Polyester vs. Nylon
Mooring Lines
A practical comparison for yacht owners
Walk into any chandlery and you’ll see two main options for mooring lines: polyester and nylon. Both are synthetic, both are strong, and both get used on yachts every day. But they behave very differently, and picking the wrong one for your situation can mean problems.
Here’s what actually matters.
The Key Differences
| Property | Polyester | Nylon |
|---|---|---|
| Stretch | Low (3–5%) | High (15–25%) |
| Wet Strength | No loss | 10–15% loss when wet |
| UV Resistance | Excellent | Poor |
| Abrasion Resistance | Excellent | Good |
| Hand Feel | Slightly stiffer | Soft and flexible |
| Best Use | Marina berths, docklines | Mooring balls, anchor rodes |
Stretch is the big one. Nylon stretches significantly under load — typically 15–25% at working loads. Polyester stretches very little — roughly 3–5%. This sounds like a small technical detail, but it changes everything about how the line behaves in use.
Wet strength: Nylon loses approximately 10–15% of its breaking strength when wet. Since your mooring lines are, by definition, always wet — this matters. Polyester maintains virtually the same strength wet or dry.
UV resistance: Polyester has significantly better UV resistance than nylon. Over years of sun exposure, nylon degrades faster. In a Mediterranean, Caribbean, or tropical marina, this difference becomes very visible after a couple of seasons.
Abrasion resistance: Polyester is harder and smoother, giving it better abrasion resistance — important where lines pass through chocks, over fairleads, or rub on dock edges.
When Nylon Makes Sense
Nylon’s stretch is actually its superpower — in the right situation. If you’re on a mooring ball in an exposed anchorage where heavy surge pulls on your lines, nylon acts like a shock absorber. It stretches to absorb the peak load and springs back, rather than transmitting a hard jolt to your cleats and deck hardware.
For anchor rodes (the line between your anchor chain and the boat), nylon is almost always the better choice for this reason. The shock-absorbing stretch protects both your ground tackle and your deck fittings.
When Polyester Makes Sense
For marina berth mooring — which is what most yacht owners need most of the time — polyester is the better all-around choice. There are four reasons:
- Precise positioning. You typically don’t want your yacht drifting around on stretchy lines in a marina berth. Low stretch keeps the boat positioned precisely in the slip.
- UV durability. Marina lines stay deployed for weeks or months at a time. Polyester’s UV resistance means they last far longer — especially in southern European or tropical marinas.
- Abrasion toughness. Lines in chocks and through fairleads experience constant friction. Polyester handles this significantly better than nylon.
- Consistent strength. Polyester doesn’t lose strength when wet — which, again, it always is when deployed.
This is why all Yachtfend mooring lines and docklines are made from 100% polyester with a 16–24 plait construction and a UV resistance rating of 9 out of 10. For permanent or semi-permanent berth use, it’s the right material.
What About Dyneema and HMPE?
You’ll occasionally hear people suggest high-tech fibres like Dyneema (HMPE) for mooring lines. These are incredibly strong for their diameter and have near-zero stretch, but they’re expensive, they don’t absorb shock at all, and they can creep under sustained loads — meaning they permanently elongate over time.
For most yacht mooring applications, they’re overkill and actually worse than polyester. Save Dyneema for running rigging and specialised applications where low weight and high strength are the priority.
How to Choose Mooring Line Diameter
A rough guideline: 1/8 inch of line diameter for every 9 feet of boat length. For exposed berths or heavier yachts, go one size up.
| Yacht Length | Recommended Diameter |
|---|---|
| Up to 35 ft | 1/2″ (12mm) |
| 35–45 ft | 5/8″ (16mm) |
| 45–60 ft | 3/4″ (18–20mm) |
| 60–80 ft | 7/8″ (22mm) |
| 80 ft+ | 1″ (24mm) or larger |
For exposed berths or heavy-displacement yachts, go one size up from the table above.
Shop Yachtfend Mooring Lines
100% polyester, 16–24 plait construction. UV resistance rated 9/10. Built for permanent berth use in demanding conditions.