Learning from Mark Chisholm

Posted by Professional Tree Climber on 4/27/2018 to Tree Climbing Safety

STIHL Chainsaws and Mark Chisholm made this awesome video demonstrating the forces that are generated when climbing SRT on a series of different anchor points. This is such an interesting topic to discuss, seeing as we have already presented part of this to you in previous blogs discussing “Forces in Rigging” quite a while ago. So let’s discuss a little bit of what’s being covered in the video to help you choose the best tie-in method while climbing SRT!




Setting a Canopy Anchor

The video begins with Mark setting a Canopy Anchor (CA); this involves attaching to your tie-in point with something like a Running Bowline with a Yosemite tie off, a cinched Alpine Butterfly, or something like the Texas Tug. In the most basic sense, you have a rope tied directly to a limb and you are attached to that limb. The nice thing about this type of tie-in is the fact that there is no increase in downward force at your tie-in point when you are hanging in your rope. Obviously, and as Mark demonstrates, as soon as you start moving around on your rope the force increases!


One of the downfalls of using a Canopy Anchor is that you need to isolate the exact tie-in point that you want to use in order for the CA to cinch down around the limb. This can be difficult if you are not well versed in throw line techniques, as well as very frustrating! Difficult retrieval is another downfall of a CA as well. If you redirect your rope with a cinched Alpine Butterfly, you will have difficulty trying to retrieve your rope. Adding in something like a Texas Tug can make this process WAY easier for you!


Choosing the Correct Tie-In Point

The second point that Mark shows in the video is that simply just ascending on a rope can cause quite a bit more force on your tie-in point. So by stepping on your ascenders, taking a swing or bouncing on your rope at all can generate some pretty substantial loads. This may particularly prove dangerous if you ever ascend into a dead tree or a tree with weak wood. Obviously, choosing the correct tie-in point based on tree species is a must know thing!


Using Base Anchors

The next point Mark moves into is using a base anchored rope to ascend into the tree. Lots of people like base anchors because they are simple to set in a tree as well as retrieve. Another thing that climbers tend to get caught up on is the fact that they make it possible to lower the climber from the ground in the event of a rescue. This is argued back and forth as beneficial because if the climber is lanyarded in while in the tree, they will not be getting lowered to the ground. Regardless, that is discussion for another post!


Mark goes on to demonstrate that the force on the tie-in point when using a base anchor is almost double what it was when he was using a CA. That’s pretty substantial! The reason behind this is the fact that Mark, weighing roughly 200 lbs, was hanging from his rope, which went up and through a pulley and was then anchored on the base of the tree. In order for Mark to hang off the ground his rope would have to be holding roughly 200 lbs where it was anchored at the base of the tree, which the other load cell showed. Now when we take Mark’s weight and the weight that the base anchored rope was holding and add them together, we get the amount of downward force at the tie-in point up in the tree. So a good rule of thumb to remember is that the force at your tie-in point with a base anchor is roughly double your body weight.


Wait Until You Calculate Weight

Once Mark starts ascending into the tree the forces start to spike even more. Ascending into the tree made the peak load 540 lbs! That’s a huge increase from 200lbs! Now imagine if he were to take a big swing or any movement that could create even more forces on his tie-in point! These are all things to keep in mind when looking for the ideal tie-in point when you are climbing SRT or using something like a floating false crotch while climbing DdRT.


Mark moves into the use of the Rigging Wrench next, but I think that is a great topic for a future post. I just felt that this great video could help illustrate some of the forces that we create while just ASCENDING into the tree! That’s before any work is being done, any logs are being handled, or any saws are being started while aloft! Please keep these things in mind while climbing and if you have any questions, be sure to post them in the comments section below and we will get them answered for you!

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