Grog’s Index of Boating Knots

 

  Check this link  a repost from playak digest

Knots Weaken Rope: Angles, kinks, and knots, stress the fibers unevenly and weaken rope.  If this concerns you, you are using rope that is too weak.  Some knots weaken some rope to as little as 40%.  For safety assume that even brand new rope has no more than 50% of its rated breaking strength.   And, if the rope is old, worn, or damaged by sunlight or chemicals – expect less.  For some useful test results visit Dave Richards’ Knot Break Strength vs Rope Break Strength on the National Speleological Society Website and Tom Moyer’s website for: High Strength Cord Testing, Euro Death-Knot Testing, and Rope Gear and Testing,