Building a Mold
The shape of a ski, i.e., the camber and the curvature in the
tip and tail, is created by pressing the ski materials against a mold as shown
below. In particular, the base mold creates the shape of a ski.
A simple base mold is shown below in the picture. The mold is made of
individual ribs glued together. Each rib is cut to a desired shape from
3/4" thick MDF material. Notice in the design below that there are
gaps between ribs. This design was used because it was cheaper and easier
to make the mold, however, the the gaps between ribs needed to be filled.
The gaps can be filled by laying two
to three sheets of 1/4" masonite board over the top of the mold and nailing
it in place.
Steps to Build a Mold The following steps outline how to build the
Step 1: Mold Design: The first step to building a mold is to decide the shape
of the mold. The mold will create the camber and curvatures of the tip and
tail of a ski. To design a mold, start by sketching out the desired
profile for the mold as illustrated below in the diagram.
the required running length (L) for your ski -- the running length is the
distance between the tip and tail contact points. Afterwards, decide on a
maximum camber height (h) the mold should have and then connect the tip and tail
contact points with an arc. The shape of the arc can be a circle, for
example. Finally, design the tip and tail curvatures (R1 and R2 if you
decide to use a constant radius of curvature). In designing the mold
profile, be sure to make the mold longer than the desired ski length (SL).
Also, take into account that a ski will relax after it is taken out of the
press. Based on experience, we have found that a ski will lose about
8-10mm of camber. To compensate for the relaxation, we added addition
camber to the mold profile design. For our first ski press, we used a mold
with 28mm of camber.
Step 2: Making Templates: After you have sketched
out the design of a profile for the mold, the next step is to draw up the design
in a CAD software and then make a template. The template will be
used to cut and profile the parts of the mold. The steps to make the
template are illustrated below:
3: Cutting Mold Ribs: The next step is to use the templates that you made for the rib and
tip/tail curvature sections as a guide for cutting out parts from MDF board for
form the mold.
WARNING: MDF material can be dangerous
to your health if inhaled, so we recommend that you wear some sort of mask, and
of course, eye protection (not shown):
the template as a guide, trace the shape of the pieces for the mold on MDF and
then rough cut the pieces using a jig saw:
secure the template to each piece that was rough cut and use a router to clean
up the edges so that you get smooth edges. The key is to make all the
what the pieces look like after they have been cleaned up using the
router. They should all be smooth and they should all have the same
Step 4: Assembly: Now it's time to assemble the pieces to
create the mold. First, make sure the pieces fit together:
Then assemble the pieces. There are a number of ways to
assemble the mold. One approach is to glue all the pieces together and use
clamps to hold everything together until the glue dries. The other option
is to use nails or screws to secure the pieces together.
Alternatively, you can make a mold that is adjustable, i.e., you
can move the tip and tail pieces to accommodate different lengths of skis you
decide to press.
Here's an example of our mold, with a couple
layers of masonite board covering the top of the mold to provide a smooth
NOTE: When the press is operated, the bladder can
generate a significant amount of force which pushes down on the mold. So
make sure you design a mold that can withstand the forces that are generated.
Building the Top Mold: After you build a base (or bottom) mold, the
next step is to build a top mold. The dimensions of the top mold is not as
critical as the base mold because the top mold is simply used fill up space
within the press cavity. Also, you can use 2x4s or 2x6s to make the top
mold. Below is an example of our top mold.
Here's the base and top mold placed inside of the press