: I need some advice, or clarification, on the suitibility of luan plywood for
: stitch and glue building. All that is available to me and my limited
: budget is luan ply. It's not specified as exterior, but other people have
: told me that most ply uses exterior glue. So, my question is this: if it's
: sheathed in glass and epoxy, does it matter if the ply is glued exterior
: or interior? I've seen conflicting information on whether or not epoxy
: saturation of wood keeps water out; and also whether or not glass and
: epoxy sheathing keeps moisture out. It seems to me that if people strip
: build with elmers glue, then epoxy and glass must keep out the moisture. I
: just don't know what to think. At $10 per sheet, I'd like to just use the
: luan. Also, I built a double paddle with interior birch ply, then
: encapsulated it in epoxy and varnish, and have had no problems yet.
: However, my boiling test on a sample of this birch ply revealed rapid glue
: failure--as compared to my sample boil of AC exterior, which did not fail.
: Any information clearing this up for me would be greatly appreciated, as
: I'm itching to bust out a few canoes and kayaks.

Hi Tim,

The conventional wisdom seems to be that you can only use Loyds approved marine ply, well at least thats what most kayak kit sellers say. I think if you use the expensive stuff your boat will probably look nicer, and there's a lesser chance that your building experience will end in tears.

However, for those of us on a budget, it's a matter of using luan or finding another hobby. I've built a Guillemot S&G using the cheapest stuff I could find, 6oz glass outside, taped inside. I've been paddling it for a year and it's fine. I had to paint it because the panels didn't match and it looked pretty awful (so it doesn't look as nice as a boat finished bright).

I'm currently building a CLC West River 180 out of sheets of ply I found on a junk heap. It looks great and so far it's only cost me $AUS17 for the sheer clamps. My wife told me today she thinks it would be great finished bright, I have to agree.

Good quality mahogany marine ply (Okoume, sometimes called Gaboon) is made with all plys of equal thickness, there are no voids (areas where the inner ply is missing), it looks real pretty when you glass and varnish it, it bends nicely and is easy to work with. With most luan ply, the plys are not of equal thickness, there are usually voids present. It may not bend as nicly as okoume. the glue is usually the same stuff used in marine ply. If the glue used softens with heat, you'll probably have some interesting problems later on though.

Water ingress through the epoxy really shouldn't be a problem, otherwise it would effect most strippers boats too. I've been lurking and posting on this board for three years now, and I've never heard anyone mentioning problems with moisture ingress, unless the boat is holed.

What this means to you and me is; if the outer veneers are really thin you may sand through while you're sanding the scarfs, be aware of this and don't. You may have voids in your finished panels, check for voids before and after you cut out your panels, if there is a void, replace the panel or section of the panel. Test some luan with a hot iron, don't use it if the glue softens. Take your time when you're buying the luan, look through every stack they've got and you'll probably find some sheets that match nicely, just don't leave a mess when you're done looking.

The bottom line I guess is; Buy top quality marine ply if you can. If you can't, buy luan and be aware of the pitfalls.

Hope this helps,

Paul.