Base Preparation

This year I bought gray Isospeed 7200 p-tex base material.  I chose this material because I had good results with it on the Panjshirs last year.  Also, I was told by my ski shop that this material was easier to grind than a similar Durasurf product.  Additionally, this material is abraded on both sides so less grinding is necessary to get the ski ready for wax.  The edges have a 1.33mm step, are sand blasted, and made from hardened steel.

  
The first step in preparing the base is to cut the base material using the template made earlier.  The base material is easily cut with a razor blade as long as it is clamped down.

Next the edges are clamped and tacked in place using superglue.  As in years past, I did not wrap the edge around the tip or tail, but ran it to the point where the tip and tail radius began.  This makes the edge simpler to manufacture and lightens the ski a small amount.

Once the edges are tacked in place, the base must be covered with tape in order to protect it from epoxy.  The tape also helps to secure the edges in place so they do not shift during pressing.

I chose to use contact paper this year instead of tape because one pass could cover the entire base (vs 3 or 4 tape passes).  Having a single sheet will prevent ridges from forming where the tape overlapped (ridges form during pressing - this means less base grinding is needed later).  Also, the contact paper should be easier to remove than tape because it is a bit thicker.  In order to apply the contact paper, I first set it outside in the ~100 degree sun and softened it up a bit.  Next, I stuck one end in place, then lined up the sheet and began to unroll it onto the base.  Once done, a cloth was rubbed over the surface to ensure a good bond.

 

A razor blade was then used to trim the excess contact paper from the base.

The base is now ready for pressing.

Base and Edges

The base of the ski is critical to the way the ski will perform since the base holds the wax on which the skis glide. The base is made from Ultra High Molecular Weight Polyethylene (UHMWPE) which has been sintered and rolled into a sheet. Sintering is a method for making object from powder until the particles bond to each other (http://en.wikipedia.org/wiki/Sinter_). The nature of sintering allows for small pores to be created in the surface; in this case the pores allow the wax to be absorbed into the surface. One side of the base material comes abraded; this process scratches the surface and allows the epoxy to mechanically bond to the plastic.

The edges are made from hardened carbon steel and are designed so that epoxy can fill in the voids and create a strong bond. The edges have also been sand blasted to create a rougher surface for bonding. Since the edges are carbon steel, they will rust over time. Stainless steel of the same hardness would be prohibitively expensive.

The base material is relatively easy to work with since it can be cut with a razor blade. The base templates created earlier are used to quickly cut out the base shape. As mentioned earlier, the base template is critical as it will give the ski its final shape.

Once the base is cut out, the edges are tacked on on with superglue. The superglue is only applied every six inches in order to leave ample room for epoxy to bond. Clamps are used to hold the edge in place until it dries.

The edges can be bent around the tip of the ski, but without engineered bending equipment, this is a cumbersome task. Since the edges are hardened steel, they can be annealed (http://en.wikipedia.org/wiki/Annealing_(metallurgy)) with a torch to soften the metal. Once the metal is cool it is more ductile and can be more easily bent. Since the metal is softened, it will wear more quickly, but since it is at the tip or tail, hardness is not as critical.

The base and edge design of these skis does not require that any edges be bent. The base material is simply brought to the edge of the ski at the tip and tail. Although this design is more susceptible to damage, it has proven to be adequate in the past, especially with a cap ski design.

I had originally ordered 12 steel edges, but was only shipped 10 so one ski does not have the edges applied yet. I have contacted the supplier (www.skibuilders.com) to find out if they will ship me the two edges they overlooked.