1 layer of luan on roof ok?

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1 layer of luan on roof ok?

Postby Kayaker1971 » Thu Jun 30, 2016 2:29 pm

I'm ready to apply the canvas and glue cover but wondering if its common to glue a second luan layer on first for strength? The sides are 5/8" sheathing plywood, top of the roof has a 2ft section with 3/4" under the luan for a standing / cargo area... ideas? advice? thx! :D

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Re: 1 layer of luan on roof ok?

Postby woodywrkng » Thu Jun 30, 2016 3:03 pm

My roof is just a single layer of 1/8" plywood, but I also have spars going from side to side every 9 inches or so. When you bend the thin plywood it becomes quite strong.

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Re: 1 layer of luan on roof ok?

Postby Kayaker1971 » Thu Jun 30, 2016 3:26 pm

thanks! hmmm we'll see what others say. I do have the extra luan to double it up.

going over it with glue and canvas, bought 3 gallons of titebond 2 and enough tarps today at home cheepo...
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Re: 1 layer of luan on roof ok?

Postby yrock87 » Thu Jun 30, 2016 5:38 pm

I want to say that when I read the old Popular Mechanix instructions for the teardrop they say to use two layers of 1/8 fiberboard glued together for the roof.

I dont have experiance with luan,and I'm not sure what the luan is like, but from accidently poking through my foam backed 1/8 Birtch ply, I would recommend a second layer or some other surface like epoxy or aluminum to provide puncture resistance. the wood by itself is strong, but still fragile in the puncture department. a second layer may help with that.
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Re: 1 layer of luan on roof ok?

Postby Kayaker1971 » Thu Jun 30, 2016 8:24 pm

OK well I went with a second layer of luan. I used about a quart of titebond in squiggles and around the perimeter, screwed across the front bottom edge then screwed in rows across as I "wrapped" it around the curve and used a 2x4 across the back edge to hold that down until the glue sets.

The screws are wide-head shorties fro home depot and I remove them after the gue sets and replace key ones (corners, edges) with exterior drywall type screws which pull in flat with the surface.

one more section of luan and then interior cabinets, and get ready for the glue-and-canvas cover.

still have to plan a door of some kind and what to do with the interior as far as cabinets and shelves etc. (the back wont open on this one, making it much simpler.)

never did this before so its a miracle its made it this far! :o
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Re: 1 layer of luan on roof ok?

Postby dwgriff1 » Wed Jul 27, 2016 10:11 pm

I built my all wood teardrop trailer 10 years ago. It has been pulled thousands and thousands of miles and has sat out in the weather, sometimes even without being properly covered.

The roof is 1 layer of 1/8 lauan. There are ribs, but not too many of them. The curve of the roof makes that skin stronger.

The weather has been hard on my little woody, but the top is doing just fine.

I'll do a major rebuild this fall, but I'll use 1/8 lauan pretty exclusively on the outside skin. The inside skin is already 1/8 ply and is doing fine.


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Re: 1 layer of luan on roof ok?

Postby Kayaker1971 » Tue Jun 20, 2017 6:58 pm

OK here's an almost 1 year update.

DO NOT USE CHEAP LUAN! USE 1 OR 2 LAYERS OF THIN MARINE PLYWOOD FOR THE ROOF! Here's why:

camper sat in back yard uncovered all winter. the exterior plywood held up well. the luan held up where it was FULLY covered. that means that at the bottom edges, water dripped along and migrated up and destroyed it to the consistency of cardboard along the front and back edges.

The Luan is only on the roof part. sides and bottom are 5/8 plywood. all is covered by glued canvas tarp and that was painted with exterior paint and that held up really well. Not a DROP got into the camper even in my home made wood door design. Not a drop. JUST the bottom edge at each end where the water backed up a couple inches and soaked into the luan.

those were caulked and painted but to no avail.

I SHOULD HAVE USED MARINE PLYWOOD.

so today i bought some marine wood restorer epoxy and waiting for the edges I opened to the atmosphere to dry out so I can TRY this $48 dollar miracle juice.

Picture shown is the two layers of luan, with painted canvas. I may have to cut off all the luan and apply marine plywood, but this is just an issue on the bottom two inches at each end so maybe the epoxy will make it "marine plywood" just where it needs to be. I will soak it through and then bolt a stout angle iron across to squish it all together until it cures.

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Re: 1 layer of luan on roof ok?

Postby Wobbly Wheels » Tue Jun 27, 2017 2:34 pm

Sorry to hear about your problems with your roof. I used two plies of 1/8 luan over spars and it's held up fine for a couple years now with no protection from the elements on the rainy west coast. That said, I sheathed mine in fiberglass and sealed the inside with polyurethane.
A couple notes about marine ply (since that's what I was going to use originally).

Here in BC at least, the thinnest marine ply available is 1/4".
Being Douglas fir, wouldn't bend to the radius I needed without kerfing it.

Plywoods in general use a lower grade material for the core veneers and most of the luan I've used (I go through lots of it) has a core that's too pithy to provide any structural support.
I think my next gig is going to be a slide in camper and I will probably skin it in luan as well, though your experiences remind me how important it is to seal it well: this stuff is looking for an excuse to disintegrate.

It may not help you much now, but you may not need to blow a bunch of dough on CPES or whatever you're using if the damaged area is accessible. Make sure it completely dries out, then thin your (mixed) epoxy of choice with acetone to manufacturer's maximum (10% for West and Interlux). Warm the wood and keep the epoxy in a little cooler with a couple gel packs until you're ready to use it. You can also warm the epoxy just before you apply it to get it to penetrate better, but that will shorten the pot life by quite a bit.
Use a basting syringe to get the resin deep into the delamination.
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Re: 1 layer of luan on roof ok?

Postby beezerboy » Mon Aug 14, 2017 9:12 pm

the birch plywood from Finland is made with waterproof glue and there are no voids in the laminations. (so I am told at my local specialty wood store).... it also has lots of plys for the thickness. I put some in as floor on my float hatches where its wet all the time & still good after 3 years. other than that, I have only built cabinets it with but I'm impressed with the quality. there are other thicknesses but I have only used 3/8 and 1/2. the 1/2 is prolly 12mm, but it has 10 plys. the only down side is it comes in 5'x5' sheets. it does come in 1/8" thickness (3mm?).... 15 bucks for that where I live.... the 12" is $37
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