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ALPINA B/2 System Installation Instructions

Revision 1 - 2009

PDF version

1. The Alpina Safety Systems B/2 system is designed to decelerate an 80 kilogram racer from 130-150 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, other than the bottom end of an A/4 net, 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 and Left hand net is the direction that it has been rolled up; some of the Skier’s Left nets are marked at the top end of the top pole with a band of red tape. If not marked, when held in the position to unroll downhill, if the bottoms of the poles are facing the right hand side it is a right hand net, if bottoms of the poles are facing left, then it is a left hand net.

2. The B/2 systems should only be installed on snow that has been prepared by a grooming machine. A 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 the pole’s predetermined rated breaking point (PRBP) is at the snow level.  The B/2 net is to be pulled snugly tight between each PC pole in order to eliminate any pockets or sags. Generally the poles are drilled into the snow at 90deg to the piste, but on steep pitches they can be drilled at 80deg to the piste (10deg up the hill) to help prevent the poles from bending downhill.

3. The systems are NOT to be dug into the snow, as this could injure the racer should the net freeze in the snow. Snowfall accumulation of 15-20 cm will require remedial action to ensure proper safety function of the system
   

4. When connecting or “splicing” B/2 nets, the overlapping surface of the nets is approximately 0.75 metres (75 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 hooking the top pole of the lower net into the top square of the upper net at approximately the 75 cm point, then hooking the top square of the lower net over the bottom pole of the upper net keeping the poles approximately parallel, then completed by threading a PC pole (without clips) into the center of the overlap of the nets from the top.  When connecting the nets in this manner, only one or two threads should be skipped on the front side (facing the piste) and 4-6 threads on the back side, thereby reducing pockets on the Racer side.  Drill these connection poles into the snow. 

5. Usually, the exact location of any B/2 system is determined by the TD and the Chief of Course and is marked with flags for installation. For information, if B/2 systems are layered, then they must be separated a minimum of 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. If the back B/2 nets are put in straight and/or with evenly curved bends, then a PC pole marked at 2 metres can be used to put in the next layers of B/2 nets very quickly. A PC pole is 2.2 metres from the top end to the PRBP, and then a 2 metre mark can be located by subtracting the distance between your outstretched thumb and little finger (approx. 20 cm) from between the PRBP to the top of the PC pole, and marking with a PC clip or tape.

6. B/2 systems linking into the uphill end of A/4 systems should overlap a minimum of two metres past the start of the A/4 system, and be placed 2 metres in front of the A/4 system, and then must not be tied or linked into the A/4 system at all.

7. B/2 systems linking into the downhill end of A/4 systems must be overlapped a minimum of 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 is connected to the A/4 system using three slip-skirt dingle balls evenly spaced on the top PC pole. The dingle ball must connect the A/4 net, the slip skirt and the B/2 net together. The slip skirt does not overlap onto the B/2 system. 

8. Small amounts of fresh snow should be cleared from the mesh lying on the snow, or preferably, the net can be raised by sliding the clips up the PC pole.  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. If a large snowfall is expected, experience has shown that raising only the bottom clip up to the centre clip should be avoided, as it forms a pocket that collects the snow, eventually overloading and possibly breaking the poles at the PRBP. Raising the bottom clip 8-15 cm is preferable and acceptable.

9. During take down, the PC poles should be loosened for removal by twisting them.  Kicking the poles to loosen them in the snow should be avoided, as it can damage the poles at the PRBP.  The B/2 nets should be dragged to a location where it is not too steep, and then carefully rolled evenly and as tightly as possible from the bottom of the net upwards, poles on top of the net, and then locked together using the spare PC pole to stitch the roll together. Start the roll by gathering the material between the first two poles, and then begin rolling, having one person rolling and one person further up the net aligning and stretching the net has proven effective. The B/2 nets should be loaded on B/2 System Cradles (B/2 Blade Carriers) with either 25 right hand or 25 left hand nets per cradle, 15 low and 10 up, with all PC poles pointed ends facing the same direction.
   
   NOTES:

   This document has been updated with information from Ingo Hopfgartner (Alpina), Mark Appelman and Jeff (Jelly) Wilson detailing current B/2 installation practices from Alpina and from our actual Race Jury approved Whistler installation experiences during the 2008 World Cup and Canadian National events. 

   ALPINA B/2 System 2009 Revision 1

   Thursday, January 15, 2009