Snubber & Bridle Sizing Calculator
The spring in the system: snubber length and diameter for your boat — sized for stretch (the actual job), not just strength.
The counterintuitive rule: a snubber can be TOO strong — oversize line barely stretches at your loads and absorbs nothing. Size for the stretch percentage, protect it from chafe at the chock, and let the chain hang in a lazy loop behind it.
Formula
⚠️ For planning and education only — verify with official charts, tide tables and your vessel's documentation. Not for navigation.
The spring in the system: snubber length and diameter for your boat — sized for stretch (the actual job), not just strength.
About Snubber & Bridle Sizing Calculator
The snubber is the most misunderstood line aboard: its job is not strength but STRETCH — converting wave-surge jerks into long soft pulls before they reach windlass, chain and anchor set. Which means it can be too thick: oversized nylon barely elongates at your loads and absorbs nothing. This calculator sizes both dimensions from your boat and surge load — length for working stretch, diameter so the design load lands in nylon's energy-absorbing zone — and reports the foot-pounds each surge gets swallowed.
How to use Snubber & Bridle Sizing Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula length ≈ 0.5–0.6 × LOA; diameter from: nylon ≈ 15% stretch at 20% of break — size so design load sits there substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Snubber & Bridle Sizing Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula length ≈ 0.5–0.6 × LOA; diameter from: nylon ≈ 15% stretch at 20% of break — size so design load sits there with sources cited on the page
- ✓The counterintuitive rule: a snubber can be TOO strong — oversize line barely stretches at your loads and absorbs nothing. Size for the stretch percentage, protect it from chafe at the chock, and let the chain hang in a lazy loop behind it.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why is an oversized snubber a real mistake?+
Nylon's energy absorption lives in its elongation: 3-strand stretches ~15% at a fifth of its breaking strength. Put a 1,500-lb surge on 3/4" line (16,700 lb break) and you're at 9% of break — barely 5% stretch, a stiff spring doing little. The same surge on 1/2" (7,500 lb) sits at 20% of break, stretching 15% and eating triple the energy. Size the line so working loads reach working stretch.
How long should the snubber be?+
Longer than instinct: stretch is a percentage, so absorbed energy scales with length — 30 ft at 12% gives 3.6 ft of give; 10 ft gives barely one. The half-boat-length rule (this tool's default) balances energy against handling and docking-locker reality. Storm practice runs longer still, with the chain's lazy loop adjusted to match so the snubber, not the chain, comes taut first.
Single snubber or bridle?+
Bridles (two legs to bow cleats, meeting at a chain hook) win for catamarans (mandatory — keeps load off the crossbeam center), boats that sail at anchor (the V damps yawing), and windlass-relief on any boat. Single snubbers are simpler and fine for well-behaved monohulls. Either way the geometry rule holds: legs long enough to stretch, led over chafe protection, with the hook or soft shackle captive so it can't drop off when the loop slacks.
What chafe protection does the system need?+
At every touch point, because stretching line saws itself: hose or leather where it crosses the chock/roller, the bridle legs clear of bobstay fittings, and inspection after every blow — nylon's failure mode under chafe is sudden once strands sever. The snubber is sacrificial by design (cheap, replaceable, protects the expensive chain and windlass); treat fuzz as the consumable's wear indicator, not a defect.
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