Edge sharpness, bevels, base structures, and wax are all important variables in the performance of a snowboard. However, base flatness is the most important variable in providing a board with the ability to perform up to its full potential. Without a flat base, all the other variables are simply bandages.
Many professional snowboarders believe that flatness doesn’t matter because they’re up on their edges all the time. Actually, in order for a rider to get a board up on edge, it must first run flat. And it must do so every time a rider changes from toe to heel edge.
There are two ways to tune a snowboard: the right way and the wrong way. The right way is to get the board completely flat and smooth prior to structuring the base and sharpening and beveling the edges. The wrong way is to achieve visual smoothness or structure from edge to edge by bending or conforming the base to the cutting or sanding surface.
Unfortunately, in most cases, the wrong way is viewed as the only feasible method to get the board out of your shop given the time-consuming process of tuning it the right way. However, the rider will definitely notice the effects of doing it the right way-a difference that will help your back-shop credibility to no end. Here are some of the techniques to flatten boards.
Always start by checking the base and the topsheet with a tru-bar. Base contour is dictated by topsheet contour. In other words, if the base is convex the topsheet is probably concave, and vice versa.
Snowboard manufacturers will grind the boards while they’re warm, or heat them up enough during production that they will change shape as they sit in the wrapper on the sales rack. This explains how a base can have good stone-ground structure from edge to edge but be far from flat.
The next step is dealing with the base edge. If the board is convex, or base high, you don’t need to do anything. However, if the base is concave, you must cut the edge down so that it doesn’t force you to flex the board in order to grind the base. Also, a high edge will damage the structure of the grinding stone, leaving ruts in the stone.
If you have a base-edging machine-like the Grindrite mini-edger-great. Simply cut the edge down so it’s lower than the base material. Be careful: overcutting and base melting can lead to mucho extra work. If you don’t have a machine, you must cut by hand. Use a file and the beveled file guide of choice and simply file the edge until it’s lower than the base.
Before you begin sanding and stone-grinding the base, you should shim the topsheet of the board. By adding shim material to the topsheet you can create an even, flat surface for the feed wheel to roll on.
Shims can be stomp pads, sheets of rubber cut into strips, foam insulating tape, cork tape, or anything that isolates the pressure to the base and cuts away only the areas of base that are high. For example, if a board is concave or edge high, we can put shims on the topsheet along the edge, running from tip to tail (providing the concavity is consistent). This will isolate the pressure to the high spots along the edge of the base. After all, you don’t want to cut away any more material than is necessary.
The Right Tool For The Job
Use the proper machines to grind the base flat. The best situation is to use a wide belt/stone combo. However, a stone-only or belt-only will also work. The most important thing to remember is that heat is the enemy, so avoid high-feed weights, high stone/belt speeds, and multiple passes. If possible, set the board outside (in winter) to cool it down prior to grinding.
Start by passing the board through the belt grinder using a low-grit (180x or 120x) belt at low weight. This will give you a good visual indication of how crooked the board is.
Next, dress the cutting stone with a very aggressive linear structure and send the board over it at low weight. Then send the board over the belt again using a sligghtly more aggressive belt (100x 120x). This will cut high peaks and valleys in the high areas of the base. Then cut them down with the belt. Repeat this process until your tru-bar shows that the board is flat. This may take several passes, so be conscientious of our heat problem.
Finally, smooth the base out with a fine belt or fine cross-pattern structure prior to putting a final structure on the base.
This same technique can be used with a stone-only or belt-only machine. With a stone-only machine, it’s necessary to change the grinding structure from aggressive linear to fine crosshatch between passes. This, of course, will take a great deal of time and stone material. With a belt-only machine, it’s necessary to start with your most aggressive belt (100x 120x) and finish with your finest belt. Send the board over the belt a couple of times with each grit, again using the shim techniques and being aware of heat problems.
Good luck and be patient. This technique is sometimes very time consuming. The end result, however, will bring customers back through your door, looking for a continued great ride.
Matt Cassidy works for Grindrite.