ISO 7798:2017

Overview

ISO 7798:2017 - "Cross-country skis - Determination of fatigue indexes - Cyclic loading test" specifies a laboratory method to determine the fatigue index of cross‑country skis. The fatigue index quantifies a ski’s resistance to permanent changes in bottom camber height (and irreversible damage) after repeated bending. The procedure applies to skis with nominal lengths of 160 cm to 215 cm and defines equipment, test conditions, and result reporting for consistent ski durability testing.

Key topics and technical requirements

• Scope: Measurement of permanent change in weighted bottom camber height after cyclic bending for cross‑country skis (160–215 cm).
• Test specimens: Five skis of the same model-size per test.
• Apparatus:
  • Cyclic bending machine with two adjustable supports, clamping fixture with elastic rubber layers (thickness (4 ± 1) mm, width 40 mm, hardness (95 ± 5) Shore A), and counter to record cycles.
  • Measuring devices for weighted bottom camber (flat plate + dial indicator) and spring constant per ISO 7139.
• Test parameters:
  • Conditioning and testing at two options: Version A: (+20 ± 2) °C (laboratory) or Version B: (−20 ± 2) °C (cold chamber).
  • Frequency: 2–3 Hz; cycles: 50 000.
  • Stroke length determined from ski spring constant and nominal length (test load varies ~500 N to 1 000 N depending on stiffness and length).
  • Recovery time: 24 h before final measurement to remove temporary deformation.
• Measurements and calculations:
  • Original and final weighted bottom camber (h and h′) measured with a dial indicator (accuracy ±0.03 mm).
  • Fatigue index K (%) = ((h − h′) / h) × 100; mean and standard deviation calculated from five skis.
• Damage assessment: Visual inspection for cracks, delamination, stress marks.
• Test report: Must reference ISO 7798:2017 and include ski ID, test temperature, fatigue index, observed damage, and any deviations.

Applications and users

ISO 7798:2017 is used for:

• Ski manufacturers - R&D, durability benchmarking, product development and quality control.
• Independent test laboratories and certification bodies - standardized durability testing for type approval and claims verification.
• Retailers and procurement - comparative performance data for selection.
• Material and component suppliers - assessing effects of constructions and materials on fatigue performance.

Keywords: ISO 7798:2017, cross‑country skis testing, fatigue index, cyclic loading test, bottom camber, ski durability, spring constant, cyclic bending machine.

Related standards

• ISO 7139 - Cross‑country skis - Determination of elastic properties (referenced for spring‑constant measurement).
• ISO/TC 83 (Snowsports equipment) technical context for related test methods and standards.