*** Rope for River Rescue *** From: rikpenny@CyberGate.COM (Richard Penny) Newsgroups: rec.boats.paddle,rec.climbing,misc.emerg-services Subject: Rope for River Rescue (was Z-rig) Date: 16 Nov 1995 16:13:58 GMT Organization: Cybergate Information Services Matthew Buynoski (buynoski@angelo.amd.com) wrote: 2.The ropes mentioned in the previous post may have a problem, at least those that are mostly of polypropylene, polyethylene,or spectra. These are low-temperature materials, and they MAY melt in the stresses found in high-tension systems. The samething can happen to plastic-wheeled pulleys, BTW if you can do it, use a nylon rope. Think about getting your lines across the river with small, lightweight floating rope, and then using them to then get the (non-floating) nylon rope into position. Nylon is generally a lot stronger for a given rope diameter than the "poly" ropes are. For example, 3/8 nylon is typ. 5800lb tensile vs. spectra equiv. of 4500. 1) The assertion that spectra-core ropes might melt under high tension is an interesting one, but not one that I have seen mentioned in the climbing literature. Can you refer me to a citation, for example in Rockand Ice or in the NSS Journal? It is worth noting that Black Diamond and other manufacturers now recommend that their hexes be slung with 5.5 mm. spectra core or spectra/kevlar blend (Gemini cord) rather than with larger diameter Perlon (nylon rope). Your post includes the suggestion that floating rope be towed across a river for a rescue operation, and then that rope be replaced with a nylon one. IMHO, this is not a practical idea:1) Requires additional, heavy equipment (3/8" nylon rope) to be carried.Kayakers are not going to do this. It is difficult enough to convince all kayakers to carry a throw bag containing 70 feet of 1/4" Spectra-core polypropylene. Under your system, boaters would need both a throw bag contining a floating rope as well as a big nylon rope. Rafters, maybe would do this. I do carry a 50M climbing rope on big rafting expeditions. But not kayakers or canoeists. 2) A nylon rope, because it does not float, can be difficult to pull across a river. It might have worked for you in a simple rapid such as are often used for river rescue classes, but in a complex rapid, there are just too many opportunities for the rope to sink and become entangled in rocks. On two occasions during the evolution of real river rescues I have had to abandon "floating" ropes that have become entangled in the bottom.You might suggest that the nylon rope be suspended in the air above the river until it is tensioned. In fact, this exercise is extremely difficult to accomplish, even using paddles or oars to hold the ends of the rope as high as possible. With a river of any significant width, thecenter of the rope is going to dangle in the water. 3) Replacing the floating rope with nylon is an addition step that (a) increases the complexity of the operation, and (2) slows its evolution. Absolutely contrary to the KISS (keep it simple, Stupid) principle. 4) I have heard of no instance that a spectra-core polypropylene rope (1/4" or 3/8") has broken in a real-world or simulated rescue scenario. I have constructed and used 11:1 Z-drags in real boat extraction operations. Spectra-core rope held up just fine. Did break an attachment point off the kayak though. 5) The prussik loops and the anchors are the weak link in a Z-drag system. In the case of 1/4" Spectra haul line, these loops are typically 4mm or 5mm perlon (or sailing dacron). I have heard of instances where prussik loops have failed. I have heard of instances where anchor systems have failed (Les Bechdel told me of causing a boulder to move that was the anchor to a Z-drag system). 6) Tensioned Z-drag systems are generally used in river rescue for the purpose of boat extraction. Such systems generally should not be used to suspend climbers engaged in aerial manuevers, because of the enormous stresses they can place on anchors and other components of the system. Since people's lives are not immediately dependent on the rope used in a Z-drag for river rescue, there is no need to have the enormous redundant strength required in a rope for lead climbing. Your mileage may vary. ---------------------------------------------------------------------------- Richard Penny email: rikpenny@cybergate.com2499 Los Altos Avenue Clovis, CA 93611 --------------------------------------------------------------------------- Subject: Re: Rope for River Rescue (was Z-rig) Date: 17 Nov 1995 01:30:34 GMT From: buynoski@angelo.amd.com (Matthew Buynoski) Organization: Advanced Micro Devices, Santa Clara, CA Newsgroups: rec.boats.paddle, rec.climbing, misc.emerg-services The stresses on a river rescue haul system are likely to be a lot larger than put on a climbing rope. It is easy to have several 1000's of pounds of tension with a mechanical advan- tage system if pulling on anything recalcitrant like a wrapped boat. Climbers may well be able to use spectra for a lot of uses that river rescue systems shouldn't. Spectra is suspicious for melting because it is polypropylene. It is manufactured a different way than the typical polypro. rope, but it is still basically the same material. I am a rafter. I carry a lot (about 50lb) of rescue gear. You are right that a kayaker can't do this sort of thing. In his case, the kayaker should go for maximum flexibility on his very limited kit. So a spectra rope is something to be considered, but the same kayaker should be very aware of its limitations and not put so much tension on it that melting may be a problem if there is sufficient friction in the system. (For instance, setting up a Z rig with a carabiner used instead of a pulley would be asking for trouble as the local high friction at the biner could heat the rope). The technique of using one line to haul another across the river is something that was taught to me in rescue classes. Use a light- weight, floating rope (it could be 1/4") to get across the river in the first place, then tow the main (heavy, nylon) rope across with it. In most river rescue situations, the only time a complex hauling system is likely to be employed is with a wrapped boat or other, similar, slow-to-develop situation. In a case like that, taking the time to do it right (maybe flagging down a passing raft with a heavier rescue kit, if the river is well traveled. Most of them are..sigh..) is probably time well spent. It is also possible that one kayaker in the group could carry light line, another could carry heavier line, etc. The sum total of all those parts could be better than each kayaker repeating the same equipment. Subject: Re: Rope for River Rescue (was Z-rig) Date: Fri, 17 Nov 1995 13:44:42 GMT From: "G.Roberts" Newsgroups: misc.emerg-services Z-drag systems using standard 4-mm Prussik loops definately function better with braided-sheath polypropylene or hollow-core polyamide ropes than with kermmantel-sheathed polyamide ropes due to better ''gripping'' of the rope by the Prussik knots- we use a combination of both but mainly 11-mm braided-sheath poly [''throwbag rope''] for heavy duty work [inc. ziplines and z-drags]. Subject: Re: Rope for River Rescue (was Z-rig) Date: Tue, 21 Nov 1995 09:36:11 -0500 From: Lyle Williams Newsgroups: misc.emerg-services -- [ From: Lyle Williams * EMC.Ver #2.5.02 ] -- Regarding the earlier post on possible melting of Spectra or other non-nylon lines due to heavy load found in a Z-drag. My question to the author regarding that statement is: where does the energy to melt the rope come from? In a Z-drag, typically you have high tension but extremely low movement. Thus, you have high potential energy (the tension) but low kinetic energy (the movement). The potential energy is maintained (unless the line loses tension), leaving only the minor kinetic energy to provide friction that results in heating the line and melting. Contrast this with climbing or other aerial rope uses (e.g., a Tyrolean) where the rope may be moving quickly through a piece of hardware. Here, there is ample kinetic energy which is transferred to the rope as heat due to friction at the hardware. Notice that the movement of the rope is the driving force for melting. Low movement = no melting. High movement = melting potential. If someone disagrees, I'd be very interested in hearing where the source of the energy required to melt a rope comes from. Russell Bailey My understanding of the failure of nylon ropes in a pull test is that the combination of tension and pressure in the line causes a reduction in the softening temperature of the fibre. This effect can be seen in the melted ends of broken (as opposed to cut) ropes. The failure of Allied Signal's Spectra fibre may be similar, but the performance of lines in real world situations is complicated by factors other than ultimate tensile strength. These factors include abrasion resistance, density, handling, wet properties, chemical and UV resistance, cost, energy absorption, bulk, visibility, knotability, and compatibility with existing techniques. Spectra fibre seems to be quite remarkable in terms of tensile strength and abrasion resistance. I know of people who are using single 5.5mm spectra lines as SRT rope in deep expedition caving, and they haven't died yet. I have yet to see figures on energy absorption, but I do have some information on Spectra that covers a lot of other parameters. I will post this in the next day or so. I guess what it comes down to is that Spectra has some really interesting properties on paper, but you need to use a product that you know and trust. Maybe this means that you have to use it in exercises and evaluations, and/or talk to people who have used it (as opposed to just tried it). Lyle Williams. -----------------------------------------