Design And Performance Of Ropes For Climbing And Sailing. Journal Of Materials: Design And Applications,

SPECIAL ISSUE PAPER 1Design and performance of ropes forclimbing and sailingA J of Mechanical Engineering University of Strathclyde 75 Montrose Street Glasgow G1 1XJ UKemail manuscript was received on 16 September 2005 and was accepted after revision for publication on 10 March 2006DOI Abstract Ropes are an important part of the equipment used by climbers mountaineers and sailors On first inspection most modern polymer ropes appear similar and it might be assumed that their designs construction and properties are governed by the same require ments In reality the properties required of climbing ropes are dominated by the requirement that they effectively absorb and dissipate the energy of the falling climber in a manner that it does not transmit more than a critical amount of force to his body This requirement is met by the use of ropes with relatively low longitudinal stiffness In contrast most sailing ropes require high stiffness values to maximize their effectiveness and enable sailors to control sails and equipment precisely These conflicting requirements led to the use of different classes of materials and different construction methods for the two sports This paper reviews in detail the use of ropes the properties required manufacturing techniques and materials utilized and the effect of service conditions on the performance of ropes A survey of research that has been carried out in the field reveals what progress has been made in the development of these essential components and identifies where further work may yield benefits in the future Keywords climbing sailing ropes modelling materials1 ROPES FOR CLIMBING A fixed anchor point is set up at the top of the route and the rope is looped through a karabiner attached to this anchor The two halves of the rope are11 Introduction dropped to the bottom of the climb to form aClimbing ropes are predominantly used for safety simple pulley system The climber ties one end toand security In particular they must hold the his harness while his partner known as the belayerweight of the climber in the event of a fall The type secures the other end to his harness by the use of aand magnitude of forces encountered depend chiefly friction device This device allows the rope to beon the type of climbing being undertaken For con taken in or paid out under control but can be climbing activities may be split into three locked to form a solid attachment to the rope Thecategories top roping lead climbing and abseiling climber ascends the route while the belayer takes inDetailed descriptions of climbing and abseiling tech the slack rope until the climber reaches the top Atniques are available elsewhere 1 2 but a brief this point the climber may untie himself from thedescription is given here to enable the reader to rope and walk down to the bottom of the crag orappreciate the context of the ropes use may place his weight on the rope and be lowered to Top roping is the most common form of climbing the ground under the control of the belayer bycarried out at indoor climbing walls and is also means of the friction device The latter practice iswidely practised on small crags or outcrops where the norm for indoor climbing wallsthe top of the route may be reached without climb Lead climbing is used in situations where the toping perhaps by walking around the edge of the of the route is inaccessible by any means othercrag Figure 1 shows the typical arrangements for than climbing Figure 2 shows the typical arrangetop roping ments for lead climbing This is typical of theJMDA75 IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications2 A J McLaren camming devices that the lead climber carries with him on the climb These are placed temporarily in cracks in the rock and are designed to take the weight of the climber should he fall Alternatively preplaced expansion ring bolts may be used In either case the rope is clipped to the anchor points by the use of a karabiner which allows the rope to continue to run through the running belay as the lead climber continues the climb Once the leader has reached the top of the climb or runs out of rope he will stop climbing and attach himself securely to the rock He then becomes the belayer while his partner climbs the route with the security of a top rope As he climbs the partner will remove all the running belays as he passes them thus allowing their reuse at a later stage of the climb On mountains and large crags where the route is longer than a typical 50 m rope lead climbing isFig 1 Typical arrangement of ropes and anchor for carried out in a series of pitches Once the second top roping redrawn from Fyffe and Peter 2 climber joins the leader at the belay they organize their equipment and begin the process again Inclimbing carried out on mountains or large crags In this way a large route or mountain may be brokenthis case the lead climber ties one end of the rope to into a series of short pitches and the climbershis harness while the belayer passes the rope progress up the route as a selfcontained unitthrough the friction device a few metres from the Abseiling also known as rappelling is used tosame end The lead climber begins to climb towing descend steep ground by sliding down the rope inthe rope behind him and the belayer pays out a controlled manner Climbers generally use thisslack at an appropriate rate Periodically the leader technique when descending or retreating fromwill stop and attach the rope to running belays mountain routes Friction devices similar to thoseThese are anchor points on the route which may used for belaying are utilized to control the rate ofconsist of pieces of equipment such as wedges or descent Figure 3 shows the typical arrangements for abseiling The usual technique is to double the rope to allow its retrieval from beneath once theFig 2 Typical arrangement of ropes and anchors for lead climbing a the leader climbing b the partner following with the security of a top Fig 3 Typical arrangement of ropes and anchor for rope redrawn from Fyffe and Peter 2 abseiling redrawn from Fyffe and Peter 2Proc IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006 Design and performance of ropes 3bottom of the