Bore Cutting the Hinge

[Spruce Pirate]

There's some interesting thoughts on this here. I totally agree that felling a couple of big(ish) trees over a couple of days does not make up for experience in felling big trees. Why not take a big saw with you from the van? If it's a ten minute walk up hill (steep hill) to where you're felling, and you've got the lunch, the flask, the breaking bar, the wedges, the hammer, the fuel can, the saw.... I'll take the wee saw every time - it's lighter to carry, easier on fuel and much easier to sned / de-limb with. The big saw only comes out for felling the ones next to the road. For preventing damage to high value timber, I think this is a valid reason for using this cut, but are most high value stems not fairly large anyway? As for getting poles to go over easier, I take the point, but, if you've got a pole, surely you've already stripped the top out of it? Why not just leave a long rope in it and pull it over? Even a big diameter, short height pole should be able to be pulled over quite easily with a simple mechanical advantage system, and these don't take much setting up. Sorry if this is a bit scatter-brained, I too have trouble gathering my thoughts into one consise post.

[Albedo]

Good post Spruce Pirate.

 

You're a forester with forests in your head and I'm a back garden tree surgeon with grannies and house wives in my head:001_smile:

[Spruce Pirate]

Fair do's Albedo.

 

Horses for courses I think.

[Chris Sheppard]

There's some interesting thoughts on this here. I totally agree that felling a couple of big(ish) trees over a couple of days does not make up for experience in felling big trees. Why not take a big saw with you from the van? If it's a ten minute walk up hill (steep hill) to where you're felling, and you've got the lunch, the flask, the breaking bar, the wedges, the hammer, the fuel can, the saw.... I'll take the wee saw every time - it's lighter to carry, easier on fuel and much easier to sned / de-limb with. The big saw only comes out for felling the ones next to the road. For preventing damage to high value timber, I think this is a valid reason for using this cut, but are most high value stems not fairly large anyway?

 

Sorry if this is a bit scatter-brained, I too have trouble gathering my thoughts into one consise post.

 

Glad it's not just me has trouble puttign it into words

 

Know what you mean, but for instance, how often would you find something in a wood that a 20" bar from both sides wouldn't reach the middle?

 

I suppose what I'm meaning is that I can't remember more than a couple of times I've had to bore the guts out because of having too small a bar

 

Higher value doesn't need to be massive diameter paricularly.

[agg221]

Know what you mean, but for instance, how often would you find something in a wood that a 20" bar from both sides wouldn't reach the middle?

 

I suppose what I'm meaning is that I can't remember more than a couple of times I've had to bore the guts out because of having too small a bar

 

Higher value doesn't need to be massive diameter paricularly.

 

I would agree with this. I'm neither a forester nor a tree surgeon - I fell the odd decent butt for milling (and using) myself. I have an 076 which will happily pull a 4ft bar, so there isn't much that I can't go straight through from one side, let alone if I go at it from both sides (not too many trees approaching 8ft!). Yes, it's heavy, but as I said, for a single tree it doesn't really matter if you lug it in and out, and I'll probably need it for the Alaskan mill anyway.

 

If I've obtained a single standing tree then I want to make the most of it. That means I'm felling as close to the ground as I can get, in amongst the buttresses, so it's probably wider. If it's big enough to take it then I would probably be considering boring the centre of the hinge. Probably I'd consider applying it to something 2ft or so in diameter upwards.

 

Alec

[Spruce Pirate]

To be honest, I can only remember one in the last year or so that the 20" bar couldn't get without taking the centre out, but most of the time I run a 15" bar and that runs out quite quickly in bigger stuff (it doesn't have to be short by much, you'll still feel a lot of pain felling a 32" tree with a 15" bar if you haven't bored the hinge). If I get into really big stuff (not often) the big saws do tend to come out, regardless of where they (the trees) are. Point taken about the value, I tend to associate high value with big, but it needn't neccesarily be so.

[openspaceman]

Slightly above - idea is to meet your back cut

 

 

I'll disagree with you there, the only reason the bore cut is above the fell cut is because the saw clutch cover has to clear the bottom of the hinge in order to take out the the middle of the tree that the bar cannot reach from the back. Not only does the retained bit stop the tree from falling it also pulls a long sliver from the butt when it goes.

 

When I started ash up to 15QG was more valuable than oak of the same size, for sports goods and before hurley sticks were heard of in Sussex and Surrey.

 

Ash was the species famous for what is now called barbers chair where the force necessary to bend and break the hinge exceeded the tearing of the fibres. A bore cut lessens the bending force of the hinge without weakening it because the hinge works on the principle that wood is most strong in tension if the hinge is correctly sized. If the tree sits back the tension on the front of the hinge prevents the tree going over backwards before the hinge fibres have a chance to bend, if it tries to go sideways its mostly the tension on the opposite side that holds it up with a significant contribution from the compression of wood on the side it is trying to go. That leaves it to bend the fibres in the hinge and topple until the gob shuts and the momentum snaps the hinge in tension. So taking out a bit from the gob face in the middle of the hinge doesn't weaken the hinge much but for a given width of hinge it lessens the force necessary to bend it significantly, in the same way Matteck advises a hollow tree has not lost significant strength till 30% of the wall thickness remains.

 

So with high value hardwoods, especially ash, using a bore cut aided felling. We also used a shallower angled gob which otherwise would have closed too early and potentially split the stem coupled with thinner than the recommended 10% hinge to maximise saw timber.

 

Incidentally if you consider the fell cut coming higher above the bottom of the sink you will see that as the fibres at the back of the hinge have little resistance to separating that the hinge has more height within which to bend the fibres often giving a bit more control. The trouble is if there is any spiral or sloping grain you need to keep the fell cut as close above the bottom of the hinge to make sure all the fibres in the hinge are working for you. Get the fell cut below the gob and the sloven pulls fibres from the tree rather than the stump, again ruining timber.

 

As to using the bore cut to fell bigger than twice the operating bar length have a look at the attached graphic of an idealised cylindrical tree and consider how far a bar that is 40% of the trunk diameter has to be pushed into the gob, the limiting factor tends to be the front handle of the saw, so it makes sense to pencil in the buttesses and make use of flutes to make sure of severing all the central fibres.

[Arctostaphylos uva-ursi]

Nice post Catweazel.

 

Incidentally, when I was younger, you were my favourite wrestler!