: Without a lecture on how okoume is better than Luan,

I didn't realize it was. Meranti, okoume, lauan and a couple other species all used to be sold as "phillipine mahogany". I still think of them as pretty much equivalent, as SPF--spruce, pine, or fir--is a group of several species of wood with roughly equivalent characteristics. But you didn't want to go down this path, so lets get back.

: I was wondering if
: anyone could shed some light on steam bending luan plywood for a cambered
: deck. Actually any bending method that results in a crack free luan deck
: would be great.

John has shown how to score your wood on the side you want it to bend on. This process can be used on ply or solid wood, and is sometimes called "kerfing"--a reference to the kerf sized slits made by the saw blade which cuts them. making "featherboards" for your table saw is another extreme case of kerfing. What is left of the wood after kerfing is thin enough to be very flexible--but strength is mostly gone. Filling the kerfs (or kerves) with epoxy and wood dust will help to restore some strength, but that epoxy is going to cost more than the wood itself.

You can find "bending plywood" at specialty plywood dealers. There are usually advertisements for the stuff in the back of woodworking magazines, too. Basically this is 3-ply plywood where the grain on all three plies runs in the same direction. You can get it with the grain running lengthwise, or widthwise.

This is very popular with cabinet makers who want to build kitchen cabinets. They can make rounded corner units, or freestanding islands, with smooth curves. Inside the cabinet there are strips of wood spaced at close distances to support the plywood skin. Looking at the inside of one of those cabinets it looks a lot like the ribs on a boat!

Bending plywood is much more expensive than the regular kind. People who don't have a ready source for bendable plywood have sometimes gone the route of making their own from sheets of wood veneer. Chairs, skateboards, and hundreds of other plywood items you see in daily life are made in from stacks of veneer which are laminated with glue, put in a press, and clamped tight until the glue hardens an the shape is set.

If you wanted to, you could make an entire hull or deck from cold molded (no steam or water needed) veneer. Set one layer over the forms, paint it with glue or epoxy resin, lay on the second layer, glue it, and add a third layer. When bending against the natural direction the grain allows the wood to bend, you use thinner sheets of veneer.

You can lay on the veneer with one ply running the length of the boat, then a ply at 45 degrees to that, then a ply which is the opposite 45 degrees (those two plies are at 90 degrees to each other) and then put on a 4th ply which is running inline with your centerline.

For compound shapes you cut the thin veneer into shapes with curved edges. When those edges are drawn together the veneer can take a compound curve.

You can buy 4x8-foot sheets of veneer, but it is almost as expensive as a full sheet of plywood, and it is usually very thin. About 1/20th of an inch. The flexibility is definitely there, but the cost is going to be too great for practical use in most cases.

One nice use for veneer is to use it as a new finished surface if you bend your wood by kerfing it. Two ways to do this. 1) You can wait until after you have filled the kerf slits and sanded the bent panel smooth before you glue on a neat veneer face, or, 2) you can fill the kerfs with thickened epoxy, and lay on the veneer while the resin is still wet. This is more of a sticky mess to handle, but it eliminates the sanding step. Clamping the veneer in place when doing this is going to be very difficult--but you don;t need any pressure when working with epoxy. You just want a fairly close fit. I'd suggest using staples. A regulur desk type stapler will be strong enough to push a small staple through a doubled piece of wax paper, and the thin veneer, and get it anchored to the underlying plywood. Such thin staples leave very tiny holes. Since these are placed at random (not in a line like on strippers built with staples) they re indistinguishable. After you pull the staples, going over the veneer with a warm clothes iron and damp cloth will close these holes completely.

If you have a bandsaw you can make your own thicker veneer in whatever widths your bandsaw can handle. And have your choice of species for the core and for the faces. With a tablesaw you can make strips up to about 3 inches wide. It will work, but it si slower going. A surface planer will be a great help in getting your veneer strips to an even thickness. Something near 1/10th of an inch should be a good thickness to try. If it is not flexible enough, you can heat it dry, or steam it, then laminate it after it cools and dries. Or, you can run it through the planer again and shave it down to a thinner, more flexible thickness.

3mm plywood is so flexible that you could use it instead of veneer in many cases.

But the 5.2mm lauan is so cheap that it just begs to be made into something useful. Again, if you have a surface planer and a table saw, you can cut your ply into 8 foot lengths which are about 12" wide and run those through the planer. The planer will remove one surface layer of that thin plywood (remove the worst side!) and cut into the center ply. You can thin the center ply greatly, and improve the flexibility of your material. Take off a bit less than half (say 2.2 to 2.6mm) and it will look like 3mm 2-ply plywood with one good face, and one really ugly face. Bend these as you wish while you restack them, and neatly join the edges, and you can make plywood as thick as you wish.

Hope this helps. Good luck with your project.

PGJ