abseil pitch is reached On mountain 12 Fall forcesroutes this may involve the sacrifice of a piece of The design of a suitable rope for arresting the fall of aequipment which is left behind at the anchor point lead climber requires an appreciation of the forces Modern mountaineering ropes are classified into that are likely to be generated Smith 3 reviewsfour classes which are approved by the Union Inter and extends the analysis by Wexler 4 of the forcesnational des Associations dAlpinisme UIAA Each generated in a lead climbers fall The geometry ofrope must be clearly marked with a standard label this ideal fall is shown in Fig 4 The which class it belongs to force Pmax N generated in the fall of a climber of Single ropes may be used on their own They aredesigned for rock climbing on relatively straight mass m depends on the geometry of the fall and the properties of the rope involved This is given bypitches and routes that do not require abseil descent the following equationThese ropes are often 11 mm in diameter Their useis common in indoor climbing centres bolted sports routes and relatively low crags 2k H Pmax mg 1 1 1 Half ropes are used in pairs The leader will clip mg Lone of the ropes into each running belay This givesextra flexibility for belay placements For instance where H m is twice the distance from the climber toif climbing a broad crack with running belay place the running belay L m the total length of rope usedments on both sides the leader will clip one rope g the acceleration due to gravity 981 ms2 and kto runners on the left and the other to runners on N the measure of the ropes elasticity defined bythe right In this way each rope will run approximately vertically which will greatly reduce frictional hx idrag Half ropes have the additional advantage that Pk 2 Lthey can be joined together for abseiling thus doubling the distance that can be descended in one where x m is the elastic extension of a rope of initialpitch Half ropes are generally thinner than single length L m under an instantaneous load P Nropes typically 8 or 9 mm diameter It is clear that for a climber and associated equip Twin ropes are also used in pairs with both ropes ment of a given mass the maximum fall force maybeing clipped into each running belay Their use is be minimized by employing a rope with a low valuevery rare in the UK but they are used in the Alps of k This allows relatively large extensions but genTheir diameter is generally similar to or smaller erates relatively small forces An extreme example ofthan half ropes making them very lightweight this effect is the use of thick highly extensible ropes The fourth category of ropes is the mountain walk for bungee jumpinging or tour rope This is used to provide security on The geometry of the fall may be characterized bymountain walks for glacier crossing or ski mountai the ratio HL This is known as the fall factor andneering It is normally an 8 mm diameter dynamic is essentially a measure of the ratio of potentialrope but is not suitable for rock climbing energy put into the rope by the falling mass to the The properties that are required for climbing amount of elastic material available to absorb thisropes depend chiefly on their task of arresting the energy Theoretically values of fall factor arefall of a climber in a controlled manner In top possible between 0 and 2 with a fall factor of 2roping the maximum fall that is possible is less corresponding to a leader fall on steep ground withthan 1 m provided the belayer is paying attention no running belays The leader will fall past theHowever depending on the vertical spacing ofavailable running belays a leader may fall a muchgreater distance Indeed the fall distance will twice the distance from the leaderto his last running belay anchor In general of anchor points andor the ability ofthe leader to hang on while placing themdecreases as the difficulty of the route falls of several metres are not uncommonIt is the function of the rope to absorb the energyof the falling climber and bring him to rest without transmitting large forces to his body throughhis harness For this reason relatively elasticropes which stretch appreciably when loaded are Fig 4 Geometry of the ideal leader fall redrawn fromdesirable in climbing Smith 3JMDA75 IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications4 A J McLarenbelayer the fall distance being twice the length of the This has interesting consequences for the practicerope between them at the moment the fall begins of abseiling The ideal rope for abseiling would be In practice the geometry of leader falls is seldom relatively inextensible This is because simple Climbing routes tend not to be straight oscillations tend to build up in the rope during desso the path of the rope becomes more convoluted cent These are undesirable for two main reasonsand where running belays are scarce the rope may the descending climber may be put off balance ordeviate significantly from the ideal straight line be disorientated if significant oscillation occurs thePavier 5 6 has developed theoretical models to rope may be loaded over sharp edges and the oscilpredict the tension generated in ropes under a var lation can contribute to a sawing action which is detiety of fall geometries His analysis takes into account rimental For this reason static ropes with limitedthe slip of the rope through the belay friction device extension are used by people who participate infriction at running belays themselves and a abseiling as an exercise in its own right eg model for the rope activity centres However since it is not practical for mountaineers to carry additional ropes for this sole purpose they would normally abseil on their dynamic climbing ropes13 Standards and has revealed that the maximum load that the human body can 14 Desired properties for ropewithstand without serious injury is 12 kN Climbingropes must be designed such that this threshold The desired properties for a dynamic climbing ropeload is not exceeded even in a relatively severe fall are therefore as followsThe rope is of little use if it arrests the fall but in so a high strength ability to support static force anddoing transmits a fatal force to the climber The repeated dynamic standard test for climbing ropes is b known