Faceted Curved Wooden Chair

Intro: Faceted Curved Wooden Chair

I've been itching to make something new for a while now and wanted to make something that would challenge me a bit more than normal. I'd seen some curved chairs that looked pretty cool so thought I'd have a go at something similar.

I had an idea to have five or six main rib section on which wooden chair section would sit upon, so mocked up a few ways of making the main curved ribs. I came up with a few options where I could cut all the rubs as singular curves on a full board of ply, divide the ribs in to a three sections and joint together with half lap joints or make the ribs out of trapeziums.

Material wise I thought that going with trapeziums would be best....I would be able to get much more out of my wood than with the other two options

I also made a 3D model of how the ribs would be made in to a frame in Fusion 360 which gave me a good idea of how it was going to look. I'm not good at Fusion but the ribs were fairly easy to do but the rest I couldn't quite get my head around, with all 3D modelling I'm sure there's an easy way to do it but I couldn't find it!

That's as far as I went with my planning but had no idea how I would attach the seat parts to the ribs, but on to that later!

STEP 1: Rib Wood

I wanted the width of the ribs to be around 70mm (3") but my oak wasn't quite wide enough to get two ribs out of each plank, so I decided to go for a stripy wood by edging the Oak with Sapele, this enabled me to use the whole oak plank.

I put all the slabs through a thicknesser (planer) to get everything to a uniform thickness. Once that was done I ripped the Oak to 50mm and the Sapele to 10mm and glued and clamped together to make the rib material.

STEP 2: Cut the Rib Sections

I had worked out the top and bottom length of my trapeziums based on an 850mm diameter circle and calculated the angle I needed to cut the rib material. In the end it was pretty close to 10 degrees so I set my mitre saw to cut to this and chopped the end off my rib. Once that was cut I set a 'stop' to the right hand side of the saw so I could butt up the rib plank to the stop, cut, turn over and cut again. I then repeated this until I had 35 individual rib sections.

STEP 3: Construct Main Ribs

I did have a few ideas about how to fix all the rib sections together but came up with the final idea to use quite thick, full length splines as I thought this would give me the most strength.

I started by cutting full length rebates in to both ends of most of the sections, approximately 5mm (0.2") wide, on my table saw, by cutting one saw width and then turning the piece around for a second cut, which made sure that my rebates were central on the ribs. For the end pieces only one side needed to be cut.

Once they were all cut, I ripped some pieces of oak on the bandsaw and passes these through the thicknesser (planer) until they were the same thickness as the rebates.

To fix the pieces together I glued the oak splines in the the rebates, clamped some pieces of pine to either side of the ribs (so the faces were parallel to each other) and then used the pine to clamp the rib sections together.

As a hobbyist woodworker I don't have loads loads of clamps so this step took days to complete as I could only glue two sections together at a time.

STEP 4: Tidy Up Ribs

With all the five ribs complete I needed to tidy up the splines so started by trimming them on the bandsaw and finished the internal trimming with a chisel. The outer splines were brought flush with a sander.

I then sanded all the ribs with a random orbital sander with 80, 120 and 180 grit sandpaper.

STEP 5: Fix the Main Ribs Together - Part 1

To create the curve between the ribs I decided to use two rows of support pieces (see the Fusion model in the introduction). I started with the widest parts closest to the front of the chair eyeing in a good looking distance and angle between the ribs. I cut one section first to check how it was going to look and once I was happy I cut the remaining three sections.

Once my front sections were done I clamped two ribs together with the support piece in between to find the dimensions of the smaller top pieces. These were a bit more fiddley to do as I needed to determine and cut compound angles for the side faces. With quite a bit of adjustment to the first piece I eventually found the correct angles so carried on with the remaining cuts.

I then cut pocket holes to each part, offsetting the holes to one side so when they were screwed in the screws didn't foul on each other.

STEP 6: Fix Ribs Together - Part 2

I started fixing the ribs together in pairs first to make the whole process easier. I started by fixing the large cross piece first, using a square and reference piece to position the wood before screwing it down on the first rib. I then removed the cross section piece and did the same to the second rib. I then ended up with one rib fully fixed and reference screw holes on the other. As space was tight I needed to use either a screwdriver with right angle head on it or as space got even tighter I used the pocket hole driver with a small spanner to tighten the screws.

STEP 7: Legs

The next challenge was to add the legs, these would be attached to the ribs so would also be angled in two directions.

