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Blanks and Components Explained - 1 of 3
 by Don Allard
A fly rod is one of the most integral parts of our tackle, yet most of us know little or none about how the rod is actually made, and how it performs as it does.
Many casters just know that a rod casts well for them, or doesn’t cast well for them. And many fly shops get in a lot of high performing new models that are incredible to cast, but so few know why. The goal of this series is to shed some light on the materials and design of a fly rod that makes a finished rod perform as it does when you are casting. I am going to try and do this in three parts. First I will go over the materials used. From fiberglass to graphite, and some other materials such as boron and titanium. Then in the second part of the article I will take the raw materials and show how they are made into rods by explaining different tapers, and how the tapers make up the different actions in a fly rod. Then lastly after the blank is made, how the components (especially the guide spacing, size, and number of guides) will effect the performance of the finished fly rod.
As a beginning point I will go over the different materials used in fly rod production and each products attributes. During this segment there will be a few items I will refer to frequently. I will refer to fiber in my article. The definition of fiber as I will use it will be a single strand of any type of material used in rod production. As any type of material I mean graphite, fiberglass, boron, etc.
Strain rate and modulus rate will be used in discussion of the different fibers. The strain rate of any fiber is a test rating of how much flex a fiber can withstand until it reaches the point at which it will break. If you take a single strand of fiber and can flex it to a 90-degree angle before it cracks, then it will of course have a higher strain rate than a fiber that breaks before it gets to a 45-degree angle. NOTE: (The angle of the flex at which the fiber breaks is not how the ratings are measured, I am using this as an example only.)
A modulus rating is the test rating of how resistant a fiber is to flexing. So a fiber that has a higher strain rate has more resistance to bending, and for the most part will have a tendency to return to its resting position quicker than a lower modulus fiber. A basic example is that if you have one single high modulus fiber and try to bend it around you will find it has much more resistance to bending than a lower modulus fiber. It should also be stated that the lower modulus fiber when released from a bent position would bounce around longer than a higher modulus fiber. This is called a recovery rate or some people call it tip shock in a finished rod.
Let's start with fiberglass. Fiberglass is the first fiber that was used in rod production. When introduced onto the scene it created a rod that had a marginal performance increase over the cane rods of the day, but a major decrease in overall weight (especially in heavier line weight rods) which made for a less fatiguing fly rod. A fiber glass rod has an incredibly high strain rate, but the modulus rate is quite low compared to entry-level graphite fibers. In order to gain the strength needed to carry a fly line the actual inside diameter of the rod tube has to be quite large. This is why you’ll see a 4wt. Fiberglass rod that looks like the butt diameter of a 7wt. (Or up) graphite rod. The larger the tube diameter the more ‘hoop strength’ you get. To put it in basics you need a larger tip section and a large rod butt diameter on a fiberglass rod in order to power a line to the casting distance that fly line needs to be cast. From a performance standpoint the larger tube diameter means more wind resistance during the casting stroke which robs distance and power. It should also be noted that a fiber glass fiber is quite large in physical size. The average fiberglass fiber is approximately .005in. in diameter. With a large physical size, even if the fiber had a high modulus rate, a fine tip diameter would be nearly impossible to produce.
Graphite came onto the scene from the aerospace industry after fiberglass. With its debut the rod industry was greatly transformed. A standard graphite fiber has a much higher modulus than fiberglass; its average fiber diameter is approximately .0003in. The only downfall is its strain rate is lower than that of fiberglass.
However when speaking of a standard modulus graphite fiber the durability of the fiber is still quite high.
Because the resistance to bending (modulus) is so much higher than fiberglass a finished rod can use less material and the tube diameter can be made smaller and still give the same performance (or higher) as the larger tube diameter needed in fiberglass to get the ‘power’. A graphite fiber being physically smaller in actual size can be made into fine diameter tips and small rod butt diameters. This results in less wind resistance, an increase in overall performance. We should all be aware by now of all the different graphite types being used. Most of the fast action rods utilize ultra high modulus graphite. The incredible resistances to bending these fibers provide allows even smaller tube diameters from tip to butt to be used. The downside is these materials are so ‘stiff’ that their strain rates are usually quite low. A higher modulus rod for the most part is more fragile than lower modulus graphite. It’s the price that is paid for increased performance! There have been some advances with fibers made up specifically for rod construction in which the modulus ratings are quite high, with a strain rate that is acceptable also, but it should be noted that these fibers are of course not the highest modulus fibers in the market. Nor do they possess as high the strain rate of the more traditional ‘standard’ graphite. It’s sort of a middle ground.
Another fiber used in rod construction is boron. Boron is another fiber that originally came from the aerospace industry. This fiber has some nice qualities. The strain rate of boron is quite high. It takes a lot of flex to break it. The modulus rating of boron is also extraordinarily high. The best of both worlds! However, there is a downside. The actual physical size of a boron fiber is quite large. Comparable to fiberglass. When rolled into blank form a fine tip diameter is hard to achieve, and if the tube diameter is not kept extremely small then boron makes a rod that is like casting a piece of steel. The line will not load properly until it is at an outrageous distance. Furthermore the resins used in bonding the fibers together cant hold well to a fiber that is so stiff in construction (I’ll talk about resins soon). So a few manufacturers have opted to use born fibers in the butt sections of a rod to produce a rod that will not ‘buckle’ when line is sent long distances.
And some company’s pair graphite with a select number of boron fibers mixed in to add modulus ratings to the blank.
Lets touch a little on some new other new products used in some fly rods. There is some rods that have ‘ground up’ titanium, or boron in the resin. It is supposed to increase performance, and sensitivity. However in my experience I cannot see how anything that is ground into a powder and added to the resin can improve anything, and since I have no proof of such I won't elaborate on the subject.
The last two items left are necessary items in rod production. The first is the scrim. A scrim is a woven thin cloth usually made out of fiberglass but sometimes graphite (for weight reduction). The scrim has the appearance of a door screen. Its purpose is to go directly to the steel rod mandrel (the tapered steel rod that the graphite or fiberglass taper is rolled onto) It purpose is to keep the graphite fibers from pushing into the mandrel when the blank is being baked in the curing oven. If the scrim is not used with its screen like woven texture the fibers will move around when they are heated and will make a finished rod that is weak on one side from the fibers pushing together. Remember each fiber is positioned side by side and they need to stay that way. The scrim of the rod should not change the performance in any way.
The second item is the resin. The resin holds the fibers together, and is a crucial part in the durability of the finished rod. I wont go into the different resins used but it should be noted that the resin has to match up to the modulus rating of the fibers to be able to hold everything together when the rod is flexed. An item that is easier said than done.
We now have a sheet of lengthwise running individual fibers positioned side by side to each other, held together by a resin that when exposed to a pre-set temperature will make the rod blank. In the next section I will show how this sheet is cut into a taper. (Ill go over the different types of tapers). I’ll show how its rolled onto the mandrel (and go over how each mandrel relates to a different line weight finished rod) and then how this end ups being the finished rod blank in the desired action.
See you soon,
Don
This is the first part of a three part series on Fly Rod blanks by Don Allard of Allard's Custom Fly Rods.
Don can be reached at FlyFishng2@aol.com
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