elastic properties that allow the rope tobased on a standard dynamic drop test 7 of rela control the force transmitted to the climber andtively high fall factor equipment during a fall The test uses a machine known in the industry as a c which performs the standardized drop d durability resistance to abrasion This simulates a leader fall for a climber with a light and repeated thermal cyclingfall factor of 178 This corresponds to a vertical fall e water resistance stability of mechanical propdistance of 5 m with a total rope length of 28 m erties in the presence of waterThe rope passes through a standard ring that simu f handling feel knotability andlates a running belay and it is generally the friction between this point and the surface of therope that initiates the failure The first climbing ropes were made of natural For a single rope the maximum transmitted force fibres such as hemp or manila They evolved directlyfor a mass of 80 kg is 12 kN For double ropes and from ropes used for general and marine ropes a single strand is tested with a mass of and were formed of twisted yarns This type of con55 kg and the maximum permitted load is 8 kN struction is known as hawser laid and generallyEach rope must also withstand five consecutive consists of three parallel helical strands The twiststandard falls without failure It is generally found of the individual strands is in the opposite directionthat the rope stiffens after the first drop test leading to the helix and this twist locks and stabilizes theto higher loads on subsequent drops structure Figure 5 shows a hawserlaid hemp rope In addition to the number of falls and maximum from the 1950sload criteria ropes must conform to minimum stan Although these ropes were adequate for simpledards concerning knotability extension under load security and top roping they were notoriously inefextension during standard falls as well as sheath fective at arresting leader falls The old ie the amount of relative longitudinal adage the leader must not fall comes from anmovement between the sheath and the inner core understanding of the likely consequences of aA concise account of the standards is contained in leader fall onto a natural fibre rope The relativelythe short review by Bennett 8 high stiffness of hemp and manila led to the gener The implication of this test is that the most import ation of large dynamic forces during falls Smith 3ant performance criterion for the rope is its energy estimates that fall factors of 05 for hemp and 075absorption By nature climbing for manila would be sufficient to cause failureropes will be designed to stretch significantly under The first advance towards modern ropes cameload during the Second World War with the IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006 Design and performance of ropes 5 and friction properties Several authors have reviewed the factors influencing the construction of modern ropes and their effect on properties 9 10 15 Modelling of ropes The literature on the modelling of textile ropes is lim ited Much of the research that has been carried out on rope structures is concerned with wire ropes more commonly used in large engineering structures and offshore applications The standard text in this area is the book by Costello 11 Several authors have attempted to model textile fibre ropes A goodFig 5 Example of a hawserlaid hemp rope from the review of work in this area was recently published 1950s after Schubert 19 by Pan and Brookstein 12 Manes 13 has applied wire rope modelling tech niques to kernmantel climbing ropes including preof nylon fibres by DuPont Initially hawserlaid dictions of stress distributions during the DODEROropes were constructed substituting nylon fibres dynamic fall test where the rope is bent around afor the natural products The results were ropes bar of 10 mm radius He also attempts to model thethat could take a fall factor of approximately 10 behaviour over a 075 mm sharp edge but his resultsbefore breaking These ropes while superior to are inconclusive Contri and Secchi 14 havethose made from natural fibres were notoriously attempted to model the cutting of a loaded rope bystiff if allowed to become wet This made the tying a sharp edge Their approach considers the rope asand untying of knots difficult and greatly reduced a hierarchical structure of yarnstheir handling plies strands and overall rope each component of In 1951 the first kernmantel ropes were produced which may transfer load to its neighbours by frictionby Edelrid The structure of kernmantel ropes is In this sense their approach is similar to that ofshown in Fig 6 The core kern consists of parallel Leech 15 who with coworkers has also of twisted strands each one of which the results of modelling work on the effects of a small hawserlaid rope The individual loading on rope properties 16strands are often twisted in opposing directions The mechanisms of rope failure have been studiedsome clockwise and some This by Phoenix 17 who has analysed load transferhelps to minimize excessive spinning or twist while between neighbouring strands in the rope or lowering The core is generally respon of an individual strand leads to partial or total loadsible for the mechanical properties of the rope with transfer to adjacent strands by friction The mechanregard to tensile strength and dynamic behaviour ical behaviour of rope structures is complex andand is covered with a braided sheath mantel The highly nonlinear which poses considerable propurpose of the sheath is to contain and protect blems for modelling of failure mechanisms particuthe core However the construction conditions of larly where contact forces strain rate effects andthe sheath have significant effects on the properties frictional load transfer are concernedof the rope particularly its handling 16 Environmental effects and service conditions 161 Rope age Blackford 18 reviews several instances of rope fail ure that have occurred since 1985 Her conclusion is that with the exception of two incidents involving chemical contamination battery acid the remain der of rope failures are associated with cutting or abrasion over a sharp edge An extensive review by Schubert 19 of rope failures among German and Austrian climbers since 1968 reveals the same pat tern Schubert