SP-21-31 skidding of full tree with clam-bunk skidder

Full trees are skidded with their butts resting on the rear axle of the skidder, while tree tops drag on the ground. The butts are retained on top of the rear axle by an inverted grapple (clambunk) and placed on that grapple using a hydraulic loader.

Functiogram

Advantages

Much reduced friction, soil disturbance and contamination
larger loads can be assembled, than it would be possible with a cable or grapple skidder

Limitations, thresholds

Large machine, very heavy and expensive
limited maneuverability, clumsy

Main use

Plantation forestry
Boreal forests on solid ground
Whenever long assortments need to be produced, and logs cannot be cut short (conversion kits for forwarders and skidder available)
Costs per m³ depending on tree volume

Economic suitability

Example:

machine costs without personal costs: 90,00 Euro/h
personal costs per person: 35,00 Euro/h
number of persons: 1
in total: 125,00 Euro/h
regression line time per tree
- b₀ = 0,0
- b₁ (load volume) = 2,0
- b2 (skidding distance) = 0,01