Tag Archives: Square Rule Scribe Rule

The Most Important Tool in the Kit

With this entry we speak to tools, or at least the simplest and most important of tools in our kit, and the one which therefore allows for the accurate and proper use of all those that follow.

String is the most important tool in any box – It is a line running though time and history and most every building that ever was or ever will ever be. It is the very beginning, and is even now like a living truth and a real world Möbius Strip, a concept ever connected to an end that never comes…

String, in all likelihood developed from a simple tool used to bind items together for storage or transport, to then be used to build snares and traps and then towards its slightly more complex use in defining strait and true, none so long after our long ago ancestors first pounded and separated natural fibers apart and then twisted them back into cohesion and a potentially unending bit of cordage. This perhaps within generations of that first great leap forward.

All this development coming about long before recorded history. How much time had or has since passed before the first human mind noticed a taut line was strait and then went on to run a string through powdered charcoal with the intent of marking a strait line on something he wished to straiten and to then affix a line to Batters is something we can never know.

It is fitting that those beginnings are yet still just that, the beginnings of most any construction – It all begins with a taut line and Batter Boards, plumbs and the snapping of lines.

My focus on it as still being primary amongst the many tools we have since developed is in part to do with my traditional approach/es to timber layout, though in truth this goes back to my first week in my first carpentry job, in being taught the proper way to string a line and my asking my then mentor who it had been who had taught him the technique he had just demonstrated. His eyes acted almost as a line that day as they belayed the thoughtful recollections and truths spinning in his mind as he thought about it a moment, then he simply said “Well hell, I don’t know, that goes back to way on before the pyramids”

THE_MERCHET

This image of a Merchet and its companion Plumb is seen here as a courtesy of Wikimedia Commons

In part this focus goes to my primary chosen system of timber layout being Plumb-Line Scribe. Though no matter the chosen layout,  (Square Rule or Scribe) I am datum-dependent. I almost without exception snap lines on every stick, more often than not I do so on all four sides. These lines physically represent two perfectly perpendicular planes of reference.

In Square Rule these snapline planes of reference are used to accurately cancel out bow and wind and to overcome any lack of squareness not achieved in the milling of the timbers, as well as lending reliable accuracy to an organic and imperfect timber in the layout and shaping of timbers to chosen mathematical constants at each of their connections. In Scribe Rule these snaplines likewise are used to cancel out bow and wind as each timber is lined out and are then used to place each timber into scribe layups aligning the two planes of reference to Plumb and Level, this often over a lofting floor on which is drawn a full sized diagram, itself described with snaplines, pinged not with a line enveloped in charcoal or chalk but one dampened with ink. Upon such placement in these layups timbers and the inconsistencies (unlike the smaller pieces of wood found in benchwork, timbers cannot reliably be milled strait and true – Timberwork requires systems of layout which therefore deal with those expected and natural inconsistencies) found in their surfaces, are scribed to each other, often with the use of a Plumb-line used to gauge those inconsistencies.

IMG_0319

Note the Level Mark adjacent to the 6″ Level – It is from that mark that the Datums are unwound – It is with both the Datums and the Level Mark that the timber is placed in the layup over the Lofting Floor – This allowing use of the Plumb Line to covey quantifiable information from each timber to the other

A snapped line, like a line on paper or a computer screen can also be used as a base line from which to develop the geometry to layout any required angles or an Arch or a desired radius or as a control line from which a trusses camber is re-conditioned in a bridge rehab/restoration or developed in a new build.

And in all forms of construction, lines then go onto be used all through the assembly and erection process as a constant reference to insure things are both strait and true and plumb and level.

Though recent advances and circumstance will sometimes demand a laser be the line of choice in the field, reels of string, be they Dry or Chalk Boxes or Ink Lines, will forever and always be, the most important of tools in our kit.

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Everything with Purpose

The somewhat unsaid case for slopes.

Just to clarify for those many among the readership who have never cut a timber joint – “Slope” is the going term for an angled cut into the backside of a mortise which receives an adjacent member which joins it at an angle, these typically being the common wind or “knee” braces typical to every timber framed structure.

This Wind Brace Mortise now sports a “Slope”

Most of those who cut timber joinery fall into either of two camps, those who cut them and those who don’t. The “don’t’s” have reason – A slope cut at an angle even a single degree too low, will simply not allow for full insertion. This added to there being in most instances, little, if any return on the time invested in (laying out – the cutting is simple) cutting them.

The other reason often held up, is historic precedent, and this is certainly there. Most Brace Mortises in North America lack any slope – Though I am going to qualify this somewhat slightly, by suggesting this, only most, and not all.

