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Thread: CHAIR DESIGN 101
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2nd June 2014, 05:44 PM #31
Hey Fletty,
I have had the privilege of taking a 12 week course with Michael Fortune, and so have had lots of time with him and the steam bending process. One thing you haven't mentioned is what you do with your pieces after you bend them. Michael takes the bent pieces off of the former after they have cooled (about 20 minutes), and then puts them on either a shaped drying rack, or a duplicate of the bending form (depending in the severity of the bend) to dry, still held in the shape of the bend. Because the steaming has made the wood plastic, it also makes it elastic, meaning it wants to return to its original shape. Once dry (anywhere from 5 to 10 days depending on the thickness and how long you steamed them for) then they have no 'memory' of ever being straight and will not spring back when you take them off the drying form. Michael quotes figures of less than 1mm variation on pieces up to 30mm thick.
Hope this helps
peteShine on you crazy diamond!
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2nd June 2014, 06:32 PM #32
draft
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!
flettya rock is an obsolete tool ......... until you don’t have a hammer!
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2nd June 2014, 10:00 PM #33
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 ..Glenn Visca
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3rd June 2014, 01:04 AM #34
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
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3rd June 2014, 10:04 AM #35
Just an example of a tight bend I recall doing this at Tech many moons ago love the lamination to achieve the finished product.
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4th June 2014, 10:26 PM #36
smokin'........
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.
20140604_162439.jpg
Then, in a space of just over an hour, I steamed and bent 5 slats leaving them to 'set' in the drying frame
20140604_204653.jpg
20140604_205213.jpg
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
flettya rock is an obsolete tool ......... until you don’t have a hammer!
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4th June 2014, 10:59 PM #37
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.
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5th June 2014, 01:32 AM #38
I just caught up on this one. Interesting read.
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6th June 2014, 10:02 PM #39
Progress report....
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
image.jpg
and I then cut with a bench hook
image.jpg
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
image.jpg
and, today, I started googling upholstery!
flettya rock is an obsolete tool ......... until you don’t have a hammer!
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6th June 2014, 10:48 PM #40
Looking good !
Sent from my HTC Sensation Z710a using TapatalkGlenn Visca
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7th June 2014, 12:40 AM #41
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?
peteShine on you crazy diamond!
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7th June 2014, 01:15 AM #42
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!
flettya rock is an obsolete tool ......... until you don’t have a hammer!
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7th June 2014, 08:10 PM #43
JUST AS SUSPECTED
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.Last edited by wheelinround; 7th June 2014 at 08:35 PM. Reason: ADD VIDEO
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8th June 2014, 12:35 AM #44
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.Those were the droids I was looking for.
https://autoblastgates.com.au
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8th June 2014, 10:18 PM #45
design drama .... or dream?
The production of slats continues apace. Ive assembled one complete back and mounted it to the EP...
20140607_135407.jpg
from the front it looked like I had hoped but
20140607_135649.jpg
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.........!
flettya rock is an obsolete tool ......... until you don’t have a hammer!
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