Pro's and Con's of using Luan Wood

[77mutiny]

Hey everyone i'm getting ready to replace the transom on my 17ft bayliner outboard, i need to get a 1inch thick board, and it's not easy to find in the right type of ply around here. and i really don't want to mess around with trying to epoxy two 1/2 pieces together.
But i found a mill that has 1 inch thick luan marine plywood, and they said epoxy sticks to it just fine.
i searched the forums a bit but i only found a few posts involving luan wood, so i'm wondering is it an acceptable boat building wood, or are there too many complications with it....
Thanks in advance

 

[Mark42]

Re: Pro's and Con's of using Luan Wood

That 1" marine is going to be expensive. I don't see the problem of gluing two 1/2" pieces of pressure treated together. Use a waterproof wood glue or epoxy and screw the two pieces together until they dry or set.

 

[ondarvr]

Re: Pro's and Con's of using Luan Wood

Maybe I don't understand the the problem. If you're replacing the wood in the transom, you're already going to be doing a bunch of fiberglass work, so gluing two sheets of plywood together should be no problem and a lot less money.

 

[tashasdaddy]

Re: Pro's and Con's of using Luan Wood

most transoms are 1 1/2 inch, laminate 2 pieces of 3/4 exterior AC ply or marine ply. most luan is not exterior glued.

 

[Chris1956]

Re: Pro's and Con's of using Luan Wood

I am surprize that you were advised that resin will stick to Luan. Luan is Phillipine mohagny, as as such is naturally oily. This is not a good property to have when you want resin to saturate and stick. Use AC or BC plywood of the appropriate thickness, laminated with a piece of fiberglass cloth as the "meat" in the sandwich, and poly resin as the "mayo". Clamp or screw it together until the resin is set.

 

[fdmsiv]

Re: Pro's and Con's of using Luan Wood

Luan is an umbrella term for about a kagillion types of wood. Luan is also only the veneer, the core wood is going to be something completely different. The main things to look for are marine or ext and lots of plies.

A sheet of good marine ply in 1" thickness is going to run you north of $100, if the price is substantially less, the guy is selling you home depot ply at lumber yard prices.

Marine ply is also going to have more plies than typical construction ply, you want to be on the look out for higher numbers, greater than 7 in my opinion. Surprisingly Marine ply is going to be lighter than ext ply and especially pressure treated ply.

For your boat I would go with the Home Depot pressure treated stuff. Get 2 sheets of 3/4 pt ply, let them dry for a week, glue em up and go to town.

 

[77mutiny]

Re: Pro's and Con's of using Luan Wood

thanks for all the responses, i guess i'll just get two pieces of ply and epoxy them together, i was just wanting to go with a solid piece of wood to save some time and trouble. the mill was going to charge me about 130$ for the 1inch 4x8 luan i talking about, which isn't bad for everything i've found around here so far. the cheapest marine fir i can find is 120$ for a 1/2 4x8.
also i know for sure the transom that was in it previously was only 1 inch, it'll be holding a 90hp johnson outboard, to the best of my knowledge it hasn't been rebuilt before, so i think that was the original transom. is that going to be an issue??? anyone know???

 

[fishrdan]

Re: Pro's and Con's of using Luan Wood

YIKES,,, $120 for 1/2" fir marine plywood...

I'm out in the middle of the desert (where marine plywood is hard to find) and only paid $60/sheet for 3/4 fir marine plywood.

 

[77mutiny]

Re: Pro's and Con's of using Luan Wood

hey guys i found a lumber yard that can get me some 1/2 marine abx plywood, he said he doesn't know what type of ply is in it, but is abx a good marine ply?

 

[j_martin]

Re: Pro's and Con's of using Luan Wood

hey guys i found a lumber yard that can get me some 1/2 marine abx plywood, he said he doesn't know what type of ply is in it, but is abx a good marine ply?

The letters refer to the visual condition of the layer. A is prerfect, B is small imperfections, C is repaired imperfections, D is holes. The x refers to eXternal grade glue. abx would be fine.

Don't use any pressure treated plywood in a boat. The pressure treatment is a wet process. Pressure treated wood is designed for ground contact, where it is usually wet. They don't even dry it out before they ship it, making it pretty heavy. The chemicals in the wood can be tough on hardware. Resin bonding would be suspect unless you thoroughly dried the wood before you laid it up.

Marine plywood is supposed to not have any voids in the inside layers. The wood I bought at a high price for the transom project turned out to have cracks and voids in the interior. If I were to do it again, I'd use abx, or acx plywood from the lumberyard.

