Wednesday, July 28, 2010

Growth - unlimited?

Once in a while I browse certain German websites, you know the ones I mean.

No, not those ones -- I mean sites with used woodworking machinery for sale. One thing I observe about German woodworking equipment in general is that it is beefy, to say the least. If the dictionary had an entry for "built like a brick sh*t house", a picture of a German woodworking machine would provide an excellent illustration.

More than just stoutness though (the same could be said in general for pre-WWII woodworking equipment produced in the US), the German equipment, by and large, is very well-made. They don't shirk when it comes to quality, at least when it comes to industrial-grade equipment. Sometimes though I come across stuff, that as some Australians I once knew used to say with some frequency, is over the top. I mean, even beyond the pale. Mind-blowing even.

Now I consider a 12" jointer to be a minimum size of sorts for the sort of work i tend to do, and a 16" or 20" would be preferred. And, the longer the infeed table the better, so long as it is well supported. This jointer in the picture below takes w i d e to a new level however with a working surface that is 860mm wide, nearly 35":

I'm trying to imagine how a human being is supposed to feed some 34" stick across the top of that unit, as no feeder is evident. That table looks to be 5~6" thick!

Then there's this one, where planer meets gargantua:

A 2-meter (6'+) wide planer with eight different motors, 4 dust collection ducts, weighing in at some 8000kg (17,600 lbs.). That's not a misprint folks- 8 tons for this machine. Apparently it is specially made for planing large glu-lams, though I imagine one could nearly put a family sedan though it.

Both machines are for sale, so if you're looking for a nice addition to your home shop...

Tuesday, July 27, 2010

Japanese Joinery Workshop 1

The first introductory workshop in Japanese joinery was held this past weekend - well, Saturday through Monday, and I thought I'd share a few images. I set up a couple of workbenches, and all of the participants seemed to enjoy working at them.

Me - I like my sawhorse of course as a work bench and did most of the demonstrating on that. I made the joints along with the students.

I briefly showed some sharpening techniques, which I normally do on the floor, and while one participant tried it later on for a couple of minutes, it appeared that there was not going to be a sudden conversion over to working on the floor. Sometimes I wonder how much of a barrier it is for Westerners to Japanese woodworking - the preference for working on the floor I mean? Of course, sharpening (and other wood work) can be done in other positions than sitting or kneeling, but there are certain advantages lost by standing. Chief among them intimacy with the work. And of course, if you're not used to squatting and kneeling, then it will feel awkward and even painful in short order. We are a civilization that spends huge amounts of time sitting in chairs, and the Japanese themselves are heading in that direction. Maybe Japanese woodworking would be an ideal fit for people who play catcher in baseball?

The participants came from as far afield as Indiana and Brooklyn, NY, and seemed to enjoy themselves. One participant allowed later that they thought I was going to be intense and severe, and were pleasantly surprised to find I am not. Me? Intense? Severe? Now, how did that impression come across I wonder? Is that what I convey?

Yah sure, intense I can be, but, well, I don't think I'm all that severe now that my 20's and 30's are well behind me :^) I only screamed once or twice during the entire course (just kidding).

Unlike previous workshops I have taught, I decided not to overload everyone with information and workload and to not push them to try and complete everything in a massive hurry (all because I had, in the past, unreasonable ideas about what could get done). This time I opted to let the students drive the pace more. I came ready to teach 3 joints per day and the completion rate ended up being 1 joint per day, and that was fine.

Here's the other Chris looking deep in thought:

Raphael diggin' into the material:

Here's Kane with the product of the second day in the course, a mitered half lap and a post joining on top with a stepped tenon:

Matt working on a tenon:

Chris looking to saw to the line:

Day 3 involved the construction of a joint called tōshi chigai hozo-zashi hana-sen shiguchi, a pair of crossing beams with half lap tenons and crosswise wedging attached to a post:

Chris using his homemade plane:

And Raphael refining the fit with one of the half tenons:

I'm looking forward to the 5-day joinery class coming up in August. It was a pleasure meeting Chris, Kane, Raphael and Matt this past weekend and I wish them well in their journey and hopefully we'll cross paths again.

