Posted by RonW on October 11, 2003 at 09:13:55:
In Reply to: Re: Okyme, Meranti - Good Marine Ply? posted by Graham Knight on October 10, 2003 at 01:01:21:
I vote for douglas fir marine plywood. I think it is getting a very bad rap over a few minor checks,and a lot of people are knocking it that has never even used it. I did a ton of research on plywood before i bought mine due to all the negative posts on the internet concerning various plywood.In cincinnati ohio i bought 3/4 douglas fir marine for $53. a sheet, a few lumber yards carry it for rebuilding of transoms in fiberglass boats. But there is no 3/8 available, period.I drove 120 miles to get 3/8 -5ply a-b douglas fir marine plywood, and paid $46.50 a sheet.I could have driven -8- miles and got 3/8 or millimeter equivalence in meranti marine for $42.50 a sheet.Upon examining the meranti, it was beautiful,looked like cabinet grade, but the two face plys where about as thick as double ply toilet paper. And for a dory that is going to be constantly beached, i couldn't believe that it would hold up to a lot of abrasion very long. There is a ton of plywood discussion on the wooden boat forum. Many posts over meranti woes, all stating the same, bubbling in the ply, and the answer is always the same, slit the bubble and inject epoxy and press down.Occume is a non durable wood.Seen many posts concerning fixing occume rot after only 10 or 12 years and these are boats that where fully encapsulated with epoxy and cloth.It seems that you can buy (if you know) meranti and occume in 6566 or 1088 and with differnt thickness face plys, so what gives. I have examined many plywood boats that where built in the 50's and in every case the douglas fir planking was still solid and sound,but the mohagony plywood used for decking and trim has delaminated and started rottening. I have 6 small pieces or 3/4 marine about 2x6inch pieces in a bucket of water now for 2 & 1/2 months, with no paint or epoxy on them, after 2 weeks they became so water logged they sank to the bottom of the bucket, but as of yet, there is no sign of delamination at all. I checked into mdo also-medium density overlay- and so far i only found 3/8 with one side overlayed and the other side was a c grade, which means all the inner plies are c grade. In 1/2 inch thick and thicker you can get a stright b grade with both sides overlayed.I do intend on ivestigating hdo-high density overlay for my next boat though. This is the same ply used on concrete panels and it is tough and durable at about 2/3 the price of marine with perfectly smooth faces. But have heard paint adhesion might be a problem. I have not be able to locate any underlayment ply, as some builders are using that i would consider using.Have seen some references to marine tech, and super ply, wish someone would enlighten us as to what these are. I think the last place to save money on a plywood boat is the plywood, that is going to lead to a big bon fire 15 years down the road.
To Graham- there was a post on the wooden boat boatbuilding forum quite a while back, concerning occume plywood, as i remember this was manufactured out of a plant in israel that was raved about the quality of for a while, but a guy from england had some that a major marine in england refunded his money due to the fact that it was delaminating.
There also was a article in wooden boat in sept. concerning plywood, but it was all focused around occume made in greece.Bottom line seems as if the quality of the plywood varies widely as to which plant makes it.
I for one wish they would be more disscussion as to what is out there in ply, as to price, quality and how it holds up. Seems to be the place to discuss it and trade information.