I have a locker full of braided lines from the previous owner. I would like to use these as mooring lines but cannot determine which are nylon vs old halyards. I've tried to stretch them compared to a known nylon line, but I can't stretch these 5/8 inch lines enuf to tell. Any ideas?
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Mooring lines
Many boats use just chain for anchor rodes which have no stretch at all. The key is to have a good catenary which absorbs the shock loads from surf, wind gusts, etc. You can use low stretch lines but put a weight on the line and run it out half way to cause a significant sag in the line. Marine discount stores sell these weights or you can make something like a small mushroom anchor shackled to a block and run the block down the anchor line, the mushroom will provide additional shock absorption by resisting motion thru the water like a sea anchor.
Many boats use just chain for anchor rodes which have no stretch at all. The key is to have a good catenary which absorbs the shock loads from surf, wind gusts, etc. You can use low stretch lines but put a weight on the line and run it out half way to cause a significant sag in the line. Marine discount stores sell these weights or you can make something like a small mushroom anchor shackled to a block and run the block down the anchor line, the mushroom will provide additional shock absorption by resisting motion thru the water like a sea anchor.
Single or double braid?
If the lines are single braid then, even if not nylon, they may be stretchy enough for mooring/dock lines. If they're double braid (cover and core) then they're probably old running rigging and won't stretch very much. Jim "Prospect"
If the lines are single braid then, even if not nylon, they may be stretchy enough for mooring/dock lines. If they're double braid (cover and core) then they're probably old running rigging and won't stretch very much. Jim "Prospect"
Use rubber snubbers in lines
You should be able to use them as docklines -- even if they are not very stretchy -- by winding each line a few times around a rubber snubber (looking a bit like an oversized rubber dogbone) available from most marine supply houses. If you want a cheaper solution and don't mind the looks of it, you might use a snubber made from an inner car tire instead. Success! Flying Dutchman Flying Dutchman
You should be able to use them as docklines -- even if they are not very stretchy -- by winding each line a few times around a rubber snubber (looking a bit like an oversized rubber dogbone) available from most marine supply houses. If you want a cheaper solution and don't mind the looks of it, you might use a snubber made from an inner car tire instead. Success! Flying Dutchman Flying Dutchman
Subber
Ditto rubber snubbers. What a difference they made in my docking lines. A bit expensive but worth the cost.
Ditto rubber snubbers. What a difference they made in my docking lines. A bit expensive but worth the cost.
Rubber Snubbers
Can you please elaborate on what you consider the benefits of these devices? I see a lot in use but am unsure what benefit they are providing. This is basically a spring in a force system but without a dashpot to provide dampening. It can be modeled like a car suspension without shock absorbers, the vibration decay rate will continue much longer from a step input . Think of it this way, a spring is an energy absorbing device so you stretch it and it stores energy (potential energy) and then it releases it as kinetic energy. The dock line will still see the total force just without the shock if the line were inelastic. Replace the rubber snubber with a coil spring with a eye on each end and tie you dock line to the eye one one end and a line to the boat tied to the eye on the other end of the spring and assuming a spring rate the same as the rubber snubber and you have an identical system. I'd like to hear from users how their experiences relate and why they recommend these items. A nylon line has a spring rate built into it as it will stretch up to 30%.
Can you please elaborate on what you consider the benefits of these devices? I see a lot in use but am unsure what benefit they are providing. This is basically a spring in a force system but without a dashpot to provide dampening. It can be modeled like a car suspension without shock absorbers, the vibration decay rate will continue much longer from a step input . Think of it this way, a spring is an energy absorbing device so you stretch it and it stores energy (potential energy) and then it releases it as kinetic energy. The dock line will still see the total force just without the shock if the line were inelastic. Replace the rubber snubber with a coil spring with a eye on each end and tie you dock line to the eye one one end and a line to the boat tied to the eye on the other end of the spring and assuming a spring rate the same as the rubber snubber and you have an identical system. I'd like to hear from users how their experiences relate and why they recommend these items. A nylon line has a spring rate built into it as it will stretch up to 30%.
Why Rubber Snubbers ? Dynamic Loads!
