Overview A core is
profiled to give its unique flex pattern.
Linear Tapered Profile The linear tapered profile is the easiest to
make and a side view is shown below.
The tip and tail portions (highlighted in blue) are typically 2-3mm thick.
If they were any thicker, the wood in these areas would have to be steam or heat
treated so that they could be bent properly. At 2-3mm the wood can
be easily bent by the forces of the press alone without any treatment.
The binding area (highlighted in red) is the thickest part of the core,
ranging 9-15mm in thickness. The length of this area can be of any
size. But keep in mind that a longer binding area will reduce the
amount of flex in the ski. For example, if the binding area in the
above illustration were lengthened towards the tail of the ski, the tail portion
would not flex as much as it originally did. This is a simple method
in which you can stiffen up certain portions of the ski. For our
first few skis the binding area was only as long as our binding mounting surface
(about 30cm). This makes for a smooth flexing core that feels similar to
our skis purchased from the industry.
Also, stiffness not only depends on the thickness of core but also on it's
width. A ski with a 110mm waist will be much stiffer than a 90mm waist ski
even if they have the exact same core thickness.
Other Profiles Although the linear tapered profile is the most
common, other profiles exist. An example of a parabolic profile is shown
in the following illustration.
It is also possible to make a hybrid profile combining properties of a
parabolic with a linear tapered. Below is a profile with a parabolic taper
towards the tip and a linear taper extending towards the tail.
These are just a few examples of how a wood core can be profiled.
Step 1: Plane Base-Side: First start off by planing one side of the blank core with
attached sidewalls. This will serve as the bottom, or base-side, of
the core. Note that if you used the "moat method" in attaching
your sidewalls you will have to plane the core enough until the sidewalls are
exposed through the bottom. If you don't have a planer you can set up your
core profiling jig with some straight rails. By passing your router
over the core with this setup you will have essentially planed one side flat.
Step 2: Create Template The next step is to create a full scale template of your
profile. This can be done by either using your CAD software or by
hand. Cut out the
template and attach to the side of the core with some adhesive. If you don't want to make a template another option is to use a ruler and marker
to draw the profile on the side of the blank core itself.
Either way, the template or drawing will allow you accurately set the depth of
the cutter while profiling.
Step 3: Profile Set up the profiling jig of your choice and profile
core. It's best to profile the core in several passes.
If you try to cut too deep at once, you may possibly ruin the cutter or most
likely the core. It's important that you take your time and profile
the core as accurately as possible. Also, be careful of the dust and
flying debris while profiling and protect yourself with mask and eyewear.
Step 4: Finishing Afterwards, check to make sure your core has been
accurately profiled. Smooth out the core with a belt sander using
some coarse grit paper. Beware that a belt sander can remove a lot
of material so only apply a small amount of pressure. Leave the core
sanded with the rough sand paper. Don't try to achieve a shiny
smooth finish because epoxy won't bond as well to a smooth surface.