Anchor Line & Rope
Description
48° North Marine offers pre-made anchor lines with high-quality, 3-strand nylon in 3/8", 1/2" and 5/8" diameters and in a variety of lengths. Pre-made anchor lines come with a stainless steel thimble spliced into a hard eye that's seized with #7 sailing twine. The boat end is melted, dipped and whipped to prevent fraying.
Strength & Elasticity
Nylon is superior to other materials for anchor rope due to its strength, elasticity and its durability in the marine environment. Of the two most common rope types - 3-strand and double-braid - the former is probably the better option for most applications due in large part to its greater elasticity (elongation) under a load. Elasticity allows the line to absorb more energy from the boat's movement at anchor and it determines the boat's acceleration-deceleration as it stretches and contracts, which affects comfort. Elastic lines make for a more comfortable boat motion. Double-braided nylon is generally stronger than 3-strand, but only slightly; however, 3-strand is almost twice as elastic for a given load. With relatively close tensile strengths and the greater elasticity of 3-strand, it's easy to understand why so many anchor lines are made from this rope type.
Cost is another factor. Anchor lines are generally the longest lines on a boat and double-braid is approximately 30% expensive more for the same size and length.
3-Strand
| Line diameter | Tensile Strength (TS) | WLL @ 12% | Elongation @ 20% TS |
| 3/8" | 3500 lbs | 420 lbs | 10% |
| 1/2" | 5700 lbs | 684 lbs | 10% |
| 5/8" | 8900 lbs | 1068 lbs | 10% |
| 3/4" | 12600 lbs | 1512 lbs | 10% |
Tensile strengths and working load limits (WLL) are all over the board and there is no standard across the industry for expressing these values. Tensile, or break strengths, frequently lack granularity. Are these values minimum, average or maximum values? As for WLL's, some manufacturers display values from 10% to 20% of the tensile or break strength. Everyone wants higher numbers. We use a WLL value of 12% at 48 North Marine and on snubberhead.com. There are some that would argue it should be 10% while others say 20%.
Anchor Line Sizing Chart
The two "rules of thumb" for sizing:
Diameter of lines - 1/8" per 9 feet of boat length
Length of lines - 8 feet of line for 1 foot of water depth
Diameter - Directional Estimates
| Boat Length | <25' | 25' - 30' | 30' - 35' | 35' - 45' | 45' - 50' |
| 3/8" | |||||
| 1/2" | |||||
| 5/8" | |||||
| 3/4" |
Note: These are directional estimates only and are based on generally accepted "rules of thumb". Please perform the due diligence necessary to ensure the diameter and length of the anchor line is appropriate for your boat and the conditions in which it's operated.
Sizing Tips
- Over-sizing anchor lines is fine if
it's not extreme. Over-sizing too much reduces the benefit of elasticity and makes for a less comfortable motion
when the boat is moving around the hook
- Boats considered heavy for their length, should size up
- Boats with high freeboard, cabin tops, flybridges, etc (trawlers, tugs, etc) should consider larger and longer options
- Catamarans should size up due to high freeboard, windage and their desire to sail on the hook
- If in doubt, choose a larger and longer option
Please contact us if you have questions regarding sizing.
