Author:  Kam S. Leang
Date:  May 07, 2005

Summary:  This article discusses plans for a new core profiler design that uses a thickness planer as the cutting element.  Compared to the traditional router-bridge method, the planer profiler can profile a wood core much quicker while featuring greater ease of adjustability at the same time.

Description:   Profiling wood cores is without at doubt the most time consuming phase of the ski-building process.   Traditionally, the router-bridge is used for profiling because of it's versatility.  However after frequent use, one will quickly discover that the router-bridge method isn't very efficient, making core profiling a chore.  New guide rails have to be fabricated with every new profile design that you come up with.  Also, routers tend to create lift of the wood.  This can create problems when routering thin sections such as the tip and tail portions of the wood core (2-3mm thick).

A solution to this is to use a thickness planer to profile your cores.  The planer profile is a simple jig that holds your core on a wedge, the angle of which corresponds to the tapered section of your core.  Running this "shimmed" core into your planer will then create the taper for your core with a few quick passes.   The design of a simple planer profiler along with operational instructions follow.

Building a Planer Profiler  A diagram of a planer profiler is shown below:

Step 1:  Gather the Following Materials

• 0.5"x 12" x 72" wood (2 pieces)

• metal hinges (2 pieces)

• 5/8" long screws

Step 2:  Prepare the Panels  Make the panels by simply cutting the 12" x 72" wood 2" (5cm) shorter lengthwise than your average wood core or ski lengths.  For my case, I usually make skis in the 175-180cm range so my panels are cut to 170cm (67").

Step 3:  Put Holding Screws In Panel  To prevent the wood core from sliding around while in the planer, use screws to hold the core in place.   Some 5/8" long screws should do the job.

Drill the screws into one panel until the tips just peek out from the surface.  The following picture shows how the screws should appear in the panel.

Place approximately 20 of these screws throughout the panel.  When placed firmly onto the tips of these screws the wood core should stay in it's place without additional help from double-sided tape, bolts, etc. 

Step 4:  Attach Hinges  Arrange the two panels on top of each other and connect the panels together with metal hinges.

Step 5:  Make Shims  To prevent the raised panel (with the exposed screw tips) from bending under pressure use shims for support.

Shims are really easy to make and can be cut from any leftover scrap wood that you may have laying around.  Make 4-5 shims of various sizes.  For this profiler, shims with heights of 35mm, 25mm, 15mm, and 10mm were made. 

As with the panel made in step 3, screws were drilled into the shims so that their tips were slightly exposed through one surface.  These screw tips help prevent the shims from sliding around.

That's it!  Everything's done and you can start profiling your cores! 

Using the Planer Profiler  The planer profiler is very easy to use and requires only a few geometry skills. 

Step 1:  Profile Design  First select the dimensions for the desired core profile.  An example of how a core is typically profiled is shown below:

Step 2:  Plane to Mid Thickness Now using your planer alone without the profiling jig simply run the blank wood core through until you have reached the "mid thickness" level.

Step 3:  Set up the Planer Profiler Next set up your planer profiler to create the tapered portions of the wood core (highlighted in red).  To set up the profiler we'll need to look at the core profile design a little closer.  In particular we'll look at the tapered section towards the tip.

X and Y are known and can be calculated or measured from your profile design in step 1.

Next, take a look at the planer profiler:

For the set up, we must set the angle of the profiler to the same angle as the tapered section of the core.  All we have to do is make sure that the ratio of T to S is the same as Y to X.   You already have Y and X measured from your design and S is simply the length of the panel (in this case 170cm).  So to find T simply use rule of similarity to perform the following math:  

T = S*Y/X  

That's it!  Use calipers or a ruler to accurately measure the height of T and set the panel into place using the wedges. 

Step 4:  Plane Your Core   Place your core onto the exposed screw tips of the angled panel and tap lightly with a hammer to set into place. Adjust the depth of your planar accordingly and begin planing your core.  You'll have to make few passes and maybe some adjustments to your profiler to get things dialed in correctly.

Step 5:  Finishing the Core  Once you get used to how the jig works profiling cores becomes a breeze making it only a 10-15 minute task opposed to the hour or so it takes using the router-bridge method.   But there are few finishing details that need to be done.  The planer puts an extremely smooth surface to the core.  You'll want to roughen up the core with some sandpaper to increase the wood's ability to bond with epoxy.

You'll also notice that this technique doesn't create the flat plateau section for the tips and tails.  These portions can be left tapered as is or you can simply flatten them out with your belt sander.  It's a millimeter or so thicker so it won't take much time at all.  I usually just leave them tapered.