Clamping Help Needed! Irregular shape clamping

[retrowoodwork]

I just joined this forum today, in search of great wisdom from great woodworkers here.

I have obtained some retro chairs, but by design, the back of the chairs have come undone, where the dowel and glue work done by the manufacturers have come apart.

I have some experience with gluing, and know that clamping is essential to get a seamless joint. But this is the first time I cannot find two parallel surfaces to clamp or to tighten with a ratchet strap. The best that I can do is to get it as close together as possible with a soft mallet, but the best I could get is shown in the photos:

20150327_115025.jpg20150327_115031.jpg20150327_114948.jpg20150327_114954.jpg20150327_115009.jpg

From the photos you can also see there's no way to clamp the two parts together.

I have tried to make a jig that fits to the front surface, but once I apply pressure, it slips upwards, and can't get the joint to close up.

Any ideas on how I can clamp these two parts together to form a tight joint? Any help will be much appreciated!

BTW I'm using PVA glue

[jazzy69]

How about if you clamp some small blocks either side and parallel to the join then clamp it back together the other way.It is a bit fiddly but should work.
Cheers,
Ross

[Evanism]

Clamping that would be impossible, however, awesome pressure can be applied with the use of either:

- a long strip of fabric or rubber
- clear packing tape

Japanese clamping involves running a strip of fabric around boxes and cabinets. Wrapping it tightly and going over and over while keeping tension will build phenomenal force. Just use an old bedsheet ripped and sewn into strips and machine sew the strips together. Wind it around a tube or cardboard sheet to help with dispensing it. 10 minute mark - https://www.youtube.com/watch?v=qRPS9jZuFeA

The tape method I use all the time. Officeworks clear tape. Glue, then a first long stripover the joint, tightly applied, then apply successive layers pulling each one very tight. 3 or 4 layers will apply a very considerable clamping pressure.

[mark david]

Simple solution....Spanish windlass.
A very simple but effective method of clamping all kinds of wierd and seemingly impossible jobs.
If it looks like it will slip off the vertical face of the arm then just put a clamp across the faces.
Tap the joints together with a rubber mallett and don't over-tighten.

You will also need to put a temporary bracing between the arms to maintain the shape of the chair or it will probably break.

[Master Splinter]

Before you glue and clamp, have you cleaned out all traces of the old glue? Most glues won't stick well to either themselves or other glues, with the exception of hide and epoxy glues.

[retrowoodwork]

I will explore each of these advice carefully, will post the one that works on in the end! Thanks.

[retrowoodwork]

@Master Splinter: I cleaned the joints of the old glue, scraped what I could with a blunt chisel, and used a drill bit to clean the glue from the holes for the dowels.

@mark david and Evanism: I actually tried wrapping the joint with strips of bike tire inner tubes, but the issue with clamping is similar, that I can get pressure that is perpendicular to the joint, thus can't get the pressure I need to close up the joint completely. (I tried to tie the two pieces in a figure-8 pattern.

I tried using anti-slip mats, clamping some clamps as anchor points, and then trying to pull those clamps together.

20150406_170003.jpg

However, as I half expected, the clamps even with anti-slip mats still slipped and was not strong enough.

Pretty frustrated, and am tempted to just mallet the two pieces together as close as possible, and use wood filling for that gap, but I know that'll obviously be a lower level of craftsmanship.

Another alternative way would be to drill holes on the pieces, put in dowels that is half sticking out, then using the suggested spanish windlass to pull the two dowels together. But obviously drilling into the vintage wood pieces is not something I desire...

Any other ideas please?

[mark david]

Are you sure that the joints are actually capable of fitting perfectly together?
Maybe there is something inside the mortice physically stopping it going together.
It shouldn't really require a massive amount of clamping pressure to bring the joints together.

I would first have to satisfy myself that the joints are physically capable of coming together perfectly.
You may need to resort to making a saddle piece that is a mirror image of the curve of the arm with cheek pieces and a vetical clamping face that can be clamped on so there is no slippage up the arm.
You may find the Spanish windlass idea works with this set-up.

@Master Splinter: I cleaned the joints of the old glue, scraped what I could with a blunt chisel, and used a drill bit to clean the glue from the holes for the dowels.

@mark david and Evanism: I actually tried wrapping the joint with strips of bike tire inner tubes, but the issue with clamping is similar, that I can get pressure that is perpendicular to the joint, thus can't get the pressure I need to close up the joint completely. (I tried to tie the two pieces in a figure-8 pattern.

I tried using anti-slip mats, clamping some clamps as anchor points, and then trying to pull those clamps together.

20150406_170003.jpg

However, as I half expected, the clamps even with anti-slip mats still slipped and was not strong enough.

Pretty frustrated, and am tempted to just mallet the two pieces together as close as possible, and use wood filling for that gap, but I know that'll obviously be a lower level of craftsmanship.

Another alternative way would be to drill holes on the pieces, put in dowels that is half sticking out, then using the suggested spanish windlass to pull the two dowels together. But obviously drilling into the vintage wood pieces is not something I desire...

Any other ideas please?

[Evanism]

You were almost onto my next suggestion, which would to be using a "draw boring" technique.

e.g. http://www.finewoodworking.com/how-t...n-joinery.aspx

You'd need to make a tenon in one, glue it, and when dry, mortice do the other side. If the tenon is wide enough, two draw bores would look nice.

Nothing wrong with furniture looking repaired.

I'll have another look at those pictures from before. Maybe they made some sort of elaborate jig originally.