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 < 20 mm/min.
  • Tip and tail: fix ski at specified distance from heel; apply 10 N preload, then 40 N quasi‑static load; measure deflection 2–5 s after loading.
• Results & reporting:
  • Perform three tests per characteristic and report the mean.
  • Unit: newton per millimetre (N/mm).
  • If values are published referring to ISO 7139:2017, tolerances are ±20%.
  • Test report must reference ISO 7139:2017 and include manufacturer, model, nominal length, serial number, results and any deviations.

Applications and users

• Useful for ski manufacturers (R&D and QC), independent test laboratories, research institutions, product certifiers and procurement specialists who need comparable flexural stiffness data.
• Enables consistent comparison of flexural properties across models and suppliers for design validation, material selection, durability studies and performance research.
• Note: measured elastic properties are objective laboratory data - ISO 7139 does not prescribe performance or "quality" rankings.

Related standards

• ISO 5902:2013 - Skis (alpine) - Determination of elastic properties (related test fixtures and concepts).
• ISO 6289 - Skis - Vocabulary (terms and definitions used by ISO 7139).

Keywords: ISO 7139:2017, cross‑country skis, elastic properties, flexural stiffness, bending test, laboratory measurement, ski testing, ski manufacturers, ISO standard.