Many people assume that creating curved wood pieces takes a lot of time and requires an elaborate steaming contraption, but that's not true. Using a simple method called bentwood lamination, you can make precise, strong, stable curves in your shop.
I used bentwood lamination to build this cook’s rack — for about $75 in materials — which rivals racks costing much more. The process involves gluing thin strips of wood together in a press that is shaped like the curve you wish to achieve. I used cherry, but you could use just about any solid wood. The project took me one weekend.
Click here to download the Bentwood Lamination Pot Rack Plan as a pdf.
Making the jig
More than half of the work required to build this project goes into making the laminating jig, which must be sturdy and stable. I built this one out of a sheet material called Woodstalk fiberboard, a lighter-weight alternative to particleboard (see SOURCES).
To begin, cut a 3/4-in. x 4 x 8-ft. panel into four 18 x 36-in. pieces. Transfer the curve pattern (see diagram) to one of the pieces of jig material. I made a compass out of a thin scrap to draw the 10-in. radii on the layout (photo 1).
Stack, clamp and screw together three pieces of the jig material. The piece with the layout drawing should be on top. Keep all screws clear of the curve. Cut out the curve using a jigsaw or band saw.
Cutting through thick stacks like this can make a band saw or jigsaw blade pull out of vertical alignment. To lessen this problem (called blade deflection), move slowly along the cut line, using a blade with a low tooth count (5 to 8 tpi). Another method is to cut inside the line by 1/8 in. and sand back to the line using a drum sander or oscillating spindle sander.
Next, scribe a line 3/4 in. in from the curved edge of the inside section of the jig (photo 2). Cut just outside this line and sand off the excess. Then reposition the two sections of jig so that there is even spacing along the curve. The spacing between the sections should be slightly more than 3/4 in. This space will accommodate the lamination.
Cut the inside section of the jig in half with a miter saw. Then trim the back corners of each half at steep angles to provide a starting notch for the wedges. (The wedges will be used to force the jig against the laminated strips.)
The final step in constructing the jig is to attach the remaining piece of jig material to the bottom of the large curve section of the jig. Position it so that it extends past the front edge of the large curve. This provides both a support area for the strips as you begin clamping and a base to push the strips against and keep them flush.
Bending the lamination
Once the jig is complete, you can prepare to laminate. You will need six strips to laminate, but some may break apart in the planer, so make a few extras. Rough cut the strips to about 3/16-in. thickness by ripping them with a table saw or resawing them with a band saw. Plane the strips to the final 1/8-in. thickness (photo 3).
If your planer will not plane the strips to 1/8 in., build a planer skid to raise the strips closer to the cutterhead. A planer skid is simply a board or piece of plywood that the workpiece rides on through the planer. It should be slightly larger than the strips with a low lip attached to the back edge to keep the strips from being pushed off.
Once the strips are milled, it is time to do a dry run. This is your rehearsal, a critical step in a project that involves large glued surfaces. If a problem is not discovered until the gluing stage, it’s easier to start over than to try to salvage the workpieces.
Center the strips and inside jig halves on the outside jig. Begin tightening each clamp a little at a time (photo 4). Carefully reset the clamps as they bottom out. When you have fully seated the inside jig halves in the outside jig section, drive wedges between the halves to force pressure on the ends of the lamination.
Look for gaps in the lamination. If there is a gap, disassemble the jig and sand down small areas of the jig adjacent to the gap. Repeat the dry run
process until the lamination is tight and free of gaps.
Now you are ready to glue the lamination. I used polyurethane glue for three reasons. First, it has a long open time, allowing me to assemble the jig without rushing. Second, it has a high viscosity, which allows for a very controlled application. Third, after it is cured, polyurethane glue doesn’t allow the pieces to “creep” or shift like PVA (yellow) glue.
Center the first strip on the jig without glue. Then apply glue to only the top face of each strip. Spread the glue with a flat scrap, similar to using a squeegee. Place each glued face against the previous strip in the jig.
