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Thread: Bending Sydney Blue Gum
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27th June 2019, 01:44 PM #1GOLD MEMBER
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Bending Sydney Blue Gum
I am making a Morris chair from Sydney Blue Gum and have now got to the problem of making the bending formers for the arms. SBG is pretty tough stuff and the plan calls for 3 x 3/8" laminations to do this but Americans have never met a piece of SBG so I am thinking of 4 x 1/4" laminations instead, I also need to make the former for the bending and I have some large pieces of 25mm MDF which glued up to 50mm might be man enough for the job. Will the MDF do it and do I need to make the laminations thinner than the plan proposes?
The other thing I have thought of is to screw one half of the former to a bench so it definitely won't move and clamp the form together and then screw it down as well so the form can't move under tension. I haven't got any large pieces of hardwood to cut the form out of. Comments and ideas are welcome.
Another question is what glue is best for this sort of work?CHRIS
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27th June 2019, 02:00 PM #2
Chris, you are on the right track. Thin lams will bend on a form way better than thick ones and will also reduce spring back. I would even consider 8x1/8. I have one of those Ikea Poang chairs and the lams on that look to be about 1/8''. I made some laminated archery bows some years ago and the rule was more thinner lams work better. Easier to bend into shape, less springback and a better end result. MDF or particle board will work fine as forms
Regards
John
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27th June 2019, 04:46 PM #3GOLD MEMBER
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Morris chair arms come in so many different configurations. I take it you are building a bow armed chair? Is it a supported arm design or does the arm self support between the front and back leg? Is it a single curve or multi curve arm. All these make a difference to the method of arm manufacture. Maybe a picture if you have one?
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27th June 2019, 05:02 PM #4Taking a break
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27th June 2019, 06:47 PM #5GOLD MEMBER
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27th June 2019, 08:02 PM #6
I know that design. They have been on my todo list for many years. I reckon the 1/4" lams will be fine
Those were the droids I was looking for.
https://autoblastgates.com.au
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27th June 2019, 08:22 PM #7
That’s not a huge bend. I don’t think you need to go to 1/8.
There ain't no devil, it's just god when he's drunk!!
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27th June 2019, 10:23 PM #8
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28th June 2019, 01:54 AM #9GOLD MEMBER
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28th June 2019, 10:01 AM #10
Having seen the pic I will go with the others and say you can get away with the 1/4'' lams as the bend is quite gentle.
Regards
John
PS Looking at the picture again I would be tempted to just bandsaw those arms. Some waste balanced against a bit of work making the forms and doing the laminating. Just a thought.
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28th June 2019, 10:48 AM #11
Just a note on mdf/chipboard. If you are making jigs check gumtree for "cover sheets". Here is brissy they can be had for $5-$10 per full sheet. That's about as cheap as material gets and for workshop duty they are perfectly suitable. There are always ads for people giving away pallets. These often have hidden nails and other problems but for some jobs they can be broken down and work well. Making sawhorse are one example.
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28th June 2019, 01:41 PM #12GOLD MEMBER
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So if I choose the laminate & bend path what glue is recommended. I spoke to Fletty and he used garden variety Titebond but I recall recommendations for epoxy?? I am leaning towards laminations if for no other reason than to get the experience but the timber we are using is slabs from a chainsaw as it came from the tree and certainly thick enough to cut out as one piece.
CHRIS
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28th June 2019, 02:36 PM #13Taking a break
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I like polyurethane glue for laminating; PVA tends to creep after a while and you can feel a ridge on each join and epoxy tends to have a darker, more noticeable glue line (well, Techniglue does, haven't used any of the more runny epoxies)
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28th June 2019, 04:54 PM #14GOLD MEMBER
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Epoxy on bluegum will eliminate creep but always gives a dark glue line. A quality chair would not be laminated, it would be sawn and shaped from a solid piece. The shaping off the saw gives an extra dimension to the grain pattern in the arms. Laminating screams reproduction.
When this style of chair is mass produced and laminating is used for the arms, the infill framing directly under the arm is made robust enough so that the shaped top edge of the frame acts as the form for the laminations. If the timber available is not thick enough for sawing, steaming would be an option, again using the under arm frame as the form. This was the usual method in the old chairs as there is no sign of laminating or grain enhancement from sawing. The arms are usually just plain, straight grained pieces which lend well to steaming.
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28th June 2019, 06:40 PM #15
If there is enough timber, I'd shape it on the bandsaw, purely from the point of view of it being less work. However, if you want to laminate it, Go for epoxy like Techniglue, which can be tinted using powdered pigments available from art stores. A small jar will last you forever - you don't need much, and if you judge the colour right, the laminations will be invisible.
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