Tuesday, November 30, 2010

X Marks the Spot (IV)

This is the 4th post in a series describing a French carpentry drawing approach to solving a carpentry problem involving two crossed sticks. It's just a couple of sticks, how hard can it be? heh-heh!

For previous installments please refer to the archive at the right of the page.

Where we last left off I had walked you all through the steps required to draw the cross section of the stick on the floor. By simply swinging an arc down from the hypotenuse of the triangle which gives the slope of the stick, we were able to locate the end point of that square cross-section on the ground. From there we drew the rest of the square by simply projecting lines up that we 90˚ to one another. If you're feeling fuzzy about that detail, I suggest you read the previous post one more time.

Onward: now that we have the red cross-section in place on the floor, we can use it to draw a few other things. First up, we'll draw the lines for the other arrises of the stick upon the slope triangle. To do that, we start by taking the other corner points of the cross-section slice, our red square, and project from those points back to the baseline of the slope triangle, and from there, swing lines back up to the line which represents the cross section plane, like so:

Notice how these two lines are simply like return 'bounces' from the initial arc we swung down. It's just like a harmless game of tennis this drawing stuff.

Since the cross section is oriented in perfect alignment with the axis of the stick, both of those corners are on the exact same line - the centerline of the stick. So the middle line being swung up in the drawing in fact is representing two points which happen to be overlapping one another. If the cross section square was rotated a little one way or another, we would not have these lines overlapping and thus there would be 4 separate lines and arcs in play. We can save that kind of fun for another day.

Noting now the two red circles marked where our new arcs ran into the line representing the cross-section, we now project new lines from those red marks parallel to the hypotenuse of the slope triangle. Since the hypotenuse of the slope triangle is the same as the top-side arris of the stick, what we are drawing here are the other arrises of the stick:

Notice how those two new lines, parallel to the hypotenuse, meet the run of the triangle. Since that line giving the run is in fact the ground, the intersection of these two new lines with the run line is where the other arrises on the stick are meeting the ground.

Next, I'll transfer the lines from their intersections with the run line across, in a 90˚ orientation to the run, and at the same time extend lines down from the cross section. These lines are parallel to the axis of the stick, that is to say parallel with the run of the slope triangle. The meeting points are shown in the following drawing by the four red circles:

Those four red circles can now be connected:

What do we have there? It's the footprint of the stick on the ground. What we need now are some trumpets. Notice what has happened to our square cross-section (in red) when the slice across the stick is a horizontal one, not square. One of the diagonals of that cross section square has stretched some in the footprint.

Now, lest we neglect the upper end of the stick, we can now pencil in the lines for the cut on the top of the stick, which, if you recall, was done so as to make the top of the stick parallel with the ground (the same as the cut on the foot). So, it is a simple matter to extend a line parallel to the ground, which is our run line, and extend the other arris lines to meet it:

Next, we can do the same process we just went through, and transfer the points defining the top of the stick back down:

Continue these projections downward, and at the same time just as we did before, extend the lines from the cross-section view up to meet them. Where they meet will define 4 points of intersection, as it did with the foot, and we will produce now the view of the top of the stick, in white, sliced on the horizontal:

Pulling back to look at the big picture for a moment, what we have now drawn on the plan is a depiction of the stick, at slope, viewed from straight above:

In case your head is swimming at this point, or you feel a need to blink a lot or go for a walk, I'll put the 3D piece of wood back into the drawing and you can see how our 2D plan just completed nicely defines the various points of the 3D piece:

Since the stick was sitting right on the ground, in the next drawing I've moved it up a bit so you can confirm that all the points from the 2D are coinciding with the 3D stick:

And if I were to flip the stick over on it's side, much as we did a couple of posts back with the light brown slope triangle, we would see the following:

Amazingly, no animals were injured during the filming of this scene.

So, that concludes the basic layout of the that stick in 2D. The next step is to repeat the process with the other stick, something that dedicated readers might want to do on their own before the next post rolls down. You will find that lines will begin to progressively accumulate on the drawing, so watch out! Those of you familiar with using layers in your drawing work will want to keep the sketch of the second stick separate from the first. Have a go at that if you're feeling like it, and when this thread takes a stab at this problem next time, I'll quickly run through the drawing of that second stick in plan and then we'll start to look at the real problem at hand: the points of intersection where the sticks cross one another. Stay tuned, and thanks for coming by today. --> On to part 5

Sunday, November 28, 2010

X Marks the Spot (III)

A short thread on describing a French carpentry drawing technique. This is post 3, with previous installments located in the 'blog archive' to the right of the page.