Friday, July 23, 2010

Fan of the Fan (II)

In part I of this thread, I looked at one of the geometrical problems inherent with fan rafters, that is the fundamental disparity between placing the rafter in a good alignment with both the view of the underside of the eave and the edge of the eave being taken into consideration. As I mentioned, the circle and the square don't get along so well in that instance.

Today I will explore another angle to the problem. Heh! - that's a pun, and will make more sense when I'm done with this posting. Consider the following picture, which shows a simple (-looking) example of a fanned rafter - two in fact, one to either side of a common rafter:

The above model is the current Level 2 carpentry exam in Japan. I did this model about 5 years back to familiarize myself with the exam material and learn some fun new stuff, and I wrote an article about it.

Here's another view, from the perspective of someone looking more or less directly up at the eave edge:

This model served as the focus for an article, the third in a series on Japanese compound joinery, that I submitted to Timber Framing Journal. This was several years back. Interestingly, after my first two articles, it was the submission of the 3rd one which prompted the editor of that journal to write back to me expressing his belief that the problem above was, in his view, not a compound joinery problem. He thought it was just a simple case of mitering the 'fan' rafters to fit against the common. He didn't get it, in other words, and I suspect that if the editor of a technical journal on Timber Frame carpentry didn't get it, there may well be quite a few others out there who would respond similarly. So, it looks simple enough -what's the big deal with the above model? Today, I'll explain that matter more thoroughly, as here on my blog I can take as much space and time as I like for such things.

What the editor of the Journal was envisioning, I do believe, was a case in which the two rafters at the side of the common are simply mitered and attached to that common. Here's that scenario:

These stick could be 2x4's, for example, and I have placed the three on a flat surface so they are all normal to one another.

In the next picture I have put them together as a group:

I'm sure for more readers the assembled view is exactly what on would expect - no fancy shmancy compound anything going on.

Next, I'll place the assembly at a slope and put in onto a wall beam (plate):

This may not look too much different than the model I showed in the first few pictures. However, when I bring a framing square in and place it plumb to one of those fanned rafters, in orientation to the long axis of the plate, this is what you see:

The rafter is rotated over on its side, unlike the common, which has sides that are plumb.

How about a look at how this arrangement fits against the plate? If we take a glance from below, you can see that I've placed a horizontal line along the intersection of the lower surface of the rafters with the front face of the plate:

The fan rafter's lower surface is in plane with the common rafters lower surface, that should be clear. Similarly, if I place a flat surface on top of the rafters, in simulation of the roof decking, here's what you get:

Thus, the upper and lower surfaces are in plane with the common, but not the sides. Now, unlike the model which has a covering board fitted, if I want to have exposed rafter tips, I would have to bring the ends of the rafters into the same cutting plane with one another. In the next picture I have done that and added some skinny rectangles to the rafter tips so we may more easily compare their alignment:

There is some skewing due to the perspective view in the drawing, but I can assure you that the vertical alignments of those three rafter tips are in complete parallelism. That's great!

if I now consider the view looking up at the rafters from below, the rotation of the side faces of the two fan rafters is very apparent:

So, a simple fanning of regular square-section timbers produces an arrangement with rafters in plane with one another in one orientation but not the other. Also, the notch on the plate to receive the rafters would have sidewalls that are not perpendicular to the long axis of the stick. Less than ideal.

What if we fanned the rafters so that the fanned rafters keep their sides plumb? The would look like this:

The result of that is that our fan rafters no longer meet the common rafter cleanly:

A close up of the interface between the lower surface of the rafter and the view of the front of the plate reveals that though the sides of the rafter are plumb, now the lower surface is rotated out of alignment with the common:

And, since the stick is square in section, what goes for the bottom surface of the stick also goes for the top:

You can see in the above picture that a portion of each fanned rafter sticks out above the plane of the roofing boards, which would obviously make for a lousy fit between those boards and the rafters. The notches on the plate to receive the rafters would have sidewalls perpendicular to the long axis of the plate, but the lower surface of the notch would be askew. Not so great - like the previous example, with the sides of the fan rafters rotated to match the common, you lose something else in the bargain.

