peterb
Well-Known Member
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As Jimi says - nylon is used BECAUSE it's stretchy and absorbs shocks.
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I'm never sure about the theory behind using stretchy nylon to absorb shocks. What shocks? The main source seems to be with the boat ranging backwards and forwards, being brought up with a jerk as it reaches its limits.
But why give it the slack to move in the first place? (I'm talking about springs here, not breast ropes, and mooring on to a pontoon so that there is no need to allow for tide.) If the boat could be fixed with springs having no slack, would there still be shock loads?
Certainly the worst case is likely to be the use for springs of old halyards (prestretched polyester or similar, with no springiness) having lots of slack left in the line. This lets the boat range back and forth, coming up with a sudden shock at each end. So the first thing to do is to take the slack out of the springs. Once this is done, I think that there is little difference between the use of springy nylon or less springy polyester.
If the boat is moving in response to sea state, then the most likely problem is pitching. This won't affect springs, which behave as if there were a pivot in the middle, but can certainly affect breast ropes. More than once I have had to rescue boats with broken breast ropes, due to snatch and chafe as the boat pitches (usually on F pontoon at Woolverstone Marina, with a flooding tide and a strong nor'wester). So I think that that is where the stretch is needed, and I don't think that you can get enough from the stretch of a short breast rope, even if it is nylon. That's probably where you need a rubber snubber, and the bigger the better.
When I've set up permanent mooring warps on a home berth, I've used a spliced loop for the bow spring, to control the position of the bow, and a longer unspliced stern spring. Once the bow spring is on, the stern spring is taken (via the stern cleat) on to the genoa winch, where it is pulled in tight and secured with a lighterman's hitch. No problem if we need to take the spliced bow spring off, because we can give plenty of slack on the stern spring.
As Jimi says - nylon is used BECAUSE it's stretchy and absorbs shocks.
[/ QUOTE ]
I'm never sure about the theory behind using stretchy nylon to absorb shocks. What shocks? The main source seems to be with the boat ranging backwards and forwards, being brought up with a jerk as it reaches its limits.
But why give it the slack to move in the first place? (I'm talking about springs here, not breast ropes, and mooring on to a pontoon so that there is no need to allow for tide.) If the boat could be fixed with springs having no slack, would there still be shock loads?
Certainly the worst case is likely to be the use for springs of old halyards (prestretched polyester or similar, with no springiness) having lots of slack left in the line. This lets the boat range back and forth, coming up with a sudden shock at each end. So the first thing to do is to take the slack out of the springs. Once this is done, I think that there is little difference between the use of springy nylon or less springy polyester.
If the boat is moving in response to sea state, then the most likely problem is pitching. This won't affect springs, which behave as if there were a pivot in the middle, but can certainly affect breast ropes. More than once I have had to rescue boats with broken breast ropes, due to snatch and chafe as the boat pitches (usually on F pontoon at Woolverstone Marina, with a flooding tide and a strong nor'wester). So I think that that is where the stretch is needed, and I don't think that you can get enough from the stretch of a short breast rope, even if it is nylon. That's probably where you need a rubber snubber, and the bigger the better.
When I've set up permanent mooring warps on a home berth, I've used a spliced loop for the bow spring, to control the position of the bow, and a longer unspliced stern spring. Once the bow spring is on, the stern spring is taken (via the stern cleat) on to the genoa winch, where it is pulled in tight and secured with a lighterman's hitch. No problem if we need to take the spliced bow spring off, because we can give plenty of slack on the stern spring.