We left off last time having formed a right angled triangle defining the slope of one of our pieces of wood. Piece 'a' to be precise. Here is the problem we are working with, showing the two sticks of wood and their respective slope triangles:

To be clear about this, I'm only showing the 3D parts here so as to aid in understanding the 2D. I am actually trying to teach the 2D only, and the 3D is merely helpful in that regard. There is no need for the reader to draw in 3D - all of this can be accomplished with pencil, straightedge and paper. Oh, and a compass too. I suggest that readers who are working along a drawing of their own along with these posts make a point of reading all the way through the post to the end before starting to sketch.

Today we will continue on with working on piece 'a' - here it is in all its glory:

I placed the slope triangle right inside the piece of wood, coloring it white in this instance so it is distinct from the piece of wood. Notice how the arris of the stick is coincident with the hypotenuse of the slope triangle.

And now, here's that slope triangle, which I have colored light brown again, rotated down to the floor, which was the last point where we left off in the previous posting:

If the step of rotating the triangle down is causing you consternation, please take a look again at post 2 in this thread.

Now, the next step in our 2D drawing is to draw the cross section of our stick. The view of the cross section of the stick will help us accomplish further steps in the drawing. A cross-section is taken at a 90˚ slice to the principal axis of our stick. The prinicpal axis of our stick is along the arris, which also happens to be the hypotenuse of the slope triangle in the picture above.

I'll just return to a 3D view for a moment so as to be crystal clear (I hope!) about what constitutes a cross section slice of our stick. I just said that a cross section is 90˚ to the long axis of the piece, which is the arris and the hypotenuse of the slope triangle. In the next picture, I have drawn in a plane which is oriented 90˚ to the slope triangle's hypotenuse:

That cross-cut plane, you might notice, intersects the floor right at the point where the slope triangle sun and rise meet. It doesn't have to meet there, as I could move that 90˚ slice up or down along the arris/hypotenuse as I might like. Placing the plane where I did however makes it clear that the cutting plane is very much like the page of an opened book, a page hinged along the line it makes at the ground. It's a convenient place to put the plane.

Next, I've placed the stick back in place so you can see clearly how the cross-section plane and the piece of wood relate to one another:

Now, if I were to delineate the position of the stick which is cut through by that cross-section plane, we would have the following illustration:

The red diamond shown above, which is actually a rotated square since our piece of wood is square in section, is the actual cross section of the stick.

Now, that's all very nice, but as mentioned last time, we seek to represent this cross-section in a 2D drawing, not a 3D drawing. We need some way of rotating that red section view down to the floor.

For starters, I'll take the stick of wood out of the picture so we can consider this in a clutter-free manner:

The red cross-section is part of the larger cross-section plane, a plane which attaches to/passes through the ground plane. If we treat that line along the floor formed where the cross section plane runs into the floor as a hinge, we can see that the entire plane may be swung down to the ground, just as if you were folding a page of a book flat:

Now I'll put that stick of wood back in their to clarify that all I have done here is swing the stick's cross section down to the floor:

That's doesn't seem too hard to grasp now does it? Let's look now at how we would accomplish that swinging down of the cross section in a 2d manner. First of all, I mark the line for the cross section plane onto my light brown slope triangle, a line that is 90˚ to the hypotenuse:

Imagine in the above picture how the same step looked in the 3d depiction. Now here's the 'tough' bit - we rotate that 90˚ line down to the ground, the ground of course being synonymous with the run of the triangle:

The red circle indicates the spot where the top of the cross section meets the floor. If you find this last move confusing, it might help to look at again at the same process as it occurred in the previous 3D renderings.

