THE EFFECTIVENESS OF A BOTTOM BELAY ON LONG DROPS by Jim Kovach This article is on the effectiveness of a bottom belay on long rappels. We had been wondering about this for quite a few years and had even done a few surveys to try and gauge the response of people who would be likely to use a bottom belay. In 1997 we handed out 150 surveys at the International Technical Rescue Symposium (ITRS) but only 22 people responded. The question we posed was "How effective would a bottom belay be on an 800 foot rappel?" 7 people said it would be effective 6 said it would not be effective 4 said it depends 4 said they don't use one and 1 didn't answer. Those were mixed results from a very small sampling of rescuers. So, in 1998 we handed out a survey at Bridge Day. Bridge Day offers the opportunity to rappel from the catwalk of an 876 ft bridge. We asked the question "How effective will your bottom belay be if it is needed on Bridge Day?" 114 said it would be effective 37 said it would not be effective 36 said it would be somewhat effective. Bridge Day is an event that is held once a year on the third Saturday in October in Fayetteville West Virginia. Fayetteville has a population of 2,200 that swells to 100,000 for this festival that is rated as one of the best in North America. This event celebrates the completion of the New River Gorge Bridge. This bridge is the second longest steel arch span in the world and is three thousand thirty feet in length with a main span of 1700 feet. It is the highest bridge east of the Mississippi and second highest in the United States. The bridge was opened in 1977 and the West Virginia Legislature established the New River Gorge Bridge Day Commission to "sanction, coordinate and promulgate rules and regulations for this event." Bridge Day began in 1980. BASE-jumping from the bridge began in 1981 and rappelling in the mid 80's. Benjy Simpson, the Bridge Day Rappel Coordinator, began keeping statistics on rappellers in 1992. From then until 2002 there were 1,783 rappellers who did 3,499 rappels. The rappellers rig their ropes from the catwalk, 25 feet below the bridge deck. Their rappels range in height from 650 feet to approximately 850 feet depending on where their landing spot is located in the valley below. Everyone at Bridge Day uses single rope techniques and many rely on their bottom belay should anything go wrong. These rappellers have ranged in age from 14 years old to 75 years of age and until the year 2002 there had never been a rappel accident. The accident in 2002 prompted us to approach Benjy Simpson, the Bridge Day Coordinator, with a request to do some testing. Our stated objective was to determine the effectiveness of a bottom belay on long drops if the rappeller is using a standard length stainless steel brake bar rack and loses control. Our test mass would be 150-225 lbs. of steel weights rigged on a standard SMC stainless steel 6 bar open leg rack with 4 or 5 bars rigged and spread apart. This would simulate a rappeller who lost control. For our testing we removed the 6th bar completely from the rack, so it could not interfere in any way with the test. We would release the test mass from varying heights, which would give different lengths of rope between the belayer and the rappeller and different lengths of rope between the rappeller and the anchor. Benjy Simpson, owner and operator of PASSAGES TO ADVENTURE, took our request to the Bridge Day Commission and once it was approved we began to prepare for the testing. To accomplish this we needed to overcome some obstacles. How do we safely release our test mass that may be 400 to 600 feet from the catwalk or the ground? How do we safely perform a bottom belay without subjecting our belayer to potential harm? These were 2 big concerns we had. Fortunately, one of our instructors, Steve Bellamy, is an electronics wizard. He spent countless hours developing a radio controlled release device that would work up to approximately 700 feet. To protect our belayer we realized we had to remove him from the drop zone. To do this we decided to use a change of direction at the belayer's location, which would move him away from the area. Next we had to come up with the equipment to perform the testing. We submitted a proposal to PMI asking for their support. PMI has a strong history of supporting research that benefits users of rope. With their background in caving and cave rescue, their involvement in industry standards and their commitment to safety, PMI offered to supply the rope needed for the testing, and we would like to acknowledge PMI and thank them for their support. Protecting our belayer was easy. Just move him out of the drop zone. But by doing that we altered the physical mechanics of an actual belay. Now our belayer would be pulling horizontally instead of pulling down vertically to affect the belay. Also by placing a change of direction in the system we were adding friction and changing the forces involved in the belay. To determine how this would affect our testing we needed to do some further research. We had rescuers pull vertically and then horizontally on PMI 11mm rope and then we compared the two. We did in excess of 60 vertical tests and 110 horizontal tests to determine how our change of direction would impact the effectiveness of our bottom belayer. What we learned was that most rescuers could pull with more force vertically than horizontally. This concurs with a U.S. Dept. of Army Technical Manual on Rigging published in 1968 that states "On a vertical pull, men of average weight can pull approximately 100 pounds per man, and on a horizontal pull approximately 60 pounds per man." A study published in 1994 conducted by Kirk and Katie Mauthner of the British