Build a Bent-Laminated Lounger
Photos by Rob BrownI spend a fair bit of time sitting, and I’ve found if I’m not careful to sit properly my back gets sore quickly. This lounge chair is made for my body, but you can, and should, customize it to suit your needs.
I started off by sitting on a chaise lounge garden chair we have on our deck, as even though it’s only comfortable to sit on for a few minutes, it was the closest thing I had to my intended design. I placed some small pillows and books under my knees and behind my back at different locations, to come up with a comfortable position. I made a very simple side view drawing of the dimensions of the chaise lounge, then added the dimensions of the extra supports I used. I faired the curves on my scaled drawing and now had a specific shape to work towards.
Test the shape
Sit Carefully – With the “seating line” created, secure it vertically, grab some strong armrests and test it out. It’s not perfect, but it’s the quickest way to see how the overall shape feels against your sitting body. Make any necessary adjustments.
I made a full-size drawing on a piece of 1/4" hardboard, starting with the overall shape of the chaise lounge I used, then adding the extra supports I needed. I joined all these points together to create the “seating line”. This was to be the finished surface of the seat that would support me. I cut it out with a jigsaw so I could test it, which was much easier said than done. After some contemplation I secured the template perpendicular to the ground, and added a few strong, stable armrests on either side of it. The armrests were there so I could rest my arms on them, supporting the vast majority of my weight, as I tested the “seating line” against my body. It was not easy, but it was the simplest and best approach I could think of.
If I found the shape uncomfortable I would have adjusted it and retested it, but thankfully it felt quite good against my back.
I then added a line offset exactly 2 1/2" from the “seating line”. This second line, what I’m calling the “lamination line”, was the back surface of the bent lamination, as the many cross-members are going to be about 1" thick, the lamination itself was going to be 1 1/4" thick and the template guide fixed to the base of my router was going to offset the edge of my router bit 1/4". I cut it out with my jigsaw and faired its surface to ensure all the curves were smooth. I then screwed it to a piece of 3/4" exterior plywood, making sure there was at least 5" of material on every side of the “lamination line” to provide enough material to construct the form with.
– Now that Brown was happy with the shape of his “seating line” he needed to account for the 1" thick cross-members, the 1 1/4" thick lamination and an extra 1/4" for the template guide he was using in his router. He offset the “lamination line” 2 1/2" and cut that shape out.
Create Lamination Cavity
– After screwing the “lamination line” template to plywood Brown uses his plunge router, 3/4" dia. straight bit and template guide to rout a 3/4" wide groove. The piece with the template attached to it will have the final shape to it, but the other half needs to have a 1/2" wide rabbet routed into it before proceeding.Create the bending forms
With my template guide attached to my router’s base, and a 3/4" dia. Bit chucked into my plunge router, I followed the curve of the template.
Multiple passes removed a 3/4" wide path in the plywood. I still had to remove another 1/2" of material, essentially creating a 1 1/4" wide gap, from the inside half of the form (the part without the 1/4" template attached to it) so the 1 1/4" wide lamination would fit between the two halves perfectly. I used my rabbet bit in my router, set to create a 1/2" wide rabbet, then used a flush trim bit to remove the rest of the material. While doing all this, I made sure to keep at least one mating factory edge on both halves of the form so I knew how they fit back together. This would be handy during glue-up. A couple of straight lines on either form, which ran into each other, would also work.
I now had to build this form up to 1 1/2" in thickness, so it would be able to press the 1 1/2" wide pieces I needed for the final bent laminations. I cut 5" wide plywood scraps, then glued and pinned them to the two halves of the form, making sure they overlapped the finished edge slightly. When they were dry, I used my bandsaw then my router and flush trim bit to flush everything up, then lightly sanded the edges to ensure they were smooth.
Build the Form Up – Once the form halves have been made, and an extra layer of plywood is attached to them, Brown flush trims them with a router.
Trim to Rough Width – A rough line is added to the form, and the waste is removed from the usable sections of the forms.
I marked and cut the forms away from the remainder of the waste plywood. One half I trimmed to about 4 1/2" wide so it would be quite rigid, and the other side I brought down to about 3" wide. The exact dimensions aren’t important, as long as you can get your clamps on either side of the forms, with the laminations between.
Machine thin strips
The middle curve in this lounger is fairly tight, so thin strips are required. I brought a few strips down to just over 1/8", but when I put them in the form a few of the pieces on the outside of the bend split. Turned out, with the clear spruce I was using, just under 1/8" worked well, but test it out with the species and curves you’re working with to ensure none of the plies split during glue-up. I made enough plies to create two 1 1/4" thick laminations, with a few extras just in case. I also sanded the exposed surfaces of the outer laminations before going any further. The plies in the finished lamination are about 76" long, so I started with plies about 84" long. What you should use will be dictated by your design.
Too Thick – Test laminations were too thick, as they broke during the dry run. If anything, you want to err on the thin side when making plies for the laminations.
Glue the laminations
Typical yellow glue will not provide a rigid enough glue-line for these laminations. A number of adhesives will work, but I selected Unibond 800, as it has a fairly long open-time, creates rigid glue lines and I happened to have lots of it around. After preparing the necessary clamps and readying the area, I mixed the adhesive, put it into a used (and clean) honey squeeze bottle and started applying it to the laminations. I brought the glued pieces against the form and carefully brought the mating form into place, adding clamps, all while making sure the two forms were coming together even with each other and the laminations were centered and even between the forms. It sounds like a lot to do at one time, but as long as there are no surprises things move along nicely.