Now that we have marked the spot where the top of the cross section meets the floor, we can illustrate the cross section itself. The cross section of our stick is a square, oriented so that the upper and lower arris are in a plumb relationship. We can project off from the ground, at the point where our cross-section arc meets, a pair of lines:

These two lines are 90˚ in relation to one another, and are 45˚/135˚ to the line giving the run of the triangle. I won't go into how to lay off those angled lines, but it will be a simple matter to accomplish with a framing square or a commonly available plastic 45˚ drafting triangle.

Next we decide what the measurement of the side of the stick is going to be. I've chose it to be 20cm in my drawing, so let's mark off that measure along each side, and complete the drawing of our cross section:

Again, it might help to re-imagine the same steps that produced the above drawing as being a representation of the process in 3D.

That completes the drawing of the cross section view of the stick, which in turn, in our next installment, will allow us to draw a few more things. One thing though - you can see how the cross section view in red and the slope triangle in light brown are kind of on top of one another. We can de-clutter this part of the drawing by the simple expedient of sliding the light brown triangle off to one side, like this:

You can see that I've slid the triangle along it's rise, moving it far enough to be completely apart from the cross section picture. Notice how the mark from the arc we swung across that light brown triangle is connected now by a straight line to the top of the cross section. Further, this line is 90˚ to the run of the triangle, as are the lines you can see connecting the lower tip of the triangle and the lower 90˚ corner of the triangle. If you imagine that light brown triangle having little nails in those spots along its run, you can see that dragging the triangle off to one side would leave a trial of marks connecting it to the line where it once was. I hope that makes sense!

The whole point of moving that triangle over is simply for clarity, as will become apparent in subsequent posts. If you are doing this drawing on the computer, moving the triangle will be a simple task. If pencil and paper is your choice, then it would be a good idea to illustrate that triangle off to one side at the get-go of the steps shown today. If I had moved the triangle over at the outset, I suspect it might have confused people.

Thanks for coming by the Carpentry Way today and if any questions come to mind, feel free to share them.

On to post 4

Friday, November 26, 2010

X Marks the Spot (II)

Post II in what is planned to be a relatively short carpentry drawing thread, detailing a French carpentry problem and its 2D descriptive geometrical solution.

Here's our problem, a situation in which 2 sticks are intersecting in the rough form of an 'X':

These sticks have different slopes from one another and are oriented differently to the floor plan from one another.

Let's give this problem some parameters, so that those who wish to try this at home can follow along more easily. Taking the left side member, which is colored light brown, in the next illustration I show some of it's particulars:

This piece is rotated in plan 60˚ from a line which connects our two sticks on the ground. I have labeled this piece as 'A' where it meets the ground, and it will be called piece 'a' from here on out. Notice that if you follow the arris of the stick from the ground, at 'A', up to the top, we reach a point marked with a small circle and which has a line running vertically through it down to the ground. This line is plumb to the floor and meets the floor 135 cm away from line A-B.

Point 'B' on the line, which is located 150 cm from 'A', defines the place at which the second piece, colored yellow, meets the floor:

This is therefore piece 'b', and it runs 45˚ to the plan. Again, following the arris of the stick from the ground to the top of the stick, we find a small circle and a plumb line back down to the ground. That plumb line meets the ground 150 cm from the A~B line.

Here are both sticks 'a' and 'b', shown in their positions relative to one another:

Note that the height of the two circles at the top of each stick is exactly the same for each piece. I chose 125 cm for that height, but it could of course be whatever height it needed to be.

Now let's translate the previous 3D drawing into 2D. What we want to create first is the basic ground plan. Here's what I come up with:

Hopefully that was straightforward enough for everyone to follow. If not, carfully compare the above sketch to the one previous, and you should see the common points.

In the next illustration, I bring in a little 3D once again, superimposing it directly on that 2D plan. I draw in a triangle representing piece 'b', from the point it meets the floor at 'B', up along its arris, to the circle at the top. This forms a triangle which represents the slope of that stick of wood:

That right-angled triangle has a rise of 125cm and a run of 150cm x √2, which is about 212.132cm. It's not critical to know or understand why the run of the triangle is √2 times longer than the distance A~B. Those who have obtained my first two volumes of the carpentry drawing essay series should be quite savvy about this, but for completing this particular drawing problem it is not too important at all. Don't sweat it if that √2 thing isn't making sense.

