Overview  A ski or snowboard is made up of many layers of materials, for example as shown in the illustration below:

One of the main layers is the core, and most often the core is made of wood.  Traditionally, wood is used for the core because it has many desirable properties, such as being damp and springy.  To see some of the typical properties of woods, click here.
 

For the design of our skis, the cores are made from maple, poplar, birch combinations.  The core is profiled from a laminate blank, which is created by gluing together thin strips of wood.  The laminated wood is then shaped on a core profiler to get the desired profile.  The shape of the core will determine the flex of the ski.  In the figure to the right, Kelvin Wu displays a sample wood core to illustrate what a typical core would look like.  (Note that the core Kelvin is holding is just a sample, made from a single piece of pine.  The sample core was NOT profiled from a laminated blank, so there is a knot in the core.  Ideally, you do not want knots or major discontinuities in the core material because they can drastically affect the flex of the core or create weak points in the core, consequently affecting how a ski flexes.)  The core that Kelvin is holding was profiled on a wood core profiler and a discussion on how to design and build a simple core profiler is presented below.

Building a core profiler is straightforward, but there are a few things you need to keep in mind.  The basic components of the profiler are shown in Figure 1 and a photograph of an actual profile table is shown below.  The profiler consists of two identical rails and riding on the rails is a tray that supports a router, which slides back and forth over the rails.  As the router slides over the laminated wood, it profiles the core based on the shape of the rails.  It's that simple.  Notice that this profiler design is a manual
profiler, meaning that you have to move the router
back and forth with your own two hands.

Figure 1.  A core profiler which consists of two identical rails, a router support that slides over the rails and a router tool to profile the wood core based on the shape of the rails.




 

Steps to Build a Profile Table  The following steps outline how to make the profile table shown above.  The dimensions of the profile table we use to make our cores are shown below:

Step 1: Gather the Following Materials:

• 4'x8'x3/4" MDF board (1 piece)

• 12"x3/8" wood dowel (10 pieces)

• 2'x15"x1/4" plywood (1 piece)

• 1"x3/4"x4' pine stock (2 pieces)

Step 2: Building the Bottom Base (BB):  The bottom base is made from 3/4" thick MDF board.  The dimensions of the bottom base are 3/4"x24"x96" (see above figure).  After the bottom base has been cut to size, measure out the locations for drilling 3/8" holes for wood dowel placement.  The wood dowels are used to secure the rails.  Cut ten 1" long wood dowels (3/8" diameter).  After the holes have been drilled into the bottom base, glue the wood dowels into the holes.  After the rails have been made, they simply snap into the wood dowels (without gluing, therefore you can make different rails for different core shapes).

Step 3: Building the Top Base (TB): The top base simply raises the laminated core material high enough so that the core is in the correct position during the routing process.  The dimensions of the top base are 19"x80"x3/4" and it is made from MDF board also.  Attach the top base centered with respect to the rails and bottom base (refer to above picture).

Step 4: Building the Rails: The rails are made from thin strips of MDF board.  There are two rails and they both have to be the same size.  Make two rails with the following dimensions:

After the rails have been cut and sanded to the appropriate dimensions, drill five 3/8"-diameter holes in each rail such that the holes correspond to the wood dowels in the bottom base.  Once the rails are complete, simply snap them in place on the bottom base.

Note: the above dimensions for the rails are just recommendations.  Rail dimensions vary depending on the ski dimensions and desired flex.

Step 5: Building the Router Tray Support: The router tray that slides over the rails is made from 1/4" plywood.  Use your best judgment to design a tray that fits your router.  Refer to the pictures to get some ideas.  Please note that 1/4" plywood can flex under the weight of the router, as well as from your weight during the routing process.  The "flexing" needs to be minimized, and one way to do that is to add support members (such as rectangular pine stock) to the 1/4" thick plywood.  See the photos of our router tray to get some ideas.

Step 6: Putting it All Together and Testing:  This is an important step.  First, assemble the router table, and then test it.  We recommend you use the following router bit for smooth profiling:

Test the router table by placing a scrap piece of wood that has the desired dimensions (length and width) of a core that you want to profile.  After profiling, double check the dimensions of the core.  In particular, check the thickness at the tip, tail and midsection.  Assess whether the profile table meets your desired specifications.  Make any required adjustments to the rails or the other components of the profile table to ensure that it works properly.  Finally, make some cores and layup some skis!