Anchor Snubber & Bridle Size Calculator

Snubber Type

Single line snubber or double-line bridle.

Boat Length (ft or m)

Boat length overall (LOA) is used in the Drew Frye calculation.

Boat Weight (lbs or kgs)

Weight of vessel fully loaded: fuel, water, gear, black water, crew, etc

Boat Speed @ Anchor (knots)

This is the boat's speed at anchor, not wind speed. To calculate the kinetic energy of the boat, the speed in knots is required. A boat's speed at anchor is difficult to measure but here are some generally accepted values used in various articles:

• .5 knots - lunch hook, fair weather boating and/or well protected anchorages (light wind)
• 1 knot - working hook, boaters venturing out in less than ideal conditions, cruisers who are likely to get caught in a stiff blow (medium - heavy wind)
• 1.5 knots - storm conditions (approximating gale force)
• 2 knots - violent storm (gale force 10 / hurricane)

Working Load Limit % (WLL)

The generally accepted range for the WLL% of 3-strand nylon rope is 10% - 20%. The calculator uses 12% as the default. Please feel free to use your own value.

Disclaimer

In using this calculator, you, the user, understands and accepts the limitations of the information provided:

1. The results are directional estimates based on the values you provide;
2. The result is not an engineered solution;
3. The calculator does not account for other forces that might be applicable or present (e.g. veering (yaw), pitch, waves, fetch, tidal current, rolling, rafting with other boats, etc)
4. The default value for "Speed at Anchor" is based on generally accepted use in publications and is not backed by actual scientific studies and you understand the value can be changed to a value you believe is more accurate;
5. The default value for Working Load Limit (WLL) is 12%. It's generally accepted the WLL for 3-strand nylon is 10% - 20% of the minimum break strength depending on the safety factor. Again, the value can be changed by you to a value that you deem to be more accurate.
6. The values for rope tensile strength used in the calculations are based on an average of values published by several manufacturers and/or the American Cordage Institute;
7. Snubbers and bridles may vary in design and the quality of construction and raw materials used in them may vary from manufacturer-to-manufacturer. This calculator assumes the manufacturer's design is sound, and the construction and materials used are of sufficient quality to support the product's intended purpose(s);
8. The calculations and subsequent results assume the rope is new and has not been altered or damaged.

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