Let's look at that Level II model again - here's the orientation of the side walls of the fan rafters to the plate and common:

And now let's look at the top surfaces and their alignment:

How is this possible? The trick my friends is that the fan rafters are not square in section, but are parallelogram-shaped in section. That's the nature of the compound joinery in this situation. Because the fan rafters flare out from the common, and the whole affair is tilted up at a slope, you end up with a compound slope. The behavior of wood in compound slopes, I have found, is counter-intuitive for many folks, if not baffling altogether.

Consider then the behavior of the cluster of rafters that make up an eave with several fanning rafters - each radiates out a different amount away from the common rafter, and thus each has a different slope than the common rafter. As each fan rafter progresses away from the common and towards the hip, the slope of each rafter becomes a bit slacker than the one before it. After all, if you brought a fan rafter all the way over to be in alignment to the hip rafter, it would have the same slope as that hip rafter. Hip rafters, of course, have a lower slope than a common rafter because their run is much longer than the common while their height is the same as the common.

And each fan rafter, having a different effective slope has a different degree of parallelogram-ism (if i might take the liberty of inventing a word) from the next. The common has no parallelogram-ism, the next adjacent fan rafter has a slight amount, the next even more, and so on. The fan rafters are differentially parallelogram. There are not something you cut in a batch.

Wait! there's more! If you also curve the hip rafter itself upwards in fan-raftered roof, the hip will also carry the roof surface upwards as it curves. The fan rafters have to follow that curve, and as they are not attached to the hip, they can't exactly go along for the ride. That means that as the curve increases as you move along the eave edge towards the hip, each fan rafter must curve a little bit more than its preceding neighbor. Therefore, not only are the fan rafters individually shaped in cross-section, but in curvature as well. AND, with all this, one has to solve the issue of how to distribute them around the fan so that have a pleasing appearance at the eave edge and from the view directly underneath. AND, on has to also take into account the view of the rafter tips and how that would change, when viewing the eave's edge from out in the yard, as they rafters fan more and more over to the hip. Each tip needs to be cut differently, in both axes, regardless of whether the tips are exposed to view of hidden behind a covering board.

Yes, there's a lot going on with fan rafters. In the next post I'll take a look at some of the methods for solving the distribution problem, and compare them. I also intend to take a look at the difference between Chinese and Japanese approaches to fan rafters. Stay tuned.

Thanks for coming by and comments always welcome. Let's go to post III

Thursday, July 22, 2010

Fan of the fan

The Japanese term for fanning, or radially-arranged rafters is ōgi-daruki (扇垂木). The latter two characters, '垂木' read taruki/~daruki literally means drooping tree/wood, a reference to rafters. The first kanji of that compound, '', is a straightforward one to describe, so why not?

An earlier form of it looks like this:

Forming a frame around the left and top is '', which is a pictograph of a single [swinging] door. That element, or radical as it is termed, is in fact the left half of the character with the meaning of door/gate, namely '' (read: 'mon'). This character is therefore about something which is like a door in some way.

The two side-by-side elements enclosed within the character, '', is an independent character of its own, and stems from a pictograph of a bird's wings. Here's an even earlier version of that character so you can see, perhaps, how the modern form derived:

So, '' is feather/wing/plumage, and combining it with door, '', you get '', which means a feathered door. Well, not quite - I jest. It means: (folding) fan, the panels of which fold into each other when closed. I guess the early Chinese saw the folding fan as analogous structures to bird wings, which are door like panels unfurled from the body. Fair enough, that makes sense.

The rafters which fan around the corners do look much like a hand-held fan:

Now, fanning rafters arranged radially around a circular wall plan are fairly simple to do, as each rafter is the same as the next, and spacing them is a straightforward matter of dividing the circumference of the wall plate into even increments to locate the rafters upon, or placing the rafters in a constant angular relation to one another, say, one rafter every 5˚ or something along those lines. The biggest problem in such situations relates to forming a curved wall plate and purlins (if any), bridging between rafters, and tying the rafters together at the roof's apex in some decently clean manner. That's not a topic of consideration in this post.

When you want to place fanning rafters at the the corner of a polygonal (3, 4, 5, 6, 7, 8 sides or more) building however, you enter a world of confusion, pain and hurt, for the circle and the square, as it were, do not always cooperate. This may not be apparent at first inspection, so in today's blog I want to explore this matter in some detail and consider also why, despite the difficulties, fan raftering might be a good idea. This is an involved topic, so I expect this to spill over into another post or two.

