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Tips on buying and using luan

PostPosted: Sun Aug 23, 2009 12:43 pm
by S. Heisley
Here are a couple tips that may help others avoid some pitfalls of bubbling or delaminating luan that I've found:

First experience & tip (bubbling luan):

Although my 4x8' luan sheets did not initially delaminate, I think the bubbling/ballooning that I encountered must've had something to do with moisture...not sure, though. No matter what I did, I could not get the luan to flatten out, even when I glued 1/4" plywood to the back of it and clamped and weighted it until dry. It still ballooned back up. The ballooning was not just on the surface. It was the entire thickness of the luan, curving upwards and out in various places in the center areas of the plywood sheets. (I ended up trashing the wall that I had done and giving the remaining unused 4x8 pieces to a neighbor, who said it is okay for use as added thickness on his attic floor. )

The bad luan was from a well-known "box" store. I called around and found another source. That source said that the place I got my bad luan from gets 'seconds', not quality, meaning you really don’t know what you’re getting. When I got the new luan home, I compared it to the box store stuff. I could immediately tell the quality difference with my untrained, naked eye. Also, working with the better quality luan was unbelievably easier. The better quality luan was just $3 more per sheet.

I have been told that 1/8” luan is not really made for exterior use and most, if not all, is made with interior lamination glue. The product is not usually considered stable in places that will see much moisture. But, if you feel you must use 1/8” luan, because it is lighter weight or whatever; and you're getting ready to purchase it, think twice about where you buy it. Call around and look for a good source. Check your purchase at the store, before you buy it. The extra $3, or even a little more, that you may have to pay is very much worth it.

Second experience & tip (delaminating luan):

When working with the cheaper luan (probably would happen with any luan), I absent-mindedly set a wet paper towel on the surface. In less than 10 minutes, the luan had delaminated. This led to an experiment. I took a scrap piece of the cheaper luan and applied one coat of Clear Penetrating Epoxy Sealant (CPES). Now, I know that one coat is supposed to only make a surface moisture resistant, not moisture-proof; but, I wanted to see how this epoxy would bond with the laminating glues and what would happen when moisture was applied. Once the CPES on the experimental piece was dry, I placed a bunched wet paper towel on it. I checked it after 20 minutes: no delamination. After an hour, 2 hours, and overnight: still no delamination. (By the way, the paper towel was still wet in the morning.) My conclusion is that epoxy (at least CPES) really helps fight delamination of luan products. I now apply a coat of CPES to the luan as soon as possible, after the underlying frame's holding glue is dry. It not only helps protect against moisture, it helps make the whole unit stronger and helps protect against accidental damage during the building stage. I will add yet another coat after my cabin is put together on the chassis. (If someone out there has a scrap of luan and some other type of epoxy handy, it would be interesting to see if the same results occur with their products.)

Last tip:

In conclusion, please don't take short-cuts with your time or your money. Even if you happen to be on a limited financial or time budget, it is well worth spending a little extra money and/or time to find and use the best products to the best of your abilities now, as opposed to the heartache and hassle of trying to repair something that may go bad later.

I'm still building 'MyAway' TTT and will probably still make mistakes and do some stupid things like the above examples. But, I hope to share my experiences and pass on what I find out, so somebody else won't make the same mistakes. That's what this forum is all about.

Wishing you all happy building and happy travels!

PostPosted: Sun Aug 23, 2009 12:55 pm
by Steve_Cox

Great post! :thumbsup: You're one smart cookie!! :lol:

PostPosted: Sun Aug 23, 2009 9:05 pm
by S. Heisley
Thanks, Steve. :) I hope this thread helps another rookie TD/TTT builder.

PostPosted: Sun Aug 23, 2009 9:17 pm
by kennyrayandersen
COMPLETELY AWESOME! A great post as I’m sure Luan (sometimes called Meranti) is not going away due to cost. If it’s going to get used, this kind of information is invaluable. :thumbsup: :thumbsup: :applause: :applause:

PostPosted: Sun Aug 23, 2009 9:22 pm
by jopasm
In the epoxy/ply boat building world the "boil test" is used to check the glue. Basically you drop a scrap of ply in a pot of boiling water and leave it an hour. If it doesn't delaminate it's probably a decent glue. Here's a description of the test and some thoughts on glues by Jim Michalak (well known designer of small boats for amateur construction:

Now, a teardrop isn't a boat (ok, well, unless you forget to put the chocks under the wheels), but if you're planning on parking your teardrop outside and/or only painting the plywood to weatherproof it you need to read that link.

PostPosted: Sun Aug 23, 2009 10:58 pm
by Steve_Cox
I've never known a boat builder that boiled his plywood..... and I've know a few.... but, now days I guess ya might just have to. The boat ply I have used was Bruynzeel, Okoume or Douglas Fir and a little teak and holly here and there.

PostPosted: Mon Aug 24, 2009 5:24 pm
by S. Heisley
KennyRayAnderson wrote:
If it’s going to get used, this kind of information is invaluable.

Thanks for the vote of confidence, KennyRay.

