If you are
a true ski techno-weenie there is more to know about a skis shape than we
would care to discuss (we have heard the engineers lectures and it seems like
so much minutia). There are many factors but we consider to be worth considering:
The overall width of a ski and the width of the tail in comparison to the
tip.
The overall
width of a ski tells a lot about how a ski will perform. We usually consider
the tip first and foremost but for discussions sake we will compare three
skis we carry. The Tua Sumo has a 110/75/100 mm tip/waist tail shape. The
Black Diamond Arc Angel has a 108/72/101mm shape while the Atomic TM20 is
106/66/90. The Sumo has more ski on the snow as it is wider through the tip
and waist than the TM20 and the Arc Angel. The Arc Angel has more than the
TM20. If you ski them all in powder and crud predictably the Sumo is easiest
to ski followed by the TM20. Remember a really wide ski with a wide waist
will be take a lot of power to get on edge on hardpack. Usually skis much
over 72mm in the waist are hard to power over on edge on groomed or hardpacked
snow. A big difference in width between the tip and waist will help to rectify
this but generally a wider ski is for powder and crud.
The width
of the tail in relation to the waist tells you how quickly a ski transitions
from one turn into the other and how well the ski holds a turn. A relatively
narrow tail tends to wash out in a long turn although good skiers can certainly
hold the turn while a fatter tail will hold. This makes a ski with a wider
tail hold long turns best. If a ski has a narrower tail the ski snaps into
a turn quickly as the tail offers no resistance while the wider tail resists
the turn slightly. To make more sense of this just picture a shaped ski on
edge. It is curved so as a ski flexes in a turn (all the ski will be on the
snow) there is more pressure where the ski is fattest. In the the three skis
mentioned above which ones do you think turn the fastest or hold the turn
longest? The TM 20 is a very quick snappy ski in comparison to the others
while the Arc Angel holds long turns the best.
Another thought
is how narrow a ski is, opposed to how wide. Compare the TM20 mentioned above
at 106/66/90 to the TM24 at 102/63/84. Although the waist in the TM20 is 40mm
narrower than the tip it will not turn as quickly as the TM 24 who's waist
is 39mm narrower. That is because the TM 24 is narrower overall and easier
to power over on edge.