The Blood Knot is a favorite knot for fly fishermen. It is primarily used to join two ropes of similar size, for example when joining sections of leader or tippet, and is one of the best knots for this purpose. The strength of the knot is increased by making at least 5 and at most 7 wraps on both sides of the knot. It has a breaking strength of around 83%.
When the Blood Knot is lubricated and pulled tightly, it changes its structure. Pulling each strip forces the wrapped turns to redistribute the twists, so the inner strip becomes an outer wrap.
The Blood Knot is usually symmetrical in the middle. Although the twists generally continue in the same direction on both sides of the center, the wraps can be tied so that they are mirror images of each other.
Works best with lines of approximately equal diameter. By joining segments to create a tapered leader for fly fishing, a series of bloodlines can be connected to the ever-decreasing strength of the leader material.
As an aside, we are often asked why it is called "Blood Knot" and with a little research we can report the following. The blood tie dates back to the old seafaring days, when a version of this knot was tied to the ends of a whip called the cat of nine tails, which was used as a tool for severe corporal punishment. It is also sometimes referred to as the barrel knot.
How to Tie a Blood Knot?
Overlap the threads to be joined and wrap one around the other, making 5 turns.
Put the end of the rope through the central loop created.
Repeat the same process with the other end, wrapping in the opposite direction.
Slowly pull the strings in opposite directions.
Returns will be wrapped and collected.
Cut off the excess ends of the threads.
Alternative: An alternative method is to overlap the two ends and twist them together for about ten to fourteen turns. Then go to the center of the folds and make a hole. Pass the two ends through the hole in opposite directions.
At the end of our article, there is a video showing how the blood knot is tied.
Blood Knot Variations
Improved blood knot - Successful in tying a thicker rope to a thinner rope. For example, from a heavy shock material to a lighter class scarf.
Half blood knot - Used to attach a hook to a fishing line. It can also tie a line to a clip, swivel or bait.
Blood Knot Advantages
Strong
Compact
Versatile
Smooth shape
Breaks less frequently
Works with lines of different diameters
Can bond braid to braid, braid to mono, mono to mono, and braid to fluorocarbon.
The blood knot is a simple, easy to learn and very effective way to join two lines of similar size.
Blood Knot Disadvantages
If not cut closely it can get caught in fishing rod guides
Alternatives
Double surgeon's knot – Although weaker, it slips less.
J knot – Although difficult to tie, it is slightly stronger.
Double uni– Stronger for braided lines.
Single knot – Sturdier and less bulky.
Uni to uni – It preserves approximately 90% of the power of the line and makes it more robust.
Albright knot – Combines lines of different diameters.
Nail knot – Joins lines of different diameters. Unlike the blood knot being used only in fly fishing, it is also used in carp fishing.