The circle and the square...actually, let's simplify that a bit. With most buildings we are dealing with squares or rectangles and the walls meet at 90˚ angles and the hip rafters are regular, that is, at a 45˚ relative to the wall plan. What happens on one side of a hip is the same as what happens on the other side, so we only need to look at one 45˚ section, not an entire square, and instead of a full circle, only that section of circle which sweeps through 45˚. Here's what I mean:

If you click on the picture it will enlarge and you should be able to see the scribbles more clearly.

Next, I'll cut out the extraneous detail, including the wall outline and focus in on that 45˚ slice of the roof plan we are considering:

The roof terminates at the eave edge, so that forms the boundary for the triangle at which we are going to look. A 1:1 ratio produces the 45˚ angle for the hip rafter, and the length of the hip rafter in plan, by Pythagorus's well-known method, is √2 times the side.

Now, let's deal with the simplest case of placing a fan rafter, where we wish to place one rafter in the middle of our 45˚ section. One apparently obvious way to do that would be to bisect the 45˚ so as to produce two 22.5˚ angles, and that line is then the centerline of our fan rafter:

While that divided our 45˚ pie wedge into two perfectly equal slices of 22.5˚ each, take a look at what happened along the eave edge. By measurement, we find that the run of 1 unit there has been divided into two subsections, one measuring 0.4142136... and the other measuring 0.585 or so. Those sections are not symmetrical at all. This means that if we were looking at the building eave from below, while the division of the rafters would look just fine, but if we instead viewed the edge of the roof from out in the yard, that fan rafter tip would not be even remotely centered between the adjacent common rafter and the hip. That's no good - looks like a hack job.

Let's do it the other way then - we'll divide the side length of 1 into two equal portions of 0.5 each and connect a line from the origin to that point:

While that now gives us a rafter tip perfectly centered between the common rafter and the hip, if we stood under the eave and looked up at the rafters, we would see that the two pie wedges to which our 45˚ has been divided are hardly equal at all - one is 26.565˚ or so, and the other 18.434˚ or so. That looks ungainly.

So that's the nub of the problem right there folks. The circle and the square are not getting along so well. What divides a given arc evenly does not do so in a right triangle, and vice versa.

Consider the above problem again: if one has, say, a 10/10 triangle forming a 45˚, one might jump to the conclusion that if we want a triangle with half as much rise, ie., a 5/10, then we would simply divide the 45˚ in half to make 22.5˚ and that would be the same thing. But it isn't so.

Let's check that with the calculator:

5 divided by 10 gives us 0.5; use the arc-tan ('2nd' + TAN) to find the angle value: 26.565...˚.

The trick to fan rafters lies in determining a method of placing them so that both the view from below (of the 'pie wedges') and the end-wise view of the eave edge out in the yard both produce even patterns. This is actually impossible to do perfectly, so we have to find a method that gets us closest. This entire issue, by the way, is analogous to that of constructing a world map (or any other map) - when trying to represent a circle (the globe) on a flat rectangle with square corners (like most maps) there is going to be some distortion no matter how you, er, slice it. Some maps distort the size of the continents, some distort the poles, etc. I imagine there are similar problems in the world of optics too.

So there we have the first few tentative steps into the swamp of the fan rafters. I hope you'll return to see what other alligators we can wrestle with in part II of this thread.

Wednesday, July 21, 2010

This One Rings a Bell (2)

I realized the other day that a bell tower is not something one comes across too often in North America, and while I could think of a couple of examples of the top, I was curious to find out how many shōrō there might be out there. It is interesting to see what company the tower I will design and build might keep.

The first bell tower that came to my mind is the Korean Friendship bell in San Pedro near L.A. California. I know this one rather well as I have stayed at the youth hostel just above it on the hill on a couple of occasions. I think this Korean structure is by far the most grand example of a bell tower in North America:

It's worth another picture:

Please click on the above two photos and you will see they are large files with more detail to be seen.

This tower is of the same basic type as found at Tōdaiji in Nara Japan, in that is is open on all sides and has the flanking posts, but the structural details are different in numerous respects to the one in Nara. None of the posts are splayed and it has very deep eaves in relation to the base, the eaves having a pronounced curve. It employs the classic Chinese pattern of round base rafters surmounted by rectilinear flying rafters, both tiers fanned. We'll compare Chinese and Japanese approaches to fan rafters in a future post.

