Thursday, May 29, 2014

A Square Deal (8)

If you are new to this blog and/or post series, you may wish to start at the beginning of this thread:

A Square Deal


For the past few weeks I've been doing nothing on this project other than monitoring the slab top for movement. What I've found over the weeks are two things:
  1. The top will move, and left alone it tends to want to bow up slightly in the middle
  2. The top is easily pushed back into straightness and held there - it can be kept in a stable position without trouble
I have the slab sitting on a couple of pine timbers atop a tablesaw:

I have straightedge on top so you can see how flat it is.

Another view:

After a few episodes of the top moving slightly and then finding I could get it back to flatness again almost immediately and without great force, I have concluded that my theory of using relief grooves on the bark side of the slab to 'break the back' of the slab's ability to cup has been borne out. Though the slab is 1.5" thick, it only has the strength of a 0.75" thick slab, or close to that.

I am quite confident at this point that the table frame, which connects to the top in eight places, will be more than adequate to hold the panel flat. Plus, when I cut the ends of the slab to mount breadboards ends, not only will the removal of wood make the slab weaker yet but the breadboard ends will add further stiffening.

I feel sufficiently confident that I have started resawing the remainder of the table components from the 'spare' 40" slab. It was in a holding pattern in case the tabletop misbehaved, and now can be brought into the process.

The slab is flatsawn in the middle, moving to rift sawn out to the edges. I sliced out the legs, stretcher, and apron pieces for the coffee table in short order. These were then jointed and planed, generously oversize, and I'll let then sit for several days to move if they are so inclined before another round of jointing and planing.

Next I needed material for the side table. Problem was though that the grain in the slab was starting to get slightly too flat for convenient cut out. So, wanting the end grain in the legs to run on a 45˚ rift line, I laid out for angled rip cuts:

The other side of the slab required greater angling:

My 14" Makita saw had a nice 50-tooth blade for ripping, however that blade ran into some metal last week while reclaiming gate material and was toast, so I had no choice but to use a 120-tooth blade for this work. Not at all a good choice for ripping, and a bit of a grunt, but it got me through, albeit with a couple of circuit-breaker trip outs along the way:

I have a new 50-tooth blade on order from Japan, but it will be a few weeks for that, so I make do the best I can. The slab was too heavy to consider lifting up onto the bandsaw and hand ripsawing - well, it never crossed my mind!

Next, over to the jointer:

After jointing I had a square arris to work from:

More re-sawing followed:

After that. a run through the planer produced the leg blanks with the desired grain orientation, at this stage about 3/16" fat:

 And then back to more circular saw work to obtain the aprons for the side table:

Next were the stretchers:

The pile of rough-cut stock gradually accumulates:

The two sticks on the left of the picture are cut from some other bubinga stock I had which was vertical grain and not curly. I thought that having crosswise breadboard ends with the same curly material as the table top slab would perhaps be a little too discordant visually, and the choice I made was to use some quieter stock for those two pieces:

The table design has been slightly revised as well. I move away from the asymmetrical breadboard ends with double hammerhead  key on one end, to having the keys on all four corners. This allows me to split the total movement of the top up between both sides instead of all at one side as previous.

The current design:

I've added an extra peg at the corners to stiffen up the mechanism a bit:

A couple of other developments have occurred as well. I've designed some custom router bits for making the hammerhead joints, and these bits, in three sizes, are being fabricated by Ridge Tool. For cutting the breadboard end joinery, I've decided to bump up the accuracy target a bit and am having a metal guiding jig fabricated. That should be ready next week, all being well.

All for now - thanks for dropping by the Carpentry Way. On to post 9.

Tuesday, May 13, 2014

Gateway (VII)

I've been spending most of the past week slicing and dicing up the remains of the old gate to see what I could reclaim of the hinoki. It's not much. There is one longish 4"x6" timber, but it has bolt holes every 2 feet, so it is of limited usefulness. Another couple of sticks might be reusable as battens for side panels or door panels, but the rest are short small pieces less than 30" in length. Such a waste!

Some more pictures to share of the devastation:

Main post foot well on its way to soil:

Support post foot:

Here's the top of one of the rear support posts, hikae-bashira:

All it needed was a copper cap. Instead, what it got was 25 seasons of expansion and contraction, baking by the sun, and wetting and drying. The strip glued into the opened kerf served to further trap moisture entering from the top. A post whcih could have been substantially reclaimed instead yielded 5%.

