Shaping chair leg question

[John15]

I have given the lower leg a taper from 40mm to 30mm on all faces which has made the upper part look a little heavy. I can't taper the inside face of the upper part because I've made the back rest shoulders square, nor the back and front faces as it will reduce the back rest reveals, although this might be just do-able.
My question is would it look odd if I gave just the outside a taper or should I leave it as is. This is a prototype for a dining chair and I want to make it as fine as possible. No abuse expected, hence no lower leg rails.

John

 

[custard]

Great to see a chair being made on the forum, more power to your elbow John!

To answer your question, in my own chair making I tend to design around chairs with a normal back height fanning outwards, like this,

And chairs with very tall backs tending towards parallel or very slight outward fanning, like this,

Personally, I would find a chair back that sloped inwards as it got higher a bit odd, if I were ever to do such a thing I'd probably make that the key design feature and have it sloping inwards a lot! But a slight inward slope? Hmm, doesn't work for me.

But, hey, I'm not the one who has to live with it, so my opinion really doesn't count for much!

 

[John15]

Thanks for your thoughts Custard. You've said what I was thinking - it would look odd sloping inwards. But having tapered the lower part I'm now between a rock and a hard place - the top definitely looks too bulky. I think I'll assemble the chair to get a better idea of how it looks.
Thanks again for your comments.

John

 

[MikeG.]

Have you got a drawing of what you are trying to achieve, John? I mean, if you want a Jacobean chair it's going to be quite a different thing from a mid- century chair, or an arts and crafts chair.

I will be making a dining table and 10 chairs next year, in Jacobean style. I'm quite happy with a heavy, carved and ornamental look, but even so, I'm planning on making a mock-up first to try to answer the sorts of question/s you are asking yourself now. If you've got the time, I suggest you follow suit with a chair in pine so that you can refine you design before tackling the job in earnest. However, the one thing I think I can say with certainty is that having the top of a chair back taper in would look a bit unusual.

 

[MikeG.]

........To answer your question, in my own chair making I tend to design around chairs with a normal back height fanning outwards, like this,
........

Those clamping arrangements look quite special, Custard. Can you tell us what is going on there?

 

[custard]

Those clamping arrangements look quite special, Custard. Can you tell us what is going on there?

A problem that's frequently encountered on chairs is how do you get really good, gap free joints between the vertical back bars and the crest rail/seat back rail? There are so many curves going on that it's virtually impossible (without CNC'd components) that everything's going to fit as well as you want.

One solution is to use fully blind tenons (ie no shoulders at all) at either the top or the bottom of the back bars. Unfortunately you can often get a bit of chipping around the edge of the mortices, and blind tenons won't have a shoulder to cover this up, which means you're then stuffed.

So if you want shouldered tenons the solution is to make the crest rail tenon about 2-3mm narrower than it's corresponding mortice at the top of the leg. This means the crest rail can "float" up and down, which gives you enough lee way to have a couple of rounds of scribing the tenon shoulders on the back bars, both top and bottom, for a perfect fit. I rarely get this dead right on the first round of scribing, it generally seems to require a second round. But even with compound curves I'll rarely have a gap of more than about 0.3mm, so 2-3mm of "float" is plenty.

That's stage one. Stage two is how do you then cramp the job up?

If the back bars are fairly straight it's not a problem, you just run a few vertical sash cramps in line with the back bars, going from the crest rail at the top to the seat back rail at the bottom.

But I prefer to make my chairs with quite a pronounced front to back curve on the back bars, in order to give more lumbar support for the sitter. So sash cramps won't really close up the joints, they'd just make that curve in the back bars more pronounced. The solution is a slow setting UF glue and these little shop made cramps that attach to the back bars and then use threaded rod front and back to direct the pressure exactly where it's needed to close up the joints. You get a better idea in this photo.

 

[MikeG.]

.....and of course if you are pulling them up, you have to hold them down into the lower rail with the same arrangement.

 

[John15]

I've done a dry assembly and I think I was worrying too much. Not a work of art but I intended it as a simple chair to suit my pay grade. Still a lot of finishing to do. Will post the completed item in a week or two. Thanks again Custard and Mike G.

John

 

[custard]

I've done a dry assembly and I think I was worrying too much

I agree, it looks excellent.

=D>

What's your plans for the seat?

 

[John15]

Thanks Custard

John