I apply all the penetrating epoxy sealer (Rot Doctor CPES) that the plywood will take, then assemble it. With epoxy you can design it so you can assemble it in place. With 7 pieces I built a 48 in wide transom and put it through a 40 inch hole. I didn't remove any major fiberglass, and the resulting transom is unbelieveably solid. I used a real slow setting epoxy (Rot doctors LLR) for assembly and literally had all night to get it right.

hope it helps
John

 

[Mark42]

Re: Pro's and Con's of using Luan Wood

....Don't use any pressure treated plywood in a boat. The pressure treatment is a wet process. Pressure treated wood is designed for ground contact, where it is usually wet. They don't even dry it out before they ship it, making it pretty heavy. The chemicals in the wood can be tough on hardware. Resin bonding would be suspect unless you thoroughly dried the wood before you laid it up.....

John, this has proven to no longer be true. Especially seeing as many boat manufacturers use pressure treated lumber in their boats now. And having been reading these boards since 2002, and participating since 2003, I cannot recall any member posting that their glass work delaminated from pressure treated ply.

And today if you shop at indoor lumberyards, the p/t lumber is not soaking wet like in the past. Althought you should be sure the ply is dry before use. I dont have first hand knowledge of p/t with aluminum, but I can tell you that there is no problem with p/t and stainless or galvanized fasteners.

Mark

 

[77mutiny]

Re: Pro's and Con's of using Luan Wood

thanks everyone, i'll get some of the abx and fiberglass away.
thanks again

 

[seven up]

Re: Pro's and Con's of using Luan Wood

hey 77 Mutiny,


The excuse that pressure treated is used by boat manufacturers is a weak argument.

The pressure treated plywood used by boat manufacturers is KDAT: kiln dried after treatment. Also, this plywood requires minimum retention percentages of at least .40 for contact with fresh water and higher retentions for salt water contact.

The pressure treated plywood available at box store chains is no where near these certifications. From neighborhood to neighborhood the quality of the box store stuff goes from bad to worse. The inner plys are weak and rampant with unfilled gaps and voids. Just look at the edge of the panel.

Every sheet of luan I have used was manufactured for interior use. Great for countertops, too.

Hope this information has helped.




Enjoy

 

[i386]

Re: Pro's and Con's of using Luan Wood

i was just wanting to go with a solid piece of wood to save some time and trouble.

Boat restoration is all about time and trouble. I think you'll look back and think gluing up that transom was one of the easiest parts of the project.

 

[Mark42]

Re: Pro's and Con's of using Luan Wood

hey 77 Mutiny,


The excuse that pressure treated is used by boat manufacturers is a weak argument.

The pressure treated plywood used by boat manufacturers is KDAT: kiln dried after treatment. Also, this plywood requires minimum retention percentages of at least .40 for contact with fresh water and higher retentions for salt water contact.

The pressure treated plywood available at box store chains is no where near these certifications. From neighborhood to neighborhood the quality of the box store stuff goes from bad to worse. The inner plys are weak and rampant with unfilled gaps and voids. Just look at the edge of the panel.

Every sheet of luan I have used was manufactured for interior use. Great for countertops, too.

Hope this information has helped.


Enjoy

You can not argue the fact that of all the projects that members have done on this forum over the years, not a single one has reported any problem at all with using pressure treated lumber. If you don't like what you find at depo or lowes, etc, buy it from a lumber yard. You can and will get a better product there for just a few dollars more.

And why is the fact that boat manufacturers use pressure treated lumber a weak argument? Because it goes against your opinion? Facts are facts and your down playing them does not change the facts or lessen their significance one iota.

Sorry, but that is the way it is.

Hope this information has helped.

Mark

 

[seven up]

Re: Pro's and Con's of using Luan Wood

Mark42

I guess you were out milkin the cows when the facts were written.

I realize you are annoyed that someone could possibly have the nerve to question your decision to support what you support. Box store pressure treated in this case.

You are just more comfortable in your "good enough", "cheaper" frame of mind.



Enjoy

 

[Mark42]

Re: Pro's and Con's of using Luan Wood

Mark42

I guess you were out milkin the cows when the facts were written.

I realize you are annoyed that someone could possibly have the nerve to question your decision to support what you support. Box store pressure treated in this case.

You are just more comfortable in your "good enough", "cheaper" frame of mind.

