Thread: CHAIR DESIGN 101

Thanks Pete,
Michael Fortune's Youtube (link posted by pjt) showed some of this but I had no idea I was looking at days!
My first former is the final shape I require and so it could be a good 'drying rack'. If they only have to be in the bending former for a short time then my bottleneck will be drying frames NOT the bending former?
I'm going to make some simple jigs to restrain the end movement while drying and, if that works, I could make many slats per day.
Today I borrowed a Festool Domino (thanks Brett) and machined the slots to take the slats .... what a wonderful tool!

fletty

Hey fletty,

Would be of assistance to build the form (or drying rack) out of light flexible sheet stock (3mm mdf ?) over a shaped substrate ? Like a skate board ramp... Rather than using the edge of sheet stock ?

Might allow better throughput of the steaming and drying process.

Just a thought ..

How about something simple like some nails (or small blocks) driven into some scrap which outlines your desired shape (or a bit more) which you could then place the slats into for the restraining period.

This is a pic of the leg braces after steaming, 25 x 50 bent on edge, basically I left them in the former (after steaming) until at least cool and maybe a bit more (half a day at most) then removed and just left them at that with no further restraint. Maybe they were in the former long enough
Once I had the system worked out they came out fairly consistant.

From memory I wanted a radius of 1500, I had to increase the former radius to 1300 to account for the springback, I think it's pretty much trial and error.
bent braces.jpg




Pete

Just an example of a tight bend I recall doing this at Tech many moons ago love the lamination to achieve the finished product.

Originally Posted by fletty

.......... then my bottleneck will be drying frames NOT the bending former?
I'm going to make some simple jigs to restrain the end movement while drying and, if that works, I could make many slats per day.
fletty

Ok, I've got it sorted out!
I got home from work via Bunnings with the traffic jam giving me time to think and design a drying frame.
I turned the boiler on and, while waiting the 2 hours for it to boil , I cut and dressed 8 slats and made the drying frame.
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Then, in a space of just over an hour, I steamed and bent 5 slats leaving them to 'set' in the drying frame

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Theres a few tension cracks on the outside radius which probably signify that I am bending too quickly so I'll keep an eye on that.
I am now much happier facing a week of very part-time work rather than 64 days of drudgery!
Thank you to everyone who has contributed AND, if ever you need the use of a steam bender in South West Sydney (or steamed dumplings or hooch), send a PM

fletty

Now thats looking like progress.

Memory recall in boiler op, fill to lowest line turn boiler on, slowly fill as it starts to warm. Is there a heat setting switch on that one Alan I can't remember? Oh maybe its because they were originally hooked up to 3 phase power not 240v that one was a conversion down to 240v.

I just caught up on this one. Interesting read.

Still going well but I'm losing about a quarter of the slats due to tension cracks

image.jpg

It is probably a combination of bending too fast and/or slats cut from timber that wasn't straight grained ....enough?
To be honest, I deliberately DIDN'T select only straight grain pieces to see what would happen and I guess I now know.

The drying frame has also been a good jig to mark the final length

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and I then cut with a bench hook

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Ive now started to assemble the first (prototype?) back splat and clamped it onto the EP to work out the mounting points
image.jpg

the splat continues below the seat but I've yet to work out if or where I need other cross braces
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and, today, I started googling upholstery!
fletty

Looking good !

Sent from my HTC Sensation Z710a using Tapatalk

Hey Fletty,

the other thing I forgot to ask was what type of timber you're using - as in how was it dried. Michael will never used kiln dried because he says the kiln drying process makes the lignin too brittle - and prone to faults as you're getting. he says that for bending purposes he only uses air dried timber.

maybe a clue?

pete

Thanks Pete, l noted that from a number of references but luckily most of my timber is air dried. This ARC was slabbed and stored for about 40 years! When l get bored with making this mountain of slats l'm going to experiment with other timbers and methods. One thing l do know though is that a piece of camphor laurel in the steamer clears the sinuses and repels moths in all nearby post codes!
fletty

I figured its a long weekend and with all these splats to make he'd be hard at it on such a nice first day so Sue & I decided to surprise the Gentleman Woodworker and see if I could learn a thing or three.

This is what we found ..........the old boiler steaming away while the other old boiler caught 40 winks.
First thought was that steam box would be needed for a different type of box.

P1060984.jpg

Not sure how or why but it must be an old woodies instinct, steam temp had been reached and it was all systems go. Never seen the man move so like a well oiled machine. YES we have video just trying to get it down to size. Anyone can assist let me know I have brought it down from 180 to 39.8 meg

Here it is in action.



Thats a great set up Fletty glad the old tub is finally getting some use
The end results are proof ARC does bend, looks good and if the girls aren't happy with them I know someone who would be

Also added Ps thanks to H for the hospitality of afternoon tea but she didn't need to go all the to the house and back for hot water did she.

Great stuff. Thanks Ray.
Good to see the old boiler at full steam. And the steamer looks pretty good too
If I didn't live so far away I'd drop in for a sticky beak as well. Looks like fun Fletty.

The production of slats continues apace. Ive assembled one complete back and mounted it to the EP...

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from the front it looked like I had hoped but

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from the back it demonstrated much better potential than I had expected.
I had done many sketches but, even so, I hadn't made all of the design decisions. It was morphing into a 'throne' rather than a dining chair. Most things I design are fairly simple and, to me elegant, but by trying to include ALL of my design elements, it had started to look clumsy.....

chair sketch01.jpegchair sketch02.jpegchair sketch03.jpegchair sketch04.jpegchair sketch05.jpeg


The sketches above all show that there are 2 pieces, one to hold the top of the slats and a separate crest rail. The piece receiving the ends of the slats was to be able to twist to stop the transfer of load to the chair frame. The crest rails were to be fixed and all designs have varying degrees of over-the-topedness (OTT) in an attempt to include design elements from the matching tables AND the family crest AND the name of one of my Orcadian ancestors! It is all too much! I am going to sacrifice the first batch of slats and design a single fixed piece to do both roles. This will lower the chair height, make it less throne-like, but minimise my matching to the tables?
Current thoughts are a minimalist family crest carved into the single piece back splat and the name, in Celtic script, possibly carved vertically along one of the legs? I have some crotch pieces of ARC (thanks Greg and Mal) which will make wildly grained crest rails which should then tie the chair design-wise to the tables. I am even considering flat topped crest rails rather than the more elaborate sketches above.
I am a bit worried about the transfer of the torsion load of the slats to the chair frame and the resultant stress but that will be less stress than convincing my daughters to sit in thrones.
I'll probably do a few more sketches of designs and do a further design of a single (workshop?) chair to use the current splat assembly.
Give me a table to make any day.........!
fletty