tested a range of ropes of different ages some as old as 30 years using the DODEROFig 6 Construction of kernmantel rope after Pavier 6 standard drop test He reports that none of theJMDA75 IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications6 A J McLarenropes tested failed after one test and because real systems that show weak interaction with waterfalls are never likely to be as severe as the drop test molecules are plasticized relatively little by theropes are very unlikely to fail by breaking at a knot action of waterrunning belay or at a belayfriction device The Signoretti 26 27 studied the effect of wetting ofonly likely instance where failure might be expected ropes on the results of DODERO drop testing Heis over a sharp edge 20 reports that the number of falls withstood is reduced Nevertheless ropes may clearly be seen to deterio to 30 per cent of the value for the original dry roperate with age Schubert 21 uses the concept of This is true for both new and used ropes He statesmetres climbed to characterize the age of a rope that even brief immersion may have a seriousHe has studied the rate of loss of effect equivalent to a short rain shower with age metres climbed Some 50 per it should be noted that every rope in his studycent of the energy absorption ability appears to withstood at least one standard fall irrespective ofbe lost in the first 2000 4000 m climbed with the condition This suggests that although as large as 90 per cent after 20 000 m absorption has a significant effect it does notHe notes that the rate of ageing will depend on the render the rope ineffective He also tested ropesseverity of use treated by the manufacturers with waterproof coatings He observes that these coatings stop162 Water absorption water sticking to the threads but do not stop water absorption in the molecules of the yarn He materials are well known to absorb water that the absorption of water has an equivalenton contact As all ropes apart from those used at effect to an increase in temperature 28indoor walls are likely to become wet through con Signoretti also reports that the first fall on thetact with rain snow or damp ground it is necessary DODERO for the wet ropes showed an increase into consider the effect of water absorption on the force of 5 10 per cent He proposes that this of the rope as a fall arrest system be due to increased friction between fibres induced Cotugno et al 22 reviewed the processes involved by wetting or possible swelling due to waterin the absorption of water by polymeric yarns The effect of water causes reductions in Recent work by Smith 29 has confirmed thatelastic modulus and yield strength This occurs by water absorption has the most significant effect onchanging the mechanisms of yield and deformation static strength and stiffness He also reports thatas well as the cutting of polymer chains by hydroly water uptake appears to be more significant insis The authors show that the equilibrium water fresh water than in simulated sea water of a specific polymer is not sensitive to In both conditions drying of the rope causes whereas the rate of absorption is but not complete recovery of the properties withcontrolled by diffusion and is therefore strongly respect to those of the new rope This is in Different polymers absorb with the findings of to different extents Polyamides tend to behydrophilic ie the molecules possess specific 163 UV lightsites that attract water molecules The authorsreport research carried out by Mensitieri et al 23 Signoretti 30 has also examined the effect of UVand Del Nobile et al 24 comparing water absorp exposure on the number of DODERO falls withstoodtion in nylon6 with a more hydrophobic ethylene He exposed samples of rope to sunlight at copolymer The nylon6 absorbs ten huts in the Dolomites and tested both the statictimes as much water as the copolymer This causes strength of filaments and the dynamic in mechanical properties equivalent to a ability He reports a 35 per cent decrease in in the polymers glass transition tempera of falls after 3 months at the Kostner hut 2250 mture The degree to which water can affect mechan and 15 per cent reduction in number of falls afterical properties depends on the exact nature of the exposure for the same time at the Carestiato hutinteraction between the polymer and the water 1834 m He explains the difference with The authors report that the technique of to the intensity of sunlight at different Transform Infra Red FTIR spectroscopy The decrease in dynamic performance of the ropesmay be utilized to identify these specific interactions is greater than the difference in static strength of25 Absorption of water involving the establish the filamentsment of strong hydrogen bonds between the water Photooxidation changes the chemical and the polymer leads to high levels of of the nylon molecules This occurs by by the breaking of secondary bonds polymerization leading to decreases in both energybetween adjacent polymer molecules Polymer absorption and elasticity The most commonProc IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006 Design and performance of ropes 7methods for reducing the rate of these processes different from any other rope tested The usualinvolve the photochemical stabilization of the failure mode involves catastrophic breakage of thenylon either by the inclusion of antioxidant pro whole rope at the failure load without prior warningducts or the incorporation of UV protection agents For the sandtreated samples the sheath failed firstsimilar to those used as filters in sunscreens at relatively low loads followed by progressive failure UV light tends to have an effect on the appearance of the core at higher load valuesof the rope The fashion these days is for and contrasting strands in the braidedsheath Signoretti observes that of 17 Summarythe sheath by UV exposure may be loosely correlated The property requirements for dynamic climbingwith loss of performance ropes are dominated by the need for effective energy absorption in a leader fall This demands164 Freezing that ropes not only be strong but that they retainClimbing during winter in the UK and at all times in wellcontrolled load elongation behaviour throughthe higher mountain ranges exposes ropes to low out their life The materials