AW Extra - Bow-Front Bookcase

Sandwich Construction

Sandwich construction uses readily available thicknesses of plywood to create thicker panels. It also lets you produce a panel that has two very good-looking sides because the best side of each piece of plywood faces outward. 

  There are two basic ways to create a sandwich panel. The first is to simply glue two pieces of plywood back to back. This is the approach we used for the end panels in this bookcase (see photo, below left). This approach works well for cabinet parts that will be fastened to other cabinet parts, such as the ends of this bookcase, which are biscuited and glued to the subtop and the bottom shelf. The reason for fastening these end panels is because the plywood parts that make up the panels are different thicknesses (1/4 in. and 3/4 in.), so there is a risk of warping. However, if the sandwiched plywood parts are the same thickness, the chance of warping is greatly reduced. Such panels can even be used where they won’t be fastened down, as for cabinet doors or adjustable shelves. 

  The second way to create a sandwiched panel is to use a center core with a layer of plywood glued to each side (see photo, below right). The center core can be either a lumber frame or another piece of plywood. The lumber-frame approach has the advantage of letting you produce a panel of precise thickness that weighs less than one made with a plywood core. Either core will make a sandwich that is resistant to warping.

Gluing together a 3/4-in. and a 1/4-in. piece of plywood creates the end panels for this bookcase. This sandwiched panel is then trimmed to final size, and the legs and applied rails are added. The final result is an end panel that is flush on the inside with a frame-and-panel look on the outside. 

Gluing two pieces of 1/4-in. plywood over a lumber-frame core creates the center panel for this bookcase. This creates an extra-thick but lightweight panel that is exactly the same thickness as the legs. With a lumber frame on the inside, you can custom-make panels any thickness you want.

Tools and Materials 

You’ll need a planer, jointer, tablesaw, bandsaw, belt sander, biscuit joiner, jigsaw, drill and finish sander, plus various hand tools, to complete this project.

We used uniform light birch plywood and select white birch lumber for the main parts of the bookcase. These materials have an overall white/light color. For the top we used flame white birch that has a wonderful figure and grain pattern. 

It takes about 2-3/4 sheets of plywood and 30 bd. ft. of lumber to build this bookcase. The wood costs about $350 (see Sources, page 67). If you use natural birch instead, it will cost about half as much to build. Natural birch contains darker heartwood and is what you find on the racks at most home centers.

Start with the Legs

Joint, plane and cut the legs (A) to final size. Then band-saw and finish-sand the tapered feet (Photo 1). Note that the center legs and the end legs have different sides tapered (Fig. A, Detail 1, below). The legs are done first because the center sandwiched panel will be made to match the thickness of the legs (Photo 3).

Build the Sandwiched Panels 

Saw the plywood parts for the center partition and the end panels (parts B, C and D, and Photo 2). See the Cutting List, page 67, for dimensions and the Plywood Layout (Fig. F) for a recommended cutting plan. Pay attention to which side of the plywood looks best. You want to pick the best side to face out on the glued-up sandwiched panels.

Next make the fillers (E and F) for the center partition and check that they’re the correct thickness (Photo 3). It’s tempting to use 3/4-in. plywood for these fillers because 3/4 plus 1/4 plus 1/4 equals 1-1/4, right? Not when it comes to plywood. Plywood is often 1/32 in. or more thinner than its specified thickness. This can have a noticeable effect on the final thickness of a sandwiched panel.

Proceed with gluing together the plywood parts that form the sandwiched center and end panels (Photo 4). When the glue is dry, trim the sandwiched panels to final size (Photos 5 and 6).

Add the Legs

Use biscuits and glue to attach the legs to the sandwiched panels (Fig. A, Photos 7 and 8). Pay close attention to the orientation of the tapered foot on the legs when you are cutting the biscuit slots (Fig. A, Detail 1). It’s easy to make a mistake here and cut slots in the wrong face of the legs (see Oops!, page 61). Also note that the legs are flush with both sides of the center panel but are flush only with the inside of the end panels. 

