11/24/2023 0 Comments Cut the rope 2 level 316 medalWe fitted each of the cutters in turn to the test rig’s P-bracket and shaft to see how easy this was to carry out. It’s worth noting that the RNLI has fitted Quickutters to its entire fleet of Tamar-class lifeboats. We would be pleased to hear of any readers’ experiences with shaver-type cutters. We were unable to test the Quickutter shaver – its maker declined to participate, citing concerns over the suitability of out test tank and rig for evaluating the performance of a shaver. Plastimo couldn’t provide us with a unit, so we bought one. We explained to all eight manufacturers how our tests would be conducted and invited suppliers to send us samples and attend the test. Pricewise, shavers are midway between discs and scissors, although you would have to add in the cost of machining the prop and sometimes the P-bracket, too. The disadvantage is complex installation and the need for accurate fitting in a machine shop. As the blades spin, the rope is gradually shaved through.Īdvantages include reduced load on the structure and transmission during cutting, plus minimal loss of boat speed. As rope or debris is encountered, it is forced into the gap between the blades and the prop. A plastic spool or cylinder is slid over the shaft and attached to the front boss of the prop, running under the cutter blades. GRP stern tubes may need some strengthening, depending on build quality. The shaver is a new development comprising fixed blades mounted on a block attached to the P-bracket or stern tube. For a long-keel yacht with a keel-hung rudder, you may have to widen the prop aperture on the leading edge of the rudder. Disc types can be fitted to any shaft-drive boat. Disadvantages include the lack of a positive cutting action – discs can struggle to cut through weed and plastic sheeting. The advantages are simple installation and low cost, plus minimal drag underway. As the shaft spins, any rope or debris that is drawn down to the disc is gradually cut through as it passes over the knife-edge. In both cases the cutter is held in place with a grub screw. The disc can be split and clamped round the shaft, or solid, in which case the prop has to be removed and the disc slid up the shaft. This type of cutter is a thin stainless steel disc with a sharpened edge. A scissor cutter is the only option for saildrives. GRP is not strong enough to stop the tapped machine-screws pulling out, though in some cases a plate can be made up to take the block, which is then glassed or bolted to the hull or tube. Scissor cutters cause more drag than some other types and are the most expensive to buy.īecause of the loads on the fixed block of the scissor-types, they can usually only be fitted to metal P-brackets, stern tubes or hulls. Every two years or so, you will have to replace the thin plastic bearings, on which the fixed cutter spins on the shaft. There are various drawbacks: it’s a complex installation and you may need to fit a spacer in the gearbox coupling. The advantage is a positive cutting action, which also shreds weed and netting. As the prop rotates, obstructions are drawn down into the scissor blades and cut or chopped up. It comprises a rotating cutter clamped to the shaft, with two or more blades, plus a fixed cutter bolted to the P-bracket. The scissors-type was the first on the market. Three are scissors-type cutters, four use discs and one is a shaver. There are at least eight different makes of cutter on the UK market. This is the most comprehensive and detailed study of rope cutters published in a UK sailing magazine. Whether it’s a stray sheet tail or an abandoned fishing net, once you lose propulsion, you lose a lot of options.įitting a rope cutter is a good way of keeping your options open, but how effective are they? We located a test tank and put seven different cutters to the test, to see how good they are at slicing through ropes, fishing nets, wire and plastic – and still keep your prop turning. On a lee shore in a gale, or in foggy shipping lanes, it could easily end in disaster. The line was soon freed and we left with nothing more serious than dented pride and a slightly shorter hosepipe, but a boat rope wrapped around the prop can often have more serious consequences. Back in our berth, I cut an 8ft length from the end of a hosepipe, attached one end to a stanchion, put the other in my mouth and stepped off the stern to investigate. Suddenly, the engine died as the fixed mooring line was now firmly wrapped around the three-blade propeller of our Gib’Sea 32. I waited for the line to sink and engaged forward gear to leave our marina berth in the Mediterranean.
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