Choosing the right rope
Three questions decide which rope you need: what load it has to carry, whether it must float, and how it will be finished. This page walks through all three.
1. UHMWPE or polypropylene
UHMWPE (also sold as HMPE or under brand names such as Dyneema) is the strongest of the two by a wide margin. A 12 mm UHMWPE rope has a breaking load of roughly 16.450 kgf unspliced. It stretches very little, floats, and resists abrasion and UV well. It is the choice for towing, lifting, mooring under load and anywhere weight matters.
Polypropylene multifilament is softer in the hand, floats, and costs a fraction of UHMWPE. It stretches more, which makes it forgiving as a mooring line on a small boat, and it is comfortable to handle. It is the sensible choice for fenders, general deck work and light mooring.
Rule of thumb: if the rope carries a load you would not want to fail, use UHMWPE. If it is handling, fendering or light work, polypropylene is enough.
2. Which diameter
Every rope page on this site lists the diameter, the weight per 100 m and the breaking load, spliced and unspliced, in line with ISO 2307. A few reference points from our UHMWPE range:
| Diameter | Weight per 100 m | Breaking load unspliced | Breaking load spliced |
|---|---|---|---|
| 6 mm | 2,33 kg | 4.390 kgf | 3.951 kgf |
| 10 mm | 6,00 kg | 11.560 kgf | 10.404 kgf |
| 14 mm | 11,40 kg | 21.930 kgf | 19.737 kgf |
| 20 mm | 22,70 kg | 41.670 kgf | 37.500 kgf |
| 28 mm | 43,30 kg | 75.120 kgf | 67.599 kgf |
Note that splicing costs roughly ten per cent of the breaking load. That is normal and it is already included in the spliced column. Always work with the spliced figure if your rope has an eye.
Breaking load is not working load. A rope should never be loaded anywhere near its breaking point. Apply the safety factor that your application requires.
3. Finish
A rope can be delivered cut to length, with a spliced eye at one or both ends, with a thimble in the eye to protect it against a shackle, and with a polyester protective cover over the eye or over the full length where it passes over an edge.
A thimble is worth it wherever the eye runs over metal. A protective cover is worth it wherever the rope runs over a fairlead, a bollard or any hard edge.
Still not sure
Tell us the boat, the application and the load you expect, and we will advise. Send us your dimensions and you will receive a quotation, normally within one working day.