1. Rien Visser, Virginia Tech
Cable Yarding
How it works….
Rien Visser, Virginia Tech

2. Problem: Extraction of trees on steep terrain
stems
waterway

3. - suspend wire rope across the slope (skyline)
stems

4. Right hand ordinary lay
Wire Rope (cable) Function: provides the elements of a rigging system to pull the stems from the forest to the landing
Right hand ordinary lay
6 x 19
Strand
Steel Core

5. - Suspend cable from tailtree (or tailhold) and a yarder
skyline
stems

6. Yarder Types Yarders Mobile Stationary Independent Steel tower/spar,
wooden tower/spar, steel lattice work.
Integral Swing
Steel lattice work.
Excavator type yarder.
Integral
Steel tube or steel lattice work.
Either vertical or leaning.

7. Tower Function: Keeps the cable off the ground and provides lift to the stems, especially near the landing
Independent or integrated
Small (30ft), medium (60ft), large (90ft)
Wooden spar, steel tower or lattice tower
One-piece, folding or telescoping

8. Carrier Function: support yarder equipment and allows transportation
Tracked, tires or skid
Self-propelled, towed or carried/pulled
Mounting for power-train

9. - add a carriage, mainline and drums
drums (winches)
tailhold
yarder
skyline
mainline and carriage
stems

10. Carriages Function: runs on the skyline to get the chokers out to the cut-over and the logs back to the landing
simple single or double sheaves (blocks)
slack-pulling capabilities
hand, mechanical or motorized

11. Winches (drums) / Brakes Function: transfers the power from the power-train to the cables to do the work
Mechanical or hydraulic winches
Water or air cooled brakes
Drum stores the cable
1 – 5 working winches on a yarder

12. - add chokers, choker-setter and operator
tailhold
yarder
skyline
mainline and carriage
stems
choker -setter

13. Cab / Controls Function: to safely ‘house’ the operator and control the operation of the yarder
Houses the operator
protection from external environment
clear vision of operating area
Controls the yarder
‘Old/simple’: Mechanical levers
‘New/modern’: Electronic switches and hydraulic levers

14. - complete system, ready to work…..
operator
tailhold
yarder
skyline
mainline and carriage
stems
choker-setter

15. - how does it work….. stems operator tailhold skyline yarder
choker-setter

16. - let carriage out….. stems operator tailhold skyline yarder
choker-setter

17. - stop carriage above stems…..
operator
tailhold
yarder
skyline
stems
choker-setter

18. - choker-setter hooks up the stems…..
operator
tailhold
yarder
skyline
choker-setter

19. - choker setter moves away…..
operator
tailhold
yarder
skyline
choker-setter

20. - operator raises the stems…..
tailhold
yarder
skyline
choker-setter

21. - pulls towards landing…..
operator
tailhold
yarder
skyline
choker-setter

22. - drop stems on landing…..and starts over again….
skyline
tailhold
yarder
choker-setter
operator

23. Yarder on the landing

24. Yarder on Roadside Limited stacking area
Bell-logger or crane mounted on yarder
Self-loading trucks on regular schedule

25. Effective yarder operation
Its one thing to run one, another to operate it effectively….

26. Three D’s of productive cable logging
‘D’eflection
More deflection: – more payload – same cable tension
skyline
tailhold
yarder
choker-setter
operator

27. Planning !!!!

28. Landing Layout Cable layout Machinery layout direction of pull
guyline location and anchoring
Machinery layout
yarder location on the landing
other machinery on the landing
location of timber stacks
processing area
loading out area

29. Felling pattern ‘Headpulls’ reduces productivity by 15%
Fell trees at an angle to the skyline = 30 + slope (degree)
20 degree slope - fell at 50 degrees
40 degree slope – fell at 70 degrees
Skyline
Felling direction
Yarder

30. Yarder Business Management – Daily production chart
Target
Average

31. Number of Chokers? More chokers means: greater ave drag volume
more tangled strops
increased risk of overloading
Max
Min

32. Human Performance ? Direct and significant influence on:
System implementation and use
Machine productivity
Mechanical and operational delays
Innovation

33. Learn-Curve Effect
Takes a new employee about 3 months to get to ‘100%’
Training helps – also increases potential
Basic cost of new employee estimated at $ $7500

34. Value of human performance?
Yarder operator = $12 / hr
Yarder costs = $110 / hr
Timber Value = $1,000 / hr