Is there a chair doctor in the house?

[derekcohen]

Here is set of chairs that my father designed in the late 1930's. Bentwood laminations of what I think is either Beech or Ash. I restored the chairs several years ago ...



A side view of a chair leg:



This evening my son (the 17 year old with muscles like walnuts) sat down hard and the chair leg collapsed!



The one piece of luck is that the front lamination is still whole, and this means that I should be able to repair the leg without it showing from the front ..



Here are details:

The break is over the tenon ..



I can push the top sections back, and I think that these can be glued back as is, if indicated ..





This leaves the lower section (made up of three leaves) ..



Is there is any point in trying to glue back these pieces as they will not be supported? Even with epoxy. Some surgery is needed.

I have solid Beech and Ash boards that can be used in the repair.

How would you go about this repair?

Regards from Perth

Derek

[Pete L]

Hi Derek

Your skills are far greater than mine and I hesitate to make a suggestion however, you must be pretty devastated. I have used laminated sections many times in vintage car bodies and in particular curved sections and wheel arches. They come out very strong even with joins in the sections, provided that the joins are staggered some distance apart. I use two pack boat glue.

In your situation I would try to separate the sections over at least an 18 inch distance and using the existing reglued long rear section as a start, with the opposite side joined where broken, try to replace new internal sections with joins away from the first two. To maximise the strength it may be prudent even though not desirable, to add a couple of screws from the inside of the leg. They can be fairly well hidden. I added a screw to the bottom of the rear leg of a balloon back dining chair broken off by a cartwheeling teenage daughter many years ago. Today I have difficulty finding the repair, having forgotten where it was!

Good luck

Peter

[derekcohen]

The first phases of the repair:

As a reminder, we started with the good ..



.. and ended up with this ...



I decided to glue up everything using West Systems epoxy, recognising that the one side of the break - the side that had staggered leaves, should create a strong join - but the other side - the side with an in-line break - would require reinforcing ...



The leaves were glued together over three sessions. At the end the joins were pretty good - there will be tidying up later - and just one gap evident ...





Luckily, this gap was precisely where I planned the reinforcing would run. My plan was to mortice along the side and epoxy in a 1/4" wide x 1" deep Beech insert (the chair is Beech, just in case you were not aware . This would extend from the foot of the leg to about 4" above the break.

Because the mortice would be about 1/32" - 1/16" below the surface of the rear most lamination, I decided that this was a job for my power router.

Here is the set up ..

The router (my trusty Elu 177e that I have had about 20 years) is supported on runners clamped to the leg.



Here is the router bit over the hole ..



Ok, I will jump ahead - the mortice was squared up, the insert epoxied in, and the excess planed away after it was set. This is the result ..







and ..



I have now to use a cutting gauge on the insert to mimic the layers of lamination, and re-shellac (amber shellac) the finish. It is feeling strong.

More after the weekend.

Regards from Perth

Derek

[ian]

Derek

I can see why you've gone down the path you have, but looking at the break it looks like the original glue bond has failed.
I think I would have built a new laminated leg reusing the front lamination (and sadly I'd also be prepared to rebuild the other 3 legs over time)

cheers

[derekcohen]

Hi Ian

The glue bond did fail, and so I am checking all the other legs to make sure they are secure. From my cursory look so far they are all OK.

Regards from Perth

Derek

[ian]

Hi Derek

My guess is that the original glue bonds have aged and are close to failure.
For what it's worth, I think the most sympathetic thing you can do for your father's memory (and design originality) is to build a new pair of chairs that exactly match the originals (including the timber if you can identify it)

I'd like to stay and chat, but I should be in bed

take care

[derekcohen]

Hi Ian

One idea that I have is to preempt any future delamination by morticing an insert into the first 2" of each leg and around the joints. That way the laminations will not unbind.

Regards from Perth

Derek

[Pops]

Hi Derek,

Looking good. Doubt if anybody will notice the repair atall when it is finished. Good save indeed.

Cheers
Pops

[ian]

Hi Derek

I can see your thinking.
My thinking is that the glue has failed -- possibly chrystalised -- inserts at points of maximum stress might prevent catestrophic failure of the rails, but in the long run, delamination is inevitable. Hence the suggestion to rebuild the rails.
You may know better than I, but ungluing the laminations, cleaning off the original glue and then regluing the laminates might be an option.

cheers

[derekcohen]

Hi Ian

As far as I can make out, the laminations are tight. I have a plan to provide a little extra protection, and I would like to hear from you and others what you think.

Initially I planned to add an insert to all legs. Now I plan to rout/drill into the underside of the foot of each leg, create a couple of mortices, and fill these with epoxy. This should bind any loose laminations.

Regards from Perth

Derek

[ian]

Looking at the picture of the failure, there doesn't appear to be any wood fibres adhering to the glue line. That suggests to me that the glue failed.
the chair is 70(?) years old. the chair is valuable because it was made by your father
the construction is a lamination, there will be stress points throughout the rails

asetheticly, for me, adding stuff like epoxy plugs, or stengthening strips, is a bit like using srews to "fix" loose joints in an antique

cheers

[derekcohen]

.. asetheticly, for me, adding stuff like epoxy plugs, or stengthening strips, is a bit like using srews to "fix" loose joints in an antique

cheers

Hi Ian

The mods will not be visible, except for the end of a dowel that will cap the round epoxy-filled mortice, which is under the foot.

It is simply not an option to pull the laminations apart - even if I could (and they are tight so there is no need) - putting them back together would be a nightmare!

The mods I am suggesting are simply a precaution.

I am interested in alternative ideas.

Regards from Perth

Derek

[ian]

Derek
I'd need to study the chair in detail to identify where the high stress points are in the design.
I'm not sure that where the legs meet the floor is the point of maximum stress.

I think it might be where the side rails meet the legs, and the extent of any weakness might be related to whether the mortices (and tenons) are crisply square or very slightly rounded.

good luck with your mods