Instructables
Picture of Ratchet Strap Chair
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closeup strap 3.jpg

This chair is made from a 1/2 sheet of plywood, uses no glue or fasteners, and is held together by a single ratchet strap. I made this chair because I was interested in the forces at play to make a chair stand up: the different parts in tension and compression that make up the structure. It's also part of a broader study I'm up to experimenting with ergonomics- trying variations on the dimensions and posture of Mies van der Rohe's Barcelona Pavillion Chair (1929).

 
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Step 1: 3D Model

Picture of 3D Model

I designed this chair in Fusion 360 (it's recently become my go-to modeling program). The file is attached here, please download it and tweak it yourself! Fusion 360 is free for "enthusiasts", and it's on both Mac and PC.

Step 2: Tools and Materials

Picture of Tools and Materials

Tools

  • I used a Metabeam Laser Cutter to cut out the pieces, because it's fast and we have one. A Shopbot would make short work of this, and you wouldn't have any burn marks to manage later.
    • IF YOU DON'T HAVE A CNC MACHINE: Before I had access to CNC machines, I did lots of projects that were just as complex using full-scale prints from Kinko's, spray-gluing them to plywood, and cutting them out with a jigsaw. Check out my Lace-Up Chair instructable for more details on doing it that way.
  • An orbital sander, finishing at 180 grit.
  • OPTIONAL: I also used a table router with a 1/4" fillet bit for some nice rounded edges.

Materials

  • 1/2 sheet (4' X 4') of 3/4" plywood.
  • One ratchet strap (1" strap).

Step 3: Cut Out the Pieces

Picture of Cut Out the Pieces

My Metabeam settings are as follows:

Material: "Hardwood .25"

Power: 100

Speed: 40

Step 4: Finish the Pieces

Picture of Finish the Pieces
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I started at 100 grit to get the burn marks and smoke residue off the wood, then stepped down to 180 grit for a smooth finish.

I used the fillet router bit on all of the edges of each piece.

Step 5: Assemble The Chair

Picture of Assemble The Chair
  1. Slot the truss into the back legs
  2. Add the front legs
  3. Add the seat
  4. Slot in the seat back

So, here's the thing: I'm a Soldier and I deployed to both Iraq (in '04) and Afghanistan (in '08). Among the egregious incidents of poor planning and spending is the fact that the military will actually haul huge, heavy, expensive pieces of civilian-style office and barracks furniture into war zones. But, we also take enormous amounts of plywood for construction of shelters (barracks, offices, etc.). A suite of simple furniture designs (bunks, desks, shelves, etc.) cut from 3/4" plywood, slot-and-tab assembled, and held together with ratchet straps would be invaluable!

JON-A-TRON (author)  Shawn Stanford9 days ago

That's a great idea. People have been making flatpack furniture for long-term camping trips (burning man, etc.) for a while- it's a great way to make sturdy, comfortable furniture without having to ship all that volume. I think the dead-simple design of this project is probably even better for this kind of use: http://www.treehugger.com/sustainable-product-desi...

All the zoomy lines and fussy details of mine require more time to cut out by hand, not so efficient.

This is another awesome flat-pack project, housing for disaster areas: http://www.wired.com/2013/11/a-disaster-relief-she...

The idea is that you show up with a CNC machine and a ton of 3/4" plywood, and you've got all the buildings you need.

jmwells1 month ago
Update on my comment. Did the cardboard thing. Worked after a fashion. Until a 350lb friend decided to plop down in it. Legs folded.
JON-A-TRON (author)  jmwells1 month ago

Pictures please!

I was preparing to shoot some when Carl crushed it. The legs were still too pointy and thin. I'm going to put on another layer, or two at the bottom of the legs. Perhaps feet too. I used contact cement between layers, the bond didn't break. The paper did. I went five layers of cardboard, for a thickness of about 3/4". The seat and back held up fairly well. We used it for a bonfire starter. Next time I'm thinking seven layers, 1"+,-. If the prototype holds up I'll spray the pieces with an epoxy paint for durability and water resistance. Got other projects right now, will update in a few months.
JON-A-TRON (author)  User11 month ago

So true. Posture is everything when it comes to furniture, and it's been pretty well figured out by the 20th century masters. The Ratchet Strap Chair is based on the Barcelona Pavillion Chair by Mies van der Rohe.

This project, by one of our AIRs, is based on the Eames LCW chair and is also very comfortable without any padding: http://www.instructables.com/id/P9L-Lounge-Chair-made-with-CNC-Router/

do you have pdfs of the pieces rather than fusion 360 format?

JON-A-TRON (author)  PetersPJones1 month ago

Just uploaded a full size PDF to Step 2. If you ever need to convert a DWG file to PDF, just do it on this site for free: http://www.zamzar.com/convert/dwg-to-pdf/

lensman8881 month ago

Great for moving day and you already have the strap to tie up the pieces!

JON-A-TRON (author)  lensman8881 month ago

Hadn't thought of that! I cut the strap so that I wouldn't have to figure out what to do with the excess, but it makes sense to come up with some kind of attractive clip solution so you can still use the strap for other purposes.

fred36551 month ago
Now for the ratchet strap table and foot rest! This awesome, can't wait to make one.
JON-A-TRON (author)  fred36551 month ago

That's the plan! Can't wait to see what you come up with.

great project!

Todd Gehris1 month ago

That thing is freaking cool!

travderose1 month ago

This is rad! Great job

JON-A-TRON (author)  travderose1 month ago

Thank you!

CobyUnger1 month ago
Cool dood!
JON-A-TRON (author)  CobyUnger1 month ago

Thanks Man!

rimar20001 month ago

Interesting design.

JON-A-TRON (author)  rimar20001 month ago

Thanks! I'm hoping it's the first of many ratchet strap furniture pieces. I got the idea from this project: http://dornob.com/no-nails-sans-screws-ratchet-strap-wood-furniture-series/#axzz39A6fNK66

howtobasic1 month ago
So ratchet ?
jmwells1 month ago
Think I'm gonna try cardboard, laminate it with alternating internal fibers, and make the legs less pointy. Looks great for a picnic chair. Easy to pack and move.
JON-A-TRON (author)  jmwells1 month ago

Cardboard's a great idea. I would recommend laminating so that they're at least 1" thick when you're done.

You're so right about the pointy back legs! They're on a 1/2" radius, they should be more like a 2" radius like the front legs are.

I agree, this is best suited for outdoor use. But that means I'll need to finish it (everyone's least favorite part).

mcep5f20091 month ago

Pretty cool!

crank_girl1 month ago
Rather neat! B)
JON-A-TRON (author)  crank_girl1 month ago

Thanks!

pretty pics!

lebowski1 month ago

Nicely done!

AWESOME!