Coopered Doors
A coopered door is simply one that is curved: concave, convex or, when you combine the two, serpentine. Adding a coopered door can make an amazing difference to a common square cabinet.
There are a few ways to achieve a coopered door. The easiest is to find a board that is naturally cupped. Since most of us aren’t so lucky, a second way is to cut the curve out of a thick piece of stock. With this method, the height of your door will be limited to the resaw height of your bandsaw. As well, when removing more wood from one side than the other, the wood may move or check. The most effective method is to cut several strips out of a single board and join them back together again to form a curve. This method is ideal for making any size of door, and for preserving grain graphics or colour.
Making the door before the rest of the cabinet frees you from having to follow exact dimensions and will give you room to make future adjustments such as straightening or positioning graphics. Choosing a board with unique colour, a shimmering curl, or maybe one that’s spalted creates a door that will provide a clear and distinct focal point for the cabinet. You can achieve a calmer appearance to the front of the door by joining several pieces of quarter-sawn material. Using quarter-sawn material also creates a very stable door, and unlike flat-sawn material, the joints can easily be hidden between grain lines. Once your board is milled up, rip the board into several strips, each 1 ½” to 2″ wide. Remember to slightly widen any strips around areas of prized colour or graphics. Using a bandsaw for this procedure is ideal and will reduce the kerf width between pieces.
Glue-Up
It’s much easier to glue up parts in mating pairs, especially with heavily curved panels. In stages, glue the parts together, then bring the two halves of the panel together using curved cauls and clamps. With heavily curved doors it might be necessary to use small clamps perpendicular to the main clamps, to ensure the panel doesn’t pop out of the clamps.
Convex Surfaces
Use a flat handplane to add a smooth curve into the convex face of the coopered panel (left). To check the overall curve of the panel, use a flexible steel ruler to locate the high spots (right).
Curved Sanding
A sanding block with matching curved bottom is great for smoothing concave surfaces. They are easy to make and work best with cork on their face.
Straight, Square and Curved
A cross-cut sled on your table saw is the perfect place to trim the coopered panels’ edges.
The Right Hinge
Simple and clean, knife hinges are perfect for many doors, including most coopered doors.
Plane some angles
I like a subtle curve for my doors, but the intensity of the curvature is a matter of personal taste. The curve is formed by a series of angles located between each of the strips. Begin by hand-planing out the saw marks on each strip. Continue hand-planing along the edge of the strips, forming your desired angle. Start small, slowly increasing your angle and checking your progress by placing the entire door into a set of clamps. Continue to make adjustments until you are left with a pleasing curve. Before adding glue, make sure that each joint fits together with only finger pressure. Perform a dry run by placing the entire door in the clamps and check to make sure that the joints are tight on both sides. Take the time to adjust each adjacent strip so the grain lines run parallel to each other. This is a perfect way to help conceal joint lines. When finished, place a cabinetmaker’s triangle over the entire door, which can be used as a helpful reference when gluing up. In order to ensure equal pressure along all of the joints of the door, you should use angled cauls, padded with cork or matting, in the clamping procedure.
The glue-up
Gluing the door together is completed in stages. For example, if you have a door with eight pieces, you would first join the outer pairs together and the inner pairs together. Next, join the completed pairs together, on each side, forming two halves of the door. The final glue-up involves joining the two halves down the center of the door. Expect to also make some minor adjustments with your handplane along the way. Your handplane is also useful for cleaning up excess glue from the joint, allowing you to determine if the joint is tight before moving onto the next glue-up.
After the door is glued together, it is time to begin shaping and, if necessary, adjusting the curved profile. To prevent the door from rocking and stressing the joints during the shaping process, place a few shims under the door. The concaved surface of the door can be smoothed and shaped using a coopered bottom handplane. I use a Krenovian-style handplane with a sole whose radius is slightly greater than the door’s curve. A flat-soled handplane is used for shaping and smoothing the convex surface of the door. When sanding the concave face of the door, make and use a sanding block with a curved bottom that matches the concave profile and pad the bottom of the block with cork.
Installation
Installing a coopered door is very much the same as installing a flat door, with a few special points to remember. First, place your finished door between the top and bottom of your cabinet opening so you can trace the curve profile of the door into the carcase. The carcase can then be shaped to match the curve of the door. Second, if you want the door to sit in front of the sides, change the front edge of the sides from 90° to an angle that matches the inside profile of the door. Lastly, installing a set of knife hinges will be less time consuming and visually less distracting than a pair of butt hinges.
Along with providing a little extra space to the interior of a cabinet, a coopered door will subtly and gently modify the outside appearance of any cabinet. This method, if learned and applied, will open the door to other possibilities such as making coopered panels, sides or other desired surfaces.
