Wednesday, October 17, 2012

Mizuya Build (1)

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I've been working on the design for the mizuya and considering various options. With so many options, sometimes it can take a while to get mental traction with a direction in which to head. I took a look again at my Chinese Classical furniture texts and magazine and found several excellent examples of cabinet forms that would work, with some tweaking. They gave me what you might call hunches about hutches. I've also looked at Korean traditional chests, which share attributes with both Japanese and Chinese examples.

At this point I am leaning towards frame and panel construction for this piece, if for no other reason than it allows for a more pure form of joinery, as, unlike joined carcase construction, the connections need not be reliant upon glue. In fact, insofar as possible, I will build this piece without any glue. Regular readers of this blog will I'm sure have a good handle on some of my reasons for minimizing the use of glue, so I'm not going to take another stroll down that lane at the moment. I do however have more to say on the matter and I was feeling a certain sense of validation though during a recent re-read of an article Bruce Hoadley wrote for Fine Woodworking, back in the day when it was worth buying. In issue #21 (March/April 1980), Hoadley wrote an article on why dowel joints tend to fail and proposed a solution involving elastomers. While I have zero interest in dowels or elastomers, I noted the following comment from Hoadley when he compared the performance of oak dowel joints held together with PVA (white) glue:

Predictably, with fairly thick elastomer layers...the joints are able to withstand severe moisture cycles (6%-24%-6% MC) without losing withdrawal strength. The same cycle destroys a standard PVA joint. For example, in oak joints with white glue, it took an average of 1,100 lb. to pull apart un-cycled joints. But after a 6%-24%-6%moisture cycle the average withdrawal resistance was only 41 lb.

It's a shocking difference in performance to see how much weaker a glued joint can be after being subjected one round of moisture cycling - at least when using regular woodworker's PVA adhesive. A change from 1100 lbs. to 41 lbs. is a 96.3% decrease.

Hoadley's empirical observation suggests that one thing missing from the 'tests' one sees every few years in the woodwork magazines, where they compare the strength of various forms of joinery, is that they do not examine the performance of the joints after moisture cycling. Therefore these tests appear to be of dubious real-world value. Unless you live in one of those places where the humidity level doesn't change much during the year, and are sure that all the furniture you make will remain in such an area, the issue of moisture cycling and its effect upon the material and the connections is something to which you need to pay attention and an in-service factor which your designs ought to reflect. Yes, that was a value judgment!

Now it is true that many modern adhesives, like epoxy, form bonds stronger than the wood itself, and that joints with decent amounts of glue surface area are typically strongest of all joints. Examining the results of destruction testing though, in most cases we see that the glue bond holds well and that the surrounding wood shreds and blows apart. However, it begs the question: if the connection is to fail, do you want it to fail in such a manner? Once the joint has failed, what about repairing it?

It's like the power take-off (PTO) winch on my Toyota LandCruiser. Driven by the engine, the winch can pull some serious weight, however the engineers who designed it thought through what usage the system might see, and wisely placed a shear pin in the system that will give way if the load becomes too high while winching. This allows a $5 part to fail instead of something more catastrophic occurring. The system is only as strong as the weakest link, and ideally the weakest link is adequate for most tasks and is inexpensive to repair and easy to repair. This aspect attributes to mortise and tenon joinery, and makes it durable, resilient, and more easily repaired down the line. And if glue is needed, as it surely is when edge joining boards to make a panel etc., it makes more sense to me to use a glue that is reversible, like hide glue or fish glue, etc. If you're designing with repair-ability in mind, you're not designing to make pieces last, and that means you're not respecting the material you work with. Quality construction generally starts with quality materials, and quality materials are generally less abundant and took longer for nature to produce, so they must be used wisely and in a sustainable manner. 'Sustainable' is just another marketing term these days it would seem, however for me it means that if the tree grew for 150 years, than anything made from that tree should have a designed lifespan of at least 150 years, and be recyclable/re-purposable if at all possible.

