SP-12-32 mechanized pre-skidding and skidding of tree lengths with yarder

Full trees are moved to a landing (roadside landing, landing pad etc.) suspended under a carriage that runs on a cable (skyline). Different types and configurations are available (live, standing, running skyline, self-propelled carriage, swing yarders - carriages with cable or grapple)

Functiogram

Advantages

capable of working in steep terrain
less soil disturbance than for ground-based
capable of pre-skidding loads (drop line)
can work with limited road network
minimum of operations on the working site (safety)

Limitations, thresholds

Relatively long set-up and dismantle time
Fixed set-up and dismantle time require relative intensive removal (ca. 0.5-1 m3/ m line)
High planning effort
Requires high operator skill

Main use

Mountain operations
Alpine forestry
Developing on soft terrain as reduced-impact alternative to ground-based extraction

Economic suitability

Example:

machine costs without personal costs: 100,00 Euro/h
personal costs per person: 35,00 Euro/h
number of persons: 3
in total: 205,00 Euro/h
regression line minutes per tree
- b₀ = 1,0
- b₁ (tree volume) = 0,5
- b₂ (skidding distance) = 0,015
plus time for set-up and dismantle