Base anchor pulling capability’s vs isolated fork

[TTownsend]

Was on site today pulling over a heavily leaning storm damaged willow with a digger as the pull. I was using a throw line to install pull line and was original going to base anchor the pull line until the boss said I had to try and isolate the a good fork as that way you get greater pull than if you base anchored. Is this true ?
 
I’ve pulled over many trees by base anchoring the pull line and has worked fine. In fairness the tree was heavily leaning so needed a big pull but I was always under the impression/thought that either way you’d have the same amount of pull/force?

(I’ll add aswell that we weren’t putting a cut in the tree we ripped out due to already being pretty crippled and in poor shape. We went with isolating the a fork and came out perfect, just interested as it sparked debate during lunch [emoji23])

[Mark Bolam]

No difference UNLESS you weren't through a decent fork and it tore out at a crucial moment, dropping the rope lower and temporarily putting slack in the system, which would be bad.

I've bagged in really high before, set up a base anchor and just cranked the winch until the rope has bust it's way into a decent fork before starting cutting.

You don't get greater pull by isolating the fork like your boss says, though.

[TTownsend]

No difference UNLESS you weren't through a decent fork and it tore out at a crucial moment, dropping the rope lower and temporarily putting slack in the system, which would be bad.
I've bagged in really high before, set up a base anchor and just cranked the winch until the rope has bust it's way into a decent fork before starting cutting.
You don't get greater pull by isolating the fork like your boss says, though.

Cheers for the reply, yeah I was through a strong fork probably 2/3rds up the tree with no danger of tearing the limb out.
He mentioned a similar situation where the line was base anchored and the line snapped just below to where it was tied off to to whatever was pulling it hence his reasoning to isolate. I just presumed it was getting pulled to hard rather than being to do with how it’s anchored

[Khriss]

Never even thought of doing this. Always top anchored. Would worry the abrasion as rope stretched in crotch would ruin casing of rope. Plus if it Did part at crotch- you have lost a good length as opposed to ruined at end of length if knot failed. K

[tree-fancier123]

The boss may have been worried about the fork breaking during winching, as with SRT - a base tie puts double the load on the anchor compared to canopy anchor. I can't explain the physics behind it but the books will have vector diagrams and loads of arrows, Newtons laws blah

[TTownsend]

Never even thought of doing this. Always top anchored. Would worry the abrasion as rope stretched in crotch would ruin casing of rope. Plus if it Did part at crotch- you have lost a good length as opposed to ruined at end of length if knot failed. K

I only base anchor when isolating a fork is difficult down to something like the trees form. Tree I worked on today wasn’t climbable either due to condition aswell

[Khriss]

Yr not wrong Re forces on rope and tree. Just has never occurred to me to do this ? k

[Mark Bolam]

10 minutes ago, tree-fancier123 said:

The boss may have been worried about the fork breaking during winching, as with SRT - a base tie puts double the load on the anchor compared to canopy anchor. I can't explain the physics behind it but the books will have vector diagrams and loads of arrows, Newtons laws blah

That’s true, but the forces aren’t straight up and down here.

Another advantage of a base anchor is that if a fork does tear out there are usually lower limbs or crotches backing you up, which isn’t true with an isolated top tie.

[Dan Maynard]

It's absolutely true you can use force vectors to describe the situation. Or, as the fork doesn't care what is on each end of the rope or what is going to happen next you can count the ropes and say the situation with two ropes going to the fork will put more load on it than only one.

In this situation I doubled the rope round the stem and back to the tow point, as it halves the load on the rope. I guess depends what you think is most likely to fail.

[scotspine1]

5 hours ago, TTownsend said:

the boss said I had to try and isolate a good fork as that way you get greater pull than if you base anchored. Is this true ?

 

Yes it's true.

 

5 hours ago, Mark Bolam said:

You don't get greater pull by isolating the fork like your boss says, though.

 

Wrong.