We pulled over trees!

It is common in Search and Rescue, and rock climbing, for that matter, to use trees as anchors. We have always been curious about how strong trees actually are. Tom Pendley has been working on setting up these tests for years to test a theoretical model used by many in the rescue community. John Morton did some calculations based on wind loading and came up with a way to model the force that trees have been subjected to based on their species and wind data for a specific area. Check out his presentation here. https://itrsonline.org/papers/tproduct/294801796-837701892791-what-if-trees-had-ratings-in-kn-tree-anc In his presentation for the International Technical Rescue Symposium, John generated an example chart with a sample wind speed of 65 mph, but you can use his model and local data to calculate more relevant anchor strength values for your area. The chart from that presentation has been passed around in the SAR and climbing communities, so that is what we used. Thank you, John, for your help with this episode. We used the predictions in Morton’s 2015 chart to compare against our results. Dozens of variables affect the strength of trees, so we were shocked when our results were all super close to Morton’s model. Until they weren't. The last tree we pulled over was so much weaker than we expected, but had we moved some logs and debris to expose the base, we would have seen that the root system was exposed and was not very supportive. That failure really drove home the point that trees are affected by so many different factors and you anchor to them at your own risk. And of course, we were testing in the Pacific Northwest, species and conditions vary greatly across the world. When in doubt, use more trees in your anchor or find a different anchor solution. We tested at 2 feet, pulling at the base is stronger. When in doubt anchor low. It is worth noting that a living tree gives you lots of warning before it fails. Big thanks to Vince Reichheld. It was awesome to pull some trees over that were going to be thinned anyway to promote forest health. Vince is a partner at Boots on the Ground Forest Services, which is focused on low-impact timber harvesting and forest services on the Olympic Peninsula. https://bootsonthegroundforestry.com/ Tom and Vince are members of the Jefferson County Search and Rescue. If you live or play in the area, consider supporting the efforts of JSAR. https://www.jsar.org/support/" For those of you who are curious, the tractor is a Duetz Fahr 5110 G, and the winch is a Tajfun EGV 55 AHK. The winch can apply 55 kN, and we had a 3 to 1 in the system. We were excited to put 100 kN on some trees, but unfortunately, none of the larger trees Vince needed to take down were in locations that were practical to pull on. Another video, maybe? Our results Red Alder: Circumference: 19" Prediction: 18.60 kN. Our Result: 18.23 kN Bitter Cherry (our forester compared it to a Red Alder). Circumference: 25" Prediction: 49.4 kN. Our Result: 18.90 kN. Tree on a mound, roots compromised. Bitter Cherry (our forester compared it to a Red Alder). Circumference: 19". Prediction: 18.60 kN. Our result: 19.57 kN Douglas Fir: Circumference: 16" Prediction: 13.90 kN. Our Result. 14.67 kN Douglas Fir: Circumference at base: 16" Prediction: ?13.90 kN?. Our Result. 17.79 kN. Pulled at the base. Check out our selection of rock climbing and Search and rescue gear at HowNot2.com. We even have Tom Pendley’s technical rescue field guide. https://hownot2.com/products/the-essential-technical-rescue-field-operations-guide 👉 Learn and SHOP at https://www.hownot2.com/ 👉 Best EMAILS on Earth: https://www.hownot2.com/signup 👉 10% off ROCKY TALKIE by clicking https://www.hownot2.com/rocky