Another beauty:

Flanking post foot:

Main post foot:

The thing is, there is so little which is reclaimable and it didn't have to be that way. Sure, a kabukimon is a type of gate in which all the gate parts are exposed to the weather, so it takes much more of a beating than would a gate with a roof. But the design details, like the foundation consisting of metal shoes holding the posts down at ground level, made a big difference. And then there was the execution in terms of fabrication, and the choices presumably made by the carpenter which did the rest. Orienting beam kerfs up to the sky, combined with slipshod face-nailed copper flashing, and bolted threaded rod connections which promoted more rot, were examples of poor workmanship.

One construction detail that really irked me were the attachments of panels to battens:

At the time on site, I had pulled the decorative nails off of the front of the panel and yet could not get the panels apart from the battens behind. We ended up sawzall-ing the panels off. I figured the battens might be held to the back of the panels with sliding dovetails, as would be good (standard) practice, however once I had the panel out of the frame I could see no evidence of dovetails, so I was a little mystified.

Back at the shop, closer inspection revealed the 'ingenious' fixing method: Phillip's head screws:

So, they actually fastened the panels to the battens using these screws, then covered them over with decorative domed nails. I'm not overcome with admiration - anyone out there ever tried to remove corroded Phillip's head screws before? They are fasteners which were originally designed to strip out during automotive assembly line installation if they were torqued too high. Why these remain so commonly used when better options exist is beyond me. They suck.

With my Wera screwdrivers having a laser etched tip for extra grab, I did manage to extricate a few out of the less-corroded examples:

Unfortunately, it was only a few screws that were found to be cooperative, and I ended up having to chop the panel to bits. Recycled material from these side panels? That would be 0%. The main doors were also constructed similarly and I also obtained almost no reclaim from those parts either.

I have completed all the jointing, planing, cross-cutting and have maybe a dozen small pieces to return to the MFA. I also have one destroyed 15" sawblade and need a new set of knives for my planer. Those mishaps are what you can expect when working with reclaimed material.

It would be one thing if the poor workmanship and short-sighted design issues associated to an inexpensive gate, however they charged the same money for the work back in 1986 as I am charging today, and I certainly won't be taking the same shortcuts. Adjusting 1986 dollars for inflation to current time works out to more than double the amount I am to charge for the new gate. So, they overcharged and under built. I'm the biggest fan of Japanese carpentry out there, and it pains me to be faced with stuff like this.

Anyway, gate removal phase is now complete, and next up is foundation work, probably later this month. Stay tuned for more in this thread, and thanks for your visit today. On to post 8.

Sunday, May 11, 2014

A Square Deal (7)

We return now to the furniture projects I'm doing for a client out in California. The first two pieces are a coffee table and side table, and I'm making them from a rare and costly slab of bubinga that I sourced in Pennsylvania.

I had cut the slab into a 40"x40" piece for the coffee table top, and next needed to reduce it down from a 3" thickness to a 1.5" thickness. There were a few options as for how to do that slim-down, as noted in the previous post.

After much head scratching, I decided that the risk/reward for slicing a 3/8"~1/2" piece off of each face was not favorable, and decided that the safe course of action was to mill material off of each face in a series of rounds, letting the panel rest and move for a few days between rounds, was, regrettably, the best way to proceed. Yes, half the panel went up the dust collector, but this method gave the best chance of the desired outcome of a flat and stable tabletop.

I could have gone the route of many when faced with processing a slab of wood larger than their equipment (jointer and planer) can handle, namely fabricating a leveling and support system and some sort of giant router sled. I decided to go another route however, and took the slab to a CNC facility in upstate New York. I know that this would produce the flattest result, and I don't process large slabs too often so the fabrication of a large specialized jig, plus the rather boring nature of endless passes back and forth to mill the surfaces, led me to take a pass on that option. I also sent the CNC place a CAD drawing of the completed panel, as I wanted them to also use a ball mill to cut relief grooves on one side of the panel, in the hope that it would dampen down any tendency for the board to cup or curl with seasonal movement. I provided a detailed milling schedule as well, and discussed the matter at the company with the very person who would be doing the work. And that person would remain the same for the duration of the project. Just trying to forestall potential problems that can come up when sub-contracting a project phase.

The milling took place in three steps, which meant three separate set ups on the CNC router deck, which made the work a bit expensive, however what came out in the end was a dead flat board:

Click on the picture for a larger view. The 'working' surface of the slab, shown above, is the face which is closer to the pith of the tree. The wood is looking quite spectacular, like a 'topo map'. If I had wiped it with alcohol for photographic purposes the figure would be more apparent to see, but I left off doing that.

