Monday, September 26, 2016

Chair Fail! How To Fix - SURVEY

A bit more than two years ago, I built my first Roorkee chair. It was constructed with black leather and pear wood. I've built a few more since then, but those were gifts, and this one is mine.

This chair didn't get used a whole lot, until I brought it with us to Spain. We have a furnished apartment here, but it was a simple thing to bring this chair along since it folds up into a neat bundle. I find myself using this chair multiple times per day here, as it is the perfect thing for watching TV in our new apartment here.

That is, it was the perfect thing. A few days ago there was a bit of a mishap:
OK, this is a bit of an exaggeration. This was after I removed the offending stretcher.
I probably was a bit careless in sitting in it that morning. I violated my "No Plopping" rule. I plopped and heard a big, "CRACK" and knew I was in trouble.

The chair was not as stiff as it had been, and upon inspection, I found the following break in the stretcher on the left side of the chair that goes from front to back. It was on the rear side of the chair.
Ouch!
Upon further inspection, I decided it was a pretty bad break.
Is it really that bad?

Yes. Yes it is really that bad.
I've never seen wood crack across the grain like this before. I think, however, that I know what caused it.

This was the first Roorkee chair I ever made, and I turned the stretchers on a lathe. This chair got me into a bad habit, though. I must confess that I always make this tapered tenon 100% with the tapered tenon cutter from Lee Valley.

The recommended way to make this tenon is to turn the rough shape of it on the lathe, and then finish with just a few turns of the tapered tenon cutter for a finished shape. This method preserves the shape of the tenon being perfectly centered on the dowel.

What I did was turn the dowel on the lathe, put it in a vice and use the tenon cutter like a pencil sharpener to make the tapered tenon from the beginning.

I determined that this really wasn't all that difficult, and since then I've made all my tapered tenons this way.

The big problem, is that it is easy for the tenon cutter to get off a bit. This particular tapered tenon looked like it was bent. What must have happened, is I must have put a bit more pressure on one side of the tenon cutter than the other while turning it, resulting in the center of the tenon not being centered on the center of the dowel.

Long story short, when I put this chair back together, this "bent" tenon was in the back on the side, a position which I have discovered is the highest stress part of the whole chair.

The best fix for this is to turn a new stretcher, corectly taper the tenon and replace.

Unfortunately, I don't think I have enough pear left to make another stretcher like this. If I do, it is in Munich, and not here in Spain with me. For the meantime, I can either try to repair it, or turn a new dowel in a completely new species of wood.

For starters, I think I'll just try to glue it back together and see if that works. I first thought of liquid hide glue, since it's reversible. On the other hand, if it doesn't work the first time, what's the point? Plus, liquid hide glue won't do squat on the crack that runs perpendicular to the grain. Pretty much no glue would.

What I think I'll try is super glue.
How super is Super Glue?
I figured the best part of super glue is it sets in just a few seconds. That is a definite plus, since I have no way of clamping this.
Glue applied.
What I did was squirt as much super glue into every part of the crack that I could. Then I squeezed it together with my fingers, wiped off the excess, and shoved it into the tapered mortise, and put all my weight on it for a minute or so.

The idea was that the tapered mortise would press everything into the shape it needed to be in.

The other thing I did was every few seconds I rotated the dowel, so it did not get glued and stuck to the mortise permanently.

Here's what I wound up with:
Glue is set.
It's ugly, but if it works I will sand it clean and make it pretty again.
The good news is it seems to be working.
When I reassembled the chair, I put the offending broken tenon in a part of the chair that I thought would get the least stress: the front left with the dowel running side to side this time.

The fix seems to be holding. I've been sitting in it for a couple of days, and there were no problems until the other night. I was leaning sideways in the chair, and I heard a snap.

To my chagrin, I could see space in the crack across the grain, but the long grain part of the crack was still holding.
The crack.
 While the crack is outside of the mortise, the long grain glue up that is still holding is deep in the mortise. This seems to be enough that the chair is still holding up.
A bit of a closer view.
I think that this temporary fix will keep together until I get back to Germany next.

