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SRG TEST Terms & Definitions

Pressure Distribution -- As a ski slides over the snow, it is continuously loaded and unloaded by the skier. The ski presses on the snow and the snow presses back. The pressure distribution is a slice of that dynamic loading and unloading. The pressure acts on the snow, compacting it and losing energy. The study of the pressure distribution is the foundation for the analysis of energy losses. The skier makes the ski go fast -- we analyze the forces which slow it down.

Glide Index is a measure of a ski's ability to glide. It is a forecast of speed based upon the principal of drag and some other simple variables. The larger the glide index, the faster the ski (or so SRG thinks).

Glide Index Skate -- As in striding skis the glide index is a measure of the lack of resistance to sliding. In the case of traditional striding skis it includes the friction of kick wax. In the case of skating skis we are concerned only with the frictions and forces of a glide waxes ski. The glide index assumes a flat ski (base surface parallel to snow) and the larger the number the faster the ski.

Grip Force % is a measure of a ski's ability to grip the track, a measure of the fraction of total kick force which is transmitted to the wax pocket of the ski -- the higher the percentage, the better the grip. Minimum grip requirements will vary with snow and humidity, with wax and track conditions. All other conditions equal -- the ski with larger grip climbs more efficiently.

ST Tracking Stability -- is a measure of a skis resistance to sideways thrust or its persistence in moving straight. The larger the index the more straight running the ski. The index is a function of pressure distribution, ski and base configuration (such as grooves and sidecut) and tip and tail flex.

SF Flat Ski Stability -- index is a measure of the skis ability to keep the base surface flat edge to edge. Skis with high SF make best use of their glide index speed. They are smooth gliders in uneven track.

SE Skate Edge Stability -- is a measure of the pressure of the edge of the ski due to loads equivalent to the skating thrust. The larger the index the better the feel. It is the least significant and most discussed ski characteristic.

Tip Loading % -- A ½ body weight and full body weight loading of the skate ski, tip loading measures the percent of load in front of the binding. It is a traditional measure in Alpine skis and gives some clues to compacting in soft track. Note that some skis shift to a lower or softer tip loading at full body weight and some do the opposite.

FC Compaction Force -- The pressure on the front end of the ski measured in Newtons per square centimeter. It yields insight into the slope of the shovel when combined with the snow compressibility data. For different track density, we can estimate the depth of compaction and calculate the energy loss -- at least it yields a comparative measure of performance in softer track.

Tip Lift -- When we transfer full body weight to the gliding ski the camber of the ski causes a lifting or reduction in pressure on the front 20 or 30 cm. Actually, it is a shift in location of the pressure. Traditionally, this effect is viewed as a lifting of the tip and is called Tip Splay. We measure it as a reduction in the compaction force and the units are the same, N/cm2.


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