This is a rehash of IAMSatisfied's chair. I did mine out of stock lumber instead of ripping stuff down.
Step 1: Materials & Tools
1x2 @ 8' - qty 2
1x3 @ 8' - qty 1
Rope (1/4" or just under) - ~100'
Using cheap wood and rope it cost about $15 from a local hardware-big-box.
Something to cut wood with (miter saw, chop saw, circular saw, hand saw, well-trained beaver)
Drill with bits (I used both a hand drill and a cheap drill press)
Router with 1/4" bit
Brad nailer (Optional)
35mm film canister (Kids, check your local museum if you don't know what this is.)
Step 2: Mark & Cut Lumber
1x2 #1 = 41", 27", 27"
1x2 #2 = 41", 17", 17", 15 1/2", 2 1/2", 2 1/2"
1x3 = 15 1/2", 13 7/8", 13 7/8"
Please note that for aesthetic reasons the 2 1/2" blocks should be cut at an angle , with 2 1/2" being the longest side. I used 30 degrees as my chop saw had it labeled. Just make sure the short side is not shorter than 1 1/2".
Step 3: Glue the Seat Support
Take the two short, angled blocks and glue them to the 17" piece of 1x2. The long edge of the angle blocks should be against the 17" piece, with the slopes facing inwards. I was using Gorilla glue, hence the dish of water to get things damp and the timer. Clamp and let the glue set.
Step 4: Back Frame Holes - Layout Back Frame
1x2 @ 41 - qty 2
1x2 @ 17 - qty 1
1x3 @ 15 1/2 - qty 1
What we are looking to do here is figure out the confines of the holes needed for weaving the back of the chair. We don't want holes going too far up or down the side rails, and we don't want them too close to the ends of the top and base rails.
For the side rails this means the holes need to be between the inner edge of the top rails and the base rails. While straight up measuring would work, I find it reassuring to actually lay it out and see the marks fleshed out.
So, put the top rail (1x3 @ 15 1/2) at one end of the two side rails (1x2 @ 41). Mark the two side rails where the inner edge of the top rail lands.
The inner edge of the bottom rail (1x2 @ 17, yes it is supposed to be longer than the top rail) should be 9 1/2 inches up on the side rails. Mark that line too on both side rails.
Step 5: Back Frame Holes - Mark Side Rails
In order for the holes to be properly spaced, measure the distance we have for weaving, mod for the spacing then divide by 2 to get your starting point. Feel free to take your shoes off if you need to count on your toes. Personally, I cheated. I plan on making a number of these, so I took a sharpie to the back of my metal ruler and marked off the 2 1/2" spacing. Then I just plunk it down and slide it back and forth until I am happy with the alignment. However you do it, make sure to strike across both sticks at once so that everything lines up nice. Also, make sure you aren't too close to the boundary markings.
Then, mark the sticks down the middle so we know our holes will be centered (or at least we can pretend that they will be).
Step 6: Back Frame Holes - Top & Base Rails
Once the spacing is laid out, mark the base rail in half for the location of the holes. With the top rail being made of wider material, scribe a line 3/4" in instead of splitting it in half.
Step 7: Seat Frame Holes - Layout Seat Frame
1x2 @ 27 - qty 2
1x3 @ 13 7/8 - qty 2
LIke we did for the back, layout the seat frame, with the front and back rails inside the side rails. Mark on side rails the inner edges of the front and back rails. If you can get a lovely assistant, feel free to make use of them.
Step 8: Seat Frame Holes - Mark Side Rails
Step 9: Seat Frame Holes - Mark Front & Back Rails
Step 10: Marking Recap
Step 11: Drill Drill Drill
Step 12: Route for the Ropes
The channel should connect all of the 1/4" holes. You do not have to do the entire length of the board, but it shouldn't hurt anything if you do.
Step 13: Add a Curve to the Back Side Rails
Step 14: Back Frame Part One - Top Rail
Glue, clamp and screw. Use the 15 1/2" piece of 1x2 as a space at the curved end so everything can clamp square.
Step 15: Back Frame Part Two - Seat Support
Attach the seat support with the angle blocks on the new marks. I used my glue and a brad nailer, but screws could work too. Just make sure to drive your fasteners-of-choice into both the main spar and the angled blocks.
Step 16: Back Frame Part Three - Bottom Rail
Step 17: Seat Frame
Step 18: Sand and Stain
Step 19: Weave It! Weave It Good!
When it came time to transition from the side rails, I used a hand drill to add another hole about halfway between the last two (see pictures 4 & 5). Proceed to weave (over-under-over-under).
Once the weaving is done, feel free to go crazy with the extra. I did a bunch of half-hitches. Crazy, huh?
You can also see that I wrapped the back bottom rail. I'd like to say it was for aesthetics (it does look nifty), or comfort (it may help), but actually it is structural. I wasn't paying attention when I fastened it and pre-drilled too small of a hole. It started to crack a little when weight was applied, so this was my fix.
Step 20: Insert Part S Into Slot C on Part B
I've seen folks add stops to the bottom of the seat so it can't slide too far through the back, but I haven't had any issues.