Instructables
Picture of Bent Plywood Night Stands
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Bent Ply is beautiful, strong, and flexible in ways that make its appeal to designers obvious, but making bent-ply furniture can be a real challenge. While many pieces simply cannot be made without gigantic industrial molds (which apply heat and steam to make the wood flex during bending), and use special glues that can only be cured in the machines, smaller Bent Ply furniture can be made in a regular wood shop without much more than a band saw, table saw, and a bunch of good clamps.

I made the single-curve nightstands in the photos above, but the same steps I've used here, including many rules of thumb and limitations I discovered along the way, could easily be applied to a wide range of bent ply pieces and parts. Once you've made the molds the nightstands are easy, so this is a great project for designs with lots of self-similar parts, too.

You can check out more and larger images of the finished product on my website. http://www.phil-seaton.com/  Click "NightStand" once you get there.
 
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Step 1: Tools and materials

Picture of Tools and materials
SUPPLIES:

In addition to some everyday items, such as a paint roller & tray, quart-size mixing container, sandpaper, etc, a few special items are needed:

Glue: I recommend DAP Weldwood Plastic Resin Glue. It comes in a powder form and mixes easily with water; it cures chemically to an ultra-hard brittle glue with absolutely no give. This is important, as the layers must not be allowed to flex next to each other to maintain the curves. Also, the chemical cure helps to make sure the glue in the middle, far from any air, still cures completely.

Particle Board / MDF: Your mold will need to be made solid, so be sure to purchase enough for both sides of your mold, including at least 2-3" beyond your actual piece. I highly recommend assuming that the two halves of the mold will come out of a rectangular area, as the parallel outside edges will need to be clamped to each other. For this project, I used exactly a full sheet of 3/4" Particle Board.

Veneers: There are several factors to consider when choosing veneer for your project. 1) The look you want on your final piece 2) The tightest curve you're planning to bend (I recommend bending a small piece around the tightest curve in your mold to make sure it doesn't snap) 3) The number of layers you'll need given the veneer's thickness and 4) The type and thickness of your interior veneers (which aren't as visible as the surface veneers).

Veneer Tape & Roller (+ a spare sponge): Veneer tape is special stuff that shrinks as it dries, closing gaps that may have been present in your veneers before taping the edges together. Chances are very slim you'll have veneers the right size & shape for your project, so you'll need this to make large enough continuous sheets. You apply water to one side (like a stamp), and then roll it on with a hard wood roller.

Dowels & matching drill bit: You'll need these to align the slices of the mold as they're cut, and also to stack them all once they're done. You'll need at least 3 dowels per side of your mold, and it helps if they're all in once piece. So if your piece is 2' wide and you can only get 3' dowels, I'd recommend buying at least six. Get a spade bit to match; 3/4" or 7/8" for dowels and spade.

Flush-trim Bit: Once you've got one slice of your mold perfect, you'll be using a flush-trim router bit to make the others exactly the same. Get a good beefy one, but make sure it fits your router. I found a bottom-bearing bit to be easiest for the setup, but you should be able to make it work with a top-bearing bit also if that's all you can find.

2x4's (qty 2 or 3) for clamping cauls (if you make these curved cauls they can save you some clamps, but they're not totally necessary)

TOOLS:

Stop and reconsider if you don't have, or don't want to buy, the following tools which can be found in most well-equipped shops:

- Table saw. A nice heavy one is always best, but even a contractor's saw should do for this
- Band Saw. For rough-cutting mold slices
- Router. For flush-trimming mold slices
- Heavy clamps (you'll always need more than you think. Make sure you have some long enough to go around the longest end of your mold.
- Drill press (it's critical that the holes you drill for registration of mold slices be drilled straight!

Step 2: Design your profile

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Explore possible designs for your bent plywood piece. Keep in mind that, except in exceptional circumstances, bent ply is only curved in one direction. That is, the shape will be a simple extrusion of one profile curve you draw.

As you explore the design, try to come up with ways to employ the special properties of bent ply. In this design, the uniform strength in all directions throughout the curve prevents the design from having weak "break points" which would require much thicker wood if separate pieces or solid wood were used.

