Used Plywood. | SouthernPaddler.com

Used Plywood.

WadeT

Member
Jul 7, 2008
21
0
Tolono IL
I get a lot of realy thin ply at work that were at one time crates from overseas.. Can anyone tell me how can I tell if they would be good for building? Looking at starting a Kayak soon
 

gbinga

Well-Known Member
Nov 7, 2008
736
2
Hoschton, GA
Cut a sample and put it in a bucket of water. Let it sit there for days and see if there is any sign of delamination.

Look on the internet and try to find info about a boiling water test. You take a small sample of the plywood and boil it (not sure how long). See if the hot water degrades the glue. Exterior glue should hold up.

Examine the plywood around the edges and try to get a feel for how many voids it has in the interior ply(s). Supposedly one of the things that makes marine plywood special is that it has very few if any voids, whereas BC pine or common luan, for instance, is allowed to have quite a few voids in the core veneer(s).

Does it bend well - consistently, that is?

How is the surface quality? Nice and smooth? Not many patches? Good looking grain? Any sign of bubbles in the surface veneer, like they maybe failed to use enough glue?

One comment I'd make is that using mystery plywood that was used for packaging overseas is obviously going to be a gamble. When you consider that a lot of us use pretty cheap wood, ($10-20 dollars per sheet), the wood isn't really that big a factor to start with. You'll have way more money in epoxy and glass than you will in plywood.

Lots of guys use common luan underlayment (about $10 per sheet). I've built a couple of boats with BC pine (about $15 per sheet last time I looked). For the pirogue I'm building right now, I used "Ultraply XL", which I found at Lowe's, being sold as "premium underlayment". The stuff I was $20 per sheet, had excellent surfaces on both sides, the "A" side was a pretty mahogany type wood, and there were very few voids. Plus the manufacturer has a website and they confirm that it is made with exterior glue (you can't always confirm that with luan; can't always figure out who even made it, much less what kinda glue they used).

So my point is, why gamble on mystery wood when you can get pretty well identified product for $10-$20 per sheet -- call it $40-$60 per boat? You will have over twice that much money in fiberglass and epoxy, so the savings just doesn't seem worth the risk.

I fully understand being on a tight budget... that's why I'm not using marine mahogany. Just wanted to give you something to think about.

George
 

Kayak Jack

Well-Known Member
Aug 26, 2003
13,976
171
86
Okemos / East Lansing Michigan
Wade,

In building a boat, you often will twist a piece of wood three dimensionally. It will twist in two directions at the same time. Weak or poor quality wood will behave differently than high quality wood.

Bad wood (has voids, cracks, plugs to fill in cut outs, very thin plys on the outside, non-directional filler or particle board filler instead of a good wooden inner ply) will twist faster in some local areas, and then less in others. Bad wood will often split and crack earlier than will good wood.

Good wood will be uniform throughout; bad wood will not. I've heard, though have not done it, that you can use a strong flashlight to actually see through plywood where there are internal voids (no inner ply).

Some builders who have experience at sorting out one good sheet from 10 to 20 bad ones, and knowing where a weaker piece of wood can be used, and other tricks of the trade have been successful building boats from materials that many builders would consider as questionable or unsatisfactory.

The safest bet is to use high quality plywood. It is rated as BS1088. You may want to be cautious if someone seems to be bragging about how they can get away with using poor quality materials.
 

JEM

Well-Known Member
Is the glue that bonds the layers together brown or black? That's a sign of exterior-grade glue being used, which is a good thing. Avoid interior-grade ply if you can.

Next, cut some sample strips of various widths and see what kind of voids you're dealing with, if any. See if the wood splinters bad.

In a dark room, hold a flashlight flat against the wood (yes... turn the flash light to the "ON" position :p ) . Move it around slowly to see if you can detect any voids.

Finally, be aware of any grease or grime since the wood was used for shipping crates.
 

WadeT

Member
Jul 7, 2008
21
0
Tolono IL
I went on the hunt last night and found 2 realy good full sheets (I think they are 4x8, I havent had time to get a tape out yet) One has a lable on it thet reads.. Samling USA 5.2mm hardwood plywood exteror 12549 CSP0086y\
I did find this http://www.boatdesign.net/forums/materi ... 10335.html I guess someone already found the same wood at Lowes...The two sheets I have look really good and have no patches and are a mahogany color. I did cut a small piece and it did splinter a bit but I was useing a rip blade on my skill saw. :shock: Im going to get my Brother in laws smaller saw with a blade with a lot of teeth on it and see how that does.

Matt I got your free plans for the Laker Im going to try it first. I am a first time builder. I have restored a pirogue and a few wood and fiberglass sailboats in the past. Im hoping to start soon as my wife and I are expecting a little one in August<<(Hince the very tight budget :mrgreen: ). If all goes well with this first build im going to build something else for me and give the first to my 10 year old daughter.

Thanks for the help yall. Its nice to know I have somewhere to go for help..
:lol:
 

jimsong

Well-Known Member
May 24, 2008
247
1
lakside village, texas
Straight cuts on thin splintery wood can be accomplished by using a quarter inch straight edge tacked to the work piece, and using a router with a top bearing flush cut bit.
Curved cuts can be made using this basic method, but it's more involved. Rip , from clear wood, 1/4X3/8 inch strips. You'll need twelve or so. Lay them on the work piece, side by side, 1/4 inch side up. Using just enough fine wire brads to hold the guide secure. Tack on both sides of the strips, following you cut line.
Using the router with the top bearing flush cut bit, follow the guide, getting close to, but never touching the brads.
Pull the brads and remove the strips of wood, and finish the cut with a carpet knife.
A laminate trimmer type router works great in this application, because of the much smaller foot.
This sounds much more complicated than it is.
By the way, if you need to copy parts in sheet goods, the top bearing flush cut bit will enable you to copy as many identical parts as you need. Just use double faced tape to stick your pattern atop the work piece. Use the same pattern on every cut to minimize error build up.
A bottom bearing flush cut bit will work here as well, just put your pattern on the bottom. But for some reason this method makes me uncomfortable. I want to see the pattern.