If you want to use CAD software to design complex geometry, you don't have to have expensive CNC machines to make the finished product. With a local copy shop and a little patience, you can produce just about anything you can design in the computer. This instructable shows you how.
The Lace-Up Chair is part of a broader study I'm up to experimenting with ergonomics- trying different materials and construction methods using the dimensions and posture of Mies van der Rohe's Barcelona Pavillion Chair (1929). This one uses two wooden sides with eyelets, dowels separating the sides, and rope laced through the eyelets that create a sitting surface that doubles as the chair's structure. I also took a cue from this awesome instructables project using rubber hose: https://www.instructables.com/id/Rubber-Hose-Chair/
Step 1: Tools & Materials
- Drill & drill bits
- Doweling Jig
- Bar Clamps
- Center Finder
- Combination Square
- Rubber Hammer
- Printed full-scale templates
- Wood Glue
- Dowel Pins (3/4" and 1/2")
- 2X6 Wood (12 linear feet). NOTE: I used off-the-shelf douglas fir, I would highly recommend spending a little more money on hardwood. Standard framing lumber is soft and will not last long. Invest in some Walnut or other hardwood and you'll get a much better result.
- Wooden Dowels: 1 1/4" Ø, 3X 26" lengths
- 1/2" rope, 100' length
Step 2: Design & Templates
This is my first project designed in Fusion 360. The interface takes some getting used to- it feels more like a web page than it does a CAD program, but once you get past the "Home" interface and start working, it's a remarkably simple program that has very advanced capabilities. Also, it's FREE if you sign up as an enthusiast! If you want to use it for professional purposes, it's only $40 per month.
When you open the file, you'll notice there are a lot of "sketches" plus the 3D parts. I used multiple sketches to design and alter the parts, then when I was satisfied with the design, I created new sketches derived from the finished parts to make the templates- to do this, you just click "create sketch" and select the face of the 3D part you want to make a template of, and there's your template!
I designed the chair so that no part was wider than 5 1/2", that way I could cut all the pieces out of 2X6 lumber.
Having created my templates with a 5 1/2" wide box around the parts (that's the actual width of a 2X6 member), I had a local copy shop print them for around $5. Then simply cut the templates out and spray-glue them to the lumber.
Step 3: Cut Out the Pieces
The quickest way to cut the pieces out is with a jigsaw. There are far more accurate ways to do it, especially on the straight cuts where a circular saw would be more reliable, but if you want to do these kinds of projects and don't want to break the bank, a jigsaw should be the first tool you buy.
I added crosshairs at the center of each circle (the eyelets) so that I could easily find the center with the drill bit. The eyelet holes are 3/4" Ø and the center holes for the cross-dowels are 1/2" Ø.
A good trick for cutting tight curves is to add perpendicular cuts to the curve- that way the jigsaw won't bind.
Make sure to go slow and steady with the jigsaw, always keep the base flush on the face of the wood, and be mindful of which side of the line you're trying to cut. With a little practice you can produce good results.
Step 4: Join & Glue the Parts
I decided to use dowel pins to join the parts of the chair because they're easy to find and they don't require a lot of fancy tools. You could also use biscuits with a biscuit joiner, or you could do dovetail joints if you want to get really fancy.
I used a doweling jig to drill the dowel pin holes: this handy tool gives you perfectly centered, perfectly plumb holes every time.
The blue tape you see on the drill bit is my marker for the depth of the hole.
Once the holes are drilled, glue the holes and tap the parts together with a rubber mallet. You can glue the surfaces that touch as well, but remember that end grain doesn't glue structurally. This is why you need dowel pins in the first place.
Once your parts are tapped together, use the bar clamps to make sure the parts glue together snugly. I also clamped them to the work table to make sure they were flush in both dimensions.
OPTIONAL: You'll notice in the photos here that all the parts have smooth edges. I used the table router with a 1/4"Ø fillet bit to get nice rounded edges, but you can do this with a more hand-crafted result with a palm sander.
Step 5: Cross-Dowels
The structure of this chair basically has two parts:
1. A rope in tension.
2. Three Cross-Dowels in compression.
The 1/2" holes are placed on the sides of the chair so that the 1 1/4" dowels will be held in place while the rope is laced up. Just like in the other parts, it's important to make sure the dowel holes are centered and plumb. Here's how I did that:
Use the Center Finder to get the exact center line of the 1 1/4" dowel. Next, use the Doweling Jig and line it up with the center line you just marked. You can't go wrong!
As before, glue the hole and tap in the Dowel Pin. Then tap the sides of the chair together using a rubber mallet as before. I didn't glue the holes on the sides of the chair in case I want to break the whole thing down later and pack it up.
Step 6: Lace It Up
As I mentioned, the rope creates the opposing tension that holds the chair together. To get the rope tight without using a turnbuckle or some other kind of hardware, use a Trucker's Hitch. This diagram clearly shows how to tie one.
First, tie a knot in the end of the 100' rope. Then starting from the top, lace the rope through each eyelet from side to side. It's basically like straight-lacing a tennis shoe.
The last eyelet gets a short loop with a knot at the end, taking the place of the "anchor eye bolt" in the Trucker's Hitch diagram. Tie a loop in the end of the 100' rope as close as you can to the last eyelet. Pull the end through the end loop and the loop in the rope- this gives you the leverage you need to get the rope tight.
At this point, you're fine tuning the rope:
1. Sit in the chair, let the ropes stretch a bit.
2. Tighten the rope by hand.
3. Tighten the trucker's hitch.
4. Repeat until comfortably tight.
Once the ropes have a comfortable resting tightness, neatly tie the end of the rope at the trucker's hitch and trim it to get it out of the way.
Step 7: Sit Down
It's a comfortable posture for a lounge chair, and the ropes make for a nice sitting surface. The dowel at the seat back digs into your back though- definitely consider placing that further down or further back in your version.
It didn't last long because of my poor choice of wood- it finally failed at the eyelets on the seat. With harder wood (or plywood for that matter), this will make for a nice chair.