After the legs are attached to the end panels, add the applied top and bottom rails (parts G and H, Fig. A). Complete the three panels by routing the rabbets in the back legs (Photo 9 and Detail 1). The 1/4-in. plywood backs (J) will fit into these rabbets once the case is assembled.

Make the Curved Shelves

The curved front shelves and subtops start out as rectangular plywood parts (K) and are tapered on the front edge using a tapering sled (Fig. B) on your tablesaw (Photo 10). To make left and right tapers on the same sled, cut four of these parts best-side up and four best-side down. This gives you three left shelves and three right shelves, all with their best side up, plus a left and right subtop.

Next, glue the solid-wood edging (L and M) to the tapered edge of the shelves and subtops (Photo 11 and Fig. C). Pay attention that the edging is flush with the good (top) side of the shelves. It doesn’t matter which face the edging overhangs on the subtops, just be sure you make one left and one right. Use the curved tracing jig (Fig. D) as a guide to draw the curves on the bottom of the edging of the shelves and subtop (Photo 12). Then band-saw and sand the edging to final shape (Photos 13 and 14). 

Assemble the Bookcase in Stages

Start by cutting biscuit slots in the ends of the bottom shelves and subtops, and the joining surfaces of the center and end panels (Fig. A). Remember that the shelves are flush with the rabbet at the back of the legs (Detail 1) and set back 1/4 in. from the front of the legs (Fig. A).

Gluing and clamping these parts together is a two-stage process (Photos 15 and 16). Practice each stage without glue to make sure the parts line up correctly and to get a feel for how they go together. Get a helper to assist with holding the parts. Make sure the case is square before leaving it to dry.

After the case is glued up and dry, flip it over on its top and add glue blocks (N) to the under side (Photo 17). Glue blocks are an easy way to add strength to the case. After the glue is dry, turn the cabinet right-side up and drill the shelf-pin holes using a self-centering bit (see Sources, below) and a shop-made drilling guide (Photo 18 and Fig. E). 

Now is a good time to take the four remaining shelves back to the tablesaw and cut 1/16 in. off one end of each shelf. It doesn’t matter which end, because you’re just trying to provide some clearance so they’re easy to install and remove from the cabinet. A regular tablesaw sled makes this step easy and safe. Add a 1/4-in. plywood spacer under the bottom of the shelf to accommodate the overhang of the edging and cut the shelves good-side up. This way, if any chipping occurs, it will be on the under side of the shelf. 

Complete this phase of assembly by attaching the plywood back panels (J) (Photo 19). 

Make the Solid-Wood Top

After selecting the boards for the curved top (P), plane them to thickness and joint the edges square. Use boards long and wide enough to produce a glued-up top that is about 1 in. oversize in length and width. You will cut the top to final size after these boards are glued together. 

Cut biscuit slots about every 6 in. along the joining edges. Keep the slots in a couple of inches from the ends so you don’t expose them when trimming the top to final length. Biscuits help keep the boards aligned during clamping, but don’t expect to have perfectly flush joints everywhere. You will most likely have a few ridges that will need to be scraped or sanded. Also, don’t worry if the top develops a little twist after it’s glued up. Our top ended up about 1/2-in. high at one corner but easily pulled flat when we screwed it onto the bookcase.

After you have the boards for the top glued up, cut it to final length. Next, mark the final width at the middle and the ends and use the tracing jig to draw the curve (Photo 20). Cut the curve with a jigsaw and sand it smooth. Attach the top to the subtop with washer head screws (Photo 21). 

Finishing

Now that you have the bookcase all together you get to take it apart for finishing (Photo 22). Remove the top, the adjustable shelves and the backs. This makes finishing the parts easier and putting it back together simple, since you know all the parts fit correctly. We used a clear satin varnish on our bookcase. It brought out the grain and gave it a warm natural look. 

Photo 1: Start by making the legs, because the center sandwiched panel will be made to match them in thickness. After band-sawing the tapered foot at the bottom of the legs, sand the taper smooth.

