1/2" Curly Koa "slabs"...

[Phil Winn]

I have two "slabs" of Curly Koa, bookmatched, each piece being
44" by 11" (widest point) by 1/2" thick. I am planning on making these into a table top, so need to attach them to some other material to make it thicker and stronger.
One of the pieces has a small crack which is 1" long, and there is one other "check mark". What do I do?
1. Which "base" material do I use?
2. Do I glue it, screw it, nail it, glue & screw, or ?
3. What kind of glue/screws/nails/ or ?
4. How to attach the two pieces of Koa end to end?
5. Should I "make" the pieces thinner before doing #2 ?
6. Could I cut the 1/2" pieces into two pieces obviously slightly less than 1/4" ?
7. Anything else?
I appreciate any help!
Thanks,
PW
philwinndmd@fastmail.fm

[Jamie Buxton]

1. Which "base" material do I use?

I'd laminate the koa to some solid lumber -- probably maple or ash. Then I'd treat the laminated plank just like solid lumber -- that is, build the piece allowing the plank to breathe with humidity changes. (Of course, this approach presumes that you're doing something at the edges of the table to hide the substrate.)

(There is another approach, which is to bandsaw veneers off your "slabs". If the veneers are 1/16" thick or so, you can use plywood for the substrate. Maybe you've got a friend with a good bandsaw?)

2. Do I glue it, screw it, nail it, glue & screw, or ?

Laminate it. That is, glue it firmly to the substrate.

3. What kind of glue/screws/nails/ or ?

Good ol' yellow carpenters glue.

4. How to attach the two pieces of Koa end to end?

HUNH???!!! You've got bookmatched pieces. Why are you attaching them end to end? The bookmatch is most obvious when they are attached edge to edge.

If you've laminated each piece of koa to some substrate lumber, you then have composite planks thick enough to easily glue them edge to edge.

5. Should I "make" the pieces thinner before doing #2 ?

There's no obvious reason to do it.

6. Could I cut the 1/2" pieces into two pieces obviously slightly less than 1/4" ?

Yes, you could resaw the planks into thinner pieces. That would allow the expensive and rare koa to go further. You need a good bandsaw, and somebody who is practiced at this particular operation.

[Phil Winn]

Jamie Buxton, thanks for the reply!

1. Do you think it will work better:
A. Keeping the thickness at 1/2" and gluing it to some maple?
Or
B. Turning it into some veneer at 1/16" or so and gluing it to some plywood?

2. Could I keep it at 1/2" and glue it to some plywood?

(My family is yelling at me to get off-line and watch the 500 !)
Thanks,
PW

[Dev Emch]

About two years ago, I did some "Russian Floor Tiles". These are tiles about 2 feet by 2 feet using very complex inlay patterns of various species of wood.

I used baltic birch ply for the substrate. This was the first time I had ever really worked with baltic birch ply and I must say I love the stuff. Its wonderful. I have virtually never seen another piece of MDF since then. I even make entire kitchen cabinets from it today. Sure its more expensive but I also charge a premium for my own kitchen cabinet design which I may actually patent. The joinery, etc. is unique.

So I would consider laminating this koa onto a section of baltic birch. Because of its thickness, I dont know if your going to get a warping issue or not. On thinner material, the word on the street is to laminate a similar board on the bottom and the top to keep it from warping. I do this with shop made veneers. Can you get some similar but cheaper straight grain lumber similar to koa if not koa? Put the good stuff on top and the cheaper stuff below and fill the space with baltic birch.

Here, I would most likely use resourcinol glue and a vacumm bag. Longer setup time and no creep.

Good Luck...

[Jamie Buxton]

Phil --
Solid lumber expands and contracts across the grain with the annual cycle of atmospheric humidity. Plywood does not. If you glue thick lumber to plywood, the composite is likely to cup and bow as the lumber moves. If you glue thin lumber (that is, veneer) to thicker plywood, the lumber will try to expand and contract, but the plywood will restrain it. You should not glue 1/2" thick lumber to plywood. 1/16" lumber is thin enough that you can glue it to plywood. Even then, if you really want the composite to stay flat, it is good to veneer both sides of the panel.

As to whether you should slice the 11"-wide curly koa into veneer, a big question is whether you have the equipment and skill. It will take a bandsaw with 11" resaw capacity. Do you have that big a bandsaw? It also takes some skill in setting up the machine and doing the cut. I suggest you practice on some less-valuable hardwood.

[Dev Emch]

We use 1/4 inch thick hardwood glued onto baltic birch and have no problems. The 1/4 inch was dictated by the flooring industry standard for wear layer thickness. This is a standard procedure used for most inlay floor.

[Jamie Buxton]

We use 1/4 inch thick hardwood glued onto baltic birch and have no problems. The 1/4 inch was dictated by the flooring industry standard for wear layer thickness. This is a standard procedure used for most inlay floor.

Perhaps that works acceptably because you fasten the tiles to the floor, which keeps the tiles flat. If the tiles were freestanding, I'd expect a different result.

[Phil Winn]

Should I let the Curly Koa float and not glue it to the "backing"?
Or is the 1/2" Curly Koa thick enough for the table top without any backing?
Thanks,
Phil

[Ian Abraham]

Phil

1/2 inch is a bit thin for a table top I think.

If you use a stable substrate (ply or mdf), maybe let it float?
If you laminate it to a 'similar' solid wood, to make a 1&1/2" board, then it will be glued solid. If you go the laminated way, look for a secondary wood that has similar shrinkage numbers to the koa. That should reduce the possibility of warping.
My table tops are usually 2" thick, but thats with cypress or cedar, not something special like your Koa. I imagine I'd have to take out a bank loan to get a piece of Koa to make one of my tables :o

Cheers

ian

[Mike Johnson - Chicago]

Another idea for you...

Why not bookmatch them again? Or slice as many veneers as you can.

You would "double" your wood and the thinner pieces would be less likely to rebel if laminated to mdf or ply.

Just another thought...

Regards,
M.J.

[Paul Canaris]

I would be careful laminating anything over 1/16 of and inch. Tage Frid who has been at this a long time claims to have seen a good many failures of laminated panels that used thicker materials, due to the expansion and contraction effects breaking the glue bond or spliting the actual lamiantion. At any rate, I agree with posters who indicate equal treatment to both sides of a substrate to prevent warping.
If I were going to attempt this with thicker material, I would vacuum veneer and use an epoxy such as made by West System, and do both siodes of substrate.
:rolleyes:

[Charlie Plesums]

See the post referenced below for a dramatic example of what can happen if a table top made of solid wood cannot expand and contract across the grain.

www.sawmillcreek.org/showthread.php?t=20253&referrerid=3056 (http://www.sawmillcreek.org/showthread.php?t=20253&referrerid=3056)

If the wood is thin enough to be called a veneer, then it can stretch and scrunch if the layer under it moves differently (or doesn't move, as in attached to plywood). I haven't seen any stone tablets come down from the mountain with a clear answer how thin the wood needs to be to act like a veneer, but generally I hear of little problem at 1/16 inch or less (as suggested by several here), and generally hear great concern if the thickness is over 1/8 inch.

[Phil Winn]

Sorry-how do I find post #20256 ?

PW

[Doug Edwards]

When I view 20256, I see a jointer for sale.

[Charlie Plesums]

My apologies for the wrong cross-reference. The link to the page that has the best (or worst) example of wood movement is

www.sawmillcreek.org/showthread.php?t=20253&referrerid=3056 (http://www.sawmillcreek.org/showthread.php?t=20253&referrerid=3056)

Charlie