Guitar side benders are simple jigs used to bend thin pieces of wood for acoustic guitar bodies. You can make one at home with a piece of plywood and some dowels. By making your own side bender, you can gauge the size and degree of bend for your hand made guitar body. Basically, a side bender is half of a figure-eight. Typically, the top half of the figure-eight is smaller than the bottom half.
Lay a guitar similar to the one that you would like to make on a piece of plywood facing up.
Trace around the guitar body from the neck to the bottom of the guitar with a pencil. You only need to draw one side. You will use the same jig to bend both sides. This makes your guitar symmetrical.
Drill holes through the plywood with a cordless drill and 3/4-inch Forstner bit along the outside perimeter of the drawing, 3 inches apart from the neck to the bottom.
Squirt some glue into each hole and hammer dowels into the holes. Wait 24 hours for the glue to dry.
Use the side bender by spreading glue on two pieces of wood, approximately 1/6-inch thick. Clamp the two pieces to the inside perimeter of the dowels. Let the glue dry for one hour. Glue another piece to the first two pieces. Clamp the three pieces to the jig and let it dry. Continue clamping and gluing until you have the thickness you desire.
The measurements are for examples. If the degree of bend is very slight, you can bend wood that is thicker than 1/16 inch. You can buy guitar wood from online catalogues or make your own.
Test the wood before bending it. If it cracks or splits, try a different species of wood or a different thickness, or lessen the degree of bend.