Introduction: (Initial Observation)
The ability of a material to resist breaking under tensile stress is one of the most important and widely measured properties of plastics including nylon filaments used as fishing lines. Most plastics stretch under tensile force and become longer. The percentage of increase in length that occurs before it breaks under tension is called the ultimate elongation of a plastic.
The amount of force required to break a line is listed on its packaging, but it may not always be true. This project is an attempt to measure tensile strength of nylon fishing line with simple equipment.
Variations of this project:
When you learn how tensile strength of a fiber or filament is measured, you can then design many different experiments. These are some of the examples:
- Compare the strength of different brands of fishing lines
- How does the diameter of a filament affect its strength?
- How does the temperature affect the strength of fishing lines?
Information Gathering:
Find out about the strength of different material as one of their important physical properties. Read books, magazines or ask professionals who might know in order to learn about the methods of testing the strength of material.
Following are samples of information that you may find.
In your research try to find out as much as you can about “Nylon”, “Fishing lines” and “Tensile strength”. Information that you gather can be related to chemistry, physics, application (usage), and market of fishing lines. Just see what you can find in your local library or the Internet.
For example about tensile strength you may find this:
Tensile strength of material including plastic rods and filaments are measured by special devices that are able to apply tension force gradually until the line breaks.
Such devices have two heads that can hold two ends of a sample firmly. When you install the sample and start the machine, two heads start to get away from each other in a very slow motion and the amount of force is being recorded or displayed at every moment. This continues until the sample breaks a part. Green sample in the picture is a plastic piece.
Types of fishing lines.
Lets start with “Monofilament”. Mono is a word that means single. In fishing line that means a single strand of line, but in sport fishing it has become know as nylon fishing line. Nylon Monofilament is a single-component product, that is formed through an extrusion process in which molten plastic is formed into a strand through a die.
Nylon Monofilament line is a polymeric by-product of crude oil processing. Premium grade Nylon Monofilament line receives more quality-control attention, more additives, and more attention in the finishing process than normal line to make it abrasion resistant, that is why the cost is more.
Then we have the “Co-filament line” which adds more resistance to the line and yet keeps the line sensitivity, and strength. This design uses an inner and an outer wrap of nylon to help insure the lines ability to resist wear and tear.
Next would be “ Fused Lines “, which are many layers of microfilaments of gel spun polyethylene fibers fused together to produce a single strand of line that is ultra thin, superior strength, and sensitivity, good abrasion resistance, and yet remain easy to cast. Great hook sets with this line. Spiderwire is the leader in fused line.
Next, “Braided lines” consist of inter-wined strands of nylon material, making them a multifilament line called Dacron. Dacron was once the primary line for fishing before the discovery of Nylon. Nylon proved to be so superior to braided Dacron which had poor knot strength, low abrasion resistance, and little stretch, that Dacron almost disappeared from the market. Today it is used primarily as a backing material on fly fishing reels.
The synthetic fiber that is added is 10 times stronger than steel, and has been used in industrial, aerospace, and military applications, and is very strong yet very thin. Due to its non-stretch properties it is a super sensitive line. For example, a 15# test braid line has the diameter of a 6# test monofilament line. There are some draw backs to this line however. You must use the knot the manufacture tells you to use or the line will come untied. Some you need to use a super-glue on the knot to prevent it from coming untied as some of the braided lines have a coating applied to the line that makes it extremely slippery and the glue assures you the knot will stay tied. This line does nick, and you will need to watch for broken, or frayed strands often. I don’t recommend you use this line on a spinning reel as it is so limp it is tough to cast.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is design and performing an experiment that can show the tensile strength of a sample fishing line.
More specifically we want to “Compare the strength of different brands of fishing lines”.
Note: You can compare the strength of different brands of fishing lines only if you can find samples of different brand fishing lines with the same diameters. Otherwise you must select a different study about fishing lines. For example you may study the effect of temperature on tensile strength of fishing lines. In this case one sample of one type fishing line will be enough for all your experiments.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable is the fishing line brand or manufacturer.
Dependent variable is the tensile strength of each brand fishing line.
Controlled variable is the temperature. (since polymers are sensitive to the temperature changes, we will make sure that all samples are tested at room temperature)
Constants are the size (diameter) of fishing line and test method.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Following is a sample hypothesis:
The strength of the sample is more than what manufacturers write on packaging.
This is another sample hypothesis:
Among Stren-Magna, Cabela and Berkley-Trilene brands, Stren-Magna has a higher strength. My hypothesis is based on my observations of price differences among the above three brand.
Question: What is the hypothesis? (my teacher said it needed to be an if then statement)
Answer: While comparing the strength of different brands of fishing line, your hypothesis will not be an If Then statement. To have an If Then statement as your hypothesis you need to change the question (and the variables) of your project. For example if your question is “How does temperature affect the strength of nylon fishing lines?”, you may have a hypothesis like this:
If we increase the temperature, then the strength of nylon fishing lines will decrease. (In this case your independent variable will be the temperature).