Photo 2: Saw the plywood parts for the sandwiched end and center panels. These parts should be cut oversize at this point. They will be trimmed to final size after they are sandwiched together. 

Photo 3: Test the center panel to make sure it is flush on either side of the leg. Adjust the thickness of the filler boards as needed. 

Photo 4: Glue and clamp together the sandwiched panels. The center panel (shown here) uses filler boards. The end panels are just two pieces of plywood sandwiched together.

Photo 5: Trim the glued-up sandwiched panels to final width. Cut a little off each edge so both edges are straight and parallel to each other.

Photo 6: Saw the sandwiched panels to final length. This is easy to accomplish with the help of a tablesaw sled. Cut a little off both ends so they are parallel to each other and square to the edges of the panels.

Photo 7: Cut slots for biscuits in the edges of the panels and the corresponding sides of the legs. The biscuits help keep the legs and panels aligned when they are glued together.

Photo 8: Glue and clamp the legs to the panels. The center panel is flush on both sides of the legs but the end panels are flush only to the inside of the legs. It’s not necessary to put glue on the biscuits since they are mainly for alignment. 

Photo 9: Rout the rabbets in the back of the rear legs. The plywood back fits into this rabbet once the case is assembled. The center leg gets two rabbets and the side legs get only one rabbet. 

Photo 10: Taper the front edge on the shelves using a tablesaw tapering sled. This is necessary because the bowed front of the bookcase makes the shelves wider at one end than the other.

Photo 11: Attach the solid-wood edge to the shelves and subtops. Let the ends of the wood edging run a little long. After the glue is dry, use a handsaw to trim the overhanging ends flush with the ends of the shelves.

Photo 12: Use a tracing jig to draw a curved line on the bottom side of the shelf edging. Drawing it on the bottom side makes band-sawing easier (Photo 13). Use a spacer board to support the tracing jig while drawing. 

Photo 13: Use a bandsaw to cut the curve into the shelf edging with the lip of the edging pointing up. 

Photo 14: Sand the curved edging smooth. Start with a belt sander and finish up with an orbital sander or by hand. 

Photo 15: Glue and clamp together one half of the bookcase first. It’s a good idea to test-assemble these parts before you use glue. Propping up the cabinet on a couple of 2x4s makes it easy to check that the parts are correctly aligned on the back edges.

Photo 16: Add the second section of the bookcase once the glue in the first section is completely dry. Again, check that everything is square before leaving it to dry. 

Photo 17: Flip over the bookcase and add glue blocks to the bottom. They add an extra measure of rigidity and strength to the legs and case. 

Photo 18: Drill 5mm holes for the shelf pins using a self-centering bit and a drilling template. Align the template flush with the front legs and the rabbets at the rear.

Photo 19: Attach the back with pan head screws. Drilling pilot holes first makes driving the screws a lot easier. The back is now removable, which makes finishing easier later on.

Photo 20: Draw the curve on the top of the bookcase using the same tracing jig you used for the shelves. Draw one side of the curve first and then the other. 

Photo 21: Attach the top using washer head screws. The holes in the subtop are oversize to allow for seasonal movement of the solid-wood top. 

Photo 22: Disassemble the bookcase and finish it with your favorite finish. A clear satin vanish looks great on white birch. 

Washer head screws are commonly used to attach drawer fronts to drawer boxes, but they also work great for attaching tops to cabinets. The large washer head holds tight without digging into the plywood. Once you’ve tried them you’ll find many uses for them. They’re available in 1-1/4, 1-1/2 and 1-3/4 in. lengths (see Sources, below).

Oops!

Uh, oh. We glued the wrong leg to the front of the center panel! This is an easy mistake to make when working with parts that look very similar. To avoid this blunder, carefully mark the legs, indicating which ones go on the ends and which ones go in the center. Also, mark which edges get cut for biscuits and glued to the panels, because it’s also easy to cut the biscuit slots in the wrong edge of a leg. The center legs on this bookcase have tapers on opposite sides of the leg, whereas the end legs have tapers on the inside surfaces.