and construction oftemperatures in all likelihood accompanied by climbing ropes have evolved from traditional naturalcycles of wetting and drying Odriozola 31 32 fibres with a hawser laid structure to the modernobserved a 30 per cent reduction in static resistance kernmantel construction consisting of parallelfor wetted and frozen ropes compared with the initial twisted yarns surrounded by a braided sheath Theperformance of the dry rope Signoretti 27 shows majority of todays climbing ropes are the number of falls withstood is reduced by from nylon6 the properties of50 per cent in the frozen condition He reports that which are controlled by the relative fractions ofthis is in agreement with the work carried out by axially aligned crystalline and amorphous phasesthe Teufelberger company Austria reported by Although environmental conditions and use doSchubert 33 affect the properties of ropes notably by water absorption UV light freezing heat glazing and par165 Heat glazing ticle entrainment none of these factors is considered to render ropes unsafe The observation is that ropesMcCartney et al 34 have studied the effects of under all of these conditions retain due to rapid abseiling or sack hauling on strength and elasticity to sustain at least one stanbig wall rotes rucksacks are often hauled up behind dard leader fall and the conclusion is that modernthe climbers using pulley systems These activities dynamic ropes do not break in service The exceptioncause localized damage to the sheath by frictional to this pattern involves dynamic loading over sharpmelting of a thin layer Although the depth of melting edges which is said to have accounted for all butis generally small it implies significant local temp two of the reported rope failures in the past 35erature increases on the rope surface years ie since the modern climbing rope was The authors report that the ultimate tensile UTS of the core was not affected by but that the extensibility of the core by 40 per cent adjacent to the damaged 2 ROPES FOR SAILINGside and by 20 per cent on the side opposite to theglazing damage They propose that the temperature 21 locally been higher than the glass transition temperature Tg which alters the molecular arrangement in Ropes are used to fulfil a variety of functions inthe yarns increasing amorphous proportion sailing boats These may be broadly divided into two categories namely the standing and the running166 Particle entrainment rigging Standing rigging consists of structural 35 observed a decrease in the number of falls that support the mast and spars together withsustained by ropes treated externally with grit par equipment such as guard rails which are presentticles Smith 29 studied the effect of sand absorp for reasons of safety By its very nature standingtion on the static strength of ropes Ropes were rigging is semipermanent and tends to be by rubbing sand onto the surface of infrequently usually when setting up the mast atthe sheath and tested in a tensile testing machine the start of the day for dinghies or the start of theHe reports a 25 per cent decrease in static strength season for yachtswhen compared with the new rope In addition the The running rigging is used to hoist andor mechanism of failure was significantly the sails Halyards are used to hoist the sails intoJMDA75 IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications8 A J sheets are attached to the sails and are Elastic stretch in ropes used to control sails orused primarily to control their angle to the boats other components would limit the precision withcentreline and therefore the wind The running which adjustments could be made For will also generally include ropes that are the tension in a halyard has a fundamental effectused to control the position of moveable com on the shape of the sail and thereponents of the boat which are used for fine adjust fore its aerodynamic behaviour It is desirable to bement of the sails The ropes in the running rigging able to make fine adjustments to halyard tensionwill generally pass through pulleys and blocks that while sailing because the sailshape used to control the line of action of the ropes vary considerably with wind strength point of sailingand increase mechanical advantage On yachts the the angle between the wind and the boats headingsheets and halyards are usually tensioned using wave conditions and tactical considerations relatinggeared capstan winches which multiply the forces to the position relative to competing boatsexerted by the human body to the magnitudes Fine adjustment is facilitated by the use ofrequired halyards that possess high longitudinal stiffness Standing rigging components are essentially This is particularly important because Traditionally they were made of rope adjustments are usually made by the use of a winchbut the most usual material in use today is twisted in the boats cockpit The total length of steel wire rope For between the head top corner of the sail and solid rod rigging often made from winch is approximately equal to the height of theNitronic 50 nitrogen alloyed stainless steel a mast plus the distance from the mast to the trademark of Armco Inc is utilized The For a typical 10 m racing yacht this distance mightstrand moduli of a variety of standing rigging be 15 m The full range of halyard tension is are shown in Fig 7 replotted from the to be accomplished by adjustments of 15 cm at thework of Gilliam 36 Strand modulus is used in winch ie 1 per cent of the halyard length Finepreference to Youngs modulus load extension data adjustment may require movements of 1 cmfrom an actual strand are used together with the 007 per cent of the halyard length Materials ofnominal diameter of the strand to calculate the high stiffness are desirable because they alloweffective modulus of the cable or rod ropes of relatively small diameter to be used while The properties required of sailing ropes have much still supporting the considerable loads generatedin common with those used for climbing These Small diameter ropes not only save weight importinclude high strength abrasion resistance stability ant in its own right for racing sailors but alsoof properties in the presence of water good handling reduce the crosssection exposed to the wind In aproperties and low