I started by clamping some left over rib parts in between two parts of oak, this would make a natural recess for me to fit the legs on to the ribs. Again this step was a lot of trial and error, fitting, adjusting and refitting until the legs were correct. Once I had all four legs I clamped them in to place and drilled a 10mm hole all the way through the leg and rib.

I made some dowels on the lathe, cut them to length followed by gluing and doweling the holes. Once it was all dried I trimmed the dowels and sanded the area to 180 grit.

STEP 8: Seat Pieces - Part 1

Ideally I wanted the seat pieces to be fixed to the ribs so you couldn't see any fixings but I couldn't think of a way to do it easily.

I did think of dowelling each part to the ribs but the overlap of rib and seat parts was too small, even for small dowels. Even if the ribs were wider, dowels would be very difficult to locate in the exact location, as the seat pieces and ribs aren't at right angles to each other so some kind of angled drilling would be required too.

In the end I used small angle brackets to fix the seat pieces to the ribs, although at some angles you can see them so weren't ideal in the end.

To look a bit better and to give the timber room to expand I decided to leave a small (1mm) gap between each seat section, so that had to be taken in to account when cutting the seat wood.

I started by ripping lengths of the oak with a 10 degree angle to each side (the same angle as the individual rib sections). Once I had these I could measure the the required top and bottom widths and determined the angle of these cuts before cutting then with a mitre saw. This step had to be repeated for each row as they are different angles and widths all the way up.

Once cut I the clamped a piece to the ribs and secured with a bracket I had bent to the follow the angle between the rib and the seat piece. I then used a spacer between the previously fixed parts to locate the next seat section. A small amount of adjustment also needed to be done so all the gaps were uniform(ish) and all sides were parallel to each other.

This was a very lengthy process as even a fraction of a millimetre to one side was noticeable.

STEP 9: Seat Pieces - Part 2

After I had fixed two rows I decided to sand and oil each part before attaching them to the ribs as taking them all off again and re-fixing in to the exact same place, I imagined, would take a long time.

As with the ribs I sanded with 80, 120 ad 180 grit and oiled with a layer of Danish oil.

The further I got up the chair the smaller the gap became and was more and more difficult to fix the brackets. On the top sections I used a tiny 90 degree ratchet screwdriver to fix the screws, although that was a very difficult thing to do.

For the bottom row I cut a 45 degree cut to the top edge which I then sanded to a curve to make it more comfortable on the legs.

STEP 10: Paint Front Brackets

The only thing I didn't really like was the obviousness of the fixings from certain viewing directions, to make the front ones (the ones that will mainly be seen) less obvious I added a coat of primer and then painted the brackets a brown colour similar to the wood. It isn't ideal but better than what it was!

STEP 11: Finished

Once it was all put together I added another couple of coats of oil on and a final layer of wax.

In the end I think it turned out really good.

If you enjoyed this project it would be great if you could vote for me in the woodwork contest. Thanks!!!!

STEP 12: Update

So following publishing this Instructable I still wasn't happy with the visibility of the brackets and one of the comments gave me an idea to make a cover for the brackets.

I started by cutting a couple of lengths of wood to a width of just wider than the bracket. I then made a groove with multiple cuts on the table saw before cutting to size. I then made some end caps for each of the pieces and glued them on to the ends. After sanding to 240 grit I stuck them over the brackets using superglue (CA glue) with a spray accelerator and finished with a layer of oil.

It does make the back much better......not as good as a method with no visible fixing but the best I could do with what I had!

Comments

[baelicole]

What were the leg measurements for this?

[petachock]

The front legs were about 250mm long and the back ones about 325mm long. They do have a compound miter angle on the bottom too.

[baelicole]

Ok thank you!!

[Nataliia]

Дуже стильно, щодо зручності потрібно спробувати посидіти у цьому стільчику. Дякую, отримала чудові враження від краси.

[MrErdreich]

Such a cool and meticulous design, beautifully done and thanks for sharing! Please show a photo with someone in it too :)

[GlueGun_RaR]

Beautiful work. I agree with a previous comment about showing a person in the chair. It looks uncomfortable. Still, looks can be deceiving. Moreover, I'd be PROUD to have this in my home solely as an art piece. Everything is harmonious even the legs.

[petachock]

Oh yeah I was meant to take a photo with someone on the chair when I did the update bit forgot, in on holiday now though so can't take one!!!!
It is a lot more comfortable than it looks, feels similar to an Adirondack chair when you use a cushion by your lower back.

[xantham]

I swear, it seems like no one can live without CA glue. I really like that sapele wood. how is it to work with?

