Duncan Loop in Lieu of Eye Splice or Bowline?

[rhumbunctious]

When one does not have time to make a proper eye splice, common practice is to use a bowline; but, a bowline halves the strength of the line and is thus suboptimal, however convenient.

There is a popular fishing knot, called the duncan loop, which is purported to preserve 95% of the line strength, and I'm wondering if anyone has used, or has any opinions about its use in lieu of a splice, as it can be quickly tied without tools, and can even be used with a thimble to prevent chafe.

The key difference that I can see between a duncan loop and an eye splice or bowline is that the loop will almost surely constrict with use over time, and as such, under significant load it's really more of a bend than a loop, but if a thimble is used, that could be a non-issue.

Though that raises the question of whether a thimble might reduce the strength of the knot, and perhaps a perfectly round thimble might be better than the typical teardrop shape.

Here is one tied with 10mm line:



Given that it is as strong as an eye splice, and can be made more quickly than a splice and without tools, one might wonder why splice at all? Cosmetic arguments aside...

[Hudson Force]

Originally Posted by rhumbunctious

............a bowline halves the strength of the line.............the duncan loop, which is purported to preserve 95% of the line strength.............

I agree with your observation that the "fishing knots" retain a greater line strength, but the 50% retained strength of the bowline is more frequently tested to be near 65% and the 95% retained strength of the duncan loop is more often reported to be closer to 75%. Many, like myself, would choose to use the bowline with it's quick formation and non-jaming character despite your valid points.

[psneeld]

Originally Posted by rhumbunctious

When one does not have time to make a proper eye splice, common practice is to use a bowline; but, a bowline halves the strength of the line and is thus suboptimal, however convenient.

There is a popular fishing knot, called the duncan loop, which is purported to preserve 95% of the line strength, and I'm wondering if anyone has used, or has any opinions about its use in lieu of a splice, as it can be quickly tied without tools, and can even be used with a thimble to prevent chafe.

The key difference that I can see between a duncan loop and an eye splice or bowline is that the loop will almost surely constrict with use over time, and as such, under significant load it's really more of a bend than a loop, but if a thimble is used, that could be a non-issue.

Though that raises the question of whether a thimble might reduce the strength of the knot, and perhaps a perfectly round thimble might be better than the typical teardrop shape.

Here is one tied with 10mm line:



Given that it is as strong as an eye splice, and can be made more quickly than a splice and without tools, one might wonder why splice at all? Cosmetic arguments aside...

I'll debate the quoted tests as a tow boat captain...I use bowlines every day to tow or unground and find the line doesn't always fail at the bowline....many times the line will melt in the bowline but it doesn't break or jam the knot. But I will admit that is with regular day to day lines with imperfections versus some new line off a spool that may be used in a test but doesn't exist in reality.

While the duncan loop looks like it may not jam..if it does...it's worthless as a boat knot.

Loops are over rated anyway for mooring...cleat hitches and clove hitches are what i use because it's either to a cleat, bollard, piling or post at most docks anyway anyway.

plus half the breaking strength is NOT sub optimal as most line size is oversized due to ease of handling or strength after some chafe....1/4 inch line will hold many boats in many situations but not if it's chafed and it's a bitc* to pull tight with bare hands.