weight However in one import yacht that derives its entire driving force from theant respect the property requirements are quite aerodynamics of the sails any item aloft that doesdifferent Sailing ropes must have high levels of not contribute to this drive can only increase dragstiffness The requirement for energy absorption andor healing force with the associated reductionin shockloading conditions is removed Indeed in efficiencythe very elasticity which facilitates this ability in While halyards are perhaps the most critical ropesclimbing ropes would be a serious disadvantage for from the point of view of fine adjustment the samerunning or standing rigging components in a sailing requirements certainly apply to most other comcraft ponents of the running rigging Sheets that control sails may be highly loaded particularly when sailing upwind when the sails are pulled tightest Winches on racing yachts are characterized by their power ratio which is defined as the ratio of sheet load produced divided by the force applied to the handle For a typical 10 m racing yacht winches with a power factor of 40 might be expected Therefore a relatively light crew member say 80 kg in weight exerting one quarter of their body weight as a force on the winch handle might be expected to generate a sheet load of 8 kN It is interesting to note that this is equal to the maximum load permitted for half ropes and twin ropes in the dynamic drop test for climbing ropes In realityFig 7 Elastic properties of various candidate materials loads far in excess of this value might be expected for standing rigging replotted from Gilliam 36 in sailing ropesProc IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006 Design and performance of ropes 922 Materials and construction Allied and Dyneema a registered trademark of DSM Corp This light strong fibre hasAn excellent review of ropes for sailing has recently also found uses in climbing It is used to make tapebeen published by Pawson 37 He reviews the slings and static cord for use in running belays Thehistory of rope materials from the early natural dynamic properties of the rope absorb the energyfibres such as hemp manila and sisal through the of the fall but the protective gear placed in thediscovery of nylon in the 1930s and the later develop rock is designed as a lightweight strong stiff butment of polyethylene PE polyester PES and flexible structure Here the weight savings that PP Of the manmade fibres nylon possible for a climber carrying a large assortmentis not particularly suitable due to its high stretch of protection equipment have led to the adoptionthe very property that makes it ideal for climbing of exotic materialsropes The high degree of stretch makes it unsuita Most recently the liquid crystal polyester LCPble for halyards and sheets for the reasons already sold as Vectran a registered trademark of In addition should a loaded nylon rope Celanese Corp and it tends to whiplash severely However zole PBO sold as Zylon a registered trademark ofnylon is often used for mooring ropes where a certain the Toyobo corp have been used by Americasdegree of elasticity is an advantage as in the damping Cup teams and are starting to make their way intoof snatch loading the regular racing market The majority of sailors use PES ropes for running None of these most recently developed fibres isrigging The ropes are heat treated and prestretched cheap but as with many sports competitors willin the manufacturing process to give high longitudi readily spend money on materials and equipmentnal stiffness The construction generally consists of a that give a perceived advantage however small thisbraid on braid structure formed from braiding an may be in reality Certainly there would seem to beeight or sixteenstrand hollow plait over a core of more scope for the use of novel and exotic hollow braid These ropes give excellent for sailing ropes than for climbing The cost of ropesfriction and handling properties in addition to and cordage as a fraction of a racing boats budget isgood stiffness relatively small whereas for the average climber PP is cheaper than PES but its wear and UV resist their rope or ropes constitute a major fraction ofance properties are inferior It has relatively low den the total cost of the equipment they ownsity which makes it float which can be an advantagefor some applications eg floating heaving line forman overboard situations 24 Knots and splices Both sailors and climbers need to make loops in the23 Exotic materials end of their ropes for various purposes Climbers tra ditionally tied the rope round their waist with a bowAt the end of the sport eg the line knot but since the development of Cup considerable development has been sit harnesses the usual method is to tie the end of thecarried out into the use of exotic specialist materials rope to the harness by use of a double reduce weight and increase performance The first knot The current advice on the use of knots byexample in use was the aramid fibre known as Kevlar climbers in contained in the BMCs excellenta registered trademark of EI DuPont de Nemours technical booklet 38Alternative trade names include Twaron a regis Sailors also traditionally use knots to make loopstered trademark of Teijin Twaron USA Inc and in the end of a rope In particular the bowline isTechnora a registered trademark of Teijin Co generally used to attach the sheets to the clewLtd It shows very low stretch is very strong and bottom rear corner of a headsail This knot islightweight However its properties in bending are easy to tie and can be untied quickly once poorer particularly over pulleys and This is better than a permanent attachment becausesheaves and this has led to the development of any rope tangles can be quickly sorted out by untyblocks with larger sheaves to alleviate this problem ing the knots if necessary Sheets also tend to beAll these fibres must be protected from UV degra stored below deck when not in use so need to bedation and chafe and for this reason the core of attached to the sail on each occasion that the boatthe rope is constructed from the specialist fibre is racedwhereas the braided sheath is usually made from Recent work 39 utilized static tensile testing toPES measure the strength of a variety of knots and