Sunday, January 29, 2012

The Clinch Knot

The clinch knot is one the most commonly used knots in all fishing applications. Many people, including myself, refer to this knot as the fisherman's knot. The funny thing is, there is an entirely different knot already called the fisherman's knot used for joining two loose lines together. The clinch knot is mostly used for attaching terminal tackle to the end of ones line. This was the first fishing knot I learned when I first started fishing as a child and I still use it to this day.

There are three versions of the the clinch knot that I know of, normal, improved, and the double clinch knot. I'm only going to cover the normal and improved versions in this post, I'll go over the double clinch knot in another post. If you don't already know how to tie these knots or you don't know what the difference between the two are, here is a quick lesson.

Start by bringing the line through the eye.
Holding both lines twist the bait or whatever else you may be tying several times, usually more for lighter lines and less for heavier lines. How the number of twists effects the strength of the knot is something I tested and will be discussed later in this post.
Feed the end of the line through the loop near the eye.
The next step is for tying the improved clinch knot only, skip this step if tying the normal clinch knot. Feed the line through the big loop you just created.
Hold both the main line and the end of the line and pull the knot tight.
The final product should look something like this. Trim the excess line off to the desired length, for me this depends on the application. If catfishing I usually don't trim the excess at all, for everything else I usually trim it to 1/8 - 1/4 inch depending on the size of the bait and line.
So this week I've been doing some experimenting with the clinch knot and its various versions. My goal was to compare line breaking strengths of the various versions and tying techniques of the knot to determine how to tie the strongest clinch knots. My testing technique was simple, I used a Rapala digital scale to measure the weight at which the line broke at, a marine battery to supply the opposing weight, a swivel to connect one end of the line to the scale, and a snap swivel to connect the other end of the line to a rope tied around the batteries handle. Both knots were tied using the same technique. Then I slowly lifted to the scale watching the weight go up until the line snapped.

I chose to start off using 6lb Stren Original line. There were four main tying techniques that I wanted to test, the normal clinch knot with and without saliva lubrication, and the improved clinch knot with and without saliva lubrication. I've always wondered if wetting your line while tying a knot improved the knots strength. The other factor that I wanted to test was how the number of complete 360 degree twists effected the strength of the knot. For each variation I tested, I broke the line three times to form an average breaking strength. Also note that for all knots I trimmed the excess line to 1 inch.

Here are the results for the normal and improved clinch knot without lubrication.
# of Twists Normal Improved
4 3.35lbs 3.48lbs
6 4.75lbs 5.17lbs
8 5.94lbs 5.67lbs
10 7.00lbs 6.69lbs

The difference between the normal and improved knots was marginal. All knots in the 4-8 twist range failed due to the knot slipping. After ten twists both lines no longer failed at the knots, maxing the strength of the 6lb line at about 7lbs of breaking strength.

After these tests, I wondered what would happen If I tied a simple overhand knot on the tag end of the knot to prevent the knot from slipping with a lower amount of twists. With only 4 twists and the extra knot on the tag end, the results were immediately good at an average of 5.8lbs. After increasing the number of twists there was no real gain. This was caused by the fact that when the knot slipped and was stopped by the extra tag end knot, this created a weak spot in the line from the slip.

Here are the results for the normal and improved clinch knot with lubrication.
# of Twists Normal Improved
4 3.73lbs 6.04lbs
6 6.21lbs 7.0lbs
8 6.56lbs

The difference between the non lubricated knots was significant. The normal knot maxed out at only 8 twists this time while the improved knot maxed out at just 6 twists. It was then easy to make the conclusion that an improved clinch knot lubricated with saliva was the best choice with a general rule that more twists prevents the knot from slipping more often. Now my next question is, will these same conclusions be made with a heavier line? This is something I've also been working on and will post the results soon.

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