ISO 7139:2017

Overview

ISO 7139:2017 - "Cross-country skis - Determination of elastic properties" defines standardized laboratory methods for measuring the elastic (flexural) properties of cross‑country skis. The standard specifies how to determine the resistance to bending of defined parts of a ski (central section, tip and tail) for skis with a nominal length ≥ 150 cm. Its objective is to ensure comparable, repeatable laboratory measurement data published by manufacturers, test labs or research institutions. ISO 7139:2017 does not attempt to link measured values to overall ski quality.

Key topics and technical requirements

• Scope: Applies to cross‑country skis with nominal length ≥ 150 cm; recommended reporting sizes: 150, 180, 200 cm.
• Test regions: Central section stiffness (cM), tip/stem stiffness (cS), tail stiffness (cR).
• Apparatus (high level):
  • Two low‑friction rollers (20 mm diameter) on adjustable supports (separation 750–1 050 mm) for central bending; one roller support can fix the ski end.
  • Fixation jaw and three clamps for tip/tail tests (per ISO 5902:2013).
  • Load application devices with specified accuracy (±5 N for central, ±2 N for tip/tail) and a linear deflection measurement device accurate to ±0.5 mm.
• Test procedure highlights:
  • Condition skis for at least 2 h at (20 ± 2) °C and (65 ± 1) % relative humidity.
  • Central bending: supports set at 0.5 × nominal length (lN); apply 10 N preload, then 250 N quasi‑static load; measure deflection 2–5 s after loading. Quasi‑static means flexion speed