Felling

 

~Pine trees in Northland~

At this work site there where approximately twelve very large pines close to the house on a sloping section. The trees where felled along side the house. To prepare the trees for felling, most of the heavy side branches were removed to reduce the weight in the crown and to ensure the remaining tree would be easier to direct down the side of the house. A hydraulic bottle jack was used behind the scarf to tilt the tree towards the direction of fall as the back cut progressed. This felling method is used to fell counter awkward leaning trees where access is limited and heavy machinery can't be used to pull the tree over with a rope. The trees were left on site with the branch material cut off the trunks leaving the pile of debris neat and tidy. This job took approximately two days to complete.







Before a tree can be felled, the site has to be assessed to determine whether there is enough room to fell the tree or trunk into. The site is checked for any obstructions like powerlines, buildings, etc. or hazards like vehicle or foot traffic. The size and shape of the tree is assessed to see if the weight in the crown will assist the intended direction of fall or if the crown will need to be pruned to change where the weight distribution to make it easier to direct the tree safely. There aren't many opportunities to safely fell trees when working in an urban environment, but often felling techniques can be applied to many aspects of tree removal eg. felling a trunk section after a tree has had limbs and branches removed or, felling pieces of trunk into a confined space. Safe removal involves several stages of setting up cuts into the base of the trunk called the scarf and the back cut. The first stage is to put the scarf into the front of the trunk at the base with a 45 degree cut matching up with a flat bottom cut going back about 1/4 - 1/3 of the trunk diameter. The scarf is the cut that determines the direction of the falling tree or trunk as it will fall 90 degrees to the scarf. So which ever way the scarf is pointing, that is the way the tree will fall. The second stage is to put in the back cut which is opposite just above the scarf. As the back cut goes into the trunk wedges are often used to keep the cut from closing on the bar of the chainsaw.              The back never goes all the way to the scarf as the strip of intact wood between the scarf and the back cut is called the holding wood and this provides the control to the tree being felled. In some cases we can leave more holding wood on the side opposite to where there is more weight in the tree to help counter balance the weight in the crown.


 Related Information:                                                                                      o.s.h tree fell.pdf  -extremely comprehensive- 



Basic Felling Technique

Step 1 - The Scarf

 

The top 45 degree angled cut is usually made first then the bottom cut as it is easier to match up the two cuts this way. It is important to note that the scarf will be compromised if it is over-cut where the two cuts meet. It is critical for the scarf to function correctly that the two cuts match up exactly with a neat, straight line at the back of the scarf.

Step 2 - The Back cut

The back cut is made just above the bottom level of the scarf to create the holding wood in between the scarf and the back cut. As the cut is being made, it is a good precaution to insert plastic wedges into the cut to prevent the cut closing and jamming the bar/chain. A hammer or mallet is used to drive the wedges into the cut as it is being made to gradually open the cut and gently send the tree over. It is imperative never to cut through the holding wood as there would be no control on the fall direction of the tree or trunk being felled which could lead to damage to property, personal injury or death.

Success! The scarf has been made to approximately 1/3 the diameter of the trunk, the holding wood runs through the diameter of the trunk intact and the back cut is made just above the level of the bottom cut of the scarf.