I have a couple of options:
  • I could just glue it again
  • saw it apart, and glue it up again with a floating tenon or a dowel. I think this is how I would fix an antique piece. Since this tenon is "bent," I'm not sure it's worth it. Although, I could scrap the current tenon, attach a new piece of wood and re-shape the tenon with the tenon cutter.
  • I could make a new stretcher - although I am pretty sure I do not have enough pear so it might be a contrasting species.
  • I am kind of leaning toward scrapping all of the wood for this chair and building a new one, recycling the leather from this chair.
What do you think? Take my survey, and I will go along with the majority:
Create your own user feedback survey

16 comments:

  1. I think the tenon cutter is a Red Herring. in addition to the other solution I left make another stretcher in a similar enough material given it's lack of visibility, you could also complete the break all the way and then epoxy or hide glue to fully repair.

    ReplyDelete
    Replies
    1. Hi Jeremy, Thanks for the suggestion.

      I think I wasn't clear on why the offset tenon was a real problem. I think it caused this break. Sometimes, it fits in the mortise perfectly, but if it is turned wrong, all the stress goes to two tiny points on the tenon.

      Delete
  2. I voted for making a complete new set of spindles of a different species of wood. But I can see that if you put the new stretcher on the back, few people will ever notice if it is of a different species anyway.
    Scrapping all the wooden parts seems a bit harsh to me.

    I am also a bit disappointed that you are not supposed to be plopping in a Roorkee.

    Brgds
    Jonas

    ReplyDelete
    Replies
    1. Well, I think plopping is ok if everything fits nice and tight. I've plopped in it plenty of times. Once to many, it would seem.

      Delete
  3. Not sure how you acess that survey thinghy, buti would simply make anew part, gluing back the broken parts, i dont think, would ever work long term

    Bob, siting on the ground with Rudy

    ReplyDelete
    Replies
    1. Hi Bob,

      Sorry you couldn't get to the survey. I just tried it with my iPad, and couldn't get to it either. It worked perfectly on my PC.

      Thanks for the advice, too bad I don't have much more pear.

      Delete
  4. If you bring the broken part with you to the DCBE we could try to find a piece of apple or something else, and you can turn a new piece on the lathe.
    Cheers
    Jonas

    ReplyDelete
  5. Hi Brian, I would not scrap the chair and settled on replacing the one piece with another species of wood. Your hard work on the rest of the chair is preserved and your "fix" is economical. By the way, I noticed that you did not offer an option to "Lose weight gained on delicious Spanish cuisine"...hmmmm. :-) Best Regards. John

    ReplyDelete
    Replies
    1. Hi John!

      I'll have to consider your suggestion...

      Delete
  6. If the chair becomes unusable, I'd try the floating tenon, then make a new stretcher even in another species when the tools and material are available. Sometimes a man's gotta plop. Btw, the survey works on an android tablet.

    ReplyDelete
    Replies
    1. Indeed, a man definitely has gotta plop. :o)

      I found a supply of broom handles for 1.20 Euro each. It sounds weird, but they are mango wood from Brazil, and have arrow-straight grain. I might have to think about this.

      Delete
  7. This comment has been removed by the author.

    ReplyDelete
  8. Brian,

    I'd make a new stretcher out of what ever wood you have on hand. That way the chair is back to its intended purpose. That said, this doesn't have to be the final permanent fix. The next time you come across some pear wood that is close to this in color, make another stretcher then.

    All the best,

    Jonathan

    ReplyDelete
    Replies
    1. Hi Jonathan,

      So far the stretcher hasn't collapsed yet, even though the glue on the crack broke. The glue holding the long-grain is doing it's job, and as long as I don't lean over or twist in the chair, it seems to be holding.

      As soon as it does break, I have scoped out some mango wood broom handles for 1 Euro 20 that will work just great, until I get a permanent fix, that is.

      Cheers!

      Delete
  9. oh man that's too bad!
    very nice fix here! If it can help ;-)
    http://www.workbenchdiary.com/2014/05/severed-tenon-repair-part-one-cone.html

    ReplyDelete