Step 3: Iterate & select final design

Picture of Iterate & select final design
It can be helpful to explore the 3-dimensional implications of the design, and refine its scale and details. Consider issues such as the tightest corner that your veneer can bend, the difference between inside and outside edges of the profile, and ergonomics of the finished piece. For my nightstands, I had to make sure it was possible for a human hand to comfortably fit in between the top and bottom layers; otherwise, the "private" space inside the nightstand would be useless!

It's helpful to do simple studies in CAD software. I use Rhino, but almost any software package would help to explore these sorts of implications.

Step 4: Build the molds

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Once you've selected your profile, carefully trace its shape onto a piece of particle board you've cut to fit it. It's very helpful at this stage to print the profile if you have a large enough printer or plotter available. You can spray-mount the profile to the first piece of particle board to make sure your cuts are precise. The two halves of the mold must have exactly the right tolerance between them, or the molds will not apply even pressure to your bent ply piece!

Once you've cut one carefully on the bandsaw, sand down using a (1" belt sander if available) to the exact edge of your profile curve.

Step 5: Cutting Mold Parts / Mold Assembly

Picture of Cutting Mold Parts / Mold Assembly
Using the drill press, drill 3 or 4 holes for the registration dowels. Make sure they're located well to hold the parts together.

Mark these first two pieces as your template. To use the template to generate an identical slice:

1) Drill the registration holes through first.
2) Drive short dowel segments through the template and the new slice
3) Rough cut  the new slice on the bandsaw. Make sure not to gouge the template, as it will affect all future slices!
4) Clamp the template piece and new slice to the workbench, and use the router flush-trim bit to cut both pieces identically.
5) Remove the new slice and repeat until you've built up the full thickness of the mold. Apply wood glue between each layer as you stack them together on the longer dowel sections. When they're all in, Clamp the mold together while the glue dries.
6) Scrape any excess glue from the mold surface. It must be completely smooth!

Step 6: Verify that the mold halves fit

Picture of Verify that the mold halves fit
Once you're set, assemble the mold halves with spacers to verify that the space between them is consistent and exactly the thickness you've planned on. If They don't look like this image (where you can see an even gap all the way through), something's gone wrong and you'll need to fix it. Note that the perspective in this image means you can't see all the way through from any one eyepoint, but the gap is consistent no matter where you stand.

In this image, you can see the positions of all the dowels, and the measurements I've used on my night stands.

Step 7: Prepare your veneers

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1) Figure out the dimensions of the rectangular veneers you'll need. This will be the total length of the profile you've drawn plus about 2" for trimming on each end.
2) Cut the veneer edges straight if necessary, and tape strips together using the veneer tape and roller into full rectangular sheets. For the outermost layers, put the veneer tape on the outside (it can be sanded off at the end).
3) Alternate grain directions with each layer (the crossgraining is very important for strength). You can likely use thicker veneers for the cross-grain sheets, as the wood will be much more flexible in that direction.
4) Make sure to use an ODD NUMBER of veneers.
5) Make sure your stack is symmetrical around the center! You shouldn't have different wood on the different faces, or a different pattern of veneers going out from the center one.

Step 8: Glue up

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As with all glue-ups, you'll have to work very quickly. The glue I've recommended has a "pot life" of about a half hour. That means you have a half hour from the moment you mix it to the moment you insert the veneers into the molds. In that time:

1) Use a paint roller to coat BOTH SIDES of each veneer sheet in glue. DO NOT coat the outside faces of course! MOVE FAST. You need to make sure you cover everything, but by coating both sides you should be saved from any quick work missed spots.
2) Place a layer of wax paper on each side of the stack to keep it from gluing to the mold with any excess glue.
3) Insert veneer stack into the mold
4) Apply clamps

Pointers:
1) If you're doing this in your living room, as I was unfortunate enough to do, don't tell your landlord about the project!.
2) Be careful not to breathe the dust form of the glue. It's nasty stuff. Mix it outside. Once mixed, it's mostly odorless and can be used indoors.
3) Don't be shy about how much glue you mix. If you have a little extra, that's fine. If you run out, it's game over for the project, and you've just ruined a whole bunch of expensive veneer.

Step 9: Wait

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The glue takes 24 hours to cure at room temperature. You'll want to pull it out sooner, but don't.

Step 10: Pull the nightstand out of the mold

Picture of Pull the nightstand out of the mold
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Removing the clamps will be easy, getting the mold apart again may take a little elbow grease if glue has seeped out or the wax paper has torn.