I have come upon historical examples, and of two types – Early Scribe Ruled frames do sometimes have slopes. This would be because both the exact placement of the spine of the brace is a known, (this is not true of Square Ruled frames) and the exact angle that the brace joins the mortised stick is also a recordable known, and with that information, it is easier to chop out a slope with a Corner Chisel than it is to bore out empty space with a Tee Auger.

The other instance in which I have seen this is in bridge joinery, and though such is most often scribed, the reasoning for the trouble taken to cut them was not about the information to cut them accurately being a known. It is about not unnecessarily removing “section” – It is for reason about not wasting out wood and unnecessarily weakening the mortised timber any more than need be.

Here we see a replicant Tie Beam with both Through Mortises for the Lateral Bracing visible on this face

Here we see a replicant Tie Beam with both Through Mortises for the Lateral Bracing visible on this face

Some of this is driven by that constantly considered aspect of wooden bridge design, this being “Dead Load” – Timber, particularly in later examples, is sized to the smallest section possible, to make the trusses as light as was possible to minimize “Dead Load”. (though then as now all is /was ticked up in size with a bit of a “failsafe”)

A knowing and careful Carpenter / Bridgewright, is and was cognizant of this, and did / does not let the joinery he is cutting unnecessarily weaken the stick he is joining.

Some of this thinking necessarily goes to the proximity of the joints being cut – Would two mortises in close proximity (should they even be in close proximity?) be better off were one or both cut with slopes?

This broken Tie is temporarily re-enforced for the rehab effort prior to its replacement

This broken Tie is temporarily re-enforced for the rehab effort prior to its replacement

As a bit of an aside, the lack of any slope leaves a void. Without exception, in every brace mortise I have ever opened up, something had moved in, and had brought with it, the stuff and sluff of life. The shredded whatnot for its bedding or its bathroom. This “stuff” often serves as an unintended sponge holding moisture, when that someday comes and an inconvenient leak points water at the spine of a brace, and funnels it into the mortise. This “Sponge” is not infrequently the secondary genesis of a huge problem…

I avoid this void in cutting new barns, (again, both mice and bats bring their stuff to these voids in every barn frame I’ve explored) and in frames subject to weather, like porches and pavilions, and of course – in Bridges


Commonly Un Common

The Square Rule is, as I suggested in the last entry, not just back on my current, but it is now my actual horizon. A part of my here is now everyday. As is this wondering as to why it was the people who chose to use it, this Square Rule, chose to do so.

It is a funny place to be in in more ways than one. As is the fact that I might gaze through a window few can share – I know what it is to wonder after the efficacy of which system to use for any given Timber Framed construction. To ask which system of Timber Layout, Scribe or Square Rule is the more, or even the most appropriate. This a window common to a few of my contemporaries. Though one last wide open for but a brief while, centuries ago now, when this rapid shift from the Scribe to the Square was yet underway.

And I think the perspective I view all this through, is far from common. To know traditional versions of both systems of layout is not common even among framers. To have a working sense of both historical framing of buildings, and those of bridges is maybe even more so. All this is a circumstance and a happenstance and a perspective, which was once commonly shared. The once sense of everyday of a common country carpenter, but now some of the little explored vagaries of a hyper niche carpenter. That said, I still see myself as a common country carpenter. Perhaps it is the every tree is a timber, commonality traditional timber framing has with the sawlogs we are often involved in “converting” – It is in this work, none so uncommon to choose timber in the woods and on the stump. Something we have done here as part of the Bernhard Barn restoration, the two Tulip stems which will serve as species in kind replacements of the one piece fifty foot hewn from the round Wall Plates still stand in their forest and yet touch the sky, and do not yet know that they will be part of the next chapter in the ongoing story that this Barn will continue to tell.

It often crosses my mind that this thing of being a Framer with an inter-discipline sense of things is an all too small club, one with a membership far far too short in numbers.

So, all that, and with the other high horizon focus, The Blenheim, seem to bring us back to where this blogging adventure began, with Long Trusses and The Square Rule and who might have taught who what, when it came to bridge framing, (see the May & June ’11 archives) now swings back and over into a parallel and perhaps as seemingly and an almost equally unanswerable exploration. Who was it who brought the roots of Square Rule to the table, and where was that place that they called home?

Semi parallel interwoven puzzles and a wonder after both, send us in search of clues to either, and we find yet another letter of shameless self promotion from the good Col Long –

All this information for but three pence, the price of a nail so small, most might think of it as a tack.


A Now Two Century Old – Overnight Turn on a Paradigm

My revolving focus is often driven by a particular bridge, or its Truss Type, or an interest in its developer or Patent holder. My current attentions have once again revolved around to focus on something of deep and long interest, something that is the core of who I am and what I do. And interestingly something of a mystery, one which is perhaps this very year, slipping into its third century of wide use.

