Roof/Luan concerns(?)

[afreegreek]

there are many grades of plywood in each species.. all Luan ply is not the same. with that said a person must be careful in selecting grades of ply for building. saving 15-20 dollars and having to spend time repairing it is no bargain.. like the old saying goes, "you get what you pay for"

as far as thin ply goes, the best stuff is marine grade. not only is the glue better, the veneers it is laid up with are better too. it is also manufactured to withstand bending (boats are curvy) unlike most thin ply that is designed to be used as paneling, door skins, and drawer bottoms..

no amount of glue, resin, paint or whatever is going to make crap into gold and trying to do so is an expensive and labour intensive struggle that you will not win..

[doug hodder]

Let it go for a while and see just how bad it gets. The epoxy I'm talking about is like a West, Raka, or System 3 type material. It may not take care of it without some cloth also. The core on big box luan is just crap, always full of voids, and the top veneer is so thin, it's not really doing much other than hiding the core. That's why it's cheap. On the Voyager, I did it in Baltic birch, the 1/8" bent really well and it's under a lot of epoxy. You could always top it with that, or skin with aluminum. Doug

[Alfred]

there are many grades of plywood in each species..

OK, I appreciate the feedback so that others may learn not to use the Home Depot inexpensive luan.

For now though, this is the luan I have already screwed/glued and sandwiched and CPES'd on my camper. Removing it entirely isn't a good option either, as I don't know that it would come off if I tried, at least not without tearing everything else up with it.

What I do appreciate is the help and support from you all on how to proceed from this point forward.

I don't want to over-react either, I've got some splits/cracks in the outer veneer. I can get to them easily, I'm glad to have discovered the situation now as opposed to later.

I've got an email out to the Rot Doctor too and will let you all know how they respond.

Thanks, Al in Asheville

[Alfred]

Let it go for a while and see just how bad it gets. The epoxy I'm talking about is like a West, Raka, or System 3 type material. Doug

Thanks, Doug. I won't be able to work on it again for a week or so anyway. We'll see.

AL in Asheville

[afreegreek]

when you bend plywood you compress the veneer on one side and expand it on the other. without actually seeing it myself it's hard to say that this is the cause but if it is and there is no delamination around the crack there is no problem other than a visible defect.. in that case all you need is to fill the crack.. you can do this with epoxy or wood glue or wood filler.. you can also cut some veneer from an off cut with a razor knife and use that. if it is delaminating then you have a real problem. it may be best to replace it or cover it with a whole new piece. sure it's a lot of work but it will be fixed. if you try and spot repair it may be a constantly recurring problem.

[Alfred]

when you bend plywood you compress the veneer on one side and expand it on the other. without actually seeing it myself it's hard to say that this is the cause but if it is and there is no delamination around the crack there is no problem other than a visible defect..

Thanks AFG - Just to clarify, there are no significant bends in the plywood, I'm building a modified Weekender, so the ply panels were basically screwed and glued flat. Right now it is just cracks but I think delaminating around the crack seems to be the next likely risk.





AL.

[RichAFix]

Okay mine isn't finished yet so I don't have any hard evidence to back up my thought but what if you just covered up your bad luan with good birch plywood and sealed it all real good?

I have been using .125 baltic birch plywood and this stuff is like a noodle it bends so easy. I know we all try to watch the cost on our builds and I don't intend to offend but if you are going through the effort to build a showpiece it really isn't that much more expensive to use good materials. A sheet of 5'x5' .125" birch ply is less than $20.00.

Mine will eventually be covered in aluminum so I could most likely get away with less expensive materials but to me it just isn't worth the headache.

Sorry you are having issues.

[Alfred]

what if you just covered up your bad luan with good birch plywood and sealed it all real good?
Sorry you are having issues.

No, the cost isn't the issue, actually it wasn't the issue at the time, I thought the luan on the front and top would be sufficient, given the sandwich construction. I honestly thought the luan would work. Incidentally, the sides are 4 panels of good baltic birch 1/2", which was $40/panel, and I agree that I am not having any issues with the baltic birch that I am having with the luan.