Another reason I'm trying to design glue-less, bolt-less connections for this piece is that I am leaning towards using Cocobolo (dalbergia retusa) for the frame components. The finest classical Chinese Ming furniture was typically made of one of two very hard highly-polishable hardwoods, huanghuali or Zitan. Neither of these woods is available, practically speaking, however huanghuali is a rosewood, dalbergia odorifera, and it seems to me that another rosewood would be a fair substitution. Generally the rosewood available today is on the small size, and most species, due to over-harvesting, are now banned for trade altogether. One rosewood still available, though not in what you might call abundance, is Cocobolo. I managed to locate a stash of it several months back in Tulsa, Oklahoma of all places - this material that was imported into the US in the 1960's and has been drying for 50 years now. So I have stumbled into a modest pile of it, some sticks of which are quite large chunks indeed. Cocobolo is an oily wood which is tricky to glue and finish, and that suggests to me that the 'best' way to use it would be without glue. It's best to avoid the conflict and downstream problems of failed glue joints if at all possible.

'Wide panels' and 'cocobolo' are two things that don't really go together. While one could glue up narrower boards into wide panels, there is the aforementioned glue problem. I know there are ways to overcome that challenge, however I would prefer if at all possible to use wood of sufficient width to make a panel without recourse to glue-up, or making an overly-busy frame with many dividing bars to accommodate individual slender panels. So, at this point I'm thinking that the panels in this piece will be bubinga, which is readily available in wide pieces.

At this point the mizuya is being designed around a cocobolo frame and bubinga panel system, however this is early days yet and the deisgn is by no means hardened into final form. This is the sketch as it sits now:


The drawers are about the only storage arrangement I have settled on so far. The very top section will have sliding doors.

Here's a view of the back, where I have positioned a wide board, double-tenoned into the post at each end:


The drawer dividers connect to the back board with multiple mortise and tenon joints and should impart decent shear resistance to the entire cabinet. I anticipate taking further steps in that direction of structural bracing yet. At this point the rear panels are obviously too wide, and will be vertically divided. I haven't set the location for those vertical divisions yet, as they relate to the arrangement of sliding doors and drawers on the front. The rear frame and panel backpieces will be made so as to be demountable, just as I did in a bookcase build several months back.

All for today - the design work rolls onward into places unknown. Thanks for your visit. On to post 2

8 comments:

  1. Yeah! another build thread. I'm watching closely.

    I build so many things at work made of veneers and held together with glue and dowels, that when I make things of my own, I'm ready to use "real" constructions. So far, I'm not at the level of using some to the joinery you showcase but I try to use joints that are dismountable and mechanical. Right now I'm making bunk beds with mortise and tenons secured with a healthy pin of white oak.

    Peace,
    Harlan Barnhart

    ReplyDelete
    Replies
    1. Harlan,

      good to hear from you and your comment is appreciated. Keep up the good work.

      ~C

      Delete
  2. Chris,
    I don't recall you mentioning it previously, but you might reference Yi-dynasty Korean furniture, if you haven't much before. Some of the design refinement is of a higher order than Japanese work, and subtlety wasn't lost in their approach either. If you are looking for challenging construction as well, some of the pieces exhibit it. Perhaps some inspiration can be gleaned from the work for yourself.

    Good luck with your project.

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  3. Dennis,

    thanks for the comment and suggestion. I've looked at some Korean chests in the book Asian Furniture, and as far as I know there is only one other reference on Korean furniture which is a book of the same title. I don't have it on my shelf. What I did notice on the Korean chests was that the chests are held off the floor on legs, and the legs are connected to one another on the short sides by runners/sills. It would make the pieces easier to slide about and is an interested in position between the Chinese pieces on legs and the Japanese pieces on sills. Otherwise they look much like Chinese pieces.

    Do you know of a good book on the topic of Korean furniture I could take a look at? Where have you seen them?

    ~C

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  4. There was a good book on Bandai on Ebay a while back, might try there....
    Bandai were probably the precursor the tansu form more so than the chinese cabinet style.
    If your cabinet is ever going to cycle thru 24% MC ( submerged in water) what you glued it together with is the last of your problems. This is the reason PVA's are not used outdoors. I wonder how the action, er, non-action of the drawers will be... Even joints that are pegged in some fashion can become loose over time after repeated cycling as the surrounding tissue gets compressed when it shrinks around the peg. Bruce Hoadly also pointed out in his book, Understanding Wood, that a kerfed, glued pegged was most effective. Though I think most all this matter is not practicle since the MC really stays within a 6% window in most parts of the US, unless you plan on putting the cabinet on the porch and leaving it there for some time with rain splashing on it.
    The design your contemplationg I assure you needs no extra sheer. There is so much strength in that many M&T joints that the resulting frame is rigid as all get out. I have a piece I built almost ten years ago and it is still stiff as a...... any way. Though I did peg the major mortises, I have not since.
    So what's your " no Glue" drawer going to be?
    Correy

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  5. Correy,

    thanks for your comment.