On the backside, on the bark-facing side of the slab, the relief kerfs were milled just as designed:

The middle kerf is shorter as there will be a central tenon at that location. Please note that while the board is at finish width, it remains an inch long on each end at this stage.

Another view of the grooves:

I've applied a coat of anchor seal wax to the board ends to dampen down any moisture exchange and will let the slab sit for a while -several weeks at least- and keep an eye on it to see what movement tendencies it may have. Fingers crossed of course! I'm sending happy thoughts towards the piece - stable...stable...stable....

I'm contemplating making a slight revision to the breadboard end design, and am waiting and watching the board first to see what it has to say.

Thanks for coming by the Carpentry Way. On to post 8.

Wednesday, May 7, 2014

Gateway (VI)

Yesterday was the day for the removal of the old kabukimon at the Museum of Fine Art in Boston. This is post six in an ongoing thread concerning the design, construction and installation of a gate to replace one at the MFA's Tenshin Garden.

The original gate had lasted only 25 years and was rotting badly. How badly it had rotted, mind you, was a matter that proved to be underestimated even by my own fairly pessimistic assessment.

After some rainy days previous, we had sunshine for this encounter. Once set up, it took only a few minutes to remove the main doors and side door:

As noted, while I knew the gate to be terminally rotten, it exceeded my expectations in that regard:

On the plus side, it was a happy home for many small critters:

There were some persons (not employees of the MFA), who, during a project meeting last year, questioned my assessment of the gate as being in dire need of repair, and suggested that the gate was not in fact in such poor repair as I claimed, that a 'lick of paint' so to speak, a 'little repair work' was all that was needed.  Just a touch up would be fine. The above pictures hopefully illustrate well that reality was otherwise. The Museum was well-justified in replacing this gate before it became a hazard.

And, the worst was yet to come in terms of the actual condition, as revealed by dis-assembly.

The header above the side door had a relief kerf cut into its top surface, which naturally allowed moisture to enter even though there was another beam 6" above it. This beam was, also to my surprise, installed with stub tenons and lag bolts. Using metal fasteners in wood in an outdoor structure just invites rotting, so I could see that this gate was an example of cheap construction originally. The header's lag bolts had corroded to the point where they could not be removed, and I had to saw the beam out with my ryoba.

The next two pics clearly reveal the condition of this piece, which was a relatively well-protected one in the structure:

When you see that even a smallish timber such as this header is boxed-heart, you know that the wood chosen for this project was not especially high quality - at least in those areas where the original builders thought they could cut corners.

I thought it was not the best move, frankly, to place a beam with the relief kerf upwards in an outdoor structure. The kerf could have been placed downwards in a side door header without aesthetic penalty, and if it has to be placed upwards for some reason, then it really must have copper flashing installed on top. Even if the kerf wasn't there, or was on the underside, copper flashing would have been a good idea on any horizontal surface exposed to the weather.

A bigger surprise came next, when I got up onto a ladder to start the dis-assembly of the main cross beam, kabuki, the one piece of the structure with the greatest exposure to the weather. Once up on the ladder, I was astonished to find this principal beam with its relief kerf also upwards, had no copper flashing to protect it:

This picture is really not doing the scene justice, but you get the idea. This open kerf to the sky meant that water had been accumulating in the kerf for years - and inevitably in the joints at the posts on either end of the beam. I could see that at some point in time there had been copper flashing in place, however, like the other bits of copper flashing on the gate, it had been crudely face-nailed through from the top, and the nails had, of course, loosened at some point, allowing the wind to pull the flashing off altogether. No one had noticed that unfortunately - a piece of flashing atop the main beam, well above the plane of view, is/was not the most obvious thing to see of course, so when it went missing it would not have been at all apparent. The issue though, is how it had been attached in the first place. You don't put copper flashing on by face-nailing through the sheet, let me assure you, if a workmanlike outcome is the objective.

As with the header, there is no reason that the relief kerf in the beam could not have been placed on the under surface, most of which rested against a secondary beam, the magusa. The magusa would have concealed almost all of the kerf, and the exposed tenons with a kerfed surface could have had shims patched into the kerf. The original builders, however, chose to orient the kerf up and put the flashing on in a slipshod manner. Furthermore, the magusa itself was lag-bolted from the top in four places and attached to the posts using doubled bolts on each end into the end grain of the beam. Anytime I see lag bolts into end grain I ask myself, what were they thinking? Fastening into end grain is a classic mistake in carpentry.