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Testing Tensile strength
Procedure: Hang an empty large bucket to any strong fixture with one strand of fishing line. start adding water to the bucket until the fishing line breaks. While adding water, watch and memorize the water level. To make it easier you can mount a ruler to the inside wall of the bucket and use it to record the water level.
Repeat this experiment at least 3 times, so you get 3 values. But what you really need is the weight of bucket with water, not just water level. You can then refill the bucket to the recorded levels and use a scale to measure the weight.
Calculate the average of the weights and use that as the strength of the nylon fishing line that you tested.
Another method for this test:
The other method for this test is using a force gauge or good-quality spring scale. Wrap the end of the dry line around the hook of the gauge or scale so the line won’t slip, then apply enough pressure to break the line. Do this a few times to get an average dry breaking strength. Then soak the line in water for about 20 minutes and perform the same test.
Another idea: Contact the manufacturer and ask for the actual wet breaking strength of specific products; some guides, charter boat captains, competitive anglers, and writers have been doing this for years.
Experiment 1:
Compare tensile strength of different brand fishing lines
Procedure:
1. Get samples of 3 different brands of nylon fishing lines with the same diameter.
2. Perform tensile strength test on dry samples of each brand fishing line 3 times.
3. Calculate the average tensile strength for each brand and record it in your results table like this:
| Brand | Tensile strength |
| Stren Magna Thin | |
| Cabela | |
| Berkley Trilene XL |
4. Use your results table to draw a bar graph. Each vertical bar represents one brand. The height of each bar will indicate the average tensile strength for that brand.
Draw a graph:
Make a bar graph to show your results. Make three vertical bars, one bar for each brand. Write the brand name under each bar. The height of each bar is the average tensile strength for that brand. This value must also be written on the top of the bar.
Materials and Equipment:
- Nylon Fishing line
- Water
- Scale
- Bucket
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Complete the tests and record the results in tables similar to this:
Tensile strength of dry and wet nylon fishing line (Diameter 0.20 mm)
| Brand | Dry | Wet |
| 1 | 6 lbs | 5.5 lbs |
| 2 | 5.5 lbs | 5 lbs |
| 3 | 5 lbs | 5 lbs |
Calculations:
You need to calculate the average of the results of your 3 tests.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
Breaking strength is the amount of pressure that must be applied to an unknotted line before it breaks. But since we did not have The equipment to hold an unknotted line, we made knots on both ends of our line. knots can possibly reduce the strength of our sample, so actual strength must me more than what we have calculated.
Also since our sample is fishing line, we must consider that strength might be slightly different when the line is wet. Gathered information indicates that Certain lines — especially nylon monofilaments, which are the bulk of fishing lines sold — experience significant strength loss when wet. Typically, nylon monofilament lines are from 20 to 30 percent weaker when wet than when dry. Braided and fused microfilament lines (called superlines by many people) and fluorocarbon lines do not absorb water and do not change in strength from dry to wet. This doesn’t mean these lines are stronger; it just means that what you get when dry is also what you get when wet. But it also doesn’t mean that these lines are immune from strength mislabeling.
References:
Visit your local library and find books or publications related to material science, material strength, Physics of force and pressure. Look for articles and chapters that discuss force, tension and tensile strength. List such material as your references or bibliography.
You can also find some online articles about material strength and tensile strength. Following are some related links:
Question: What is the hypothesis for this project? (my teacher said it has to be an if, then statement)
Answer: IF we increase the room temperature, THEN the tensile strength of plastic wraps will decrease.
Question: Can you direct us to resources other than the internet, something specific to ask for at the library?
Answer: Nylon fishing line is a very specific subject. I have never seen any book about nylon fishing lines myself. What you need to do is finding separate books about fishing, Nylon, Polymers, and material strength. There are at lease 100 published book about each of these subjects and it really does not matter which one will be found in your local library. They all contain similar content. If I name a book, it will most likely be the one that does not exist in your local library.
Following books may be found in your local library or found online (Amazon.com):
Fishing Lines by Chuck Bracke
Guide To Saltwater Fishing Knots for Gear & Fly Fishing: Knots for Super Braid, Dacron, Braid and Monofilament Lines by Larry V. Notley (Paperback – Mar 2002)
Question: I need to know what is the “Application” in a science report. My daughter’s teacher is asking for “Application” and I’m not sure what she is referring to.
Answer: Application means practical use in life or industry. We measure the strength of different materials in order to make sure that they are appropriate for our needs. You may want to use fishing line to catch a 10 lbs fish. How do you feel if the fishing line easily brakes with a force of 3 lbs? Can you use that? Is it important for you to know about the strength of your fishing line before going to a fishing trip?
Strength is not just about fishing lines. Think about phone wires and electrical wires in the street. How would you feel if they easily brake by a bird sitting on them? If you are in charge of buying wire, do you want to know how strong they are before ordering them? Almost every material that may be subject to some force needs to be tested before being approved for use. Such tests are known as material strength tests.