Now let's look at the triangle which defines the slope of piece 'a', which I'll just add on to the previous sketch:

Again, piece 'b' runs along 45˚ to the line on the floor A~B, while piece 'b' sets off at a 60˚ from that same line. Both triangles rise the same amount, 125 cm.

Of course we are looking at a 3D illustration at this point, and, to follow traditional carpentry practice what we want to work with is a 2D drawing. You need to be able to visualize the 3D and translate it into 2D - that's the key to this sort of drawing work, and it by no means comes easy, especially as the constructions gain complexity.

Those triangles which are sticking up in the 3D drawing need to be placed on the floor somehow. What we do is to treat those triangles as if they were a folded-up flap of paper attached to the ground. We simply fold them down, using the run of the triangle as if it is a long hinge. Let's do just that with the light brown triangle representing piece 'a':

The illustration attempts to show, through the use of the multiple triangles, how the triangle for the slope of piece 'a' is rotated from a plumb position down to the ground. Maybe one day I'll get all fancy and do some sort of animation for this, but for now the above will have to suffice I'm afraid. When the triangle is down, it would look like this in our 2D plan:

Note that nothing has changed in regards to the geometry of this triangle - it still has a height of 125cm, only now we've drawn that on the floor directly, and at a 90˚ angle to the run of the triangle. We'll be doing the exact same thing with the other triangle which represents the slope of piece 'b' too, however we'll stop here for today. We'll do some more work on this light brown triangle next time. If you are finding the whole 'rotate the triangle' part of this a bit mystifying, I would suggest making a cardstock triangle to represent the slope of piece 'a' and rotate it on the drawn plan just as I have illustrated. It's a simple 90˚ rotation downward. Up down, up down - it will be clear after staring at it long enough I hope.

Thanks for coming by the carpentry way today. --> on to post 3

Wednesday, November 24, 2010

X Marks the Spot

I recently received an email from a reader, a fellow named 'Mo' who recently graduated from the timber framing program of the American College of the Building Arts in Charleston, South Carolina. The instructor there is Bruno Sutter, who is French, and part of Les Compagnon's Du Devoir. A craftsman. I've been in touch with Bruno on and off in the past few years and he comes across as a dedicated educator and experienced woodworker.

Apparently, as one of the parting gifts to program graduates, Bruno distributes a carpentry drawing with a problem to study. Mo passed one such drawing he had received on to me in the past few days. Hah! - truly the worst case of a spam attack I have ever suffered. Well, funny enough, I welcome that sort of mail very much indeed. Send me your poor, your wretched, your layout drawings....

I thought it would be fun to explore the drawing on the blog here, and, who knows, this might possibly of interest to some readers(?). Mo has given his permission to do so, providing I credit his teacher. So, I'm starting a micro build thread on this topic, to be nested in between the two other design build threads I've got going on. Hopefully for those readers who are interested in the topic of carpentry drawing it will be a nice sojourn, and for those who feel, well, ill at the sight of descriptive geometry, have no fear, as this will be a relatively short series and there will be other stuff to read about along the way. My aim is to demystify the French drawing technique and make it of interest to more people out there.

So, the problem exercise looks like this:

Hopefully the title of this post now will make a bit more sense. What you have in the above drawing are two square-section sticks of wood which cross one another. Each piece is rotated so as to be on a diagonal orientation to the floor, like a splayed sawhorse leg, and both sticks terminate at the same height from the ground. The challenge in this problem is to determine the lay out lines for the point of intersection between the two sticks, so that one could make such a construction if need be.

The first piece of information I will share, to help clarify things, is that each of the sticks is rotated, in plan, a different amount:

The green stick is 45˚ to the plan, and the light brown stick is 60˚to the plan.

I'll share a couple more views of the problem:

And one more:

Were those pictures 'X-rated' or what?