Of course, the lags were all rusted and a bear to remove. They had gone beyond lag bolting though, actually gluing the magusa to the kabuki(!). I found other places where wood strips had been glued in around the side door opening as well. The glue was failing of course.

Much of the remaining flashing on the gate was just loosely hanging on. Nails and wood. The wood shrinks and swells, the copper sheet expands and contracts with temperature, and the nails get popped up and loose after a while. Many of the flashing fasteners had simply fallen out and were missing.

I had some hope that the main crossbeam might have some salvageable material which could be reused in the new gate, but seeing the situation with the exposed kerf and exposed lag bolt holes in the beam's upper surface, I was immediately disabused of this notion.

I had been thinking to try and carefully extricate the kabuki to save it for reuse, and hopeful that the upper 2/3rds of the main posts might be salvageable. That no longer any sort of possibility, gate dis-assembly was vastly simplified: out came the chainsaw.

We didn't have a crane, so some ropes were rigged up, and the main beam chopped from the post on one end. The opposing post was then cut, and the assembly persuaded over a few inches to the side before it was pulled down, the upper portion of post landing on the top of the rear support post, according to plan:

Now the kerf in the kabuki is clearer to see. My helper Matt is visible in the above picture - I couldn't have accomplished the work near as smoothly and quickly without his help, so I was most grateful for his assistance. 

We then dropped the post chunk-beam remnant to the ground, and I drove the remaining portion of beam out of the intact post with a sledge.

With the beam out, we could get a view of the condition of the wood at the top of the post:

It's a poor joint design anyway, as the mortise is nearly 3/4 of the post thickness.

Once the main beam assembly was down we managed to crack the magusa and kabuki apart, and it didn't take too much longer from there to pull the rest down:

As you can see, there is a temporary chain link fence in place, and the garden will be closed until spring of next year.

I had some hopes of re-using material from the old gate, but I now think at best I might get 1~2% recovery. The poor recovery, along with rather short lifespan, is largely due to poor design detailing and poor carpentry practice during the original install. A lack of maintenance, especially in regards to the piece of flashing that had blown off sometime in the past 25 years, did the rest. I already had seen the shortcomings as a result of the design, but I was a bit surprised to see the short cuts and bad decisions on the carpentry end when I pulled the gate apart. In the tear-down, I got to know the carpenter a bit. This gate, I had been told, was the work of a 'master carpenter'. I guess I would disagree with that characterization, sorry to say.

Sure, maybe the carpenter had to work within budgetary constraints, but that doesn't excuse some of the decisions that were made by the carpentry company (the poor kerf orientations, the use of metal lag bolts instead of proper joinery, the defective flashing installation, the use of metal shoes instead of granite foundation points, etc.).

You've got to know that, as a carpenter, your work will be assessed by those who come along later and fix it or take it apart. While they might never know you, and you might even by dead by that point (this is not often the case given the durability of much which is built these days) they will know you through your work. They will find your mistakes, and see where you covered up an error, or fudged it in some other way, or, see where you did something really well. Your work is your legacy, and the only ones who can really assess it are other carpenters. I'm always trying to learn from older construction, what worked and what didn't, so I can bring these lessons forward.

The other task at hand yesterday, with the gate out of the way, was to poke around and get a handle on how the foundation was detailed. There were no provided as-builts from the initial installation, so the detailing of the concrete under the gate remained speculative at best. Out came the shovels....

The digging was pretty easy, and we found that the foundation supports were the same in each post location: a square concrete column, presumably placed down to below the frost line, and a 3/8" welded metal saddle, with the post shoe welded on top:

The metal shoes are a poor way to connect the timber structure to the earth, as the metal, along with the four through-bolts which tie the posts down to the shoe, a combination which simply promotes rot. All of the posts were rotten on their bottom 24". The main posts, with the openings provided on top by way of the exposed kabuki kerf, were rotten from the ground right up to the beam mortise.

The metal saddle was composed of two angled and gusseted brackets, which connected to one another through the concrete with four threaded rods:

It appears possible that the post shoe and its plate below could be cut off of the angled support brackets, and the bracket removed by undoing the nuts holding it onto the concrete. In this 'best-case' scenario, the metal can all be removed without having to break up the concrete. If the central shoe, however, is also cast into the concrete in the middle portion, then the concrete will need to be demo'ed.

All for now - thanks for coming by the Carpentry Way. On to post 7.