What would we need to consider when deciding whether one would carry out top-end or butt-end skidding?
Even though many site factors can influence the decision, we highlight and compare five of the main factors which need to be considered:
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Top-end |
Butt-end |
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| 1. Ease of choking |
Sometimes top-end choking is preferred when the tree is debranched (delimbed), as choking is faster.
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It is usually quite difficult to get the choker cables or chains around the butt-end of the stem. However, a grab rod (see below) can be pushed under the butt end to hook up a choker chain and pull it through, under the butt of the log.
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| 2. Break out | Top-ends may also allow an easier break-out of the load, as the smaller top-ends are lifted over obstacles and other trees more easily. However, more friction could make break out more difficult – see below. | Where butt ends can be properly lifted, breakout is easier to achieve. |
| 3. Energy required for skidding | The lighter parts of the tree length are lifted off the ground. Although less energy is required to lift the top-end of the tree, much more energy is required to pull the heavy butt-end along the ground. | Less energy is required as the weight dragged on the ground is lighter. There is also less “bending” of the tree resulting in less of the tree length contacting the ground. This results in lower friction, meaning the tree is easier to pull. |
| 4. Choking quality | Shorter chokers can be used. However, the chokers may tend to slip off during skidding. | Because tree diameter increases towards the butt (butt-end swelling), the chances of the choker slipping off are less. |
| 5. Breakages | Due to the power applied to the weaker (thin) end of the tree, the chances are higher that the tree will break during break-out (especially if felling direction is poor or when the tree gets stuck behind an obstacle). However, the thin-end has more bending capabilities when pulled around and obstacle. | The power is applied to the thick-end, resulting in fewer breakages. |
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The lean of the tree and terrain conditions sometimes make it impossible to carry out butt-end skidding. Source: Michal Brink