By Simon Smith
Sawyers and carpenters hold the keys to unlocking the mysteries of turning logs into useable components for building, restoration, and conservational work.
The right cutting allows the timber to use its natural forces and alignment of grain and other characteristics in the tree to its best advantage. In our lives, it’s mainly European white oak in use, however, getting the very best out of all logs regardless of species is important.
Around 90 years ago, timber was being tested in several ways to compare and contrast with other SPP, and through this process, some standards for building and building predictability were created. These include the key engineering testing such as compression, tension, shear, torsion, crushing along the grain, crushing across the grain, as well as tabor and janker testing.
A building is invariably a box with vertical posts in compression and tie beams in tension. There are, of course, some changes to those timbers in situ, and often the strength characteristics improve in certain conditions. Drying, for example, equates to better stiffness results in bending, which improves in drying, especially for cantilever bracing. Posts in compression can carry a greater loading when they are fresh sawn!
Choosing the right cut
Timber from the log can in effect come from three key zones; tangentially cut where the growth rings run from right to left across the board, the centre where the pitch or heart can be boxed into a square, or rectangle bigger sections which can rhomboid in drying. Radially the growth rings are vertical to the face, which gives them a greater impact resistance but shrinks more in thickness, rather than width.
Movement is also to be considered shrinkage when timber dried below fiber saturation point [FSP] approx 30% Moisture Content – the timber cells start to shrink on further drying, timber is hygroscopic and will best fit its end use when it becomes stable, and where the equilibrium moisture content is very similar to its surroundings. Timber is hygroscopic and will attract moisture in an environment where the timber is too dry, or will lose moisture and shrink if the timber is too wet in a dry environment.
Imagine a restoration project where the building or wooden ship has settled into its framework over time to a moisture pattern that can change with the season. Timber tends to expand and contract during the seasons, which is something the specialist artisan needs to take into consideration.
With major projects occurring around the UK you must find a sawmill such as WL West that can work with the artisan. The sawyer and the artisan need to understand exactly how the other sees the same project, as cutting a log is full of the black art of sawmilling and milling to achieve a bow or spring, which can be a huge advantage to the artisan and the project. Jowl posts cut with the flared claws at the butt of the log can have huge benefits in carrying a big tie beam. Using the pith or heart to benefit the component, which will fissure the first on-air drying to enable the gross fissure to be uppermost in its positioning. Natural bends in timber work well for bracing for wind bracing in roofs, cantilever curved braces and ribs on a boat greater strength than cutting across the grain.
WL West & Sons Ltd is a timber merchant and sawmill business with 150 years of experience. We provide a wide range of air-dried oak and kiln-dried oak timber products and supplies. We also build and install custom projects for our customers.
Our wood products, building materials and certified wood are manufactured and sold with the endorsement of forest certification and the Forest Stewardship Council FSC
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