Issue #6: September 15, 2014
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Rigging from Trees: Part 2

Last month's issue of The Flywire generated a lot of feedback - mostly positive, but there were some criticisms. Because there was so much interest in rigging from trees, I decided to devote this issue to an related article written by Steven Santos.  I hope you find it helpful.

Inspecting Trees

By Steven Santos

Tree rigging is often seen as a black art.  Not many of us talk about it.  I want to continue a public conversation that was started by Delbert Hall in his FlyWire article on the physics of rigging to trees.
First, I want to give Delbert some high praise for starting a conversation that I think is very sorely needed in our industry. Right now tree rigging is seen as either a dark art, or as a cheap place to rig. I don't believe it should be seen as either. It bothers me to see aerialists jump into what I consider the most complex type of rigging to do properly without the knowledge or understanding of the complexities involved. The fact is that even most professional aerial riggers don't have the education and training to do it properly. Rigging trees shouldn't be a dark art, but its also not a cheap solution to where to rig.
If we are going to rig a tree, we need to respect the tree. Many trees are not safely riggable in a way that doesn't cause lasting damage to the tree. Many trees are killed each year by aerialists that don't really understand what effect their actions have on a tree, and I don't think that's a good place for our industry to be. 
My critiques (both public and private) of Delbert's article centered around what I believe are key pieces of information that is missing from the discussion:
Inspection of trees

  1. What trees to use for rigging aerial arts
  2. Protecting trees when we rig them
  3. Proper hardware connections to trees
  4. The different rigging plot plans for tree rigging
  5. Wind loads, and how to deal with them
  6. The range of safety, and where rigging trees falls into that
In response the critiques of his article by myself and others, Delbert has invited those of us that delve in this dark art to write articles on the subjects I outlined above and others related to this.  I will begin with the subject of inspecting trees, and I will eventually add at least one more article to the fray (though I will give others a chance to add to the discussion first).
Like Delbert, I strongly discourage people from rigging to trees, though my reasoning is different.  Tree rigging is complex, tedious and expensive.  Properly rigging a tree so that it is both safe for the aerialist and for the tree takes a lot of time, a lot of expertise, a lot of attention to detail and it is expensive to do it right (often more than the cost of buying a freestanding aerial rig).
In this article, I will talk about inspections for tree rigging. The reader is warned that this is not a “how-to” guide on inspecting trees (that would take hundreds or even thousands of pages), but an overview that should give the astute reader a framework towards further research in this topic.
1. I do an inspection of the general area. I am looking for signs of blight, tree damage, soil conditions, and anything else that may make me question the health of the trees in the general area. Lots of texts are available online about assessing the general health of trees in an area. If you are thinking about rigging trees, you should be reading up a lot on this subject alone.
2. I inspect the trees we want to rig at 2x drip line. I am mostly looking for soil health. Things like soil compaction, ledge, and other conditions that may make the roots of the tree weaker. I conduct a number of tests at this distance as well, including auguring out a 5-foot hole and looking at the results.  Again, this is an area where you should do a lot of reading up, and a lot of talking with experts. 
3. Inspect the drip-line of the tree. Health of the soil, insect populations, signs of animals, birds in the trees. Each of these is a subject you could spend moths learning.
4. From under the canopy, look up at the branches of the tree. Are they healthy? This is again a subject that takes a lot of research to actually know what you are looking at. Its worth the money to take a class in maintaining trees to help learn about this.
5. Inspect the soil at 1/2 the drip line.
  • What kind of traffic does this area see?  Research the topic of soil compaction and how it effects the health of different trees.  This is a lot more complex than you might think.
  • In at least three places around the tree dig down and inspect the trees roots.  Research what the different colors and textures of the roots tell you about the health of the tree.  I am still learning a lot on this.
  • Look at the makeup of the soil. Is it Sandy? Loamy? Rocky? Dry? Moist? Do you find worms?  How active is the biology in the area? All of these things matter in terms of what kinds of loads the tree can take, and how the weather will affect the tree.  Research this until you have a good understanding of what effects these have.
  • What is the water table? How deep the water table is plays a BIG part in how strong the root structure is.  This is yet another area where you will need to do some research to learn about.
6. The 6' (root ball) inspection comes next. The soil conditions at the root ball are VERY important. A LOT has been written on inspecting the root ball of a tree, especially in the tree house and challenge course fields. You should thoroughly research this area if you will be rigging trees.
If you do the inspections correctly, it will take you a good 6 to 10 hours to complete the above steps. At the end of these inspections, you will know a lot about the trees you have inspected. This inspection may disqualify a tree from being rigged, but still not enough to know if the tree itself is riggable. For that, we need to inspect the tree itself.
Different species of trees have entirely different parameters for what is riggable. You will need to research this extensively before rigging ANY tree, but especially older trees.  
1. Take a good general look at the tree.  Is it healthy?  Is it in good condition?  Does the tree have widow makers living in it?  Anything odd or off about the tree?  In order to make these judgments, you will need to know a lot about the species of tree, so make sure you read up on that.  This is another good area where taking the right class can help a lot.
2. Inspect the tree for wildlife, ESPECIALLY endangered wildlife. Where you are will determine what wildlife you need to look for, and how you check for it. This will take you a little research to be able to do. Bees/wasp living in the tree won't like you rigging to it (and they may painfully tell you so!), termites can totally disqualify a tree from being rigged.
3. Inspect the trunk of the tree. You will need to do the research to determine what is correct for the trees you are looking at:
  • Inspect the bottom of the trunk, the first 3 feet from the ground. Is it in good condition?
  • Inspect the bark of the tree.  Is it peeling or does it show signs of excess wear?  
  • Inspect the trunk for signs of burls.  These are cancers, and any tree with one should not be rigged.
  • Inspect the trunk below where you will attach to.
  • Inspect the tree above where you will attach to.
  • Sound the tree, looking for hollow spots. 
  • If the trunk splits, you need to inspect how it splits, and if you have any rot issues at the splits.  The parameters for this are different depending on the species of tree.  You will have to research this for your particular species of tree.

4. Inspect the branches. You need to inspect every major branch of the tree (not just the ones you are using). What you are looking for are signs of rot or other damage. Exactly what you should look for depends on the species of tree and the area you are in, so plan to spend a few days in the library on this one as well.
If you are going to rig a tree, you need to do the research on how to inspect it, and you really need to understand what each of these means for your specific trees.
Both Delbert and I invite critiques, criticisms and further articles from others knowledgeable in  this subject area.

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Previous Issues
Issue #5
Issue #4
Issue #3
Issue #2
Need to learn rigging math?  Check out my book Rigging Math Made Simple, 2nd Edition.

Delbert L. Hall

President of D2 Flying Effects, LLC
ETCP Certified Rigger - Theatre
ETCP Recognized Trainer

Copyright © 2014 Delbert L. Hall, LLC, All rights reserved.

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