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ideal for building kayaks and wood that is acceptable.
This is not an attempt to give a complete list of wood terms. I only list some of the terms that I have run across in the process of building boats and buying wood and trying to decide what kinds of wood are best to use for particular applications.
Plain Sawn, Quarter Sawn
Quarter sawn logs produce more lumber with grain that runs perpendicular to the wide face of the board or at small angles away from perpendicular. Plain sawn logs produce a few boards near the center of the log where the grain runs perpendicular, but the majority of the boards will have the grain running at various angles from parallel to the wide face of the board to perpendicular.
Vertical Grain, Flat Grain
When you go to a lumber yard as a consumer, you don't really care how the mill cut the wood. As a consumer, you are concerned with the orientation of the grain in the boards that you buy. Hence, lumber yards tend to label their wood as flat grain or vertical grain. Flat grain boards have the annual rings running parallel to the face of the board. When you're looking at the end of a flat grain board that is laying down, the grain runs in the horizontal direction. Vertical grain boards have the grain or annual rings run perpendicular to the wide face of the board. When you're looking at the end of a vertical grain board that is laying down, the grain runs in the vertical direction.
Strength and Weight of Wood
The US Department of Agriculture publishes a wood handbook that lists various properties of different species of wood. The ones we are most interested as boat builder is how heavy the wood is and how strong it is. Most of the time, what we want is a light yet strong boat.
Weight of wood is usually recorded as specific gravity, that is, the ratio of the weight of a given volume of wood divided by the weight of an equal volume of water.
Strength of wood is specified in a number of ways depending on what property of wood we are interested in. For boat building, we are most interested in modulus of elasticity and modulus of rupture.
Modulus of Elasticity is a measure of wood's stiffness. To establish stiffness a piece of wood of a certain cross section and length is supported at one end and a weight is placed on the other end. The less the deflection or bending, the higher the modulus of elasticity.
Modulus of Rupture is a measure of wood's breaking strength. To establish its modulus of rupture, a piece of wood of a certain cross section and length is subjected to increasing force until it breaks. The force at the point of breaking is related to the modulus of rupture. The higher the modulus, the greater the force needed to break the piece of wood. The modulus of rupture can only be determined for brittle materials. For instance, you couldn't determine a modulus of rupture for a copper wire since it would bend without breaking.
Softwood vs. HardwoodSoftwood and hardwood are terms of convenience. In general, any wood with needles is classified as a softwood everything else is classified as hardwood. These terms are slightly misleading since some softwoods such as yellow pine and douglas fir are quite hard.
Lumber may be named by species, though at times a number of species go by the same name. For instance, yellow pine could be any number of southern pine species. The same goes for terms like red and white oaks. Both terms encompass any number of species.
All content copyright © 2007 Wolfgang Brinck. Personal non-commercial use permitted.