Alternatively, just cut one line to create the inner curve, and use clamps to press the lumber against it. There will be a small amount of spring-back after you release the wood with this method. Bend it slightly farther than you want the final shape.
For a curve with a 2 to 4 inch radius (5–10 cm), plane the wood into 3/32" (2. 4 mm) strips. For a curve with a 4 to 8 inch (10–20 cm) radius, plane to 1/8" (3. 2 mm). For an 8 to 12 inch (20–30 cm) radius, plane to 3/16" (4. 8 mm). For a radius greater than 12 inches (30 cm), plane to 1/4" (6. 4 mm). These are guidelines to use as a starting point. The wood species and grain slope affect the result, so you may need to experiment.
Distribute the glue as evenly as possible. Rolling a 3/8" (9. 5 mm) threaded rod over the wood can give better results than brushing on the glue. Flip every other strip end-to-end before gluing. This will prevent the grain slope from lining up, removing lines of weakness.
If you soaked the wood, don’t forget to keep it wet for the first three or four hours.
Hackberry and oak are among the best hardwoods for this approach; a 1 inch (2. 5 cm) thick piece can bend to a curve radius as tight as 2 inches (5 cm). Maple, cherry, and poplar are prone to damage and only accept slight bends. [10] X Research source
If you are only steaming parts the size of walking sticks or smaller, you can use a length of ABS pipe with a 2 to 4 inch (5–10 cm) diameter instead. Another alternative is to melt 6 mil polyethylene into a plastic bag around your lumber. You can then bend the lumber while it is still in the steam bag for maximum flexibility. [11] X Research source
Connect a 1½" (3. 8 cm) diameter hose to the steam source with tightly fitted nuts. Cut a hole in the steam source if necessary to accommodate this. Cut a hole in the base of the box and attach the other end of the hose. Drill a few small drainage holes into the base of the box, especially toward one end. Set up the box so it slopes toward this end. Optionally, drill a hole in the top of the box and plug it with a stopper. This allows you to insert a thermometer.
Metal straps may discolor your wood. If this is an issue, use an oversize piece of lumber and remove the affected area. If you will bend the wood to a curve radius less than 4" (10 cm), you will need a stronger material to bend it around. Cut off the tip of the plywood corner and replace it with a piece of hardwood.
If you have a thermometer, use a small hole at the top of the box to check the temperature. If it’s too cool, wrap the box in an insulating material. To avoid steam burns, wear work gloves and keep your face back when opening the steam box.
If the wood cracks, it needs more steaming. If the wood wrinkles along the inner edge, it may have steamed too long, or there may be too much compression.
