In our last blog, we learned that over the years clever marketing campaigns have pitched a variety of "Mahogany" species as true exterior hardwoods that stand up well to foot traffic and will endure the challenges outside for many, many years.
Today we will examine some of the mechanical properties of the various Mahogany species to see if all species are indeed created equally and find out which of the species sold as Mahogany are best suited for long-term use outdoors. In order to help us better understand the data we will also compare the species with other common decking materials such as Western Red Cedar and Redwood.
MECHANICAL PROPERTIES - WHAT ARE THEY?The mechanical properties of wood are those which influence the performance of the species and determine how easy the wood is to work with as well as giving us clues to how it will potentially perform in service.
By reviewing the mechanical properties, we can tell if the wood is strong enough, if the wood is hard enough and if the wood is stable enough for our project. For our review, we will work with data derived from The Wood Handbook – Wood as an engineering material, USDA, General Technical Report 113. https://www.fpl.fs.fed.us/research/centers/woodanatomy/
A good general indicator of a wood's strength is its density which is usually measured by specific gravity. In most cases, the higher the density is the stronger the wood will be.
The density of wood, exclusive of water, varies a great deal within and between species. Density variations within a particular species of approximately 10% should be considered normal. A wood’s weight is always partially contingent on its moisture content, so moisture should always be taken into consideration. The figures below represent the density at approximately 12% moisture content.
HIGHEST DENSITY = BATU / RED BALAU
The hardness of a wood specie refers to how resistant a wood is to scratches, dents and other forms of abuse and tells us how long the wood can stay looking new and unmarked.
The industry standard method for determining the hardness of wood products is called the Janka hardness test. Janka hardness of a given wood species is defined by a resistance to indentation test as measured by the load (pounds of pressure) required to embed a 11.28mm or 0.444″ diameter ball to one-half its diameter into the wood. The Janka values presented are the average of penetrations on both flat grain or plain sawn and vertical grain or quartersawn boards.
BEST RESISTANCE TO INDENTATION = BATU / RED BALAU
STIFFNESS / MODULUS OF ELASTICITY
The stiffness or modulus of elasticity indicates how much the wood will bend (or deflect) when a load is applied perpendicular to the grain. This will tell us how well the deck boards might resist sagging when a person walks over them.
BEST MODULUS OF ELASTICITY = BATU / RED BALAU
STRENGTH / MODULUS OF RUPTURE
The modulus of rupture is a measure of the maximum load carrying capacity of a given species proportional to the breaking point or maximum strength (perpendicular to the grain) as borne by the specimen.
HIGHEST STRENGTH = BATU / RED BALAU
Based on superior mechanical properties, the Batu / Red Balau species is the true star of Mahogany decking.
Batu is engineered by nature to withstand the test of time. Professional builders and do-it-yourselfers should choose Batu for it's strength, high quality and consistency. You can be confident that when you choose Batu Decking you are selecting the best high-performance Mahogany material on the market. For further information on Batu please visit www.novausawood.com