry is ok also if you are just putting the boards together and cutting them to shape after. If you make cuts in the plywood and find some voids I would also use the 5200 to fill them and seal the edges. The boat in the picture at left has a "5200 bottom" mahogany."
 
"Treated plywood, like pressur

"Treated plywood, like pressure treated??? I'd suggest using only marine grade plywood. If you don't you'll be repeating the job in a few years."
 
"I agree also on using only ma

"I agree also on using only marine grade plywood, if you have trouble finding it it can be special ordered from a local home depot store, expensive but worth the effort.are you going to coat it with fiber glass and gelcoat or leave it plain?"
 
"Do not sandwhich in fiberglas

"Do not sandwhich in fiberglass, one small leak and the plywood even "marine" grade will rot.
Here is an article I robbed from another chatroom.

"Marine and exterior plywoods have similar glues but there are two primary differences that apply to all marine rated plywoods in comparison to exterior rated. . 1. There are at least 2 more plys in marine plywood over 1/4" thick. 2. The interior plys are fitted better resulting on fewer voids.
For domestic fir plywood that is as far as it goes other than the face veneers are usually A/B on marine and A/C on exterior. When it comes to imported BSB rated plywood like meranti and okoume, there are more differences. There will be 4 to 6 more plys glued together under more pressure, even less voids and better face veneers that do not raise grain or check as badly as fir and pine faced ACX..
The net result is that marine plywood bends more evenly to a fair curve than exterior, has a slightly better ultimate strength and there is less possibility for water intrusion into interior voids.
From a practical standpoint, if the boat will be trailered and stored dry, has no critical curves and weight is not an issue, good old ACX will do fine. OTOH, if it will soak in water for its lifetime, has has fine lines or weight is critical, marine is the better option.
I include weight in this comparison even though ACX and marine plys of the same species weigh about the same with marine fir being slightly heavier than ACX fir.. The reason being that some imported woods, particularly okoume, are much lighter for the same thickness as the fir and pine used in ACX.""
 
"Cal, did not mean to imply to

"Cal, did not mean to imply to sandwich in fiberglass,that would not be good, forgot we were talking about an alum. boat, my 3 working brain cells got overloaded. nice post on the differences,"
 
Well...I already did the deal.

Well...I already did the deal. I used resin coating; no glass. resined each piec individually and then bonded them. I hope I get 5 yrs out of it anyways. sure seems tight for now but I know how that can go.

Thanks so much for your help
 
"we would redo boat floors, co

"we would redo boat floors, coat it with resin instead of carpet glue and lay marine grade carpet over top and it seemed to work."
 
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