Now, this is not too tough a problem to draw in SketchUp, a 3D drafting program many readers are already familiar with. I'm sure it would be easy in other 3D modeling programs. One could easily draw the sticks, tilt them up into their respective slopes, and intersect their surfaces. It would then be a simple matter of measuring the pertinent angles and distances needed to go to the wood and start laying out. However, if one did that what results is next to zero in the way of practical carpentry skill, as one is entirely dependent upon the computer software to solve the geometry. Powerful as it may be, 3D drawing can be like a crutch. I think 3D is great for working out lots of kinds of problems and for communicating with non-carpentry specialists and clientele, however I think it is wise to develop the skill of working with the basic manual lay out tools and descriptive geometry techniques to solve such problems. Good old 2d was enough to build the cathedrals of Europe and the great temples of China and Japan after all. So, that is what we will do in this series, though I am going to take advantage of the benefits of 3D from time to time as a convenient means of explaining what is going on in 2D. 2D geometrical drawings, as I'm sure many will agree, aren't always so easy to get your head wrapped around. I think the 3D will help with that visualization as we work though the drawing in 2D. Does that sound like a reasonable plan?

Forgive my presumption to be teaching anyone this material, however I do find it quite interesting and, I must confess, there is a bit of a selfish motivation at work too. You see, one of the best ways I know how to consolidate one's understanding of something, especially something complex, is to try and teach it. I hope to learn a lot from the process too, and won't embarrass myself too much!

Stay tuned. Those of you into carpentry drawing might want to have a crack at the problem on a sheet of paper. In the next installment we'll start sketching in the elements of the basic plan view of these two sticks of wood.

Hasta la vista. --> on to post 2

Monday, November 22, 2010

Ming Inspiration (6)

Today marks the sixth post in this series describing the design and construction of a dining table drawing inspiration from a unique Chinese Ming side table. Previous posts are archived to the right side of the page.

After looking at Chinese tables generally in the first post, and corner leg forms more particularly in the second, and then delving into some of the framing and joinery options for the connection between the leg and upper table structure, we cruised in to the last post, where I went over the process of analysis that led me to conclude that bubinga would be the best choice for this project. Happily, the client also likes that material, and trusts the reasons for my choice (not all of which were explained to him at the time in interests of brevity). We have sourced the material with a supplier in Pennsylvania and it should be on its way to me in the next week or so.

Today I'll like to share with you some of the details of the design I have worked out for this table. Hopefully it will be clear to the reader where I have drawn inspiration from the table featured in post 4, and where I have chosen to diverge. Time will tell whether my choices have been good ones, though I feel confident in my route so far.

As mentioned in the previous post, a dining table brings with it certain aspects which will dictate some design differences from the Ming side table original. One of those aspects, mentioned in the previous post, is that the width of the dining table pretty much precludes the use of a single piece of table top wood in this design. I have accordingly designed it around two pieces of wood, both of which should be around 90% VG material.

Another factor here is the size of the table. At first the client was talking about seating for 10 diners, however a table of a size to accommodate that many people was actually too large for his dining room. We have since settled upon seating for 8. Normal practice is to allow 24" width per diner, and add an extra 12" at each end of the long side runs so as to allow room for the diner and his setting at the table ends. So, for 8 diners, we have 3 on each of the long sides and one on each end. Three diners on the long side, plus a foot of space at either end gives an 8' length. Measurements taken in the dining room of the client's house suggested it would be good to trim that length a tiny bit, and we have settled on a length of 7'-10", or 94", as I prefer to describe it. I always tend to use whole inches instead of feet and inches, even on large projects, as it eliminates, for me at least, a possible source of confusion and number inversion, etc, which can happen with 'imperial' measurements sometimes.

The width of this table is to be 40". With a table measuring 94" x 40", and the legs placed at the corners, we are close to the practical span limit for a conventional corner leg table, in terms of avoiding problems with the table sagging in the middle from its own weight and in terms of adequately supporting the table top while giving room for a diner's legs to fit underneath.

However, this is not a standard type of table with a solid plank top, though it may look like that. The design I will be employing, borrowed closely from the Ming example, slices abut 60% or so of the weight from the table, in relation to a top that was to be constructed from a thick slab. I've come up with another trick to reduce weight - more on that later.

I first showed the client a table design at the furniture show which was very much a preliminary sketch - here's how it looked:

Another view:

This table was of the un-waisted variety and was meant to be a drawing table or computer desk. Again, very, very preliminary.