First of all, I am not advocating the use of rubber snubbers on nylon dock or mooring lines with good elasticity and of adequate length (although, if you need to short-tie your dockline, e.g. in order to use a mid-cleat, you need to realize that the total elastic stretch of that line may have become inadequate to protect your tie-off points). The assumption of the original poster was, however, that he had lines of unknown elasticity (possibly not nylon) which otherwise appeared to be in good condition, so he did not want to throw them away. I completely agree with your argument that the use of an elastic snubber (or an elastic nylon line for that matter) will not change the static load (or "force" as you call it) on the tie-off points once the system has reached equilibrium. The same is true, of course, of your anchor chain when you use a nylon snubber to protect your bollard, Samson post or other tie-off point. So why use the elastic properties of snubbers (and/or naturally elastic lines) if this does not change the static loads working on the tie-off points? The answer is: to protect these points -- and all that is attached to them -- against excessive dynamic loads. The destructiveness of dynamic versus static loads is easily seen if one thinks of the way a slatting sail in a windless situation will destroy its shackles, slides or fabric in a relatively short period of time (because of the high dynamic loads imposed by the slatting) whereas the same sail will last a long time in strong but steady winds (i.e. at much higher static loads but low dynamic loads). Last summer, as I returned to Townsville to free "Rivendel II" from her 20- month long bondage to the finger pier (which included glancing blows from one or two nearby cyclones) I was quite sorry not to have followed my own advice, as one or two short-tied nylon docklines had caused a lot of play (and consequent rainwater leakage problems) in the midcleat. Incidentally, under protracted static loads nylon will loose some of its inherent elasticity much faster than rubber because the individual macro-molecules in nylon are not as strongly linked to their neighbor molecules ("cross-linked") as in properly crosslinked rubber. This causes them to slip a bit over time and a line made of pure nylon will therefore not return to its exact length after having been stretched for a long time. So, if you have an old, "tired" nylon line you may still want to use the unique properties of rubber to enhance its snubbing action. Flying Dutchman
First of all, I am not advocating the use of rubber snubbers on nylon dock or mooring lines with good elasticity and of adequate length (although, if you need to short-tie your dockline, e.g. in order to use a mid-cleat, you need to realize that the total elastic stretch of that line may have become inadequate to protect your tie-off points). The assumption of the original poster was, however, that he had lines of unknown elasticity (possibly not nylon) which otherwise appeared to be in good condition, so he did not want to throw them away. I completely agree with your argument that the use of an elastic snubber (or an elastic nylon line for that matter) will not change the static load (or "force" as you call it) on the tie-off points once the system has reached equilibrium. The same is true, of course, of your anchor chain when you use a nylon snubber to protect your bollard, Samson post or other tie-off point. So why use the elastic properties of snubbers (and/or naturally elastic lines) if this does not change the static loads working on the tie-off points? The answer is: to protect these points -- and all that is attached to them -- against excessive dynamic loads. The destructiveness of dynamic versus static loads is easily seen if one thinks of the way a slatting sail in a windless situation will destroy its shackles, slides or fabric in a relatively short period of time (because of the high dynamic loads imposed by the slatting) whereas the same sail will last a long time in strong but steady winds (i.e. at much higher static loads but low dynamic loads). Last summer, as I returned to Townsville to free "Rivendel II" from her 20- month long bondage to the finger pier (which included glancing blows from one or two nearby cyclones) I was quite sorry not to have followed my own advice, as one or two short-tied nylon docklines had caused a lot of play (and consequent rainwater leakage problems) in the midcleat. Incidentally, under protracted static loads nylon will loose some of its inherent elasticity much faster than rubber because the individual macro-molecules in nylon are not as strongly linked to their neighbor molecules ("cross-linked") as in properly crosslinked rubber. This causes them to slip a bit over time and a line made of pure nylon will therefore not return to its exact length after having been stretched for a long time. So, if you have an old, "tired" nylon line you may still want to use the unique properties of rubber to enhance its snubbing action. Flying Dutchman
Rubber Snubbers
Just a note for David Lewis: Rubber is elastic but it is no spring. Rubber has a very high level of energy dissipation when stretched (known in the industry as hysteresis) and when properly formulated provides its own damping (dashpot). The original Austin Mini had rubber suspension with no shock absorbers as dissipation in the rubber damped oscillations very effectively. How's that for an arcane answer?
