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What's the best way to divide up the parts of this chair for strength and ease of construction?

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Forum topic by n00b posted 01-27-2021 01:02 PM 367 views 0 times favorited 3 replies Add to Favorites Watch
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n00b

18 posts in 3778 days


01-27-2021 01:02 PM

Topic tags/keywords: chair joinery question joining

This is my first attempt at a chair. It will have a leather or canvas sling, and I’m planning to construct it out of maple with “loose tenons” (Rockler beadlock).

I was planning to make all the straight sections out of strips about 1×2in (2.5×5cm), and the junctions would be cut from 2-inch thick stock. But that ends up being quite a few pieces, and a lot of joinery.

So I started to wonder if I should simplify. For instance, pieces CFGH could all be one piece, cut from 2-inch thick stock, and maybe ABE could also be one piece.

What’s the best way to divide this up to create a chair that’s strong and reasonably easy to construct? Are there some simple rules of thumb, some do’s and don’ts for this?

Note that I’m not 100% sure that the sling will be attached to the crosspiece at the front of the chair. I might add “wings” to it and attach it to the armrests, in which case there will be much more stress on those parts.

Thanks for any advice!


3 replies so far

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Madmark2

2277 posts in 1595 days


#1 posted 01-27-2021 04:46 PM

The design you show is generally laminated and not constructed out of individual solid pieces.

1×2 isn’t 2.5cm x 5 cm. Nominal lumber size is the raw stock size. A 1×2 is actually 3/4” x 1-1/2” (~19 mm x 37 mm).

This material may be too thin for bead lock.

C, E, G & K are going to have grain direction issues. K is especially problematic as there is no grain orientation that will make a strong U-bend. Being at the bottom rear, this will fail the first time someone leans back in the chair.

You might be ok at C and G, but E is also destined to fail. No matter which way the grain in E is oriented at least one side will fail under load.

Build one side and then break it to see where it fails.

-- The hump with the stump and the pump!

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Loren

11010 posts in 4655 days


#2 posted 01-27-2021 06:21 PM

If you can make peace with it perhaps breaking on you within a short time, it may be worth going with the divisions you’ve already chosen.

I suggest making a mock up out of 2×4 pine material sawn up to the shapes you need and held together with pocket screws and glue. It can take a lot of design iterations to develop a successful chair and mockups are important to the process in many cases.

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n00b

18 posts in 3778 days


#3 posted 01-27-2021 07:27 PM

Thanks for the replies!

Madmark2: I was planning to find lumber larger than 1×2 and mill it to that size, so I think the Beadlock would work, but as you say, that doesn’t necessarily mean it will be strong enough. I see what you’re saying about K in particular. My design is based on this existing chair, kind of flipped around, but I now see that that chair has a joint right in the middle of the tight U-bend, which seems challenging to replicate at my skill level.

I know lamination and bending is a better way to go, but that’s beyond my capabilities. I had actually originally thought of a laminating in the other direction, though, by routing the profile out of plywood and stacking those. But then I’d have ugly plywood layers, and I wanted to avoid edge banding since I’d like to have a rounded or chamfered edge.

Loren: Thanks for the wise tip about doing a mockup. I’m a fairly inexperienced woodworker, so I like to just jump into things and learn (a lot) as I go, but maple and leather are not cheap, so this could be a costly lesson if it fails.

Hmmmmmm….

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