Clamp it Up – The first lamination is drying between the forms. Be sure to make the plies longer than they need to be, so you have enough length to work with during glue-up. A helper also makes the task of pressing the laminations go much smoother.
Trim the laminations
With the laminations dry I used my router equipped with a straight bit and an offset base support, to trim about 1/8" from one edge of the lamination before removing them from the form.
Not So Fast! – Before removing the cured lamination from the form, Brown uses a router, straight bit and offset support block to flatten one edge. This creates one flat, straight edge on the bent lamination. You can also add small reference marks on each part before removing them so you can align them down the road.
This leaves me with one flat, true reference edge so I can put the lamination through the planer to clean the other side. I took the first lamination out of the form and glued the other one up. After it dried, and its top edge was trimmed, a couple of passes through the planer were all that was needed to produce two sleek, weird looking laminations just over 1" wide. A word about planing these tricky beasts – keep the area around your planer clear of obstructions while planing them, as you must do your best to constantly rotate the part, keeping the short portion that’s currently running under the planer knives at a right angle to the cutter head, to reduce tearing.
Trim the Ends – While the cross-braces are temporarily installed mark where the laminations need to be trimmed.
Groovy – With a sharp V-gouge, Brown adds shallow grooves near the ends of the cross-members for aesthetics.
Machine enough cross-members as you feel are required. I brought them all down to 1 3/8" square, attached them to the laminations then checked the comfort of the lounge. If I needed a bit of material removed from one area I still had room to do that, by planing a few cross-members down.
I spaced the 18" long cross-members about 1" apart and used 29 pieces in total, but this is more art than science. Once made I drilled a counter-sink hole 3 1/2" away from either end, centered on each of the cross-members. I then lined up the two laminations 10" apart and started to temporarily secure the cross members with screws. I check for square often, as I work my way along the lounger. Using spacer blocks is a great way to keep the gaps consistent. Having said that, slight adjustments need to be made when working on inside or outside curves, to keep the visible gaps even; like I said, it’s more art than science. I started attaching cross-braces in the middle, but feel free to start where you would like. When done, I numbered the crossmembers so I knew how to put everything back together. I cut the foot ends of the two laminations to length, flush with the last cross-member, and cut the top ends so they protruded a couple inches beyond the top of the upper cross-member.
Take a seat
Eager to test the fit, I sat down and was pleasantly surprised. The only knock I had was there was a bit too much lower back support, so I marked which pieces needed thinning, then removed all the cross-members. I ripped 1/4" off the outer face of each cross-member, except for the few than I marked; they were reduced by 1/2".
With all the cross-members removed I marked a pleasing curve on their undersides, removed the waste with my bandsaw and sanded all the surfaces smooth. Before removing the ends of each cross-member, make sure you copy the part number to another area on the part, so they can all go back together properly. I also added a matching curve to the rear faces of the two bent laminations.
Before re-assembly I made sure each of the countersink holes were deep enough to accept a 3/8" plug, since I removed 1/4" from their faces. Most of them had to be re-drilled on the drill press.
At this point I added a series of shallow V-grooves to either end of the cross members, strictly for visual reasons. Because there were so many cross members to do I used an offcut of the same length with the general location of the grooves marked on it to transfer to each cross-member.
With all the parts ready I set the laminations side by side for one last time, and readied my glue and small brush. I installed a few of the cross-members without glue, just to hold the laminations steady, and attach the others with glue. With all the cross-members permanently installed, I cut western red cedar plugs, glued them into the counter-sink holes and when dry flushed them to the surface.
One Last Time – Brown re-installs the cross-members, this time with glue.
Angled Feet – To ensure the feet sit flush on the ground, Brown uses a long straightedge to mark the correct angle, then trims the waste with a handsaw.
I flipped the lounger over, balanced a straightedge on the center curve, and marked where the foot of the laminations could be angled to meet squarely with the ground. I wanted to create a 1" square flat area, and did so with a handsaw and block plane. I brushed on two fairly heavy coats of polyurethane, as the softwood soaked up the finish like crazy. I gave the entire surface a sanding with 320 paper and sprayed on the last coat of finish with a rattle-can sprayer. Once it was dry, I used #0000 steel wool and wax to smooth all surfaces then enjoyed another quick break.
As I have never made something like this before, and want to continue to explore the general form down the road, this prototype has answered a lot of questions for me. I initially considered adding two small support arms, which would attach to the side of the laminations, at lower back level, and run behind the lounger to the floor. These supports would provide more support and strength for the laminations, as well as stop the lounger from lilting backwards. I decided not to add them, as two laminations seemed to be strong enough for my liking, and the lounger is very steady when I’m seated in it. It is, however, a bit tippy while I’m getting into it, and I have to do so carefully or the entire lounger (and user) will end up on its back.
Another consideration was the general shape of the piece. Would it be appropriate for reading? For relaxing and talking? For sleeping? You must have a specific purpose in mind when designing a piece like this, as there is no “one-shape-fits-all" approach. I made mine for sitting in while using a laptop and for some light reading. After using it for a while, I would make three minor modifications to the overall shape of the laminations; (1) a little less low back support, (2) a bit more head support, and (3) a slightly gentler curve in the middle section of the laminations (the tightest bend). This last modification would have made the laminating process a little bit easier.
Rob edits Canadian Woodworking & Home Improvement Magazine, builds studio furniture in Peterborough, ON and tries to keep his kids from hurting themselves while climbing on his new lounger.