Jopasm wrote:
In the epoxy/ply boat building world the "boil test" is used to check the glue.

You sound like Andrew Gibbens, an expert boat builder and well known design expert here, on this forum. His PM comments were similar to yours. I don't question that both of you are correct. Your words are well written and you bring up a good, solid point.

As I wrote previously, one coat of CPES only makes an item water-resistant, not water-proof. CPES was all I had on hand for the test. Also, as stated previously, I would love to see someone else run a test using RAKA or some other form of epoxy to see what the results would be. Although some forms of epoxy are mixed and used like glue, CPES is not glue and is not represented as such; but, it can help. Also, CPES is not meant to be used alone as it is not UV stable. It must be covered with a suitable UV resistant product.

CPES is touted as being waterproof on wood if you completely cover the wood with at least 3 coats and add some type of UV protection. Obviously, my test was ( on words...) 'watered' down. :roll: :lol:

My test was not to prove water-tightness or glue-tightness in extreme conditions (boiling water). It was to show that thin, fragile Luan (Meranti) can be greatly strengthened and often protected from damage during building if you at least coat the bare Luan with a layer of epoxy as soon as possible after securing it to your frame. While the one coat of epoxy will offer a small amount of on-going protection, you should use another product on top of that, for added water and UV protection. (Some people may kibosh this, saying they did fine without epoxy. I'm not that brave; plus, I hope to make my TTT last many years.)

Thanks for your fine comments and I hope this clears up your concerns.

PostPosted: Wed Aug 26, 2009 6:51 pm
by Jiminsav
you sure that was luan?..I left a piece outside for 2 years and it was just a little warped..and then the wife made me throw it was my favorite piece...of wood. never had any delaminate, but did have a piece of 1/8 PLYWOOD try to tie itself into a knot.

PostPosted: Wed Aug 26, 2009 8:16 pm
by madjack
Sharon, EXCELLENT :thumbsup: :thumbsup: fact, I am goin' to make it a sticky!!!!!!............... 8)

PostPosted: Thu Aug 27, 2009 11:27 am
by S. Heisley
Jiminsav wrote:
you sure that was luan?..

...Absolutely certain.

MadJack wrote:
Sharon, EXCELLENT fact, I am goin' to make it a sticky!!!!!!

Really? Wow! Thanks, MJ! :) That's high praise, especially coming from you!

luan story

PostPosted: Sun Sep 06, 2009 10:16 am
by jesse c
for the last 30yrs ive been working with 1/4" and 1/8" luan and have noticed in the last 5yrs or so a lot of it is junk.We buy it by the pallet load and some is delaminated right off the stack and some is sanded with major deviations in thickness,sometimes nearly double in sections,due to ,i guess manufacture sanding machine malfunction on assembly line,and where theres one in a skid theres usually many,many cause they come out of the same manufacture lot.In the early years i was so impressed with 1/8" a put a piece in a drywall bucket of water and took it out maybe a year later and excapt for raised grain there was no change or delamination. Ive changed companies and sources dozens of times over the years so i dont know if its the product or provider that explains the changes.
Oh-the rumor is that the ply is made onboard a factory ship as it shipped across from the rain forest lumber harvesters

PostPosted: Sun Sep 06, 2009 2:47 pm
by S. Heisley
At the local hardwood store, I was told that all plywood is now made in China.

Made in China

PostPosted: Tue Sep 08, 2009 9:25 pm
by Wild Bill
That should explain the poor quality. Made in China. Not a lot cheaper to purchase, just a lot more profit margin for the stores and poor quality.
Too bad nothing is made in America any more, that is why we are in the "recession" we are in now. I call our current economy a Greater Depression than that of the 1930's Lots more unemployment than 10%, but they do not count people that are no longer looking. This "global economy" is actually just lowering us down to the 3rd world level. Thanks for letting me rant, not trying to Hi Jack your post. Good study on plywood, I am at the stage where I just went to a big box store and bought 4 sheets of tongue and groove to build my floor. A big tear is called a drip I guess. going to be 12'-6" long by 6'-3" wide. a biggun. I like to take everything I own with me when I camp. And No I am not one of the millions that are unemployed, If I was I would have more time to build my trailer and no money. It is always one or the other. Bill

PostPosted: Wed Oct 07, 2009 1:10 pm
by LMarsh
I've used luan from the box stores and poured hot water on it to help bend it. No delamination. It said exterior rated on it though. Also I've been told by "lumber people" most plywoods use exterior rated glue anyway. That being said I don't disagree. Pretty much all the plywood at the big box stores is garbage. You definitely get what you pay for. Also though, in my opinion, even at professional lumber yards and building suppliers I'm not sure they really know what they're talking about. I can ask the same question to 10 different people or even ask different people at the same yard and get a different answer every time. Not to mention I worked at a large lumber yard chain (84) while building our teardrop. No one in that whole company could ever answer my questions to my satisfaction. I did buy luan from them though. It was actually pretty decent. :R

PostPosted: Wed Oct 07, 2009 8:13 pm
by S. Heisley
If you are lucky enough to be able to get exterior rated plywood, go for it! :thumbsup: