In the last few years I was fortunate to work with a lot of different tree-climbers, and also to watch them climb in competitions. Two of the most memorable events were the ASPTCC in Auckland and the New Zealand NTCC in Blenheim. Watching these incredibly talented climbers finding the perfect line through the tree was very impressive and I must admit I am quite excited about the ITCC in Australia next year.
When we watch these top climbers, they often use different anchor points in the tree to achieve an efficient and fast climb. But how does the climber know that the anchor point 25m over him in the tree is good to climb on? Most people will say it is experience – and that is part of the truth. But the tree itself and simple physics will tell us a lot about an anchor point.
Three simple rules are:
- A vertical leader is always a better and stronger anchor point then a horizontal branch.
- Anchoring close to the branch collar will put less force on the branch and result in a stronger anchor point.
- A large diameter branch is stronger than a small diameter branch.
The big differences between a competition masters challenge and the everyday work is that the trees in the competition are pre-examined and hazards are eliminated or isolated. Before the climber enters the tree he needs to receive approval for his anchor point by the judges. In our everyday work we do not have this luxury so we should be more conservative about our first anchor point in the tree. The first anchor point we need is for our access rope. This anchor point should be strong, close to a horizontal leader, and optimise the access into the tree. The access rope can be set up in a double or single line configuration, for body thrust, footlock, motorised or mechanical ascend into the tree. All these techniques have their place in the tree climbing world. What is important is that we do not damage the tree while accessing it.
Damage to the tree can be caused by:
- Body thrusting without a cambium saver.
- Single line being tied off to the base on thinly barked trees (When tying the rope to the base of the tree we increase the load on the anchor point. This increased load can cause a similar damage to the bark and cambium as body thrusting without a cambium saver)
- Branches or anchor points breaking out.
As our hazard identification states, we need to check the tree for hazards before we climb it. This checking for hazards should carry on throughout the climb. When we start with a lower and more solid anchor point for the ascent, it will allow us to pre-check all our further anchor points.
A good anchor point will:
- Let you retrieve your cambium saver.
- Allow for work positioning with a safe rope angle.
- Carry the dynamic load of the climber as well as the load of a second climber in an emergency situation.
- Withstand side loading and will retrieve to its natural position after being dynamically loaded.
I would say in 95% of trees you can find a multitude of anchor points that allow you to easily reach all work positions safely in the tree. If we cannot find this anchor point, we need to find a safe compromise.
Scenario 1: We have a good anchor point but we cannot reach a work position with a safe rope angle because the tree is widely spread.
Solution A: Rope redirect.
Awareness: This increases side loading of the main anchor point, and the force on the redirect can be one and a half times greater than the force on the anchor point.
Solution B: Use a second anchor point with your rope tail to prevent falling and swinging.
Awareness: Debris like branches and wood can catch in the created rope loop and cause injuries.
Scenario 2: The tree does not provide a safe anchor point high enough to allow for an efficient climb.
Solution: By bracing or tying together weaker branches we can create an anchor point or a false anchor point.
Awareness: A badly set up bracing can increase the force on the supporting branches. This can cause them to fail. Also bracings and false anchor points cannot be retrieved from the ground.
Finding an anchor point (or building one through bracing) that you feel safe with will increase your productivity as a climber. You will waste less energy used by holding on to branches and trying to keep your balance.It is easier to reach your work position and you will have more energy left to do the actual work.
There is no rule of thumb that will determine what branch diameter you can rely on for fall protection. The strength of a branch can vary depending on the position of the branch in the tree, the species of the tree, the time of year, the amount of moisture in the wood, defect in the wood, cavity in the branches, bark enclosure or union shape, the surrounding of the tree, and probably a few more factors that I have missed. This is something you need to learn from more experienced work mates or tutors.
Have fun and climb safe.
Published: (Tree Matters, 2010,12/2)
by Andreas Ross