After I started working with the client and in light of the dimensions of the table required, I sent him a 'mark-II' drawing. Now the table is about the right width, height, and length, and now has a waist, albeit a very narrow one:

At this point I was following the Ming side table in terms of having a support frame and a separate table top frame, components which would be attached to one another using stub tenons atop the legs and floating tenons along the mid-points of the length.

Further reflection upon the matter however led me to veer away from this approach. I had access to adequately large stock so that I could construct the entire side of the table from one piece of wood. This would be much stronger than a two-piece design. Given that the height of a dining table needs to be in the 29"~31" height zone, and that 24" of vertical clearance is required for a diner's legs, I am left with about 6" vertical measure at most with which to construct the side structural arrangement of the table.

In considering the primary long support rails for this table, of which there are three, one way to lighten them while retaining their strength came to me as I considered them in purely structural terms. A beam made of steel, for example, needs to only have material where it is needed -economy in material in other words. A common form is the 'I'-beam, in which you have steel oriented on the top and bottom surfaces so as to resist compression and tension, connected by a slender web of material. A wood beam behaves essentially in the same way as that 'I'-beam, and as past posts on that topic have indicated, so long as the top and bottom surfaces of the beam are left relatively intact, material may be removed from the middle, i.e., the neutral axis, and a large percentage of the beam's strength will be retained. This is the logic of the tusk tenoned (and here too) connection, for example.

Considering this piece, then, I could see that making the waist wider, while leaving the overall height of the outer long rail sections the same, would be akin to moving in the direction of the ideal 'I'-beam configuration. So, the frame now has a taller waist:

There was a balance point to be struck there in terms of deciding about the waist, given the vertical constraint of 6" for the long rails. The taller the waist becomes, the smaller the apparent thickness of 'table top' rail and 'apron rail' become. That balance point for me was an apron of about 0.5" in height, slightly above center, between the apparent 'top' and the apparent 'apron'. The 'apron' is left appearing to be a slightly thicker piece than the apparent table edge above it.

Another difference to the Ming side table with this piece is the treatment at the narrow ends of the table. In that side table, everted flanges were incorporated into the end pieces. Such flanges, while beautiful and serving to restrain a cylindrical scroll from rolling off the table top, are not appropriate at all for a dining table top. Still, I needed to cap the table top panel end grain portions, and provide some restraint against any tendency which the top may have to warp. For the most part, restricting the top from warping is handled by the vertical grain orientation of the panels, along with the transverse battens which are affixed to the underside of the panels with long sliding dovetails. I just needed some clean way of terminating the table panels at the ends- I settled upon a variation of the double mitered breadboard end:

The next significant point about this table in relation to the Ming side table is that even with the table top weight reduction and configuring of the long pieces to slice more weight, the fact remained that this table overall had a heavier mass than the inspiration piece did. So, I felt I needed to add some form of additional support, and as mentioned in an earlier post in this thread, my choices devolve to:
  1. humpbacked or straight stretchers
  2. banwancheng, or giant's arm braces
  3. spandrels
  4. some combination of the above
The most discrete option are the giant's arm braces. The typical ones seen on Chinese tables, stools, and so forth are serpentine, 'S'-form pieces. They are arranged this way on account of the method by which they are attached to the leg and the underside of the table:

The 'S'-form allows the grain of the brace to be more or less perpendicular to the leg where it attaches, so as to keep good grain orientation. The joint at the leg is formed by a sliding dovetail, and fixed in place by a plug inserted afterwards from below. On the underside of the table, the brace is pinned in place.

On square tables, the banwancheng can all meet at the center, and a form of 'cap and trap' is used (from Ecke's book):

I am trying to avoid the use of pegs if at all possible on this piece, and I thought that the 'S'-form braces, while having a pleasing form, had the defect in this case of being likely to interfere with diner's legs. So, I have come up with a giant's arm brace which arches upward, and drawn upon my background in Japanese carpentry to employ hiyodori-sen, or crossing and piercing wedge-pins, to attach the braces to the underside of the table:

The use of hiyodori sen is typically associated to attaching hanging jack rafters to a hip rafter, or reinforcing the connection of perimeter fascia where they meet atop the hip rafter. Here they provide a means to directly attach the giant's arm braces to the table's center beam, thus providing a very direct load transmission path. It's a strong connection linking end grain bearing surfaces, and no pegs in sight. The connection between the lower end of the giant's arm brace and the leg is accomplished with a fairly novel connection, which I will be detailing later on in the build.

