Parallax problems

[Burnham]

Over in the Odds and Ends Forum there's a thread going about problems we individually have with tree work. I mentioned my recent issue of missing an intended lay because I failed to properly allow for parallax viewpoint. I off and on secumb to this pitfall, mostly when the ground or the brush makes seeing the intended lay difficult, but sometimes just because I blow it.

Here's a crude attempt I made at diagraming the different results a faller will get if he doesn't allow for parallax viewpoint.

Black lines are what happens if he properly allows for the fact that his gunning sights are not in the center of the hinge.

Green lines are what happens if he uses a target point way out there at the head of the lay...the angles are pretty close to the black line, so the tree hits pretty close to the intended lay.

Red lines are the results of choosing a target point close to the tree, well down from the head of the lay. You can see how much farther off of the desired lay the hinge points to.

Hope this helps rather than being more confusing .

 

[stehansen]

I always mentally account for the gunning sight line being off to the side of the center of the tree. I now understand what you were talking about though. Plus I have now been warned about picking a target too close to the tree, any mistake is magnified, and any difference between the gunning sight line and the targeted lay is also magnified. Thanks Burnham. I guess why I was lost in this post was I didn't understand the terminology. But now I do, thanks to our handy dandy drawing.

 

[stig]

I don't use the sights at all. I trained myself to putting trees into the lay by just looking in the direction I want them to fall, then the saw lines up automatically.
Like when you shoot a handgun at something by pointing it, without looking over the sights.
I learned this in the 70es, before the mechanical harvesters came onto the scene. We felled an awful lot of smallish spruce and fir trees by hand back then, and hitting very exactly when falling them didn't matter so much, which left room to experiment and train.I'm talking 10-12000 trees a year, so if you worked on it, you could get very precise indeed.
Today it doesn't matter whether it be hard or softwood, I don't have to sight.
Of course I loose the occasional tree sideways, but usually not from the undercut being off, more due to general sloppiness.

 

[gf beranek]

Parallax error really shows up when you're gunning from two corners. Which is the usual case when falling larger trees with a short bar and you have to cut from both sides.

That, and gunning to a close target will produce a hinge that instead of being straight across the stump will more resemble the peak of a roof.

I've had young fallers ask me how I manage to keep my hinge-wood consistently straight across the stump on large trees. And when I explained it to them you could see when their brain clicked and grasped the concept. And then some others you couldn't beat it into them with a stick.

 

[stig]

Parallax error really shows up when you're gunning from two corners. Which is the usual case when falling larger trees with a short bar and you have to cut from both sides.

.

If you make a traditional undercut ( as opposed to a Humboldt) and do the 45 degree cut first, you don't have that problem, since you can simply set the bar into the cut made from the first side of the tree, when you go around to do the other side.

Something I wonder, is the whole gunning thing more difficult when you make the horizontal cut first. Never having done it that way, I can't really picture it, but it seems to me that the possibility to err would be greater.
I mean ,when you do the 45 degree cut first, once you've set the saw to the tree, it pretty much takes care of the rest,the sighting is done. All the operator has to do is finish the cut.

 

[squisher]

That makes total sense to me now with your diagram Burnham thanks.

Stig we've hashed this over in a few threads about which cut makes it easier to gun the tree with. I'm still not following at all how making the angled cut first could possibly be easier to gun with. Of course I use the sites on the saw and not just experience to aim my trees. I also don't follow how there could be any advantage to not using the gunning sites when a exact lay is important. Just having the proper 'feel' or 'eye' for it is not going to be as consistent as having a easily repeatable procedure based on geometry. I also worked the bush for many years, but not before feller bunchers came along just in the areas where they can't get around, highleading.

 

[squisher]

I mean ,when you do the 45 degree cut first, once you've set the saw to the tree, it pretty much takes care of the rest,the sighting is done. All the operator has to do is finish the cut.

So what happens if at the start of your angled cut you didn't line up your lay perfectly? In order to change it you are going to have to redo your cut I would think? When you aim with the horizontal cut you can make as much change to your aim as you want right up to the end of the cut. Your saw is held by the cut and you can easily gun down the sights.

Now I can see your point about falling by feel in the bush, yes most of the time it's not all that important to have an exact lay but get into some big wood with some big stumps around and you will need to be very exact or you're going to be busting up wood. That's when I wouldn't rely on feel and rely on geometry and sights instead. But that's just me. As far as how that applys here? Most arbs aren't going to be consistently falling enough trees to develop your 'feel' so it's probably best to stick to proven geometry/gunning to get an exact lay.

 

[Burnham]

Parallax error really shows up when you're gunning from two corners. Which is the usual case when falling larger trees with a short bar and you have to cut from both sides.

If you make a traditional undercut ( as opposed to a Humboldt) and do the 45 degree cut first, you don't have that problem, since you can simply set the bar into the cut made from the first side of the tree, when you go around to do the other side.

