14ft Grumman Makeover

[AgTires4295]

Hey all, Im giving my 14ft Grumman a makeover and am about 99% done. I just happened to read the imfamous "dont use pressure treated wood" topics that are posted all over the web. Well guess what I used?...

Anyway, I think it's a little sketchy of a topic because everybody claims scientifically "it's bad" but nobody has any direct proof!

Does anybody have any immediate life experience with this and if so, do you have photos? I'm getting tired of seeing regurgitated info posted on the websites without any photos and immediate proof. I feel like I'm a teenager at a church seminar being counseled on sex... only answer: "Its bad. Don't do it!" :lol:

 

[GT1000000]

Re: 14ft Grumman Makeover

I don't have a specific answer for you, but I did a cursory search on the internet and came up with these...
While they are not specific to marine applications, they do mention ways that pressure treated lumber can be put in contact with aluminum and ways that it shouldn't...
Check them out and decide for yourself...

Search-Pressure Treated wood in contact with Aluminum

OAA

Facts About Pressure Treated Lumber - YellaWood?

Pressure-treated wood and aluminum don't mix - Philly.com

As far as proof, there have been many guys here on the forum, that while demolishing their aluminum boats in preparation for restoration, have found that pressure treated lumber was used in a previous attempt at repairs, and it has caused some significant corrosion issues...

Best of luck and we would love to see pics of your almost restored boat...

 

[gm280]

Re: 14ft Grumman Makeover

Hey all, Im giving my 14ft Grumman a makeover and am about 99% done. I just happened to read the imfamous "dont use pressure treated wood" topics that are posted all over the web. Well guess what I used?...

Anyway, I think it's a little sketchy of a topic because everybody claims scientifically "it's bad" but nobody has any direct proof!

Does anybody have any immediate life experience with this and if so, do you have photos? I'm getting tired of seeing regurgitated info posted on the websites without any photos and immediate proof. I feel like I'm a teenager at a church seminar being counseled on sex... only answer: "Its bad. Don't do it!" :lol:

I'm definitely no chemical engineer but I think the reasons to not use pressure treated lumber has to do with incompatibility with the chemicals used for treating the lumber and aluminum...of course. With that stated, maybe you could do some research and figure out what chemicals are used and how they interact with different types or alloys of aluminum. Could be that not all pressure treated lumbers use the same chemical mixes and therefore some may be okay to use... I certainly don't know the absolute answer but if I were confronted with restoring an aluminum boat, I would research the chemicals and make my own decisions... I also know there are not using the same mixtures these days as they used too in pressure treated lumber(s). So maybe you could find out for your own piece-of-mind... I have to agree with one thing you stated though...too many folks just state what they have heard about the subject and seriously don't know the true answers as to why...

 

[jbcurt00]

Re: 14ft Grumman Makeover

Sums it up pretty good, and has some more info for you to add to what you may have already read:
Why not pressure treated plywood?

I've never handled mercury or liquid nitrogen, but BELIEVE I shouldn't, because someone else said NOT TO, some of them may have had direct experience w/ the problems associated w/ handling hazardous materials, many don't.

 

[Woodonglass]

Re: 14ft Grumman Makeover

Results of a transom made from PT Plywood after several years of use..
http://forums.iboats.com/boat-restoration-building-hull-repair/pt-wood-aluminum-528313.html

 

[AgTires4295]

Re: 14ft Grumman Makeover

Thanks for the additional info everybody and thanks Woodonglass for the photo :thumb:

 

[64osby]

Re: 14ft Grumman Makeover

To throw a little more fuel on the fire, just google G3 boats transom pre 2006.

 

[slowleak]

Re: 14ft Grumman Makeover

The newer PT wood is a definite no-no when it comes to contact with most metal. My neighbor built a deck three years ago, all PT, he used SS screws. This past week he began making some changes and noticed that nearly every screw was eaten away, the stuff ate the SS screws, it ate the aluminum stands the legs sat on atop the concrete footings as well.
He's now torn the whole deck down and replaced it with PVC boards over metal beams.

The only fasteners that are rated for PT wood are coated, and nothing rated for marine use fits this bill.
A PT transom will eat the bolts, the hull, everything it contacts. The only option would be to encase it in epoxy or fiberglass, which at that point, you might as well have saved the added money and just coated plain exterior ply.

I did notice that on some models I've seen they used MDO, a coated type of PT ply for the seats and floors. My Grumman was done this way, with the screws and rivets all having plastic sleeves over them through the wood.

If you put PT in contact with aluminum, I'd venture to guess you could see major damage in only a few years, or less.
Nearly every aluminum boat I've worked on over the years has had some degree of corrosion on the inside of the transom panel, whether from salt, electrolysis or some reaction to the water itself. Those with PT wood are usually perforated to the point of needed new metal or to the point the hull was just scrapped.

 

[jbcurt00]

Re: 14ft Grumman Makeover

MDO isn't pressure treated ply, but it is exterior grade plywood and if available, it is a GREAT plywood choice for both fiberglass & aluminum boats.

Interesting about your neighbors deck though. Bummer to have to redo a 3yr old deck.

Purpose made 'deck' screws are coated to prevent degradation of the screw. Their aggressive threads also make them a good fastener for boat building when using plywood.

 

[slowleak]

Re: 14ft Grumman Makeover

The MDO I last priced here was listed as being PT with a finished face on both sides?
The supplier specifically noted that it requires special fasteners and insulators if used around water.
The version I looked at was dark brown in color inside, not blonde like the stuff found at most lumber yards.
It came factory as the bench seat tops and floor in my 1990 Grumman 14' boat. It deteriorated bad around the edges.
It was also insulated from metal contact with some sort of plastic sheeting and with sleeves in every drilled rivet hole that held the panels in place.

It was also very heavy compared to the ACX ply I replaced it with, which I coated with epoxy and glass mat prior to install.
The original seat panels on mine were riveted, I installed threaded inserts and used SS screws so I could easily remove the seat tops for repair or refinishing.
If the MDO didn't come with a warning from the seller, I'd probably have used it again just to maintain a stock appearance but I went with plain ply to avoid any issues. Basically they told me that the MDO was the same as marine plywood but with a phenolic coating on both sides. Its impregnated with something that makes it that dark in color. The sawdust is also toxic according to the warning info at the supplier.

 

[jbcurt00]

Re: 14ft Grumman Makeover

That was pressure treated MDO, which is available, but shouldn't be used in an aluminum boat because its PT. And why it had those warnings. Just like any other PT wood, its the PT that makes it a poor choice

Typical MDO isn't PT & is a good choice.