Luan for Brightwork

[Victor]

What about it? Sold as a vapor barrier, so it must be resistant.

[ 01-07-2005, 06:40 PM: Message edited by: Victor ]

[Jim Goodine]

I wouldn't use it. My teak deck had been laid over lauan plywood and the plywood completely delaminated and rotted. A mess. And as for it being a vapor barrier, I doubt it. It may be a vapor retarder at best. Good luck with the project.

[Victor]

Well mahogany would turn to mush under those conditions too, wouldn't it?

[Jim Goodine]

Well, that is an interesting question. On the boat I bought, everything up to the gunwhale was Doug Fir and Cedar and was in perfect shape. When the builder put on the cabin and deck, he used mostly lauan plywood but some Doug Fir plywood. The lauan all had to come off and all of the fir stayed.

The teak was laid in a black epoxy bed and the lines between the strips were done in black epoxy which seems like one of the normal ways of doing a teak veneer deck but it was coming off the rotted lauan plywood in sheets. The hatches, flush boards and cockpit locker lids were done the same way but on fir plywood. They are fine.

Maybe the best test would be to put a piece of each in the dishwasher for a month or so. I've used lauan on a bunch of single-sheet kids boats but I wouldn't use it on a nice project.

[NormMessinger]

And aside from all that, the grain patter in luan is about as interesting as okoume, pretty uninteresting.

[JimD]

Did you have a particular boat or application in mind? I've used it for a budget kayak but mainly because if you need eighth inch plywood there aren't a lot of choices without spending several times as much $ for marine okoume.

[Art Read]

One wonders why Luan would ever be used under teak in the first place? Perhaps my impressions are wrong, but isn't Luan generaly just that cheap "doorskin" stuff they sell for 7 bucks a sheet at the Box Stores? Splintery, void-filled and covered with "footballs"? I've never used for anything more than making patterns. You must be refering to higher grade material than I'm familiar with. Still... with all the expense that even a teak deck veneer implies, why would you scrimp on the foundation? And was that subdeck ever sealed at all prior to epoxying down the teak? Something doesn't add up...

[Tom Lathrop]

Good grief,

Looking at apples and discussing walnuts! :rolleyes:

Lauan plywood is as durable as occoume and a usually bit stronger. Trouble is, the stuff sold to construction trades and by big box is usually poor quality and not made with waterproof glue. Even the lauan sold as "underlayment" is a step below marine grade. Both occoume and lauan are lables of convenience stuck on several species from Africa and the South Pacific. Neither should be used under a teak deck.

Neither lauan nor occoume is as durable as fir which is less durable than cedar, etc., etc.

If the plywood was made with interior glue, you could substitute almost any wood for lauan in this thread and have the same negative comments. Even the stuff sold as 1/8" doorskins is not so bad if you get the exterior kind.

[ 01-08-2005, 02:58 PM: Message edited by: Tom Lathrop ]

[Victor]

I said brightwork, was just thinking of using it as a sort of throwaway laminate, not for underlayment. I think it looks a lot like mahogany, but then I like cheap wine too.

[paladin]

Luan is a poor grade tropical cedar that will turn urine yellow when exposed to sunlight even though epoxy coated or varnished so i wouldn't use it anywhere where my head would be underwater if my foot went through it.

[Scott Rosen]

Why on earth would you want to put in the time and effort to varnish Luan?

[Cullen T.M. McGough]

[Luan is a poor grade tropical cedar that will turn urine yellow when exposed to sunlight even though epoxy coated or varnished]

I have to second that- I've seen it done (luan used as house sids and then coated with epoxy) and it does indeed turn piss yellow, even if heavily varnished.

-C

[Victor]

All right then I won't waste the varnish. Just curious.

[Ex-Oceangoddess]

About a thousand years ago when I took my first night school woodworking class at a vocational high school in North Vancouver, British Columbia, the teacher was this really cool guy called Chris Marai, an East Indian from one of the Caribbean islands, who instilled in us the idea that since you are going to put so much time and energy into your projects, using cheap materials is an insult.

I have never forgotten that advice. I get the best materials for the job, and the result is that you end up wanting to match the workmanship to the quality of the materials.

A useful lesson from thirty years ago.....

Notwithstanding, I have built half a dozen cheapo ocean kayaks from 1/8" mahogany plywood, liberally saturated with epoxy, coated with 6oz FG and painted, which are probably still floating around the PWNW, probably with my children's pals, but they sure ain't fine boatbuilding!

[Roger Stouff]

There's good luan and bad luan. One local building supply store (a locally owned one) carries the most excellent grade of exterior grade luan I have ever seen. Very few voids, none in some sheets, and pretty grain. I wouldn't build a schooner with it, but with epoxy, I'd build a little pirogue or bateau with it with no hesitation.

I have used the cabinet grade 3/4" from that store, and it looks great varnished.

[Osborne Russel]

Originally posted by paladin:
Luan is a poor grade tropical cedar that will turn urine yellow when exposed to sunlight even though epoxy coated or varnished
No it isn't. Lauan AKA Phillipine mahogany is cabinet grade wood. With grain filler, solid wood or plywood -- assuming you got quality stuff -- it varnishes well, retaining a beautiful golden brown color, over 10 years of exposure to sun and salt water.

[Victor]

AKA Philippine mahogany? That's interesting! Boy what a variety of replies! I recall leaving a sheet from the Depot out in the elements for years. It actually weathereed pretty well, turned kind of a silver color, not bad considering. I don't really need to use it - mahogany's not that expensive - but it's there and it's cheap and some of it looks pretty nice. Preusmably it's an abundant wood or it wouldn't be in the Depot, right?

[paladin]

as I said...LUAN is a tropical cedar. Period. Philippine mahogany is a registered trade name for what was originally supplied to Chris Craft and in fact was the species Tanguille which is still a cedar but pretty much emulates honduras Mahogany.....because of the popularity of cheeeep "mahogany" several varieties of the wood, both domestic and imported from around Asia are being marketed as Luan or Philippine Mahogany. I've been living over there for 20 years and have used the stuff for nearly 40 years for boatbuilding and a host of other projects. Look at the source of the wood (the laminating mill0 and I'll betch i can tell you where the wood came from. for the various species available in thailand and the Thai names check a previous post.

[John Blazy]

Like Tom Lathrop and others have said, Luaun is only as good as the glue in the plies that holds it together, and the surface treatment chosen and executed by the boatbuilder.

I would never use big box luaun due to thin face skins, and poor adhesives, BUT I would, and HAVE used Luaun when the luaun was incorporated in a wonderful plywood known as Superply (Roseburg Forest Products), marketed for exterior use.

Two major points:
1. exclusively waterproof, exterior glue
2. Thick face veneers (luaun) with doug fir core veneer

I then glassed over it heavily and its my entire hull - sides and bottom, and then veneered over it with ribbon-stripe mahogony as the fore and aft decks.
http://www.imagestation.com/picture/sraid139/pfbcc9bc73468518a7ee5d9f984b6796a/f700a25d.jpg