Crack in chair base

[jb94]

Annoyingly the lovely chair I spent the last few months making has developed a crack in the base…

Seat base is Laminated and joined with 3/4 inch dowels

It was properly dried wood ~12-15% moisture initially measured on my probe before making the chair.

The room it’s in is ~ 50% rh and doesn’t fluctuate much no drying of clothes etc. The garage I made it in is also at ~50%rh has a dehumidifier set to this target rh all the time.

I know it’s positioned near a radiator but this radiator is rarely ever on, and when it does it’s warm at most.

I think the crack has extended and widened slightly, but the chair is still rock solid.

I would have just put a bow tie in but it’s in an awkward spot between the spokes for the back.

Whats best course of action? I’m worried it’ll continue to split.

 

[Fitzroy]

That's a lovely chair, sorry to hear about the splits!

Looking at the pictures I think it is a shake in the timber, ie the defect was there before you made the chair. There look to be others in the chair seat, all the small black lines. Without these the limited movement in the timber due to bringing it inside would likely have been insufficient to cause a crack/split, but this one has widened as there is nothing to stop it.

As you said a bowtie/butterfly would be the ideal solution, with the access available a deep one from the underside may be the only option. Drilling and gluing in a dowel from the edge would give some structural strength to the are but not sure it would do much to limit more movement.

Fitz.

 

[Jacob]

Annoyingly the lovely chair I spent the last few months making has developed a crack in the base…

Seat base is Laminated and joined with 3/4 inch dowels

It was properly dried wood ~12-15% moisture initially measured on my probe before making the chair.

The room it’s in is ~ 50% rh and doesn’t fluctuate much no drying of clothes etc. The garage I made it in is also at ~50%rh has a dehumidifier set to this target rh all the time.

I know it’s positioned near a radiator but this radiator is rarely ever on, and when it does it’s warm at most.

I think the crack has extended and widened slightly, but the chair is still rock solid.

I would have just put a bow tie in but it’s in an awkward spot between the spokes for the back.

Whats best course of action? I’m worried it’ll continue to split.

They are not laminated they are edge joined boards and inherently weak. They also look too thin and the cracks look inherent to the piece of board - others have inherent cracks too.
Not much you can do except perhaps glue/screw some battens across from side to side underneath. "Butterfly" would look nice but probably weaken it further.
Have a look at some Windsor chairs. Mine here has seat varying from 40 to 35mm thick, but bottomed out thinner in parts. It's one solid piece of elm, uncracked and probably 100+ years old.
"Laminated" means layered, like plywood, with crossing over grain directions, and is very tough.
Pity, as it looks good otherwise. It's a learning experience!

 

[Eshmiel]

Annoyingly the lovely chair I spent the last few months making has developed a crack in the base…

Seat base is Laminated and joined with 3/4 inch dowels

It was properly dried wood ~12-15% moisture initially measured on my probe before making the chair.

The room it’s in is ~ 50% rh and doesn’t fluctuate much no drying of clothes etc. The garage I made it in is also at ~50%rh has a dehumidifier set to this target rh all the time.

I know it’s positioned near a radiator but this radiator is rarely ever on, and when it does it’s warm at most.

I think the crack has extended and widened slightly, but the chair is still rock solid.

I would have just put a bow tie in but it’s in an awkward spot between the spokes for the back.

Whats best course of action? I’m worried it’ll continue to split.

Nice chair.

With that variety of cracking (probably due to inherent tensions in the particular bits of timber, as others note) I've found that the best solution is to let the tensions out (i.e. don't try to draw the crack back together) leaving the piece until any other such cracks appear (hopefully they won't).

To stop crack spread, though, drill a small 'ole at the end of the crack that's the narrow-to-nothing end, which will usually stop the crack creeping further.

When its stopped doing its cracking, push a gluey wedge into the crack (without making it crack more) and make/locate dowels/plugs in the small anti-cracking holes. Do your best to match the grain directions and colours, of the same kind of timber.

If the crack is not wedgeable with one piece of wood (and yours isn't 'cos of the wriggle in it) you can successfully stuff the wonky crack with successive pieces of gluey veneer, wood chip or other smaller pieces (again, of a matching timber/colour/grain direction if possible). Hide glue is generally best. Chisel, scrape and sand it all to shape once stuffed.

***************
You'll inevitably be able to see the mend - but in some ways it adds to the character of such pieces.

I've not, though, needed to mend a chair in this way. Chairs have some large stress applied to them unlike, say, a cabinet or bedside table. Nevertheless, the above mend might suffice and be strong enough as well.

 

[recipio]

I would run some glue in the crack with a slip of veneer and bring it together by clamping two blocks for a G clamp. Another approach might be a pocket hole screw or two under the seat. You never know.

