Wooden Boat People
By McKenzieDriftBoat.com
Thoughts on pressure treated wood...
Just thinking about pressure treated wood versus ash and marine ply versus pressure treated ply. I'm hoping some of you veterans will chime in with your thoughts.
I'll start with the frames of the boat and using pressure treated versus ash. I know the look of ash is going to put the pressure treated stuff to shame, but for ease of maintenance, I was thinking about using pressure treated and just using a really dark stain. This way if the stain ever fades, all I need to do is apply another coat of stain. The other option is using the ash, applying epoxy to seal it and most likely some type of poly coating. My thoughts are that if the coating on the ash wears then we have water to wood contact, and eventual problems. With the PT wood, it is "supposed" to last 25 years without any coating.
On the same page, the PT plywood is also supposed to last 25 years, is much cheaper than marine, and I am thinking much less maintenance for the above reasons.
Am I completely off base here, or should I really consider this as an option?
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Replies to This Discussion
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Permalink Reply by Rick Newman on
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The pressure treatment is essentially skin deep. So if you machine or cut the wood you pierce the barrier. So as long as you leave the wood in the as-treated dimensions it works pretty good. That would, no pun intended, make for a pretty heavy boat. Why not choose woods that already have natural rot resistance than can be cut and machined like Alaskan Yellow Cedar or Port Orford Cedar. Lighter, stronger, rot resistant and also good looking. Unfortunately they don't make it in a plywood form. Here's a link to a source for information that I quickly googled up; http://www.bearcreeklumber.com/species. I have no idea of the glue used on PT plywood and whether or not there are any voids enclosed between the outer layers which can lead to problems if any water gets inside the layers. Hence the British organizations standards for marine woods that refer to the glue used and the guarantee of no hidden voids.
Even pressure treated wood that has been machined to a finished size prior to pressure treating is not as rot resistant as a non-machined post that still has the sap wood intact and then pressure treated. I built numerous cattle and horse fences and got to learn a lot about wood life from the old timers I worked with. Nature does a pretty good job that sometimes we mess with.
Here's an article from Wooden Boat Forum
http://forum.woodenboat.com/showthread.php?133874-Ten-Years-of-Hard...
where the author shares some thoughts on a boat he has used for ten years in some very rough conditions, with some good thoughts on wood choices.
Rick Newman
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Permalink Reply by Frank R on
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Any marine grade plywood must have no interior voids and use waterproof glue. Pressure treated wood fails the first test. Bending it creates problems.
Also, they only guarantee that pressure treated wood will not rot. But the wood will twist, crack, and split.
Remember that most boats rot under a tarp than from use. Garge kept is best.
I did post this recently: http://www.woodenboatpeople.com/forum/topics/chemotherapy-for-rot?x...
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Thanks Frank, I did search around for older posts, but missed this one.
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Do you have access to Atlantic White Cedar, Northern White Cedar, or Bald Cypress where you live?
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I have the ribs all built using Ash right now, but before I toss them onto the jig and attach the keel, I thought about the treated lumber - 1x4's. Mostly for ease of maintenance, simply stain them and move along.....if the stain ever fades or wears, just restain. About the only other options I have are Eastern White Pine, Red Cedar and Red Oak. The EWP is quite expensive, the Cedar is even worse and from everything I have read the Red Oak is a definite "no-no".
I plan on using AC fir (not the best, but the best option I have) for the hull itself, but while I was poking around the lumber yard the other day I noticed the pressure treated ply and was mostly just curious about the stuff.
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Actually I do have access to Maple as well, but the cost is pretty steep, and I haven't read anything about the water/rot resistance of maple......
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Maple is a definate no, its rots easily. Maple is never used as an exterior wood in house building for example.
Red oak is a no because it turns black under clear sealers. Also the end grain absorbs water more than white oak. But if you seal the pores with epoxy and paint the wood you may have a good option; other people have done this.
Check out Ultraply XL at Lowe's for plywood. The downside is it only comes in one thickness which is slightly thinner than 1/4 inch. I don't know what size boat you are building so it may not be substantial enough. But you might double it up on the bottom.
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I saw that Ultraply, but I need 3/8 for the sides, and 1/2 for the bottom. I am building a 14' drift boat. Another appeal for using that Ultraply is that it seems much lighter than regular ply too - not sure if that is true or not. I was going by the "feel" in the store.
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I don't know if Ultraply is the same as the plywood that Don Hanson recently tested. A good initial test on new plywood's is to submerge a piece or two in water for a few days and see how it responds. The plywood he tested swelled up quite quickly, failing the test. Search for Don's posts with the search function and see if it is the same stuff.
Rick Newman
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