Just a note for David Lewis: Rubber is elastic but it is no spring. Rubber has a very high level of energy dissipation when stretched (known in the industry as hysteresis) and when properly formulated provides its own damping (dashpot). The original Austin Mini had rubber suspension with no shock absorbers as dissipation in the rubber damped oscillations very effectively. How's that for an arcane answer?
Rubber Springs
Definition Hysterisis - A retardation of the effect of an action which causes a difference in absolute position upon direction reversal. This "lost" motion is caused by the elastic deformation of drive train components (as contrasted to finite inaccuracies of mating drive train surfaces in backlash). An example is torsional windup of a leadscrew or coupling. I took the above off some web site. A spring is simply an energy storage device and in mechanical system modeling that's all it means. It can take a lot of different forms, coil springs, leaf springs, torsion springs, a branch of a tree deflected and then released, etc. An axial load is applied to the rubber, it stretches, reaches a maximum length at which point all the kinetic energy is stored as potential energy and then it releases it and returns to its' original shape (assuming only elastic deformation). In any process there is some losses due to entropy and in the rubber and attached line some energy is converted to heat and lost through convective,conductive, and radiant heat transfer. There is also an effect with these items where the line is coiled around the snubber and when placed in tension the line coil will compress the rubber radially which complicates this from being a pure tension problem. Since the line is flexible this can't be a compression problem so it is a cyclic loading problem of a step input of tension then back to zero, of course in a real world the loading is constantly varying in magnitude due to wave and wind effects. Because of the very low frequency of the vibration in a dock line a dashpot or dampener is probably not required. On the other hand the tension load applied to the lines and dock cleats will still be equal whether there is a snubber or not. When the snubber reaches it's maximum axial deflection and the system is at equilibrium the tension load is equal over the entire system. So the load required to deflect the rubber is still transmitted to the dock cleat, line, and boat cleat (and chock) just like if you only had the line and the line stretches. So my question is, are these items really worth the expense or just a scam to relieve boaters of more of their retirement funds? The elastic modulus of the rubber is likely very different than nylon line and thus a change to the shock loading (due to a time constant change in the response characteristics of the mechanical system)is predictable so I just wanted users to explain why they like these items and feel they are worth it.
Definition Hysterisis - A retardation of the effect of an action which causes a difference in absolute position upon direction reversal. This "lost" motion is caused by the elastic deformation of drive train components (as contrasted to finite inaccuracies of mating drive train surfaces in backlash). An example is torsional windup of a leadscrew or coupling. I took the above off some web site. A spring is simply an energy storage device and in mechanical system modeling that's all it means. It can take a lot of different forms, coil springs, leaf springs, torsion springs, a branch of a tree deflected and then released, etc. An axial load is applied to the rubber, it stretches, reaches a maximum length at which point all the kinetic energy is stored as potential energy and then it releases it and returns to its' original shape (assuming only elastic deformation). In any process there is some losses due to entropy and in the rubber and attached line some energy is converted to heat and lost through convective,conductive, and radiant heat transfer. There is also an effect with these items where the line is coiled around the snubber and when placed in tension the line coil will compress the rubber radially which complicates this from being a pure tension problem. Since the line is flexible this can't be a compression problem so it is a cyclic loading problem of a step input of tension then back to zero, of course in a real world the loading is constantly varying in magnitude due to wave and wind effects. Because of the very low frequency of the vibration in a dock line a dashpot or dampener is probably not required. On the other hand the tension load applied to the lines and dock cleats will still be equal whether there is a snubber or not. When the snubber reaches it's maximum axial deflection and the system is at equilibrium the tension load is equal over the entire system. So the load required to deflect the rubber is still transmitted to the dock cleat, line, and boat cleat (and chock) just like if you only had the line and the line stretches. So my question is, are these items really worth the expense or just a scam to relieve boaters of more of their retirement funds? The elastic modulus of the rubber is likely very different than nylon line and thus a change to the shock loading (due to a time constant change in the response characteristics of the mechanical system)is predictable so I just wanted users to explain why they like these items and feel they are worth it.
Burn the end
Just burn the end. If the lines are nylon, they will melt. If they are narural fibers they will just burn...
Just burn the end. If the lines are nylon, they will melt. If they are narural fibers they will just burn...
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