splices Another fibre now in relatively common use is used to make loops in the end of PES sailing polyethylene HMPE sold under the Four knots were evaluated bowline double bowlinetrade names Spectra a registered trademark of perfection loop and double figureofeight All knotsJMDA75 IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications10 A J McLarenbroke at between 55 and 84 per cent of the rope Other manufactures have developed coversstrength with the double figureofeight being containing Nomex a registered trademark of stronger than the others This result is DuPont de Nemours or Aramid fibres These helplikely to be reassuring to climbers who use this prevent melting due to frictional heating on winchknot for tying into their harness but for sailors the drums when sheets are being eased These ropesknots extra strength is outweighed because it is may lead to scoring of carbon fibre winch difficult to untie once it has been loaded so rope and winch manufactures are workingThe authors also examined the strength of splices together to solve these problemsused to make loops in hawserlaid as well as braid It remains to be seen to what extent these developonbraid ropes Compared with knots splices ments from the extreme top end of the sport willprovide a significantly stronger loop However they propagate down to club and regatta sailors Howevercan only be used where the loop is required to be it is interesting to note that parallel have occurred in the materials and construction Other workers 40 41 have addressed the subject methods used in sail making It is common to seeof splices and end terminations for both steel the same club and regatta sailors using laminateand polymer fibre ropes The nonlinear nature of sails reinforced with such exotic materials asthese materials and the complexity of their struc Kevlar carbon fibre and Vectran This may indicatetural interactions make modelling in this field that more exotic ropes will to be used by sailors outside the elite group In contrast the average climber is unlikely to be willing to pay a high premium for a small increase3 FUTURE DEVELOPMENTS in performance The general conclusion from the study of climbing accident statistics is that ropes doPawson 37 gives an insight into future develop not break other than when loaded over an edgements in sailing ropes in his review Current ropes Reasonable weight savings have been achieved bywhich have cores made from the exotic materials the use of smaller diameter ropes in section 23 are generally protected by among sports climbers However larger weightuse of a PES or occasionally PP cover The strength savings are possible by enhanced design of runningand extension properties of the rope are governed belay equipment and this has seen considerableby the core material so traditional braidonbraid development in recent years Improved rope coatsplices are inappropriate for these constructions ings may increase UV resistance and reduce have designed new splicing tech absorption which will be of benefit to in order to make coretocore splices Thepractice of stripping off the cover and using thecore alone is commonplace particularly for ropes 4 form standing rigging components such as backstays or spinnaker pole bridles The tails of sheets The apparently similar ropes used by sailors andand halyards cannot be used without the cover climbers are in fact very different The majorbecause this makes for difficult handling using design constraint for climbing ropes is the requirewinches and jammers The solution is the produc ment to absorb and dissipate the energy of leadertion of tapered sheets and halyards stripped at the falls without transmitting large forces to the climberworking end but covered at the tail This requires a rope of moderate to low longitudinal Future developments are likely to involve the stiffness but high strength This is achieved by theinclusion of exotic materials in the structure of the use of polyamide nylon6 formed into a itself Pawson 37 mentions several examples structure of parallel twisted yarns surrounded by amostly from developments for Americas Cup teams braided protective sheathcovers have been used that contain prestretched Environmental damage due to ageing waterDyneema over cores of Vectran Dyneema or PBO absorption UV light degradation freezing heatCovers containing PBO have also been developed glazing and particle entrainment has a significantto give greater wear resistance Despite the fact that effect on the properties of the rope and decreasesthese ropes are very expensive their use actually the ability to withstand standard drop tests Howsaved money because the standard PES covered ever none of these treatments reduces the needed to be replaced after each race The of the rope to levels that would cause failure in userelatively poor UV resistance of PBO is not seen as The most significant threat to safety is the cuttinga problem because the ropes need to be replaced of a rope that is loaded over a sharp edgefor reasons of wear after two race series long The relationship between structure and the effects of UV become apparent is complex and although the problem of describingProc IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006 Design and performance of ropes 11it has responded to various modelling techniques 12 Pan N and Brookstein D Physical properties ofthere is still scope for further work in this area twisted structures II Industrial yarns cords and Sailing ropes especially for boats involved in racing ropes J Appl Polym Sci 2002 83 610 630require a different portfolio of properties In particular 13 Manes A Analysis of a textile rope with analytical models In Nylon and ropes for mountaineering andhigh longitudinal stiffness to weight ratios are domi caving Italian Alpine Club Technical Committeenant constraints Precise control of sails and other Turin 8 9 March 2002 available from by rope actuators leads to the need for materials Traditional natural fibres have 14 Contri L and Secchi S Snapping of ropes underbeen replaced by manmade polymers notably PES stress In Nylon and ropes for mountaineering andformed into ropes with a braidonbraid structure caving Italian Alpine Club Technical Committee In applications more exotic core Turin 8 9 March 2002 available from usually