Overview  The majority of ski and snowboard manufacturers use wood for their cores.   Some of the reasons for doing so is that wood creates a more responsive ski and is also very durable.   We use wood for other reasons too - it's easy to find, simple to work with, and less expensive compared to other core materials.   Typically a wood core is composed of separate strips of wood glued together to form a laminated blank core.   This piece then undergoes a profiling process that tapers the thickness of the core; thickest near the center.   The product, called a profiled core, defines how your ski will ride.  

Selection  The first step in core construction is wood selection.  The most common types of species used within the ski industry include: ash, maple, birch, spruce, aspen, fir, and poplar.    When choosing wood, the major parameters that should influence your decision are:  stiffness (modulus of elasticity), strength (modulus of rupture), and weight (density).  The table below compares these properties for several common wood species.

Most if not all of the above woods can be found at a decent lumber supplier.   The cost is pretty moderate depending on the grade averaging $2-$5 per board foot.  

There is really no easy way to figure out which wood will best suit your needs without some experimentation.   One approach is to use a single specie for the first few cores.   This way you can concentrate only on the measurable dimensions (core thickness, wood strip thickness, etc.) to determine their affect on the core’s stiffness, torsional rigidity, etc.  Once you feel comfortable with how these properties correlate to the measured dimensions you may then want to investigate how other woods react.    

After the wood is selected the next step is lamination.