Something I wonder, is the whole gunning thing more difficult when you make the horizontal cut first. Never having done it that way, I can't really picture it, but it seems to me that the possibility to err would be greater.
I mean ,when you do the 45 degree cut first, once you've set the saw to the tree, it pretty much takes care of the rest,the sighting is done. All the operator has to do is finish the cut.

Stig, for you this clearly is not an issue...but the thing that can easily go wrong for someone less experienced, or someone for whom "horizontal", or "parallel", or "level" is not obvious by eye, then getting both sides of that cut to match one of those adjectives is a challenge with your method too, I think.

Perhaps I am mistaken...I know you work regularly with apprentices and are thus not inexperienced when it comes to seeing how people progress learning these skills.

 

[pete mctree]

I have only had this issue when cutting the horizontal cut first. This method has the potentioal to overcut a corner especially if the saw is dogged and the cut continued until the gunning lines are drawn into the desired direction.

With making the top/angled cut first the direction of fell is determined pre cut by the lining up of the saw 90deg to the direction of fell (still using the gunning line on the saw). With this method any overcutting will result in a deeper than desired gob as opposed to an undesired felling angle

 

[Burnham]

I have only had this issue when cutting the horizontal cut first. This method has the potentioal to overcut a corner especially if the saw is dogged and the cut continued until the gunning lines are drawn into the desired direction.

With making the top/angled cut first the direction of fell is determined pre cut by the lining up of the saw 90deg to the direction of fell (still using the gunning line on the saw). With this method any overcutting will result in a deeper than desired gob as opposed to an undesired felling angle

I reckon I really should give this "angled cut first" business a better trial than I did several years ago when I first heard of it...but I swear, it just feels wrong. Then I'd be better able to criticize it . Or I'd find out I'm full of bull .

Once before I think I mentioned that a couple of years ago Doug Dent said he didn't care which you did first, so long as the face was formed correctly and the results met expectations. He doesn't teach felling thataway, but he has an open mind on that point.

 

[woodworkingboy]

I can't get with the program on the angled cut first. I also do tend to over cut on the far side when making the initial horizontal cut. A gap, even a small one at the hinge, seems more and more desirable when the flop is at a tight spot.

 

[GASoline71]

I just close one eye...

Gary

 

[squisher]

I have only had this issue when cutting the horizontal cut first. This method has the potentioal to overcut a corner especially if the saw is dogged and the cut continued until the gunning lines are drawn into the desired direction.

What do you mean by overcut a corner Pete?

 

[squisher]

With making the top/angled cut first the direction of fell is determined pre cut by the lining up of the saw 90deg to the direction of fell (still using the gunning line on the saw). With this method any overcutting will result in a deeper than desired gob as opposed to an undesired felling angle

But if you need to change your gun after starting the angled cut first what do you do? As I said earlier to me that is one of the big advantages of doing the horizontal cut first is you can make infinite changes right up to the last bit of cut.

If I'm understanding correctly with the angled cut first you need to hold the saw in the correct gunning position before or as you start the cut to acheive the correct angle. I'm not seeing this happening effectively in larger wood with a larger saw many many times in a day. Granted we're discussing arb work here and not forestry work and herein possibly lies a difference in techniques.

When making the horizontal cut first when you do your fine gunning the saw is held in the cut you can let go of it if you want and get right down and gun down the sights. If I'm understanding the angled cut first technique you're gonna be holding the entire saws weight trying to gun and start your cut at the same time?


As always I'm not trying to be an ass here I just love tossing these sorts of ideas around and enjoy the discussion.

 

[pete mctree]

What do you mean by overcut a corner Pete?

i have a tendancy to overcut the far corner with the tip of the bar as i set the felling direction

 

[sotc]

i dont follow that either?

 

[pete mctree]

But if you need to change your gun after starting the angled cut first what do you do? As I said earlier to me that is one of the big advantages of doing the horizontal cut first is you can make infinite changes right up to the last bit of cut.

Granted that adjustment cannot be made at the end of the cut, but it's easy to check the direction of fell early on, hence readjustment is done at that point as opposed to re-cutting the entire face

If I'm understanding the angled cut first technique you're gonna be holding the entire saws weight trying to gun and start your cut at the same time?

Yes, but i'm used to it. I find it also helps with longer bars as they don't bend as much when held on an angle as opposed to horizontal.



It's all good squish, i'm not saying one technique is right and the other wrong. It all helps understand, and optios and variations are invalable. If i'm using a humbolt then i do make the horizontal first, as i find it impractical any other way

 

[Stumper]

I reckon I really should give this "angled cut first" business a better trial than I did several years ago when I first heard of it...but I swear, it just feels wrong. Then I'd be better able to criticize it . Or I'd find out I'm full of bull .