Pay close attention to the faces you apply glue to — it is easy to get carried away and apply glue to too many faces. When all the strips are in position, clamp the jig together as you did during the dry run (photo 5).
Remove the top rack after the glue has fully cured, at least 24 hours. The rack will lose a small amount of its curve; this is known as spring back. Spring back is affected by several factors including wood species, wood dryness, lamination strip thickness, glue type and bending radius. I took the specific spring back of this lamination into account when designing the cook’s rack. If you decide to create your own projects using bent lamination, do a test lamination to check the amount of spring back.
Cut off the ragged ends of the top rack to the point where a full thickness of the lamination begins. Remove dried glue buildup with a chisel or rasp, and finish the edge with a jointer, scraper or sander (photo 6). Cut the end of the rack so that when it is standing upright it is symmetrical and 12 in. tall.
Cut the bottom rack, sides and wall brace to size. Cut a 3/4-in. radius in the ends of the bottom rack with a router, or round over with a sander. Use a jigsaw to cut 1-in. radii in the top and bottom corners of the sides. Cut dadoes in the outside faces of each side (photo 7). Sand and finish all parts with three coats of wipe-on polyurethane.
I bought the aluminum rail and tubing for the rack at a home center. The rail was malleable enough that I could bend it by hand. I left it long initially and bent it in small amounts, checking it frequently against the top rack until they matched. I then marked and cut the rail 2 in. shorter on each end than the top rack. The bottom rail is a straight 24-in.-long piece of the same aluminum stock.
Drill four 7/32-in.-dia. holes located 1 in. up and 3-1/2-in. and 12-in. in from each end. Transfer these hole locations to the aluminum rail, and drill matching holes at each location. Fasten the rail to the top rack (photo 8).
Position the top rack in each side dado, and clamp the wall brace between the sides and top rack. Drill 1/8-in.-dia. pilot holes, and fasten each end with two No. 10 x 2-1/2-in. flathead slotted wood screws with decorative washers to match the fasteners on the top rack and rail.
Then attach the bottom rack to the sides. Drill 1/8-in. pilot holes 2 in. from the bottom of each side and a 7/32-in. pilot hole through the bottom rail. Attach with the same screws and washers used to fasten the top rack and sides (photo 9).
Hang the rack by driving screws through the wall brace into at least one, but preferably two, wall studs. If only one stud falls behind the rack, use a wall toggle as a second fastener to keep the rack level.
Gorilla Glue; 800-966-3458 www.gorillaglue.com
Dow BioProducts (Woodstalk) 800-441-4369, www.dow-bioproducts.com
Step 1: Drill 1/8-in. holes 10 in. apart in a thin scrap to create a compass for drawing the arcs on the top of the bending jig.
Step 2: Use a combination square to scribe the inside curve line 3/4 in. in from the edge of the inside curve of the jig.
Step 3: After rough cutting the strips, mill them to the final 1/8-in. thickness with a planer. (See text for how to use a planer that can’t be adjusted to 1/8 in.)
Step 4: Test the laminating jig with a dry run, clamping the strips without any glue. Adjust the sliding end of the clamps in as you force the strips into the jig.
Step 5: Drive wedges between the inside jig halves to apply pressure to the ends of the laminations. Wax paper taped to the jig prevents the lamination from adhering to the jig.
Step 6: Clean up the dried glue with a chisel or rasp. Then finish the edges of the lamination with a jointer, or use a scraper, hand plane or sander.
Step 7: Cut 3/8-in.-deep by 2-in.-wide dadoes in the outside faces of the sides. Use a backer board attached to a miter gauge to prevent chipping.
Step 8: Attach the bent aluminum rail to the inside of the top rack using machine screws. Cut 3/4-in. lengths of 1/2-in. aluminum tubing as spacers.
Step 9: Attach the bottom rack and rail with screws. Drill 1/8-in. pilot holes in the side pieces, and apply beeswax to the screw threads to make them easier to drive.