Cutting the GOB out

[rowan lee]

How's it going.

 

Just thinking about gob cuts. From a lay mans perspective (me ), I've seen two basic gobs cuts. One where there gob extends up into the trunk and one that extends into the stump. I believe this has something to do with maximising the potential for planking profitability in the lumber trade(?).

 

Anyways both of these gob styles have one thing in common, the horizontal top or bottom cut and the angle cut. My question is this - when starting a gob cut do you generally cut the horizontal or the angle out first, because i have seen a combination of starts in the past, and i'm just wondering if there are hard and fast rules about which start is more favourable given the situation - i.e. big trees (40'' +) vs. small trees (1st thinning), back leaner's, hollow/or rotten trunks etc etc.

 

Cheers.

[Paul Jenks]

Typically the angle first on a conventional felling cut I.e. the angle at the top. The theory, as I understand it, is the horizantal cut is easier to line up with the angled one. Understanding the engineering principles behind the hinge is what underlays good felling. Some of the cuts I've done on big trees with small saws look like an angry beaver has been at it. But the important bits line up and the tree falls in the right place.

Dead trees can be a challenge as sometimes there is no strength at all in the hinge so wedges and ropes may be in order to control the direction of fall.

Even trees with no appreciable lean can have grain that may compromise the hinge if it's angled. Hollow trees aren't always a challenge as it can save the effort of letterboxing.

As always training and experience. A few close calls and the occasional screw up embed care and attention for most of us.

[TRADITIONAL LOGGERS]

I noticed in Canada unlike in England the tree stem is cut level first and then an upward sloping lower cut. Is this to gain more wood at the mill?

[scottythepinetree]

I personally cut the the angle of the gob out first as it helps getting the aim right easier. However, I have worked with a few lads who do it the other way perfectly well. Practice makes perfect etc. That said I have seen many more who do it this way get it wrong than get it right and would always recommend cutting the angle first if someone is learning. As for the angle of the gob I think the recommendation is no less than 45 degrees.

As far as I can remember from doing my first chainsaw course with Coillte, foresters prefer a shallower angle as it does indeed increase timber yield.

Also I would recommend as shallower angle if you are felling over twice guide bar length as it makes the letter box cut a lot easier as more of the body of the chainsaw can fit in the gob allowing you to take out more material.

If you need a hand you can PM me and I'll pop over and have a look. Not that far from you as I recall. Parked a tractor in your yard for a couple of nights last year.

[Stevie Mac]

I noticed in Canada unlike in England the tree stem is cut level first and then an upward sloping lower cut. Is this to gain more wood at the mill?

 

I think its because the tree are mainly on slopes. But I could be wrong.

[Brushcutter]

Upside down face cut is called a Humbolt. It leaves the waste in the stump. I use it on slopes or on leaning trees where its hard to get a face cut in.

 

As for which to do first i chop and change between doing the angled cut and the flat cut. I also chop and change the angle of the cut depending on how long or short i wnat the hinge to hold. Don't forget the old birds beak felling cut or an open face to give it's propper name. Say a 45 degree top cut with bottom cut following the angle of the ground.

[slack ma girdle]

When i cut with the bottom side of the bar i cut the angle first then the horizontal. When cutting with the top side of the bar, i cut the horizontal first then the angle.

[rowan lee]

Thanks fellows, some interesting comments there to digest.

Just to clarify - letter-boxing (haven't heard the term before), is this where you bore through the centre of the hinge perpendicular to the gob? before commencing your back cut?

[Taupotreeman]

I was always taught to do the angle cut first in order to get the direction of fall correct and then the hoizontal. In NZ I've seen a lot of humbolt cuts but that may be because the fellers tend to leave a lot of stump rather than cutting low to the ground. One guy I worked with in a clear fell operation always had me wait until the tree was starting to fall (Larch) and then cut through the hinge to prevent it splitting up the stem and ruining valuable timber.

[Brushcutter]

Thanks fellows, some interesting comments there to digest.

Just to clarify - letter-boxing (haven't heard the term before), is this where you bore through the centre of the hinge perpendicular to the gob? before commencing your back cut?

 

yes it is. Stops fiber pull and allows you to fell a big tree with a smaller bar.

 

It must of been big Larch or very valuable to have to stay and chace the hinge? I've done it some big and expensive Oaks & Chestnut. Its a rather scary experence and not exactly best practice.