Chair design and repair question on good deed project

[Dave huber]

I inherited a project. I told the widow of a woodworker that I would complete assembly and finish a chair her husband began before he fell ill and died.

The chair is white oak. Basic design. However, it has two problems that I think need to be remedied.

First, it is not built with a rear rail between the uprights under the seat.
Second, the mortises holding the rails to the uprights are small and poorly fit.

I plan to replace the mortises with floating tenons.

However, It seems that the lack of a rear rail allows all the force pushing the back of the chair away from the seat to bear on the mortises along their weakest point, pulling them out easily.

Does anyone have any suggestions about whether I can get away without the rear rail if I replace the tenons with larger, loose tenons?

I have a scheme for adding the rail, but it involves resawing a rail that I've cut for floating tenons, then gluing the sandwich back together in place. the back of the chair is assembled and finished. I don't want to disassemble it if I can avoid it.

The only chair I've built is a Morris chair, which is so completely overbuilt that I'm having a hard time gauging how much I need to worry about the addition of the rail.

Thanks, Dave

Pix are below.
The tenons are about 1.5 inches long, only 1/2 inch deep.
They are not fit particularly well. The glue failed on the first test, which consisted of me sitting in the chair and leaning back.

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[lowell holmes]

It seems to me that you are going to disassemble most of the chair anyway. I would take it apart and add the back rail it needs.

[Sam Murdoch]

There are plenty of examples of chairs built without lower back rails though the remaining construction should be done in such a way to make the entire assembly rugged and durable - DUH. I know you already know all that I'm just thinking out loud. Perhaps after you reinstall the existing rails with better fit tenons you will find that the chair design is substantial enough without those elements.

My suggestion for adding rear rails as an after thought is unconventional but perhaps worth your consideration - 1/2 lap 1 or 2 rails into the back assembly. Likely, just add a seat rail. Though more of a challenge this can be done with the chair all assembled. You can do the joint from the back side and perhaps play it up as a detail, e.g, leaving the outside face a bit proud of the back legs. In any event you did not want to disassemble the back frame anyway. I didn't say it was a good idea :).

[Jim Tabor]

I agree with Lowell, I would take the chair apart and start over. Sometimes the easiest fix (and best) is to take a deep breath and jump in. For long term peace of mind you'll want to add the rear rails.

[pat warner]

KD hardware, (x-dowels and bolts). Even the worst of connections won't come apart with them.
Black headed and counterbored, the hardware won't be conspicuous.

[Dave huber]

I never thought of KD hardware for this.


That's why these forums are here, and so wonderful.


My other idea for a rear rail is similar to a sandwich half lap as suggested above.


I am loathe to disassemble completely, but generally subscribe to the "if it ain't right, start over" approach.


I'm truly torn.


There will be a fair amount of beard scratching on this.


Thanks!


If anyone has other ideas, I'm still working on it.


Thank you everybody!!


dave

[John TenEyck]

IMO there is no need to add another rail under the seat. The chair has two pretty substantial back rails and if they do their job the legs won't splay. Adding longer loose tenons as you plan to do should be sufficient to resist front to back racking forces; another rail won't help with those forces anyway. Last, and probably the most important point is that's the way the man designed the chair. To change it would be like telling his wife he didn't know what he was doing. Just my opinion.

John

[Bill ThompsonNM]

I agree with John, i don't think the weakness is from lack of a rear rail, its the poorly fitting tenons. If you replace them with floating tenons well fit, that will probably be enough, if you want extra insurance, decorative pins for the tenons should work great

[Pat Barry]

I don't see a rear rail as providing any great improvement either. The connection is the key so beefing up and improving the tenons is the way to go.