Traditional / historical timber framing layout systems became a preoccupation of mine something over twenty years ago now. In part with a growing understanding that the non-traditional layout used by the shops in which the first frames I helped cut did not have a practical level of success, and in part because it was a connection to history and a historical continuum which drew me to this Trade. That and ample example that historical layout systems did possess a level of predictable success and practicality “then” suggested to me that they would still share these same practicalities in the now.

I sought out practitioners of these systems – The Scribe Rule & The Square Rule. (Scribe being the direct transfer of information from one timber or set of timbers to another – Square Rule being the shaping of timbers to a mathematical constant at each of its connections) And have gone on to, as a rule not an exception, regularly practice both, and also to teach traditional layouts in a series of workshops over the last dozen or so years.

Though in part it is out of preference, it is happily also out of practicality that I lean towards the Scribe side of things. With much of my work being Bridge related, and with Timber Bridges being the seeming lone exception (this due to slightly dissimilar pieces in what appear to be like, redundant and, mirror image Panels – Small inconsistencies driven by camber) to an amazingly rapid and geographically vast shift (here on the North American continent) away from variations of Scribe which had been the norm for timber carpentry for millennia.

Scribe layout survived all the many changes humanity brought to its fellowship and the need to house itself, including this migration to a new continent, this particularly well exemplified here (forty or so miles from the coast and just outside of first period settlement) in my little patch of Northern New England. Here settlement was, for the best part of the first two centuries of the then Colony’s existence, incredibly slow to expand. Long hostilities with the neighboring colony of New France including cross border raiding, and raids encouraged from those neighboring colonials among Tribal peoples from both sides of the border. This pressure saw to it that settlement here in Northern New England held fast at a standstill from the 1630’s through the 1760’s – As did building technology. As is found elsewhere in the New World, settlement patterns heavily influenced construction, in that colonials brought with them what they knew. This is particularly true of Timber Frame Carpentry, with country of origin and even regional variation in the home country heavily influencing the many regional variations found in the former Colony/ies. Framing style, technique and typology were brought from the Mother Country. Here in New Hampshire that transplanted Mother Country typology would be English Tying, in dominant use from the early 17th Century – the “First Period” on through to an end to the expansion standstill, and on into an area wide expansion and building boom. (settlement beyond coastal areas and nearby river valleys) The building boom and now rapid expansion of settlement brought on by an end to these formerly unending hostilities, this end coming with the close to what is little realized as, but was in truth the real first “world war” one encompassing multiple nations simultaneously on multiple continents – Known here as the French & Indian War, and elsewhere to history as the Seven Years’ War. Both Scribe and English Tying would survive this war and follow the boom of settlement into interior sections and remain in dominance another fifty years until a somewhat mysterious rapid change would morph both long used systems (Scribe & English Tying in both houses & barns) out of use in little more than a decades time.

An English Tying frame in Strafford County NH dating to the post F&I Boom-time

An English Tying frame in Strafford County NH dating to the post F&I Boom-time

This mystery of an almost overnight sensation shift away from what even here was a centuries old tradition in Scribe type layout has been high on my mind of late, with the current project being a Settlement Period barn in Bernhard’s Bay New York (here “settlement” was the mid 1790’s through 1815 or so) on the north shore of Oneida Lake. The Bernhard Barn is Square Ruled, and though the exact year it was first built is not yet determined. (research perhaps including Dendro is in the works) In part due to some unusual detailing, I believe it may be the earliest Square Ruled building I have ever put eyes and hands on.

A settlement period building, the Bernhard Barn is an early Square Ruled example of a common barn typology

A settlement period building, the Bernhard Barn is an early Square Ruled example of a common barn typology

Tax records suggest the property was held by John Bernhard - The Farm was developed by his son John - Improvements beginning in 1815

Tax records suggest the property was held by John Bernhard – The Farm was developed by his son John – Improvements beginning in 1815

With long study, exploration and preservation work on historic structures in my home region on the edge of First Period development and what might be the Nation’s first building boom, the sudden move to Square Rule and the concurrent move away from English Tying has long intrigued me. This seems to have begun sometime in the second decade of the 19th Century, and somehow saw total acceptance as the norm as not just common practice here in layout, this rapid shift to Square Rule would become dominant practice over the entirety of the then young nation. Everywhere north to south and as far west as settlement carried, and in this same contracted time-frame.