The issue now is the luan is what is on there and I do not want to deconstruct it. Figuring out what to put on top of it is where I'm at (so far suggestions have been epoxy, filler, more CPES, a layer of baltic birch and/or fiberglass cloth).

AL in Asheville

[S. Heisley]

So, it sat all winter without any CPES protection applied? Oops! Now that you've had it out in the sun and under a fan and put on the CPES, it's drying out and moving a bit.

It's good to ask the Rot Doc. I think the he's going to tell you that once it has dried and stopped cracking, sand any loose stuff off and apply a little more CPES over the new and old cracks and let that dry. Then, fill and smooth the cracks with Fill-it and let that dry. Then, apply your aliphatic paint. Whatdyawanna bet? A small set of Fill-it? An RV book or magazine? …Hmmmm.....

Alfred, everything will work out and I honestly don't think you'll need to replace your plywood. (Unless it got really, really wet, which I doubt.)
I have a lot of faith in the Rot Doc's products.

[Alfred]

So, it sat all winter without any CPES protection applied? Oops!

Hey Sharon,

Yes, that's what happened. I thought as long as the camper was parked inside it would be OK. I was thinking I should wait until I got the doors done and do the CPES all at once. Although, I just did eventually CPES it without the doors. Your feedback seems reasonable, and it is my hope that the Rot Doctor will concur! I'll keep you posted!

AL in Asheville

[afreegreek]

in plywood factories the glue is applied by wide rollers. it's more complicated but similar to those old washing machines with the roller doo-dad on the top. sometimes the glue runs low and does not cover the width of the roller but rather gets applied in lines.. this is the most common glue up defect in plywood and will be fairly consistent along the length.. it is rare but not impossible for spots to be missing glue but as I said, this is rare.. with that, you can check for this if you have any scraps of that sheet left.. just go along the width of the veneer with a chisel or pointy knife and try to separate the plies (you can also burn off the top layer of veneer with a belt sander or hand plane and get down to the glue line). if it's the sheet as a whole that is effected then it will be better to replace or cover it with a better piece.. if it's just localized then follow the wood doctor's advice and repair the area..

also, a lot of plywood plants use hot presses to form the sheet and set the adhesive.. logs are sliced or peeled when they have been soaked to soften the wood.. this veneer then goes through ovens to dry it.. if the wood is too damp then the heat of the hot press can cause shrinking cracks to occur. these alone do not matter (other than appearance). this also may be the problem with you sheet. if it is you're on easy street.

[Dan & Julie CO]

I had alot of cracking even after using moisture and steam I finaly cut a section out, the bend was to extreme it started to bend the spars the Luan at big box stores is cheap and lacking in quality. I was trying to use it on the interior as well I saw the forest for the trees and used 1/4 inch ply on outside and masonite inside I had to do more sanding but it hasn't cracked yet

[Alfred]

Hi Y'all,

I received this response from the Rot Doctor this afternoon:

Simply mix a little of the Fill-It Epoxy Filler and with a putty knife smooth it into the crack. Job done. You can sand the Fill-It, if required, after it cures. And feel free to come back if you have additional questions. Doc -- The Rot Doctor

Sharon, looks like you called this one. So, I think this is where I will start. I will keep you posted.

AL in Asheville

[S. Heisley]

To be on the safe side, Alfred, I would dab a little more CPES on those new cracks before filling them with the Fill-it.

Are you still on spring break?

[Alfred]

:thumbsup: To be on the safe side, Alfred, I would dab a little more CPES on those new cracks before filling them with the Fill-it.

Are you still on spring break?

Hey Sharon - I'm starting back to work tonight. Alas, Spring Break has sprung and is over! I probably will not be able to get back to the camper until Friday or Saturday. If I add more CPES first, do I need to wait a few days for it to finish curing before I add the fill-it?

AL in Asheville