Once before I think I mentioned that a couple of years ago Doug Dent said he didn't care which you did first, so long as the face was formed correctly and the results met expectations. He doesn't teach felling thataway, but he has an open mind on that point.

Nah, Burnham. You are right. So is Dent-it doesn't matter if you end up with a prper face. However, it is easier to end up with a proper face making the horizontal cut first. The thing about old dogs is we don't NEED to learn new tricks if we mastered the old ones that were important.

 

[Stumper]

I can't get with the program on the angled cut first. I also do tend to over cut on the far side when making the initial horizontal cut. A gap, even a small one at the hinge, seems more and more desirable when the flop is at a tight spot.

Jay, So long as what you mean by gap is trimming out so that the back edge of the face/front of the hinge is a flat wall. A kerf into the hinge turns it into a dutchman that will either tend to steer the fall to one side or, if made evenly across the hinge will cause early tearoff and less control of the fall.

 

[stig]

So what happens if at the start of your angled cut you didn't line up your lay perfectly? In order to change it you are going to have to redo your cut I would think? When you aim with the horizontal cut you can make as much change to your aim as you want right up to the end of the cut. Your saw is held by the cut and you can easily gun down the sights.

Now I can see your point about falling by feel in the bush, yes most of the time it's not all that important to have an exact lay but get into some big wood with some big stumps around and you will need to be very exact or you're going to be busting up wood. That's when I wouldn't rely on feel and rely on geometry and sights instead. But that's just me. As far as how that applys here? Most arbs aren't going to be consistently falling enough trees to develop your 'feel' so it's probably best to stick to proven geometry/gunning to get an exact lay.

You're right. If you don't get it right first time, you'll have to redo it.
The trick is of course to get it right first time. Constant practise will take care of that.
At first when I started falling, I couldn't hit for shit, but eventually I got better. I still religiously checked each and every undercut after setting it, by standing in front of the tree and sighting it in.
Then I'd change them if they were off. After logging for many years, I realized that I never had to change the undercut any more, so I stopped checking them.
The same happened with the sighting stuff. After a long time using the sight lines, I realized i could do just as well without, so I stopped.
By the way I'm NOT trying to say that doing the angled cut first is better, it is simply the only way I know.
Around here we are required to make our stumps so low, that a humboldt would go into the ground.

Burnham, As for teaching apprentises, some have a really hard time getting this, others not.
The one I have right now is a natural. I've never seen anyone more gifted when it comes to felling trees. When he started, I showed him how I do it and after a few weeks, he was sighting by feel, like I do. What a gift to have..

 

[squisher]

Yah it's interesting how different ways/techniques have developed around the world. Humboldt I beleive has traditionally been used around here to end up with a flat butt. Our logs only go to the mill with a flat butt. Which has also lead to my worst habit of not having enough of a step to effectively prevent stumpshot. Damn whiny buckerman have lead me into improper technique.

While the traditional cut definetly is your lowest stump possible when working on a hillside that is pretty well negated and a humboldt can usually be effectively used to get your stump quite low as well.

I've been thinking of starting another thread about the advantages/disadvantages of each type of undercut but maybe one of you more seasoned fellers could do that with a good description on each eh?

 

[Burnham]

Heck yeah, go for it Justin.

 

[gf beranek]

Words that say my exact same feelings about it, Justin. Geographically you and Burnam, and Gary and the rest of us West Coasters all come from the same old school. And you know? It works pretty damn well!

Though in southern latitudes it may not. And certainly the Coriolis effect may have something to do with that/

 

[TheTreeSpyder]

This is something that can really show up if trying to 'crush a can' with trunk because can is so close. i like a bar that reaches across, cut down slant first while siting beside lay/then stay on that target thru down face and back cut. If can't reach a cross, define a control side and trim backcut to it, then stay siting from that side. Stix in face can give direct target if saw kept straight; siting besides that mark can help keep straight. As all ways, the farther spread apart the 2 points defining a line are, the truer that line is for siting etc. If can't help but have close site target, site 1/2 diameter from gun of equivalent polesaw poles.

The Parallax View was an excellent Warren Beauty, densely packed, sleeper movie; that many other movies kinda became based on IMLHO.

 

[stig]

Though in southern latitudes it may not. And certainly the Coriolis effect may have something to do with that/

When I came from almost totally flat little Denmark and started logging in the mountains of Switzerland, the first trees i felled just went whichever way they felt like.
Switzerland being a lot more to the south than Denmark, of course I initially blamed that on the coriolis effect.
Then I realized that I was so used to the ground being horizontal ,that on a mountainside I couldn't tell lean in a tree!
I soon learned to shut my eyes, find my "inner" horizon, and look at the tree without seeing the slope.
But man, those first trees just killed my self confidense!