The other example which came readily to mind was the bell tower at the University of British Columbia in Canada. This is one that I have never seen in person though I have lived not too far from it on several occasions:

A winter shot of the same tower:

The tower looks a bit over-sized for the bell to my eyes, but I like the structural design with the boat-shaped bracket arms, funa-hijiki, along with arched upper support beam, and the minimal carving.

Another tower which I had seen a picture of and have not visited is in Duluth Minnesota. It is the Ohara Bell:

Curiously, the nuki, or penetrating tie beams, have been oriented plumb when they are normally placed in slope with the splayed posts. The rafter spacing is also a bit out of whack - observe the rhythm of the rafter tips and see how it is too crowded an interval next to the hip rafter. I suspect this tower was not built by a Japanese carpenter or by someone especially familiar with Japanese carpentry, though it looks tidy overall. The hipped roof is a less common roof form for these towers.

The bell in the Duluth tower is a replica of one with an intriguing story behind it, and is the subject of a 2008 film. The trailer on that site is worth a view.

At the United Nations in NY there is a beautiful shōrō, called the Japanese Peace Bell and installed in 1954:

The post splay is more pronounced on this one than on most others of its type - the 4-legged or yotsu-ashi (四足) type. Another hip roofed version, with the copper shingles having achieved a lovely verdigris close to 60 years on.

In Seattle WA there is a nice bell tower with an irimoya roof, the Kobe Friendship Bell, presented to the city in 1962:

The roof is lovely, and this is of the flanking post variety, designed by an architect in Japan, not a carpenter. The posts have no splay, which is a design shortcoming in my view. The continuous granite sill is unusual. The copper shingled roof is very similar in appearance to the one I will be making. Here's a page with some more detailed background information on this bell.

Here's a bell tower located in Des Moines Iowa:

Called the Bell of Peace and Friendship, this bell is a 1962 gift from Des Moines sister city of Yamanishi - a return for Des Moines gift of hogs to that city some time earlier. Another interesting story there! It's currently in need of restoration work and a funding drive is underway.

Another flanking post type of bell tower can be found in on the West Coast:

This is the 'Bell of Dana', a part of the Nishi-Hongwanji complex in Los Angeles. It was installed in the late 1970's. Here's another view of this gable roofed structure:

The posts are minimally splayed if at all, and the under eave is rather bereft of architectural detail. The corner posts are exceptionally large. It's chunky overall.

One example of a small shōrō is located in the Montréal Botanical Garden in Quebec:

The bell was given to the city by Hiroshima in 1988. Here's another angle:

Like the one at UBC, the structure is too large in relation to the size of the bell. it sorta has the flanking posts, though the structural system is not particularly sophisticated. A western carpentry approach to a Japanese structure for sure.

One last one - this is a bell tower located in Oakridge Tennessee:

The International Friendship Bell structure is obviously not a Japanese design at all, but the bell is from Japan, and like many of the others mentioned in this post, was a gift to the city. Yet another complex story with a lengthy chronology - quite controversial in fact, given the significance of the location in regards to WWII. Here's a view from the side:

I'll hold off on making comments about the architecture in this case. It's outside my area of interest, I'll say that.

That about covers the more notable bell towers located in North America I do believe. If I missed any that you consider significant, please let me know. I'm always interested to discover more examples.

Thanks for dropping by the Carpentry Way on your journey today. Comments always welcome.

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This One Rings a Bell

Following up from some recent postings on the subject of Japanese bell towers, or shōrō, I'd now like to introduce the subect of about a gajillion posts to come: the design and construction of an actual Japanese bell tower. I could have equally titled this thread "Saved by the Bell", as I had been wondering if the opportunity to build a purely Japanese traditional structure would ever come my way. And it has in a big way - I have become engaged in the drawing process in the past few weeks and it looks very much like the project will take up a good chunk of a year's time to follow. It was a long wait for a job of this awesomeness to come along, but definitely worth it.

Sometimes I need to pinch myself to check that this isn't some sort of dream that I will wake up from. The client has commited funds and he is serious. So, onward we go.