 

[Inspector]

If it is no longer moving you could join the "River Table Crowd" and fill with a high quality epoxy. Traditionalists everywhere are cringing but it does have some advantages. By using good tape, hot glue, etc, to create a dam along each side of the crack you can poor the epoxy into the crack and let it seep in over the day or three it takes to set and cure, it will fill every bit of the crack. It has the advantage in that you don't stress or weaken the wood with wedges, drilling dowel holes, and trying to draw together with clamps etc, and the epoxy is as strong or stronger than the wood. You have the option of using colourants to try and match the surrounding wood, a black, or you can use bright colours to "feature the flaw". The choice is yours. It is a modern repair that if done properly will last for decades but it has a disadvantage of not being easily reversible. If you are not confident in doing it yourself there is likely a local doing epoxy/wood furniture that might help you out.

Pete

 

[jb94]

They are not laminated they are edge joined boards and inherently weak. They also look too thin and the cracks look inherent to the piece of board - others have inherent cracks too.
Not much you can do except perhaps glue/screw some battens across from side to side underneath. "Butterfly" would look nice but probably weaken it further.
Have a look at some Windsor chairs. Mine here has seat varying from 40 to 35mm thick, but bottomed out thinner in parts. It's one solid piece of elm, uncracked and probably 100+ years old.
"Laminated" means layered, like plywood, with crossing over grain directions, and is very tough.
Pity, as it looks good otherwise. It's a learning experience!

Apologies, I meant made from several pieces jointed together with dowels rather than one single piece of wood forming the seat.

It’s made from 2 inch English oak which I undercut on the front edge quite a bit to make it look less chunky. Final size is 1 5/8 inch at the deepest where the crack is.

 

[jb94]

Thanks for all the ideas, I think for now I’ll watch and wait and see if it significantly expands. If so will probably try and secure it from the underneath +/- wedges to fill the crack or possible epoxy

 

[skeetstar]

Lovely chair, good skills . A variation on a theme.. you could try something like a 'domino' or loose tenon cut in from the back edge to lock the two sides of the crack to each other, then fill the crack with a coloured hard wax. I'd be wary of trying to clamp and glue, cos you might just move the stresses elsewhere.

 

[Eshmiel]

Lovely chair, good skills . A variation on a theme.. you could try something like a 'domino' or loose tenon cut in from the back edge to lock the two sides of the crack to each other, then fill the crack with a coloured hard wax. I'd be wary of trying to clamp and glue, cos you might just move the stresses elsewhere.

Clamping or banging in a wedge too hard are, as you say, things to be avoided. The best approach is to let the stresses within the wood leak out (i.e. crack the seat) until they stop doing so, then plug the crack with wood bit that have the grain, colour and wood type matched as far as possible. Clamping or force-filling the crack is likely to see existing stress come out elsewhere; or even introduce new stresses.

 

[Phil Pascoe]

Alternatively kintsugi - accentuate the repair rather trying to hide it. Whatever you do will be noticeable, so it had just as well be deliberately different as poor match.

 

[spanner48]

The basic problem is simple – and incurable. You have used oak. And tangentially-sawn planks. Oak is normally considered strong; but is actually weak in radial splitting. So it is likely to continue to split along the grain and parallel to the medullary rays, with people siting on it. In the day, ALL Windsor chairs were made with Elm seatbases. Because Elm famously has "crossed grain" and will not split. Elm planks of that width were notably prized and expensive even then, and are now uobtainable – until we can grow full stands of Dutch-Elm-Resistant varieties. In the meantime, the amnswer is to reinforce the seatbase with glued-&-screwed battens running right across underneath.

 

[Cabinetman]

The basic problem is simple – and incurable. You have used oak. And tangentially-sawn planks. Oak is normally considered strong; but is actually weak in radial splitting. So it is likely to continue to split along the grain and parallel to the medullary rays, with people siting on it. In the day, ALL Windsor chairs were made with Elm seatbases. Because Elm famously has "crossed grain" and will not split. Elm planks of that width were notably prized and expensive even then, and are now uobtainable – until we can grow full stands of Dutch-Elm-Resistant varieties. In the meantime, the amnswer is to reinforce the seatbase with glued-&-screwed battens running right across underneath.

Quite right - unfortunately for you! The very first Windsor I made was during the Elm disease period, I wish now that I had bought up some Elm as there was loads of it about and inexpensive, but not the easiest wood to work. I can attest to its cross grain, I tried to split a piece for firewood logs once - almost impossible.
I think that your Oak was a bit on the wet side at 12-15% and it hadn’t finished drying out or moving. It’s a shame as it’s a nice Captains bow chair.
Ian