Tree Rigging For Removal Part 1
by David Steg on 10/21/14
RIGGING FOR REMOVAL
The intent of this paper is to briefly detail principles
and concepts of rigging for tree and tree
limb removal. This paper is intended as a
reference tool for tree workers already skilled in
tree removal techniques. It is in no way a
substitute for hands-on instruction by skilled professional
arborists. Rigging becomes necessary
when free-falling is not possible because: a) a
structure is in the way, b) sensitive landscaping
would be damaged, or c) energized conductors or
some other obstacle present a hazard.
Rigging
Rigging becomes desirable when:
A. Roping large pieces provide better control
and greater efficiency than chunking down smaller
pieces, ie: piecing back a limb on a hillside
backyard. If you don't rope it, you might have to
chase a piece through two or three yards and fish
it out of a swimming pool.
B. Large pieces may produce an option in a
more useable by-product than firewood.
Sometimes taking down a tree in saw-log lengths
provides saleable lumber. Black walnut, redwood
and fir come to mind in the S.F. Bay Area, but you
must have a known ready market. An lot of
sawlogs have collected borers for several years
waiting for a buyer before it has ended up as cordwood
anyway.
C. Margin of worker safety is increased. In my
opinion and philosophy,- rigging's primary function
is to decrease worker exposure to hazard. Consider
this situation: you are faced with a long,
horizontal limb. You can chunk it down if you make
20 small cuts, hold on to them and throw them out
10' to clear an obstacle. It wjlK take you 15
minutes to rig a tip tie and a tag line, but then you
can take it in one cut. One cut means you have
reduced your exposure by a factor of 20 to 1.
Those are excellent odds. Also, even though
those 15 minutes of rigging might seem like a long
time of doing nothing with a crew, when done properly,
the time invested works out to be less than
the time needed to physically chunk out 20
pieces.
Rope
Rope design and construction for tree work has
seen a revolutionary change since 1970. We
used to do everything with 3 and 4-strand manila.
Now, we use synthetic braids and 3 strands.
Although the ropes of today are much stronger
than the manila of yesterday, there are some
specific rules for the safe use and handling of
rope.
Selection. As noted, synthetic rope is much
stronger, but Navy regulations require a 1 to 1
replacement ratio. A %" manila shall be replaced
by a %" synthetic. Tree Work, being less
restricted by regulation than the Navy might well
consider down-sizing by no more than one increment
as a reasonable down-sizing by no more
than one increment as a reasonable standard. Example:
%" manila could safely be replaced by a
5/8" synthetic. When down-sizing from a 3-strand
manila (or even 3-strand synthetic) I would personally
recommend down-sizing to a braided type
construction. You'll get more strength and less
stretch than you will from a 3-strand synthetic.
Braid. Highest strength to weight ratio, less
stretch, easier handling, highest cost, greater
abrasion resistance by 1 Vz to 2 times.
3-Strand. Durable, more stretch than braid,
lower cost, heavier weight.
Persona/ Favorites. Stick with ropes designed,
manufactured and warranted by the manufacturer
for tree work. There are several good brands out, I
like Arbor-Plex braid and New England's Multi-line
for a 3-strand. Rope type? I prefer braided rope.
Originally designed as winch lines, they work best
on the lowering device.
Note. I'll say it again, don't judge a rope by it's
tensile strength (that's when it breaks). One-half
inch dacron (6400 Ib) is stronger than 3/4" manila
1. Presented at the annual conference of the International Society of Arboriculture in Vancouver, B.C. in August of 1988.
Journal of Arboriculture 15(4): April 1989 85
(4,200 Ib), but I stay close to a 1 to 1 on sizing. I
will say that the 5/8" arbor-plex is a super rope for
general use. We also use a lot of 7/8". We've
never had a rope fail because it was overloaded.
When in doubt, use a bigger rope.
Special Considerations. When doing critical rigging
involving the use of two load-sharing lines on
the same piece, be sure to use "SAME
SIZE/SAME TYPE" lines. Don't mix a braid with a
3-strand. Reason: they stretch at different rates,
so they won't share the load equally or as intended.
In general, 3-strands stretch more. In practice,
under maximum loading, the braid will do all
of the work. When it breaks the 3-strand is all
alone and it will fail too. Believe me, it's happened
just that way. Two braids or two 3-strands is ok,
just be consistent.
Load Lines. The work horses. Be careful not to
slam-dunk weight into them. Five hundred pounds
freefalling 5 feet will hit the rope with a real impact
shock load of 3000 lbs.
Balance Points:
A. In the middle: hardest to judge, not recommended
for the bigger stuff. It's too hard to get it
right. Always practice new techniques on smaller
non-critical branches and trees. Turning a
medium-sized tree in an open area into a rigging
exercise can be a good investment in time for
when you really need to make the experience
count. When rigging to the middle, be wary of
heavy endweights of foliage.
B. Butt Hitch (only): tied near point of
severance, tip will drop down. Climber has to be
wary of getting hit.
C. Tip-tie (only): given the load line is crotched
directly above the hitch point, butt will fall away
and down.
D. Double Hitch: combining a Tip Tie with a Butt
Hitch gives the most control and security. It is also
the hardest and most time-consuming to rig. You
also have to be mindful of the direction of swing on
the Butt Hitch. If the crotch on the Butt Hitch is
back of the point of severance, the limb can come
at the climber like a battering ram.
