NH 59 Page Page 1 of 1 #59 Contents Overleaf 1. An Analysis Of Bowlines (PDF, 2.7Mb), by Mark Gommers Return to NH Issues Page 2. Rescue Knot Efficiency Revisited (PDF, 339Kb), by John McKently 3. Slow Pull Testing of Progress Capture Devices (PDF, 664Kb), by DJ Walker & Russell McCullar 4. Minutes of the 2014 VS General Meeting (PDF, 199Kb), by Ray Sira 5. Secretary's Report - 2014 (PDF, 31Kb), by Ray Sira 6. Treasurer's Report - 2014 (PDF, 61Kb), by Ray Sira (Download free ACROBAT Reader ... to read PDF files) Return to the Top of the Page Copyright © 2002-2015 Vertical Section of the NSS, Inc. All Rights Reserved. Page Last Updated on July 5, 2015 file:///D:/Data/INet/Vertical/nh/59/nh59.html 7/ 5/ 2015 Nylon Highway Terry Mitchell ........................................ Chair ISSN 4207 Brant Drive Springdale, AR 72762 Year 2014 ISSUE #59 Miriam Cuddington ................................ Vice-Chair 109 Beacon St. Moulton, AL 35650-1801 Raymond C. Sira ......................... 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Christiansburg, VA 24073 e-mail: [email protected] In short, if you’d like to submit something for possible publication, send it to the Editor. Otherwise, send it to the Secretary/Treasurer. AN ANALYSIS OF BOWLINES Foreword The bowline has received extensive criticism within the climbing and rope rescue community – and some commentators have argued for its discontinuation. This paper deals in facts – and presents another side of the Bowline, one that is positive and constructive. If a bowline was employed in a role where it could remain in equilibrium with a steady/unchanging application of load, it would function perfectly – and there would be no security issues (and this paper would probably never have been written). However, in climbing and rescue applications, a bowline would be subjected to a dynamic environment with constantly changing (cycling) load and continuous movement. It is in this type of environment where a bowline can fail – and climbers and rope rescue technicians have long understood and tried to overcome this. In life support applications of a mission critical nature, “ABoK #1047” (Figure 8 eye-knot) has wide support and is taught in virtually all entry-level roping courses. Its popularity is linked to the fact that it is easy to tie and relatively easy to learn (and remember) – and it is both secure and stable even under cyclic loading conditions. However, the figure 8 eye-knot can be somewhat difficult to untie after high loading events – and it is this point that makes it unpopular amongst some climbers. It is also worth noting that in order to tie a figure 8 loop through a climbing harness or around a tree, a two stage process is required (that is, the figure 8 eye-knot is not Post Eye Tiable – ‘PET’). The bowline has the property of being easy to untie – even after high loading events. This is why it remains the knot of choice for riggers and doggers (cranes/lifting/construction industry). The Bowline is also ‘PET’. I originally embarked on a journey to find the ‘ideal’ knot that has the properties of a bowline (easy to untie after loading events and ‘PET’) and the security and stability of a figure 8 eye-knot (“ABoK # 1047”). This paper has evolved to much more than that – along with many new discoveries and expanding theory and analysis. A paradox for some of the bowline creations is that in making the structure more secure, simplicity has been sacrificed. Recent efforts have tended to focus on finding ways to secure the tail or to enhance the nipping turn component. Not all of the knots perform equally well with stiffer ropes – and this needs to be carefully evaluated before entrusting a life to a particular knot. No peer reviewed (reproducible) technical data is available for the properties of the various knots illustrated. Behaviour under static and dynamic loading and raw strength are generally poorly documented or of dubious origin. It is the view of this author that strength is not the most important characteristic of a knot. Of greater importance are the properties of security and stability. Bowlines will generally fail at a point somewhere in the 70’s % points – which is more than adequate for climbing and rescue applications. Of greater interest to this author is testing the theory that the radius/curvature of the nipping turn plays an important role in the (eventual) rupture of the rope. Page 1 of 32 Bowline Analysis DRAFT Version 2.1c 30 July 2013 (for comment) Prepared by Mark Gommers Since this paper was originally published in Jan 2009, several new secure and stable bowlines have been discovered – but not all have been extensively field tested. Disclaimer: This paper does not constitute advice. All of the knots illustrated in this paper are loosely tied and oriented to give the best possible photographic appearance. To the maximum extent permitted by law in your respective nation, the author and contributors to this paper will not be held responsible for any death, injury or loss arising from any use or reliance on the information published herein. Mark Gommers July 2013 Page 2 of 32 Bowline Analysis DRAFT Version 2.1c 30 July 2013 (for comment) Prepared by Mark Gommers CONTRIBUTORS: I would like to personally thank the individuals who provided suggestions, comments, critique and support – without which, this paper would not exist. Producing work such as the subject material of this paper is time consuming and difficult. What was surprising to me, was the lack of any coherent body of universally agreed theory on knots. On the particular subject of bowlines, there appeared to be much confusion, disinformation and inconsistencies. I initially turned to the International Guild of Knot Tyers (IGKT) forum to spur interest in examining the theory of bowlines – posting the topic; ‘What defines a Bowline?’ That initial post sparked a surge of responses with at times heated debate. As of July 2013, there was something like 18,539 viewers of the post and some 299 written replies. This paper was largely born out of that Bowline post, in an effort to gather together all the information into one coherent body of theory. I am certain that there is still much work to be done to refine the theory – and this paper is therefore a ‘living document’ that can be updated over time. This paper is freely available in the public domain – as a contribution to our collective knowledge on knots. I hope this will inspire others to write papers on other interesting knot structures. End-to- end joining knots such as the so-called ‘Zeppelin’ bend is just waiting for us to produce a paper. … My sincerest thanks go to the following individuals: Zeppelin / Rosendahl bend Dan Lehman (USA) Scott Safier (USA Constant Xarax (Greece) Mark Gommers 15 July 2013 Page 3 of 32 Bowline Analysis DRAFT Version 2.1c 30 July 2013 (for comment) Prepared by Mark Gommers The Anatomy of a Bowline Standing part (‘SPart’) Collar Note: The collar is a specific region of the bight. It is where the bight makes a U turn around the SPart. Core (nub) Nipping turn (a closed helical structure) This photo shows a Bight Bowline based on a right- hand helical nipping turn. C Note: A helix cannot be described as rotating Crossing point clockwise or counter- clockwise. Handedness (or chirality) is a property Entry region of of the helix, not of the SPart into the perspective.