Usually one might expect some compromises in doing any larger structures of a Japanese flavor out here in North America. The residential architecture is a loose fit at best since not many of us live on the floor, so to speak, and few of us in the colder climatic regions would be content in the archetypal Japanese uninsulated house with thin walls, huddling by the kerosene stove in the winter, so adapting the useful and paring off or modifying the rest is the order of the day in most parts of the continent. Almost everything of this sort, save for the odd detached tea house, is a product of compromise and of varying design success.

A bell tower is another kettle of fish altogether. Here is the opportunity to build a purely Japanese traditional temple structure without trying to adapt it to Western lifestyle or needs. There are no plastered walls, in most cases, so most of the structure is exposed to view. It's a unique building designed with a definite functional purpose in mind, and yet one with a large range of aesthetic and structural possibilities. Very intriguing.

This is a really exciting opportunity for me, and one for which I feel I am feeling very well prepared after my extensive study/exploration of Japanese roof carpentry as well as splayed post structures of various kinds over the past dozen years. This bell tower is for a temple garden complex in Southern California. I'll be doing the design and cut out here in New England and, when it is done, plan on taking it all out to the west coast to assemble the structure to completion.

The bell has been cast and is currently being packed for shipment. It weighs 2600 lbs., about 6' tall and with a 46" mouth. Here's a picture:

This is a serious bell. It's not kidding around at all.

I've been drawing the support structure for the past few weeks and have just started in on the roof design. I'd like to share a few pictures to start off this thread, though the design will undoubtedly evolve over the coming weeks and months.

I've looked at hundreds and hundreds of different bell towers and, in consultation with the client, narrowed down to a tower deriving from the early form of open-framed tower first seen at Tōdaiji - the type with the flanking posts at each corner. I've looked at many examples of this type as well, and compared structural systems, which can vary quite a bit. There is no standard form really when you get down to brass tacks.

My design employs cylindrical corner posts with rectilinear flanking posts:

Here's another view:

In the middle of the run of two beams you can see a strut, termed a 'bottle-neck' strut. I'll be talking more about those later. The raftering will be of the fanning variety, and the roof will be curvilinear. In the above two drawings the straight hips and commons are only in place provisionally as part of a method of determining eave projection. The curved parts will be created on separate drawings and added in shortly. At this point the eave depth looks to be a little over 5' (160 cm).

The roof will be a hipped gable, or irimoya, and I will be using the hidden roof/decorative roof system, along with concealed cantilevers inside the roof. A drop ceiling will conceal the interior of the roof from being seen from below.

If one could combine into one project some of the most difficult technical layout issues in Japanese carpentry practice, it would be a bell tower like this one. It's a big challenge for me, and certainly the most complex structure I've designed. What makes it so difficult? Well, consider some of the features inherent in the design:

- the corner posts are regular compound splayed, cylindrical with piercing tie beams
- the flanking posts are irregular compound splayed, with piercing tie beams
- the visible hip rafters are regular in plan and curved
- the hidden hip rafters are irregular in plan and curved
- the perimeter fascia is comprised of four levels, completely curved with no flat sections, shaped to compensate for visual foreshortening, and features the infamous 'fuki-ji' problem (more on that when the time comes)
- the fan rafters are unique in length and cross section at each position, are also individually uniquely rhomboid in cross section and differentially curvilinear
- there will be use of compound-angled through splines in several locations in the roof structure
- the interior roof cantilevers are compound fanned and rhomboid in section
- the gable roof end will be curvilinear and has the minoko feature
- there are to be several carved elements, including but not limited to the bottle-neck struts, pillow blocks, bracket arms, barge boards, gable pendant (gegyo) and beam ends, etc.

The wood for much of this, by the way is Yellow Cedar coming from Alaska. One of my favorite woods to play with. I'm hoping to use a fair amount of Black Locust on some of the hidden roof components, depending upon whether I can find good material. The roof is to be shingled in copper, a task which I will also be undertaking.

There's a lot to occupy my mind on this project that's for sure and I'm looking forward to the fun. There's so much to explore, learn and share and I hope you'll come back to follow the thread. I will occasionally be blogging on other topics in upcoming months, but this bell tower will be the focus.

As John Donne said, Ask not for whom the bell tolls. The bell tolls for thee.

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