If you examine the foregoing picture a little bit, you will note that the perimeter frame is thickened at the ends and thinner in the middle. Here my design follows natural forms - just as bones are thickened at their ends to provide more material at the connection points - the frame rails do the same. Another parallel could be drawn to the use of 'gunstocked' posts in English (and American Colonial) timber framing. This enlargement of the ends (or reduction of the middle, in actuality) of course allows the corner joints to be beefy without a concomitant weight penalty in the rest of the table.

After sending my rendition of the arched banwancheng to the client, I was most pleased when he got back to me with an enthusiastically positive approval. That's the great thing about collaborating on the design with a client who is willing to be involved and engage in the process.

Subsequent conversations with the client led me to explore further options for reinforcing the corner connections - like these spandrels:

He didn't like those so much, citing their obstruction of the view of the giant's arm braces, and neither did I care for them, for a variety of reasons. Mainly I thought them unnecessary.

Next I explored humpback stretchers, however I didn't like that direction much either. Then I tried a simple curved brace pair in each corner, used in concert with the giant's arm braces:

It's starting to look a bit like a tree here, and much as I do like trees, it wasn't a direction I was at all interested in, however I wanted to explore it on the client's behalf. Here's another view:

A significant aspect of the problem with these was incorporating them in terms of the assembly sequence of the top, giant's arm brace, and leg. Also, knee braces are problematic to join to other pieces in any case. In timber framing, pegs are often used to attach them, but the reality is that the peg's greatest asset is one of holding the braces temporarily in place for assembly of other components. If, in service, the braces are actually loaded by shear so as to create any tension at the joints, the minimal relish in the tenon leads to near-immediate failure at the connection. A lot of times in fact the driving in of a draw-bored peg will shear the relish (shh!). Braces work in compression, at least when the connections are all wood. Besides, I was really wanting to avoid pegging.

I was delighted when the client got back to me and said he didn't like the added braces, and that he much preferred the clean lines with only the discrete giant's arm braces. I was most pleased, if not feeling a bit vindicated, as that had been my conclusion all along.

So here then is an overview of the table after design is more or less complete:

Getting the leg shape sorted out was a most onerous task. I noted wryly to myself at one point, in the middle of some hair-pulling, that Nakashima never seemed to have had much concern for the legs in any of his slab tables - all you see are simple little turned spindles. I'm jealous - how easy could that have been? In all honesty I find the leg treatment on his tables to be one of the design shortcomings of those pieces - they look like legs sourced at Woodcraft or something like that. Anyway, please excuse that brief aside.

I found the legs quite a challenge to get right, and tried many variations - here's but three:

Finding the right point between ornate/organic and clean/modern lines was tricky, not for the least of which because it took a while to tease out from the client exactly what sort of look he and his wife were after. In the end I found something all of us liked. The legs and apron will further be integrated to one another by the use of a beading treatment along the lower/inside arris. Just drawing that bead in SketchUp was a royal pain, but I was able to produce something adequate for the purpose in the drawing. I explained to the client that certain forms were extremely time-consuming to render in SketchUp and that I would prefer to simplify them in the drawing. In lieu, I sent him photos of Chinese pieces with similar detailing so he would have an idea of what I was intending. I still haven't settled on the exact size and configuration of that bead at this time. Some things I leave for a point down the line in the making process where the physical appearance will be more defined - more so than a computer drawing - and I may draw fresh inspiration from that. Just having more time to mull it over often helps as well. I might even do a few mock ups, experimenting with different edge beading treatments.

Here's another picture showing more clearly the 'spine and ribcage' like arrangement of structural members on the underside of the table:

Another view of the table corner:

The banwancheng are only at the roughed-out stage in the drawing still - I will be refining their profile later in the actual build. Sharp-eyed readers may have noted certain things going on around the corner joints of this table, and I will reveal my joinery solutions for those corners soon enough. Also, there are joinery details for the transverse table supports that not even the client is privy to at this point. All will be revealed soon enough. This post is long enough already!

Thanks for coming by today, and comments are most welcome as always. On to post 7