Don't be disappointed if the piece is very rough looking around the edges. It'll clean right up!

Step 11: Clean up the final piece

Picture of Clean up the final piece
Depending on the size of your mold, you may be able to run the entire workpiece + mold combination through your table saw to clean up the edges in one go. Since the overall mold is rectangular, you can use it to guide any sort of tool for the cleanup. You can rough-cut on the bandsaw and then flush-trim using a router if you want. But use the mold's rectilinear edges if it's helpful!

If everything has gone to plan, you'll see the beautiful edges of a new bent-ply piece of furniture! Congratulations!
primosanch1 month ago
Very, very nice. Thanks for sharing.
dimdiode2 months ago

Fantastic work, absolutely excellent. If you put a few of these on Etsy, you'll make a bundle. Well done indeed.

Mamagreen2 months ago

Stunning, great work.

kirnex1 year ago
All I can say is: WOW. Well done. Brilliant, really. Thanks for taking the time to share with us.
Carleyy2 years ago
I didnt know you made this! I love this project.
jamietie2 years ago
This is fantastic. Any thoughts on whether it might work on a larger piece, like a chair? Or something that bears a lot of weight, like bentwood legs?
pseaton (author)  jamietie2 years ago
Thanks!

After working through this with the nightstands I'd say it'd be a real challenge to make a full single-piece chair or anything like the Wave Desk in size. These little nightstands required a full sheet of 3/4" particle board, so they were quite heavy and awkward to work with, even for a small finished piece. If I had to guess, the molds for something like a desk or chair would probably weigh over 200lbs; also I suspect it would be hard to paint all the glue on before it starts to cure.

That said, I definitely think there are ways to be clever in the design process that would enable you to make a larger piece out of several self-similar pieces. Like the butterfly stool, or the zumi stool , for example.

As for legs, absolutely. The nightstands are pretty much unbreakable. I had one where I messed up during the glue-up; to throw it away I wanted to break it, but even with my full body weight on top of it, I couldn't break it. Legs, also, don't necessarily need the tight curvature that I used in this design, which would mean you could start to use much thicker laminations. It would become a more normal bent laminations process at some point, once they curvature and surface area decrease substantially.

Thanks for the comment and the great questions!
I made a lot of longboards with rather complex compound curves. I used a similar method in construction but rather than particle board, I used high density foam (like the sheets of insulation foam you can get at hardware stores). This foam is really useful because you can shape it with a hotwire foam cutter and sand it down, then you can fiberglass the foam so it won't warp under pressure or wear over time.

I generally use a vacuum press for my molds but before I had one I used a similar sandwich type technique. I used 1/16" maple so I had to lay it up over several pressings to get the tight curves but the result is very satisfying.

This would be a decent, lightweight way to craft larger projects.
This is awesome! I always wondered how bent-ply was done. I figured it was just steamed, like how they made the curved spars for boat hulls. Thanks for the detailed instructable!
chicopluma2 years ago
great way to make the mold, I love the results
This looks great. I learnt a lot from your tutorial, thanks for the instructional.
GibParadox2 years ago
Great stuff!
I had always thought this was done on a single regular piece of ply-wood, and then molded with heat and steam...

You have just opened Pandora's box! :)
ravanjavan2 years ago
This is amazing....looks like a bit of work though. I would be interested in buying one if you decided to make a few extras :)
pseaton (author)  ravanjavan2 years ago
Thanks! I'm not going to lie.... it's a ton of work. 21 Layers is easy to type, but each one has to be roughcut (twice) then flush-trimmed.... but each nightstand isn't too bad !

Wish I could offer you one! Unfortunately I don't have the molds anymore, so I think these may just be two of a kind.... next time I'll hang onto the molds until *after* the instructable is posted :)
Very nicely done, and well written. It makes me think that even I could do it.
badart2 years ago
Thanks great work.
robbied2 years ago
This is incredible and looks complicated, and yet you have made it so simple that anyone could attempt it. Nice photography too.
Great pictures!
Charles and Ray would be proud. Nicely done.
angelabchua2 years ago
Wow, this is impressive. The design is fantastic and the directions are really thorough. Great pics too!
Carleyy2 years ago
This is gorgeous! I've been looking for a design like this for a desk. Great work!
mzlady2 years ago
I love this !!!
dimtick2 years ago
nice design!
Awesome design!
This is amazing! Great instructions. :)