covered with a braided PES sheath used These materials give enhanced stiffness to 15 Leech C M The modelling of friction in polymer fibreweight ratios but incur a considerable monetary ropes Int J Mech Sci 2002 44 621 643cost Although their use was initially confined to the 16 Leech C M Banfield S J Overington M S and Lemoel M The prediction of cyclic load behaviourtop echelons of competition they are becoming and modulus modulation for polyester and othermore widespread at all levels of the sport large synthetic fibre ropes Oceans 2003 Proceedings Loops may be formed at the end of ropes by both 2003 3 1348 1352knots and splices Spliced loops are significantly 17 Phoenix S L Statistical theory for the strength ofstronger than knots but their use is restricted to twisted fibre bundles with applications to yarns andthe manufacture of semipermanent loops cables Text Res J 1979 49 407 423 18 Blackford J R Materials in mountaineering In Materials in sports equipment Ed M Jenkins 2003 pp 279 325 Woodhead Publishing Cambridge UKREFERENCES ISBN 1855735997 19 Schubert P A number of rope failures amongst 1 Langmuir E Mountaincraft and leadership 3rd edition German and Austrian mountaineers and climbers 2003 Mountain Leader Training Scotland Aviemore since 1968 In Nylon and ropes for mountaineering UK ISBN 1850602956 and caving Italian Alpine Club Technical Committee 2 Fyffe A and Peter I The handbook of climbing 1997 Turin 8 9 March 2002 available from httpwwwcai Penguin Books London ISBN 0720720540 3 Smith R A The development of equipment to reduce 20 Bailie M Ropes dont break Summit 2000 17 17 risk in rock climbing Sports Eng 1998 1 27 39 21 Schubert P About ageing of climbing ropes J UIAA 4 Wexler A The theory of belaying Am Alp Club J 2000 3 12 13 1950 7 379 405 22 Cotugno S Mensitieri G Musto P and Nicolais L 5 Pavier M J Derivation of a rope behaviour model for Water sorption and transport in polymers In Nylon and the analysis of forces developed during a rock climbing ropes for mountaineering and caving Italian Alpine leader fall Proceedings of the 1st International Confer Club Technical Committee Turin 8 9 March 2002 ence on the Engineering of sport Ed S J Haake 1996 available from pp 271 279 Balkema Rotterdam torinohtml 6 Pavier M J Experimental and theoretical simulations 23 Mensitieri G Del Nobile M A Sommazzi A and of climbing falls Sports Eng 1998 1 79 91 Nicolais L Water transport in a polyketone terpolymer 7 BS EN 897 Mountaineering equipment dynamic J Polym Sci B Polym Phys 1995 33 1365 1370 mountaineering ropes safety requirements and test 24 Del Nobile M A Mensitieri G and Sommazzi A methods October 1996 Available from http Gas and water vapour transport in a polyketone terpolymer Polymer 1995 36 4943 4950 8 Bennett F Learning the ropes Summit 2000 20 25 Cotugno S Larobina D Mensitieri G Musto P 28 29 and Ragosta G A novel spectroscopic approach to 9 Karrer R The perfect ropeproduction and use In investigate transport processes in polymers the case Nylon and ropes for mountaineering and caving Italian of waterepoxy system Polymer 2001 42 6431 6438 Alpine Club Technical Committee Turin 8 9 March 26 Signoretti G The influence of water ice and sunlight 2002 available from on the dynamic performance of mountaineering ropes In Nylon and ropes for mountaineering and10 Beal M Influence of parameters in the rope construc caving Italian Alpine Club Technical Committee tion In Nylon and ropes for mountaineering and Turin 8 9 March 2002 available from httpwww caving Italian Alpine Club Technical Committee Turin 8 9 March 2002 available from httpwwwcai 27 Signoretti G Wet and icy ropes may be dangerous J UIAA 2001 2 25 2811 Costello G A Theory of wire rope 2nd edition 1997 28 Kohan M I Ed Nylon plastics handbook 1995 Hanser Springer Verlag New York ISBN 0387982027 Gardner Cincinnati OH ISBN IMechE 2006 Proc IMechE Vol 220 Part L J Materials Design and Applications12 A J McLaren29 Smith M An assessment of the effects of environmental 39 Milne K A An assessment of the strength of knots and conditions on the performance of dynamic climbing splices used as eye terminations in a sailing environ ropes Final Year Thesis University of Strathclyde ment Final year Thesis University of Strathclyde Glasgow 2005 Glasgow 200030 Signoretti G Ropes and sunlight a matter of colour 40 Leech C M Hearle J W S Overington M S and La Rivista del CAI 1999 Luglio Agosto 76 84 Banfield S J Modelling tension and torque properties31 Odriozola J A Estudios previos para ensyos de of fibre ropes and splices Proceedings of the 3rd cuerdas a baja temperature Revista Pen alara 1968 International Offshore and Polar Engineering Confer Abril Junio 37 40 ence Singapore 1993 pp 370 37632 Odriozola J A Comportamiente de una cuerda de 41 Leech C M and Zhang S The use of inhomogeneous montan a a baja temperatura Revista Pen alara 1969 finite elements for the prediction of stresses in rope Enero Marzo 14 21 terminations Eng Comput 1985 2 56 6233 Schubert P Was halten nasse und vereiste Seile im DAV Ta 1971 73 197 20634 McCartney A J Brook D and Taylor M The effect of APPENDIX heat glazing on the strength and extensibility properties of polyamide climbing ropes In Nylon and ropes for Notation mountaineering and caving Italian Alpine Club Techni cal Committee Turin 8 9 March 2002 available from g acceleration due to gravity ms2 H twice the vertical distance between the35 Pavier M J Failure of climbing ropes resulting climber and the last running belay m from multiple leader falls Proceedings of the 2nd k rope elasticity N International Conference on the Engineering of sport L total length of rope used m Ed S J Haake 1998 pp 415 422 Blackwell Science m total mass of lead climber and equipment Oxford carried kg36 Gilliam J History of sailing yacht masts rigging and P instantaneous load transferred to the sails 1900 present day available from httpboatde 2002 rope N37 Pawson P Rope yarns Yachts and Yachting 2005 Pmax maximum load transferred to the 1513 42 46 rope N38 British Mountaineering Council Knots Technical Tg glass transition temperature 8C Series 1997 British Mountainearing Council Manche x instantaneous elastic extension of the ster UK available through rope mProc IMechE Vol 220 Part L J Materials Design and Applications JMDA75 IMechE 2006