Various knots, and types of splices, have been tested to see how well they preserve the strength of the original line; an eye splice with a thimble steel internal support is one of the better designs; the overhand knot illustrated in the question is one of the worst. Every rope is weakened by tying a knot! If you have a damaged usually frayed section of rope then it is possible to knot in another section of rope to take the load.
Typically you would do this with a sheepshank or one of its variants. In this case the knotted rope will be stronger than before, because its strength was seriously limited by the damaged section. Now the damaged section is no longer taking the strain, you've fixed that weakest link. The answers above are already very complete considering strength. There is however one other point that I'd like to add.
If you have a knot in a rope that gets wet, the knot will stay wet longer than the rest of the rope. This will allow mold to grow more easily in the knot, where it has a wet and probably warm place to stay and grow. Of course it goes without saying that mold will weaken your rope. Side remark: you don't need knots to grow mold; in time even a straight rope will probably start growing mold. Another point I'd like to make is that for the application you are mentioning it probably will not matter since the weight of your clothes is not that large compared to the breaking strength of rope.
Of course if you really put a lot of tension on your system this can start to become relevant. Finally the rope will probably be hanging permanently outside exposing it to UV and hence UV damage on your rope. Conclusion: If you'd like to put knots in your rope you can do this for a regular clothesline. Your biggest enemies will probably still be moisture and UV damage, which will cause the rope to decay over time. The system with knots will probably not last quite as long as the system without knots.
But from practical experience I knot that the difference in lifetime will be small. With mono-filament fishing line, there are a number of issues which cause the knot to be weaker than the line. With heavier gauge of twisted rope this may be less, but is still real. The uneven tension in the knot will cause distortion and stress to not be evenly distributed, causing uneven wear to the line or rope. Most knots have some level of slippage when stress is applied.
The slippage will cause the rope or line to rub while under stress and slowly cut, weakening the line. Some of this varies by diameter, with different configurations favoring different knots due to line slippage, so fishing knots that are relatively strong might not be good choices for braided lines.
That said, the general principle remains that a knotted line will be weaker than one with no knots. An exception might be forming a compound rope by knotting more than one line together in parallel which could be stronger than a single line but more stable than multiple lines simply looped together. A curvature in the rope causes the tensile strength of a rope to decrease. The strongest configuration is the one where the stress distribution across the rope cross-section is close to uniform, i.
When the rope has a knot it may seem more stable, simply because the overall rope is thicker. However the rope will usually not break in the knot, but at the end of one, where there is a curvature. If you are looking for data on the topic there are two main applications: industrial ropes and steel wires and slacklining. For the former knots are not very common try tying one in a steel rope One place where one has to tie a knot is the ends of a slackline. In fact there are special devices, called slackline weblocks that try to achieve that with minimal curvature see picture.
If you are searching for actual data on this the best place to search might be the Slackscience Blog by Balance Community. They have tests of different weblocks and how investigate how their structure effects the tensile strength. All the answers so far have talked about strength, but the OP asked about durability. If the clothes were pinned onto the knots only, then it should be more durable than an unknotted rope as the wear would be concentrated on an area with multiple layers of the rope.
The load on each part of a knot is less than on an unknotted section, so any fraying on the knot would not affect the strength over time as much as if the unknotted rope were frayed. Ultimate breaking strength is weakened by knots as has already been stated multiple times. If strength of termination is critical then a splice is always the preferred choice.
There is much healthy debate about what knots work best for any application and which knot is strongest. Tying knots is a skill, it needs to be practiced!
There are numerous examples of accidents and injuries caused when an incorrectly tied knot behaves unexpectedly. Notice some of the same knots can be used for many different applications. If you only learn one knot, learn a figure 8 and how to use its many variations.
Marlow Ropes is a trailblazer in the technical development of leisure marine ropes from dinghies to super yachts and particularly service high-speed sailing with its Marlow Grand Prix MGP range. For further information about rope care, splicing and to watch our splicing tutorials click on the following links:. View the discussion thread. By subscribing to our mailing list you agree to how we use your information. Please tick to confirm.
The Clove Hitch is also used in closed climbing systems to attach the rope to the climber's harness before tying their friction hitch. Another great use for the clove hitch is for sending water bottles up into the tree for the climber! This knot is relatively compact and is easily identifiable.
It does cinch down quite hard after use and is hard to undo. The Anchor Bend is more bulky than the Double Fisherman but is still very identifiable and easy to tie. The Anchor Bend does not cinch down as hard as the Double Fisherman so it is easier to untie after use. We can go further in depth in a later blog post about Safe Working Load and the likes.
All knots and hitches pictured were done so to illustrate the said hitch or knot, not to illustrate their exact uses. Some hitches like the Clove Hitch should have a backup tied with the tail around the standing part of rope.
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