K im seriously confused about green treat and marine ply!

OK now iv been talking to alot of people about this issue and it's like a 50/50 ratio some say yes u can use green treat an some say no you cant because it eats metal and alum.

Now i have a very good friend that is a carpenter and he also builds houses hes been doing it for 20 or so years, hes also a hardcore fisherman. He says the old green treat would eat metal and alum in a heart beat the new stuff doesnt at all, the gov made the wood companys change their chemicals in the wood because it was actually eating the flashing and screws in the frames of houses that werent even more than 10 years old, He says as long as you dont use certian types of sealer that reacts with the chemical in the wood that creates a reaction that will eat the metal, you will be just fine. If you read some lables on the sealer containers some actually say not to use with green treat and some that are just for green treat.

So i personally intend on using the green treat because it's cheaper than marine and also if you seal it, it will last longer exposed to UV and the stress of being walked on etc etc

So what do you guys think ?

I wouldn't use pressure treated or marine plywood. I would use Exterior grade plywood it has the same glue as marine ply it just has a few voids.

Treated wood and ply is a no-no is Tin boats. As previously mentioned, Exterior Grade ply is the way to go. Its slightly more expensive then the pressure treated, but no way as expensive as marine grade. When properly sealed, it will last years and years.

If you have a little time between now and when you want to use it, you can always team up with someone and go to a Building Material Auction. You have to usually buy a pallet, but you can get some great deals. My friend got some amazing deals on 2x4's and ply--he paid about 1/4 the price that Lowes sells the same stuff for.

If I was super strapped for cash, I would go down to a regular ply wood before I went to pressure treated, and just seal it like crazy... but I do not recommend that either.

Use exterior grade plywood. How you seal it is up to you. I did not coat mine in epoxy resin. I used several coats of exterior porch paint. You will read that I wasted my time and money. I don't think so. I keep my boat covered. Rot will eventually find its way into a boat. Spending to much money repairing your boat is not going to get you more back when you sell it. If you plan on keeping it forever then build it to last one time.

I do agree with the pressure treated wood discussions. I would not use it. My main reason is because I want to finish my project and pressure treated wood is wet which also makes it heavy. As it dries it shrinks. What will happen to your boat as the wood shrinks?
Are you planning on letting it dry out before you use it?

So much to think about. In the end, do your project how you want to. I use this site for ideas and advice. I will also offer MY opinion from time to time. Who's right and who's wrong? Does it really matter in the end as long as we get the results that we are looking for? JMO

You are not alone in the confusion on Treated vs non-treated. I was recently nicely corrected on my mis-understanding on the post shown below.

https://www.tinboats.net/forum/viewtopic.php?f=21&t=22940&hilit=+treated

Seems that there have been at least THREE sets of lumber treatment recently. The last one...MCA...is way less problematical than the prior iterations.

That said, the issues of added weight (due to the treatment itself) and ANY potential future issues would still move me to use exterior plywood.

R

Yah...don't do it. All due respect to your friend...but don't do it.

Use exterior grade as recommended by the others here and coat it well.

Best of luck.

Look, I am a wood scientist by education, and I would not use ANY form of treated wood in my tin boat. If you think that the "new stuff" will not cause as much corrosion, just look at the new coatings for fasteners that is recommended nowadays. Most of those screws have a plastic or ceramic coating so the treatment chemicals won't make contact with the steel.

The problem is the copper, whether it be in chromated copper arsenate (CCA) or alkaline copper quaternary (ACQ) or micronized copper (MCA).

As for ply, an exterior grade is PLENTY. Don't waste money on marine grade. If you look at my posts, I have gone in pretty good detail on this issue in the past.

thanks...msumoose. Your comments should be a "sticky" IMHO .

Rich

Okay, so let me ask a really really dumb question here....so sorry in advance.

The general consensus is to get Ext grade plywood and seal it. So what is the sealer to use? Thompson's Water Seal? A deck stain? Sorry, and I'm a scroll sawer...you'd think I'd know this kinda thing.

For coatings, here is my order...

1. Epoxy Resin. Try West system 105.
2. Vinylesther resin. Cheaper, but not as awesome...mildly awesome.
3. Urethane....doesn't matter what kind.
4 A-Z paint. Too many to mention here.
5. Leave it bare.
.
.
139452. Thompson's or the like.

I think I would rather use Thompsons than leave it bare.

I used spar urethane...have seen a bunch on here doing that...some splurging on epoxy resin and fierglassing.

Oh yeah, DUHHHH....

I have some Spar Urethane....two hardened cans...lol
Chase the wife and kids out of the house when I open one. Gosh that stuff STINKS.

I used spar urethane also.

Used it for my mod also. Def stinks but works.

For "brightwork" ( varnished surfaces on sailboats)...Spar varnish has been around for longer than I have.

A "Spar" is a part of a sailboat!

However, Spar varnish, if left exposed to the UV rays, will deteriorate with-in a couple of years.

On my sailboats, that meant having to strip it off of the teak rails...and then re-coat. Not a fun job, I can assure you. Most of us went to teak oil in lieu of the Spar Varnish. Oil was not as fancy a finish, to be sure, but we could re-oil the wood every year or so with nothing more than a rag dipped in oil. Many other oils were also used, instead of the more expensive packaged "Teak oil".

So...if your wood is exposed to sunlight most of the time...keep in mind that Spar varnish is great stuff, but has to be stripped and re-coated from time to time.

I've read of some good home-made wooden boats (hulls and all) being done with...believe it or not...simple latex house paint. It protects your house in all sorts of weather. A Google search will turn up more info.

R

Wow i go away for the weekend and i come back to all this great info, thanks alot guys ext grade is it then!

Keep in mind, Rich, that we said Spar Urethane and not Spar Varnish....there is a difference and it is another one of those topics that has been discussed here several times.

Ah yes, Urethane. Certainly better in some ways than the old stuff. I believe it is more difficult to get off, though.

An old woodworker's adage is.... whatever you do on ONE side...you should do on BOTH sides, otherwise there will be warping. Makes sense.

I always coat both sides when doing cabinets, etc....but...just thought I'd mention it.

regards, R

makes perfect sense