We recently had a letter from Teun and Chantal Bos, who were trying to determine what diameter anchor snubber to use. Practical Sailor did extensive testing in this area, but unfortunately some of the formulas used to determine the right size snubber—strong and chafe resistant yet elastic enough to absorb shock loads —were lost in translation as we migrated to the new website.
As a result, the equation online yielded some clearly absurd results. In the case of the Bos’s, it recommended a 12-inch diameter snubber for their 49-foot Oyster pilothouse, Beryl, clearly out of wack with reality.
As a result, we reviewed the equation and the table, and increased the range to include larger boats.. You can see the full report online (https://bit.ly/2VH64BZ). The correct equation is now online and is:
Diameter (inches) = 0.00067 x (length overall in feet) x (loaded weight in pounds)^0.3
When in doubt, round up to the next larger size. For moorings or use in consistently windy conditions, go up one size. In general, the snubber will be one size smaller than the ABYC recommended anchor rode.
Alternatively you can pick from a chart. You will need to make a judgment call regarding whether your boat is light, medium, or heavy, bearing in mind that a boat with high windage or that yaws excessively at anchor, will have higher rode tension.
In truth, there are a range of right answers. Stronger lines last longer but absorb less shock. Lighter lines will need to be retired sooner but will put less stress on the anchor and rode. As long as you stay in the range, you should be fine.
Drew Frye is technical editor of Practical Sailor, he blogs at his website www.sailingdelmarva.com.
SNUBBER SIZING EXAMPLES
|BOAT MAKE & TYPE||BOAT LENGTH||DISPLACEMENT||SINGLE SNUBBER DIAMETER||BRIDLE DIAMETER||SNUBBER LENGTH||TYPE||LENGTH||DIAMETER|
|PACIFIC SEACRAFT 34||34 Feet||13,500 lbs.||3/8” /9mm||N/A||44 feet||3-strand||45 feet||1/2” / 13 mm|
|MORGAN 41.6||42 feet||27,000 lbs.||1/2” / 13 mm||N/A||54 feet||Climbing rope||50 feet||3/8” / 10 mm|
|CABO RICO 38||38 feet||21,000 lbs.||7/16”/ 11 mm||3/8” / 10 mm||49 feet||3-strand bridle||30 feet||5/8” / 16 mm|
|VAN DE STADT 47||47 feet||30,000 lbs.||1/2” / 13 mm||N/A||61 feet||Climbing rope||20 feet||7/16”/ 11 mm|
|LIGHTWAVE 38||38 feet||12,000 lbs.||9/16” / 14 mm||3/8” / 10 mm||49 feet||Climbing rope bridle||25 feet||3/8” / 10 mm|
|PDQ 32||32 feet||7,800 lbs.||1/2” / 13 mm||3/8” / 10 mm||42 feet||Climbing rope bridle||35 feet||5/16” / 8 mm|
|STILETTO 27||27 feet||1,700 lbs.||1/4” / 6 mm||1/4”/ 6 mm||35 feet||Double braid||15 feet||5/16” / 8 mm|