[petachock]

Ha ha yeah CA glue does have its uses!
So the Sapele wood I used to edge the ribs with is really nice to work with, it cuts and finishes well.
The only problem I had is that it sanded easier than the oak, so after sanding the ribs they did end up being curved on the surface rather than flat.....maybe hand sanding would have been better in that case.
Sapele seems to be widely available here on the UK although mainly sold in builders merchants, but not at the wood shop I go to.

[LeslieGeee]

Hi Pentachock, this is a beautiful chair but I wish someone sat in it in one of the finished photos to see the relationship of the chair with how a body fits into it and the comfort level of the incline in relationship to where your head is. I hate doing a critique but maybe for your next chair you could think about the suggestions. They are not bad but just things to think about. If this is supposed to be a lounge type chair, why did you not just extend and flatten out the curve a bit so that legs and feet were supported, or make a reverse curve to follow the leg structure. If the headrest ends at a persons neck wouldn't that be uncomfortable too? If you want to keep the curve of the base, longer back legs might have worked better to make the sit area more upright and comfortable. I am sorry to say I groaned when I saw the back of the chair with the screwed in brackets to help support the wooden pieces. There must be a way to make a tongue and groove adaptation like with wooden floors and a way to use a small nail nail gun to fortify the joints. The metal brackets even with the paint destroy your design. The other thing I can think of to do is to slide in a veneer of thinner exotic wood like the Sapele and glue in if you want to keep permanent. I love the idea of the chair and the wood you chose to make it. Add a long pillow and my two cats would have claimed that chair in an instant :). I hope you don't mind my suggestions but my brain went into fix it mode. Thank you so much for sharing your idea and the hard work you put into it.

[petachock]

Hi LeslieGeee, no problem! All ideas and suggestions are welcome.
The chair is actually surprisingly comfortable and a really nice shape, with a small cushion by the small of your back it's perfect.
The part I don't particularly like, as you say, is the brackets. Things like a tongue and groove joint would be super difficult to implement as there is an angle between each piece, which varies as you go on to different rows. I also wanted to keep the gap between each piece to accommodate any movement.
I was thinking dowels and convinced myself enough to go out and buy some, but as I was playing around with them I came to the conclusion that the doing was going to be much more difficult than the idea.
I guess some kind of wooden shroud over the brackets could work which would be akin to your veneer idea.
Thanks for reading my Instructable and commenting. It is appreciated!

[LeslieGeee]

Hi again and thank you for being understanding. In todays world ya never know lol. After I read your post in todays Instructable email there was another post for joinery. Not sure if you get the same posts overseas as we do here in the States. I am enclosing the link in this post and maybe if you know that the joinery solutions he has won't work maybe a collaboration could be made. Hope this helps.
https://www.instructables.com/My-Favourite-Joinery-Method-for-Plywood-MDF-OSB/?utm_source=newsletter&utm_medium=email

[petachock]

Hi, I have was thinking about what we were discussing and thought I'd make some covers for the brackets. It does make the back much better.
I have added an additional step if you want to take a look.

I pretty sure we get the same email here in the UK and saw the post you referred to. I'm not sure I could have used any of these methods either as they are all for 90 degree joints but good suggestion!

Thanks

[LeslieGeee]

Hi again. WOW big difference and a lot of patience getting the small pieces to fit to look like a single piece. Good work ! LOL now take your beautiful chair put it in your yard get a drink and a pillow and relax :). Job done well.

[wallace54]

What he said.

[petachock]

It might be. I've only got a tiny CNC machine so I hadn't thought of it. The ribs could easily be cut on a CNC machine but if cut whole, would take up a lot of material.
The seat parts are full of compound angle cuts so if this could be done on a CNC machine and you could draw the 3D model you could!! My modelling skills are not that good though ;)
When putting the rib sections together you'd need to be super accurate too otherwise the joints between the seat parts wouldn't work. Even fractions of a millimeter is quite visible when the gap is only 1mm. I would have thought some whittling of each section would still need to be done.
Thanks for the comment!

[edknoles]

A beautiful chair, just not lumbar friendly to my eye.

[petachock]

Thanks, but it is pretty comfortable with a small cushion!

[plctim]

I found a chair like this at Costco and though it would be super nice to make one.
I am confident that I can follow your steps. Thanks! I'll vote for this beautiful char.
Can you share where you got the room divider posts in the background of the first picture?

[petachock]

Thanks!!! The post are part of an outside balustrade system but I didn't install that myself so don't know where they were sourced from....sorry!!!!