Snowboard turns – basic mechanics
Forces, which cause a board turning, come from three sources:
- Gravitation,
- Environment resistance (snow, air in high speed),
- Boarders muscles.
The base of board is affected by forces coming from the snow surface, and board bindings are affected by forces coming from a boarder’s body. These forces cannot be seen, but rider and board movements can bee seen, and after these movements some guess can be made, what forces are acting. For educational reasons, a significant simplification is useful. For these reasons, it is enough to distinguish and understand three basic mechanics of turns that differ by the way the forces are generated:
- Turns based on a shape of board.
- Turns based on a snow friction and resistance.
- Turns based on a rider’s body rotation.
The three mechanics of turns are at some proportion present in almost every turn. Basic turning styles are then determined by the most comprised mechanics:
- Curving turn style uses a shape of board;
- Counter-rotational turn style uses a snow friction and resistance;
- Rotational turn style uses a rider’s body rotation.
Turns caused by a shape of board
When a board slides lengthways, the curved edge of snowboard together with a flex of snowboard causes the board turning. The board is cut with its edge into a snow surface and is forced by a solidity of snow to follow and extend the line cut into snow. A diameter of the turn depends on the diameter of the board side-cut and the board flex. The side-cut diameter is fixed for a given board, but the board flex can be changed within the ride.
The greater flex of the board, the sharper the turn is. The board flex is a matter of a centripetal force and the centripetal force is a matter of the turn sharpness and the ride speed. Generally, higher speed and more dynamic start of the turn at the beginning of the turn produce higher centripetal force and thus sharper turns. This mutual dependence makes it difficult to start and balance precise turning using this mechanics in a pure form, so it is considered as the most difficult to learn and use this mechanics.
This way of turning is basic when making carving turns; otherwise its significance is minor.
Turns caused by the snow friction and resistance
When the board slides sideways (transversely), certain conditions generate a couple (pair of forces) that causes the board to turn. This occurs when the board is weighted unevenly (the boarder puts more weight on the tip or on the tail of the board) and at the same time the speed of sliding in the transverse direction is continuously changing.
It is important to remember that both conditions must be met. The sliding with an even speed does not cause the rotation even if the board is weighted unevenly. The couple is the result of unbalanced driving and braking forces affecting the board. A dominance of driving forces results in the sliding speed increasing. A dominance of breaking forces results in the sliding speed decreasing. The nature of breaking forces is the resistance of snow which is proportional to the pressure board does onto snow, and this is proportional to the driving forces. This proportionality is held across the board length. The bigger is driving force the bigger is breaking force, and the bigger is difference between them, too. So the integrated force difference on the more weighted side of board is bigger than the integrated force difference on the less weighted side of board. This imbalance can be expressed as one force affecting at the board centre that causes an overall speed change, and the couple that causes a board rotation.
It can be observed that:
- If the board speeds up (or slows down) transversely, its more weighted end speeds up (or slows down) more than the less weighted end;
- The more unevenly the board is weighted, and the bigger an overall change in transverse speed, the more sharply the board turns.
This way of turning is basic in the counter-rotational turning style and has a supporting role in the rotational turning style.
Turns caused by rider’s body rotation
When the board is edged into a snow surface then bindings give driver a support to gain a body rotation or to stop the body rotation against the snow surface. This is due to strong resistance of the snow against a rotational board movement. When the board is flat on a snow surface or free in the air then the rotational movement transferred from the body to the board trough bindings causes the board rotating. This is due to little or no resistance of the environment against this rotational board movement.
Gaining rotational movement of the body, while the board is edged, and then transferring it to the board, while the board is flat or in the air, is the base for the rotational turning style and has supporting role in the curving turning style.