Tree Service Pros - Tree Service in Lincoln, Nebraska
Tree Rigging For Removal Part 2
by David Steg on 10/21/14
Tag Lines. These are the reins to control the
work horses. While load lines carry the weight,
proper use and placement of Tag Lines will control
swing. Without them, a log in motion can become
a potent battering ram.
KNOTS: Good knots to know are:
1. Bowline
2. Running Bowline
3. Running Bowline with a half-hitch
4. Clove Hitch
5. Clove Hitch with 2 half hitches
6. Clove Hitch with 2 half-hitches and a Figure
Eight in the tail. Use this combination on heavy
rigging. The Figure Eight will jam the half-hitches
and help prevent slip-through.
7. Timber Hitch. I only recommend this knot
for cinching up a block rope. Do not use it for
lowering limbs or skidding logs.
8. Truckers Hitch
9. Figure Eight
10. Sheet Bend
You can do a lot of work with combinations of
these knots. Remember: In general, a knot will
weaken a rope by 50%. Bowlines even more. A
good Rule of Thumb for calculating PRACTICAL,
SAFE WORKING LOADS is to:
A. use only 10% of the published tensile
strength, and
B. cut that figure in half to allow for the use of a
knot(s).
Crotch
Natural. They're great when they are strong
enough and in the right position. When selecting a
crotch, make sure it is "U-shaped" enough to
keep from binding and strong enough to handle
the job. On a removal (only) it is a good idea to cut
the bark out of the crotch so the rope will run on
sapwood. Otherwise, you may find that the rope
will cut a groove into the bark and jam solid. Also,
the extra heat generated can fuse the rope into
something that looks like a brown candle at best
and cause a melt-through failure at worst.
Rigged (False). Now we are rigging. False
crotching gives you the option of hanging your
ropes where you need them. Classic False Crotches
were always of rope. With synthetic line,
rope to rope contact generates too much friction/
heat and can lead to premature aging of both
rope and climber. False Crotches consist of the
following components: block (pully) and slings.
a. Block (pully). They come in all sizes and
shapes. Be sure to select one that is rated well
86 Blair: Rigging for Removal
above the ropes you will be using with it. Learn to
use, rely upon and love blocks. They will save you
money on rope, make you money on your job, and
give you a measure of precision control and
security that you wouldn't think possible without
using them.
B. Slings. You've got to hang the block to the
tree with something. Sewn slings come in sizes
from 1" to 3" and larger. Working strength can
range from 500 lbs as a choker to more than
5000 lbs. You can also rig a sling out of eyespliced
rope. Use a rope that is larger and
stronger than your bullrope. SAFETY NOTE: If
you're using a rigging rope fashioned out of an
eye-spliced 3-strand to hang a block with a timber
hitch, be careful not to take wraps into the spliced
section of rope. A sudden jolt can cause the splice
to pop apart and fail.
When selecting a sling, keep shock-loading
stress in mind and specify one that can handle the
unexpected. I recommend that all rigging components
exceed the rating of the strongest rope
employed. If your weakest link in design is the
rope, then you can be more assured of dealing
with a known factor of performance.
Control
We've got the rope selected, we've rigged a
false crotch in the right place with a sling, next we
have to control the weight. A human body check
jammed in a crotch works, but its messy and painful.
Wraps. There is a better way, that way is called
wraps. Human flesh doesn't hold much weight. It
has a tendency to burn and bleed, making the
rope slick and even harder to hold on to. Take a
wrap or two or three around a tree trunk or truck
bumper made of pipe. A round object to take
wraps against is called a bollard in Naval terms.
The minimum ratio is 3 to 1. So, if you were going
to take a wrap around a pipe bumper (bollard) with
a 3/4" line, the minimum diameter should be 2V*".
Whatever you use, the key is the ability to hold
and release at will and with precision.
Compared to a Lowering Device, the biggest
drawback to taking tree wraps is the difficulty in
taking up enough slack to avoid stretch.
Lowering device. The Lowering Device is such
a remarkable tool that it has been a basic component
of many of our rigging practices. Some of our
techniques are impossible without it. With the
Lowering Device, you can be precise with your
wraps, take up all slack and even raise a piece
above an obstacle.
We've got things pretty well in hand now. We
didn't have a good enough crotch so we rigged a
block to a sling for a false-crotch. We've selected
a bull-rope large enough to do the job and in good
condition. We have double-checked to see that it
is long enough. We opted to use a Lowering
Device instead of taking trunk wraps. We're gaining
control. Are we ready to cut yet? NO!
We've got a problem. If we butt hitch, the tip is
going to hang up in some lower scaffold limbs that
we still need for later work. If we tip tie, the butt is
going to smash into the side of the house we're
trying to avoid. We'd better add another line. Now
we're Double Hitched. Ready yet? NO!
We've got the weight under control, but we
don't have any control over swing. Add a tagline
and take a wrap. Are we ready? Maybe!
Cut. What kind of a cut are you going to make?
A. Top Cut all the way
B. Top Cut with Undercut
C. Face Cut and Back Cut
D. Undercut all the way (with a tiny top cut for
safety)
It is understood that this whole rigging scenario
is dealing with a horizontal limb.
Top Cut. Creates a hinging effect that causes
the tip to drop as the cut opens up. Depending
upon the type of tree and whether or not it is alive,
dying, dead or rotten, it is going to react in one of
the following ways:
1. Break over nicely and hold on a hinge. With
ash or pine, that hinge might be a bundle of
splinters.
2. Break over nicely until the hinge lets go and a
long barber chair tear rip along the standing section
of limb. On elm, it could tear all the way to the
ground.
3. Snap off without warning, dead oak. KNOW
YOUR WOOD.
Top cut With an Undercut. The old 1-2-3. It
won't tear, but it can "cock" a tremendous
amount of energy if it hangs up and holds without
falling free in one smooth motion. If that happens,
be prepared for a pretty good jolt when it let's go.
Journal of Arboriculture 15(4): April 1989 87
The old tree toppers in logging used to let them
hang up on purpose just so they'd have a good
ride to brag about after work. Also, using an axe
and a handsaw made it harder to get a clean letoff.
Face Cut with a Back Cut. Even on a horizontal
limb, you can make use of a notched undercut and
then a top cut. You'll gain a controlled drop into
the face and a more or less predictable letoff.
Undercut. When using a crane or the Lowering
Device, the Undercut Only works very well. With
all slack taken up, the rigging operator lifts the
piece up off and away. Done properly, there is no
drop, and no pinching on the saw. You have to be
extremely careful when working with a crane. Too
much tension can cause the piece to barber chair
off unexpectedly, fly into the air with more lift and
greater force than anticipated. EASY DOES IT. A
"tiny" kerf laid into the top of the limb is a good
idea to insure a clean lift off.
Hardware Glossary
We've touched on the basics. Herein is a list
and definition of some special tools that come in
handy.
