Forming plywood is not a new idea; it has probably been around as long as plywood itself. Back when airplanes had a lot of wood components, plywood was often used because of its superior strength to weight ratio.
Much of this plywood had to be bent or formed for its intended purpose. Since that time, airplanes have been made of other materials, predominately metal, but many other uses have been found for formed plywood. Furniture is a good example.
When forming or bending solid wood, the technique generally involves the application of heat and steam in an enclosed space. There are easier methods for plywood because of its character.
Plywood is composed of a number of layers of veneers glued together under heat and pressure. The veneers are put together with each veneer’s grain going the opposite direction of its neighbor. This is what gives plywood its characteristic strength.
Kerf Cuts Method
There are two basic approaches to forming plywood. The first is used if the plywood you are working with must be one half inch or more and the desired radius is not too severe. This method involves making kerf cuts on the non-finish side of the plywood. The kerf cuts need to be a precise equal distance apart as well as a certain depth.
When you make your cuts, be certain there are a minimum of two laminations (on the finish side) remaining in the plywood. The purpose of this is to provide strength on the outside.
If your cut is overly deep, the plywood will split when you attempt to bend it. On the other hand, if your cut is not sufficiently deep, you will end up with a flat spot between the two adjoining cuts.
This is why when making your kerf cuts, you must keep to a consistent depth. Another thing to be aware of is to make sure your plywood does not have any voids in the remaining veneers. If it does, chances are that when you bend it will break.
Multi Layer Method
The second approach involves using multiple pieces of plywood. The plywood that you work with should be no thicker than one eighth of an inch (0.317 5 centimeters) thick. The general rule of thumb here is that the tighter the finished radius will be, the thinner the plywood should be.
The number of pieces of plywood you will need to cut is dependent on how thick the finished piece of formed plywood needs to be. Now, cut the pieces of plywood but make them bigger in both directions so you can trim the finished product to size.
You will now need a form to mold the plywood on. It should be made of wood preferably. Lay one side of the first piece of plywood on the form and staple it down. Next carefully bend the plywood over the form and staple the other edge. Once that is done, spread a coat of relatively slow drying wood glue on the plywood.
The next step is to repeat the stapling and gluing routine with the second piece of plywood. Do this with the remainder of your cut pieces. You might consider using a high quality veneer for the final piece if the finished product will be something nice to look at, not merely serving a utilitarian purpose.
When the glue is dry you will have your formed plywood. Carefully separate the finished piece from the mold, remove any visible staples, trim to size and apply the finish of your choice.
See Also: Wood Working Tool Basics
Photo by Jesse Hull/CreativeCommons