Enjoy

No where did I say "good enough" or "cheaper". That is your incorrect interpretation. I also did not say to buy at box stores. I said to shop at indoor lumber yards. Where I live, most of the lumberyards are now indoor. And I did specify if you shop at a lumber yard, you will get a better product than home depot or lowes.

Please take the time to read accuratly what I post so you don't make yourself look foolish by not understanding or misquotine my posts. Also, there is no need to be insulting or to fabricate the notion that what I propose is not safe. In fact, "good enough" is what boat manufacturers build. Just good enough to meet the regs.

If you cannot be civil in your responses do not respond at all.

I have stated the facts. If you disagree, please just state that you disagree. I will have more respect for you than when you are being insulting and twisting my words or try to make me look foolish.

Have a good day, and hopefully, a change of attitude for the better.

Mark.

 

[seven up]

Re: Pro's and Con's of using Luan Wood

Well

Mark42 all you have recommended here to mutiny77 is a substrate available en mass which is not up to the standards recommended in the marine industry.

Either due to your naive nature or because you read "this is what everybody uses" it is nonetheless no relief of culpability.

It was in my post that the proper ratings were listed but yet you would rather quibble over your feelings.

Whatever. My intentions were and are that mutiny77 receives proper information.

If an inspection of the restoration is required for certification...well, Mark42, your materials list wouldn't cut it.



Enjoy

 

[Mark42]

Re: Pro's and Con's of using Luan Wood

Well

Mark42 all you have recommended here to mutiny77 is a substrate available en mass which is not up to the standards recommended in the marine industry.

Either due to your naive nature or because you read "this is what everybody uses" it is nonetheless no relief of culpability.

It was in my post that the proper ratings were listed but yet you would rather quibble over your feelings.

Whatever. My intentions were and are that mutiny77 receives proper information.

If an inspection of the restoration is required for certification...well, Mark42, your materials list wouldn't cut it.



Enjoy

Seeing as the vast majority of boat projects on this forum do not use marine grade plywood, are you going to point out your opinion on those posts/projects where regular ply or CDX or something else was used ?

The point is, which you seem to totally miss, is that these products are well suited to repairing small craft.

And seeing as none of these craft require certification of any sort, and are probably repaired to be stronger than when new, your point of not meeting certification that is not even required, is totally mute.

And the p/t ply you buy at the lumber yard is better quality ply than was used by Bayliner to build the transom in that 17' boat to begin with. Bayliner is NOT REQUIRED BY ANY INDUSTRY OR OTHER REGULATION to use marine grade plywood anywhere in that 17' boat. So there is no violation of any regulation. That is why Bayliner and so many other boat manufacturers just use standard ply.

Regarding regulations, all that this boat has to meet are the SAFETY requirements as set down by the Federal government and the US Coast Guard, neither of which specify the grade of materials used in construction of the vessels. There hundreds of pages of Maritime regulations that apply to SHIP building, but they do not once mention plywood. And again, this is not a ship, it is a pleasure boat.

Your reference to Industry Standards is interesting because industry standards do not specify marine grade ply for transoms or floors. It would be nice if it did, because there would be a lot fewer rotten transoms and stringers/floors, etc.

If you can supply links to specific regulations indicating the grade of materials used in small pleasure craft, either Industry or Federal or Coast Guard, please do post them as I want to get the correct information if I am wrong.

I understand your point, but as far as I can determine, you are disagreeing with the facts I posted because his boat won't meet unspecified regulations that do not even apply to his boat. Like saying the pickup truck I am restoring won't meet regulations for tractor trailers. It's rather poinless, isn't it.

Have a nice day, and its good to see you took my advice.

 

[fishrdan]

Re: Pro's and Con's of using Luan Wood

Hmmmm, just because it's called marine plywood, don't think marine manufacturers only use marine plywood.

In my 01 Crestliner the decks are (were) made from CCA pressure treated 5 ply plywood. It was NOT marine grade plywood since there are knot holes all over the place and not 1 of them is patched. How about the transom you ask??? 5 ply 3/4" treated plywood with knot holes all over the face and none of them are patched. If the face veneer of the plywood has 1-2+" knot holes all over the place, then interior plys have the same,,, and voids through out the sheet of material.

Marine plywood has specs, all knots over a certain size must be patched, plys laid at 45 degrees(instead of 90 degrees as in normal plywood), no voids (,,, or from my experience minimal voids),,, and I'm sure a bunch that I'm not aware of.

If Crestliner can built, certify and sell boats built with pressure treated exterior grade plywood (even though it's probably not the same exact plywood available locally), I think it's pretty safe to assume it will be OK to use for a rebuild...