improper bypass cut consequence

[ramanujan]

a friend of mine made a bypass cut on a leaning alder log. first cut lower and on bottom of lean, second cut higher and above the lean. (most of) the saw stayed in the kerf and went to the ground with the log.

broken ms200t

JPS this is the saw i mentioned a while ago that you had wanted to see a pic of

 

[Kneejerk Bombas]

Wish I had a picture of the o20 I ran over with the loaded dump truck in someone's yard...you could have driven a lawn mower over it without hitting it.

 

[Treeman14]

That's a good case against bypass cuts AND saw lanyards. OUCH!!!!

 

[TREETX]

Not really, my experience has shown me that the ring on the 020T will break away.

 

[TREETX]

Brian - you made that suggestion before. I have been doing that since and no snatchers. If I didn't say it, thanks.

 

[Keener]

Box it up and send it over in the mail to the island here.
I can use the parts (maybe thats wishful thinking), I can use the part to keep mine going.
I think the choke lever is still good, just bolt another MS 200 to it.

 

[John Paul Sanborn]

The idea of the jump cut is to make the top cut farther back so that there is a spring release, hence the "jump" in the name.

When chunking down spars using a bypas, snap or mismatch cut; I will make the deep cut first, opposet to the direction I want to push the chunk, then a shallow cut on the fall side so I can extract it easy and so that I can get it off easier. Also less likely to get a pinch or trap if the holding wood fails because I made the cuts too close, it is more likely to fail towards the deep cut.

 

[Yellowdog]

Could one of you guys with sketching ability draw out what happened for us novices to learn from?
Thanks!

 

[John Paul Sanborn]

I will try it with words,

Picture cutting a large lateral branch.

you make the under cut and then the top cut a little out on the branch.

when the wood fails there is a small curff in the limb as it pops out that traps the saw, in this case ripped it apart.

With a jump cut, one makes the top cut slightly in towards the tree so that when the wood releases it springs out, and the small curf is in the stup, not the branch as it falls down.

 

[Yellowdog]

So, on a long, large branch that is heading out almost perpendicular to trunk, you make undercut then make the top cut a couple inches towards the trunk from where you made the undercut? On the undercut, how deep do you go? A 1/3 of diameter or something like that?

 

[Stumper]

Yellowdog,
You got it! Yes-the undercut should be about 1/3 of diameter.-More than that and your saw gets pinched. 25%will ususally work well to. In some situatons you can just score the bark on the underside to minimize peeling-but that isn't reaaly a step cut and only seems to work reliably on little stuff.

 

[TheTreeSpyder]

There is an excellent Sherrill tip on 'Saw Snatcher' in catalogs but not on web i think. Under proper pruning on pg.54;2003/57;2002.

The pull is down, so if the saw is in region after under cut, wood would naturally flex and break around undercut, taking saw with freefall. i've found in some cases i can turn my wrist as the piece starts to flex over to keep the saw straight inline with the cut as i pull it out; as my best chance of reddeming being 'sloppy' and getting myself into that position. Trying to pull saw straight up as piece is turning, flexing down, can take more effort to quickly get saw out as bar scrapes sides of kerf.

i prefer to under cut (how far depends on leveraged load pressure for me), then 'box' out sides (for less wood fibre on final cut; more controlled/quicker complete release); then come straight down quick to snap out; slow down and across for straight drop. Finding that throwing to the side slightly, takes away som,e of the force that would be throwing back under you.

i think that mechanically this is a version of a KerfDutchy extending across the face to interupt normal face closing and cause a 'hopping' as the faces slam together suddenly early, and are thrown apart. This tops a tree to jump over a fence on vertical, snapcut on horizontal and releases, 'hops' towards early obstruction in fall (uphill, close branches of other tree etc.) as to not hang up on stump and obstruction to fall. Though with the immense forces of felling can cause the splitting and barber chairing from internal force buildup and possible stalling before release, methinks. Just as bringing an under cut past a top cut in felling i think can be more prone to barber chairing etc. for the same reasons. This puts a Kerf DutchFace inside the hinge, that takes command, as it clsoes first. i theorize that even having the top cut extend further than the bottom cut is safer in that regard; but also think such in felling could take the saw with it as well, for similar reasons as we see here with the saw snatcher example.

IMLHO

:alien:

 

[Kneejerk Bombas]

Originally posted by Yellowdog
On the undercut, how deep do you go? A 1/3 of diameter or something like that?

The deeper the undercut, the better it works, so you can watch the tip of the branch you are undercutting and as soon as it starts to move down, stop the undercut and do the topcut.

 

[John Paul Sanborn]

I usualy describe it as cutting to beginning of failure. You cut the 1/3 then ease it up till you see the branch move or curf start to close.

On a similar note, i was working the ground for a guy who's been in the buisness for a number of years and he was hinging a lateral to swing away from another tree.

His mistakes were having the face cut so that the hinge was too close to perpendicular, fighting gravity so to speak. then he cut the top of the hinge first so that the whole thing failed too fast. After we talked he slapped his head wondering why he always did it that way.

My method of doing this is to have the hinge rotated maybe 30 degrees form paralel to the deck and maybe leaving the top fat and cutting the bottom out to stear better.

The face is usualy wide because I do not want it to close. when the swing is to where i want it to fall I will cut the hinge out so it will not tear and swing wild.

May seem a no brainer to many, but I've seen a number fo peoiple that don't think it through.

Some who want to rig everything

 

[ramanujan]

on the avoidance of rigging, this sort of bypass cut is also the best method i've found for causing a limb to land as flat as possible on the ground, preventing it from landing tip first and then springing back or forward-usually directly towards the nearest ground level window