ALPINA B/2 System Installation Instructions (Draft)
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The Alpina Safety Systems B/2 system
is designed to decelerate an 80
kilogram racer from 80
kilometers per hour
without significant injury if installed properly. B/2 systems should
stand alone and never be tied or linked to any other object in order
that they will properly absorb and dissipate the energy and decelerate
a racer. The Alpina B/2 nets come preassembled with poles and
clips and are rolled as either a Right side or Left side net, with the
net on the racer side of the poles
The only difference between a Right or Left hand net is the direction that it has been rolled up, and they are not marked at this time.. linking -
A 6 mm rope should be used as a layout line to guide drilling for the PC poles in order to achieve straight or evenly curved systems. The PC poles are to be drilled 30 cm into the snow, or deep enough to ensure poles with a predetermined rated breaking point is at the snow level. All clips to end up facing away from the racer. The B/2 net is to be pulled snugly tight between each PC pole in order to eliminate any pockets or sags
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The systems are NOT to be dug into the snow, as this will injure the racer should the net freeze in the snow
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When connecting B/2 nets, the overlapping surface of the nets is approximately 0.5 metres (50 cm). The net coming from the higher part of the slope must be placed on side of the piste. (Racer shedding!!). The nets are connected by threading a PC safety fence pole (without clips) into the center of the overlap of the nets from the top. When connecting the nets in this manner, only one thread should be skipped on the front side (facing the piste) and 4-6 threads on the back side. Drill these connection poles into the snow. There is no other connection treatment at a splice.
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Usually B/2 systems exact locations are determined by the TD and Chief of Course and marked with flags for installation. For information, if B/2 systems are layered, then they must be separated TWO metres each in order that they do not ramp when the first layer lies down. If there is not enough room to maintain TWO metres separation between each layer, then a maximum of one-half (0.5) metre spacing is acceptable. When possible, the poles in layered systems should be staggered by one metre instead of lining up. Multiple layers of B/2 are not connected with a taper at the top of the net as in the past; instead the outer net starts with the full separation,and the layers are parallel to one another.
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B/2 systems linking into the uphill end of A/4 systems should overlap at least two metres past the start of the A/4 system, and be placed 2 metres in front of the A/4 system, and must not be tied or linked into the A/4 system at all.
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B/2 systems linking into the downhill end of A/4 systems must be overlapped at least two metres uphill from the end of the A/4 system, and when possible, be shaped to slightly deflect the racer away from the end of the A/4 system where hazards such as power braid and wire rope high lines pose risk. The B/2 system must not be connected to the A/4 system, just started tight to the A/4 net. The slip skirt does not connect to or overlap onto the B/2 system.
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Fresh snow shall be cleared from the mesh lying on the snow, or alternately, the net could be raised by sliding up the bottom clip. Very strong winds can put excessive strain on the B/2 system, and the net should be pulled together when not in use, that is the top and bottom clips are pushed toward the middle of the safety fence to effectively reduce surface area.
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During take down, the PC poles should be loosened by twisting them to remove. Kicking the poles to loosen should be avoided, as it can damage the poles at the rated breaking points. The loose PC Pole from the splice should be lightly woven beside the first pole at the bottom of the net, then the nets should be rolled evenly and as tightly as possible from the bottom of the net upwards, poles up, and tied in such a manner that the centre will not fall out like a telescope, creating a mess for the next user. Nets should be loaded on B/2 System Blade Carriers 22 per carrier.
NOTES:
An extra PC Pole can be added parallel to the first pole at the top of the first net in a system to help stiffen up the net.
A PC Pole can be used at the end of a system by clipping in the top end of the pole at the top of the last pole at the end of the net and pressing the bottom of the pole into the snow diagonally up the hill to form a triangle an pressure the net tight. Do not drill this pole into the snow.
This document has been updated with information from Mark Appelman detailing current B/2 installation practices from Alpina.
ALPINA B/2 System 2008 (DRAFT)
Friday, January 04, 2008