    Yeah, definitely the case that it is hard to get around using glue for drawer construction, though it could be done with sliding dovetails for the most part, and I am considering that.

    You know, for me the goal of using little or no glue is a matter of having ideals and trying to meet a challenge that counts the most. The Chinese pieces I admire used no glue or just lacquer to reinforce the mechanical connections, and I admire that. Many pieces were fully demountable to boot. If I can achieve a construction in which most connections are left without glue, and just a few parts have to be glued, it's not as if that is some sort of 'hang my head in shame, or 'why-bother?' result. I'm not going to let perfection be the enemy of the good, if you follow.

    Your comment that, "I think most all this matter is not practicle since the MC really stays within a 6% window in most parts of the US" appears to be an attempt to minimize the issue. Sure, some places are like that. Here in the Northeast, as you may remember, things are not quite so friendly in terms of humidity swings. As Hoadley put it succinctly in his article:

    "The humidity variation in typical indoor situations is wide. In Northern states, humidity in the 80% to 90% range may prevail through August and September, only to plummet to 15% to 20% relative humidity in the subzero days of January and February. This may cause the average equilibrium moisture content of wood to cycle from as low as 4% in winter to as high as 15% in summer. Even great extremes occur in such areas as basement rooms, with condensation dampness in the summer and a nearby furnace causing excess dryness in winter."

    Hoadley is citing a typical 11% moisture swing, not 6%. I work in the northeast, and my client base is mostly in the northeast, so I have to build in respect to reality on the ground here. Regardless, I'd rather design and build a piece to perform in conditions a little worse than what might be reasonably expected. I think that is one key to longevity.

    Hoadley's tests cycled to extremes, particularly on the high MC end, so he could see the results in weeks and months instead of waiting years. He accurately described it as a "severe moisture cycle". Regardless, anyone who's repaired furniture knows that is doesn't take that many years for a doweled joint to fail, and the curbsides are littered with countless doweled furniture pieces as 'free', pieces which have come apart from moisture cycling and use. And they're not that old.

    Finally, while a pegged or wedged joint can experience loosening for the very reasons you describe, in most cases they are easily tightened up. Larger pegs can be fitted, thicker wedges, etc. You can disassemble the piece and get at the affected surfaces. And while there are repairs that can be made to some types of glued joints, especially those that employ reversible glues, the work is often more problematic. And, it must be said that a pegged or wedged joint that comes loose is still going to hold together in most cases, unlike some types of glued joints which can fail catastrophically, as anyone who's ever sat in a doweled chair which gave way when sat upon can testify.

    ~C

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  6. Chris,

    i suggested Korean furniture because your drawing reminds of the book cases. Some were quite elegant in a simplistic way. I particularly like the more challenging way of doing the top, where the stiles and rails are tenoned together with a sloping shoulder that meets in the corner, and the top is paneled in. The name of the joint escapes me, but you probably know.

    I met Ed Wright, once. After his untimely death, his fine collection of Korean furniture was bequeathed to the University of Minnesota. I recommend his book. http://www.amazon.com/Korean-Furniture-Edward-Reynolds-Wright/dp/0870116525

    It is interesting about the feet or lack of on Asian furniture, the different arrangements. With Korean furniture, the floor heating system was often a factor in the designs. The woodwork could be meant to be moved around as well, similar to some times of Japanese furniture, and unlike Chinese furniture, which I believe was viewed as mostly intended for a specific permanent location.

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  7. Dennis,

    many thanks for the reply. I have thumbed through that book you mentioned some years ago. I think the sled/feet on the korean chests would certainly make it easier to slide them around. My impression is that they weren't made as light, portable and movable as most Japanese pieces. They really do seem to sit right in between the Chinese and Japanese ways of making. I find most of the Korean pieces I've looked at a little busy-looking. And where are the Korean beds and chairs? I'm thinking they must have lived on the floor like the Japanese(?).

    As for the mitered frame/style connection, I am mulling over whether to use that sort of joinery or not. There are so many ways this design could go!

    ~C

    ReplyDelete

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