Columbia Council of Technical Rescue that was titled Gripping Ability On Rope In Motion, showed that "the average gripping ability of the sample population was 47 lbf with a standard deviation of 16.6 lbf." This was for a rescuer gripping a moving rope with one gloved hand in a horizontal orientation. It should be noted that all their tests were performed with the rescuer wearing rescue gloves and the testing was done on 11mm low stretch nylon Kernmantle rope. When we discuss belaying it may be considered that a bottom belay is an extension of your brake hand. Excluding all other factors a rappeller will always be able to brake or stop if they have enough friction rigged. And a bottom belayer will always be able to perform a bottom belay if there is enough friction in the system. If a rappeller can't stop or a bottom belayer can't stop them, then there is not enough friction in the system. For the purposes of this article a "system" is comprised of a rope, a brake bar rack, the person on rappel and a bottom belayer. The manufacturer of the rope, the diameter of the rope, the construction of the rope, whether the rope is new or old, clean or dirty, wet or dry are factors to consider. The rack length, the diameter of the brake bars, the material the bars are made of, and the number of bars used, are all factors to consider. The strength and weight of the rappeller, the gripping ability of the rappeller, the health and competence of the rappeller are all factors to consider. The strength and weight of the belayer, the gripping ability of the belayer, the health and competence of the belayer and the attentiveness of the belayer are all factors to consider. Together these factors determine the system. And the system determines the effectiveness of the rappeller or bottom belayer to control the situation. One way a person on rappel can stop is by pulling down on the rope with his or her brake hand. This is the same thing a bottom belayer does. Only a bottom belayer has the advantage of using two hands and his or her body weight if necessary and can pull from above the waist not at or below the waist. So traditionally, we like our bottom belayers to be big. Big meaning large in mass, and strong. The bigger and stronger they are the more reliable we believe they will be. Through the course of our testing we found that this is not always true. Size matters but only in weight, not in strength or gripping ability. The Mauthner's define "gripping ability" in their study Gripping Ability On Rope In Motion as "The resultant holding force exerted on an object after taking into account grip strength, surface friction, and the shape and size of the object being gripped. In belaying, it is the useful grip actually applied to the rope." What they found through observation in their study was, and I quote "that there is no correlation between height and/or mass and gripping ability." Our testing also bore this out. As an example, in one series of tests we did, we had 1 male firefighter and 2 female firefighters perform the same tests. If you were to see them standing together it's pretty obvious which rescuer most of us would pick to be our bottom belayer. The man is 6 foot 6 inches tall and weighs 240 lbs. He has a master's degree in human physiology. He understands the mechanics of belaying. He was also a world-class athlete. He was a tight end for the Super Bowl Champion New York Giants in 1991. His glove size is extra, extra large. The two young women are also career firefighters. One weighs 125 pounds and wears a medium rescue glove. The other weighs 140 pounds and wears a small rescue glove. All three of these rescuers participated in vertical and horizontal pull testing. The forces that were recorded were very similar with the male slightly out performing the females on the vertical pull testing. In the horizontal pull testing the women recorded forces that were equal to or greater than what the male was able to pull. We then compared the difference in hand size of these three rescuers. Imagine the large male hand trying to grip a small 11 mm rope, but how easy it would be for the smaller female hand to grip that same size rope. Later we performed a series of pull tests on 7/16 inch, 3/4 inch and 1-1/4inch rope and compared the results of these same three rescuers. As the diameter of the ropes increased, so did the force exerted by the male as compared to the force exerted by the females. The larger the diameter of the rope, the better the grip the male was able to achieve and the higher the forces he recorded. In another series of tests we had firefighters pull on an 11 mm PMI low stretch rescue rope at a distance of 15 feet and then repeat the test on the same rope at 140 feet. Of the 12 that were tested, 8 pulled with greater force 15 feet from the anchor and with less force 140 feet from the anchor. 1 pulled with the same force 3 pulled with slightly higher force at 140 feet from the anchor. How does this relate to the following questions? Does the amount of rope in the system make a difference or is it the amount of rope between the belayer and the rappeller or the amount of rope between the rappeller and their anchor? In another test we had 4 rescuers pull vertically on a rope that was anchored at 100 feet. Then we added 50 feet and a pulley at the bottom for a change of direction and pulled horizontally. We followed that up by adding another 150 feet of rope and moved the change of direction to an upper anchor so that our rescuers were pulling vertically. So our test and results looked like this: The 1st test is a vertical pull on 100 foot of rope and no change of direction. The difference in the 2nd pull is the change of direction, an additional 50 ft of