Some few have suggested, and having seen first hand great numbers of timber framed structures from the period, in not just my home region, but also in most all of those areas then settled – I adhere to the theory that the rapidity of this universal acceptance over a hugely wide geographic area is directly attributable to another violent international struggle, one this year marking its bicentennial – The War of 1812 – The theory holds that high hundreds if not thousands of Carpenter’s from all over the country were brought into the war effort (Hundreds did participate in a strategic effort to build Naval ships at pace on Lake Erie to outnumber British craft in what came to be known as the “The Battle of the Carpenter’s”) to build watercraft, bridges, earthworks & barracks buildings. They shared ideas and also a need to produce needed constructions quickly. An ability to throw more carpenters into an effort which lays out individual pieces mathematically than could possibly fit / fold into a Scribe layup assemblage, made this sheer numbers strategic advantage of Square Rule the Layout of choice for the wars duration, and upon its end Carpenter’s in great numbers returned home with a new tool in their kit, one that despite a generations long practice and tradition, and a tendency in humankind to resist change – Somehow, this became a new beginning, a foundational shift, a season change uncountable hundreds chose to use and share. And in little more than a decade’s time, carpentry would forever be changed.

It is not impossible that Square Rule is also now marking its bicentennial year as a widely accepted widely used system, and that this paradigm shift was in part responsible for setting the tone that the rest of the century would take. That conceptually the idea of interchangeable parts and mass production became an accepted norm and expectation and became part of the human psyche. All through this paradoxical chain of events, this bit about the horrors of war somehow leading to wide and rapid dissemination of a useful idea, coupled with humanity’s unending and simple need to house itself – And that this would in time and in turn, lead to techniques of mass production being used to also build, The Cotton Gin, The Springfield Rifle, and one day, The Tin Lizzy.

 


Crossing Childs’ Living Legacy

Happenstance had me helping out on the rehab of a 19th century cape this past Friday in Contoocook Village, across and up the hill from the Train Depot and almost within sight of my old haunts on the Railroad Bridge. When we wrapped the day, I headed for the far side of Hopkinton to visit the Rowell’s. Both to compare details with those seen recently on Long Truss sister bridges, the Bement and Blair, but also to again put eyes and hands on the Childs’ living legacy.

Some photos from the visit, and observations explored in the details found.

Here is seen the west Portal, the far end has suffered some recent but minor damage. The driver apparently ignoring the impossible to ignore clearance sign, but not the screaming protests of portal trim tearing into the aluminum and fiberglass in the trucks box. Damage thankfully, limited to the Portal, and not carrying on into the Through Truss proper.

Top Chord splices at mid-panel, six laminations, iron spacers, just the single bolt.

Somewhat unusual, the Upper Lateral Braces are in a single plane, one broken and tenoned into the other. More unusual, this system is “Square Ruled.”

(note how the shoulders are truncated down to a common width)

Though many bridges have both systems of timber layout.

Square Rule is typically employed only on secondary systems, Rafters and Knee Bracing. Major systems such as Lateral Bracing, like the trusses, are more commonly “Scribe Ruled,” pieces literally scribed to one another in the direct transfer of information. This to compensate for changes in angles and lengths in the framing introduced by intended camber.

Unnecessary for a Long, these as the “Description” tells us, were built “flat,” with light camber being driven into them during the wedging / pre-stressing process.

The solid encased Arch comes up and kisses the Top Chord at mid-span. (See the July ’11 Archive – Children of Childs, for thoughts on the use of an Encased Arch used similarly on a Long Truss by Nichols Powers on New Yorks’ Blenheim) An Arch being harder to plan and layout than first glance might suggest.

This kiss tells us Horace was well versed in their use and that Rowell’s was likely no one-off or odd experimentation.

A unique detail I’ve seen on no other bridge is this Purlin Post / Purlin Plate system, which support the Rafters at mid-length by providing a load path to the Ties. Built of seemingly undersized timber, this is another suggestion that the Childs Brothers shared understandings learned from their cousin. This framing being kept as slight as engineering calculations allowed, to help keep the bridges dead load as light as was possible.

In some ways, this completes the circle, and in a single generation and within an extended family. The Engineer learns from the bridgewright how to achieve lightness in design and framing, the Bridgewright learns from the Engineer how to max that lightness through calculations, to keep his framing timber as slender as was possible.

Though Long is widely credited with breaking ground in engineering, in using formulas and calculations in the design of trusses, and the sizing of their webs, it is Haupt and Whipple who are widely credited, through their work and writings with disseminating this information to the wider bridge building community. Long’s influence along these lines is perhaps under realized. It clearly began with the publication of “Description” and then through the work of his agents, and their interactions with bridgewrights over widely scattered parts of a growing nation.

Preparations for, and the coming Wason Pond Covered Bridge workshop in Chester NH, are bound to distract me for a bit. We will temporarily suspend the continuing series on NH bridgewrights and patent holders. The next few posts will highlight the Chester activities and all we hope to share and learn from each other there.