rope and the fact that it is a horizontal pull. Notice that the forces exerted by the rescuers decreased in this second test. The last one also has a change of direction, a total rope length of 300 ft, but it is a vertical pull. From previous testing it appears that most rescuers are able to pull with greater force vertically than horizontally. So even though there is more rope in the system in the 3rd test, it may have been overcome by the fact that it was a vertical pull and not a horizontal pull. So the change of direction and a horizontal pull or a change of direction and greater rope length or a combination of these factors was cause for less force to be recorded at the anchor. Obviously this testing needs further study. So far this article has focused on the ability of rescuers to exert force on an anchor by pulling an 11 mm rope in a vertical or a horizontal orientation. It was our hope that you would come to the same conclusion that we reached. That conclusion is that most rescuers can pull with greater force vertically than horizontally. Because of our concern for our belayer's safety during the testing at the New River Gorge Bridge, we installed a change of direction at the bottom of the drop, which allowed us to move our belayer to a safer location. Realizing that our belayer would not be as effective pulling horizontally, and having to overcome friction in the change of direction, we chose a much stronger than average belayer for our testing at Bridge Day. Our belayer is 6 ft 1 and weighs 260 pounds. He's 46 years old and bench-presses 300 pounds. His glove size is extra large. He's an instructor and has been teaching rope rescue for over 20 years. For all of the tests the 11 mm PMI pit rope (Max Wear) was anchored 700 ft above at the catwalk, came down to the ground and was revved through a change of direction pulley that ran horizontally to our belayer 50 ft away. Our belayer was ready and wearing rescue gloves but did not apply any tension to the rope until the mass had been released and allowed to "get out of control". This would simulate a rappeller who had let go of the rope because of rock-fall, fatigue, a mental lapse or a medical reason. So the person in charge would release the test mass and count "one one thousand two one thousand" and then yell "BELAY" and our rescuer would attempt to slow or stop the falling mass. The results of each test are as follows: Test # 1 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 5 bars and raised to a height of 115 ft. After the release of the test mass the belayer was able to stop and control the lowering of the mass. Test # 2 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 115 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 3 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 230 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 4 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 300 ft. After the release of the test mass the belayer was unable to slow or stop the mass and it impacted the ground. Test # 5 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 225 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 6 Our mass of 150 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 200 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 7 Our mass of 150 lbs. was attached to the SMC stainless steel rack that was rigged with 4 bars and raised to a height of 400 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 8 Our mass of 175 lbs. was attached to the SMC stainless steel rack that was rigged with 5 bars and raised to a height of 395 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 9 Our mass of 225 lbs. was attached to the SMC stainless steel rack that was rigged with 5 bars and raised to a height of 240 ft. After the release of the test mass the belayer was unable to stop or slow the mass and it impacted the ground. Test # 10 Our mass of 200 lbs. was attached to the SMC stainless steel rack that was rigged with 5 bars and raised to a height of 240 ft. After the release of the test mass the belayer was able to stop and control the lowering of the mass. TEST # # BARS MASS (lbs.) HEIGHT (Ft.) BELAY 1 5 175 115 CATCH 2 4 175 115 FAILURE 3 4 175 230 FAILURE 4 4 175 300 FAILURE 5 4 175 225 FAILURE 6 4 150 200 FAILURE 7 4 150 400 FAILURE 8 5 175 395 FAILURE 9 5 225 240 FAILURE 10 5 200 240 CATCH In summary this testing suggests some points to consider for an out of control rappeller. The length of the drop matters. The further the rappeller is from the bottom belayer, the less likely the bottom belayer is to notice an out of control rappeller. The greater the rope length between the bottom belayer and the rappeller, the less effective the belay effort may be. The slower the reaction time of the bottom belayer, the less likely he or she is to be successful in his or her belay effort. The gripping ability of the belayer may be more important than the overall strength of the belayer. The size of the belayer may be misleading. This research would not have been possible without the help and support of the following individuals and organizations: Benjy Simpson, Bridge Day Rappel Coordinator New River Gorge Bridge Day Commission Pigeon Mountain Industries Stephen Bellamy, Barb Born, Russ Born, Marcus Chapman, Marie Cress, Dale Cubranich, Justin Cubranich, Billie Hall, Gary Hamilton, Jerry Hille, Ron James, Kevin Mohr, Daniel O'Brien, Tom Robinson, Brian Szuter, Ed Thomas, Judy Thomas, Gordon Thompson, Mike Warner, Phil Way, Chris Vatty, Mike Vatty And all the students and team members that participated in our pull testing.     Return to the Top of the Page Return to the NH #49 Contents Page Copyright © 2004 Vertical Section of the NSS, Inc. - All Rights Reserved.