What is ultimate fly line weight for your fly rod? Or what is the ultimate fly rod for your line? The goal is distance.

[Paul Arden]

Blimey I’m not sure how to fix the calculator. But I’ll have a look!

[RSalar]

* this measurement method is popular in the German speaking countries

Ron,
There is a thread on the details of the 15 degree system and how it compares to the CCS and Hoffman/Kyte line-rod matching systems that you might be interested in at http://sexyloops.co.uk/archivedboard/vi ... 86#p212479.

A related thread to this one is at http://sexyloops.co.uk/archivedboard/vi ... an#p247806

Gordy

Thanks Gordy — lots of good stuff in those two threads. The 15 degree system makes sense to me. I have been doing static bend tests in a different way. Using the same amount of weight to compare the resulting amount of bend. It makes more sense to measure the amount of weight required to bend the rod 15%. The only thing these static bend tests don’t take into consideration is where the rod is bending. They just measure the amount of total tip deflection (in degrees or inches). So if you have a stiff butt, soft tip rod you can get the same amount of deflection as a soft butt, stiff tip rod with the same amount of weight — but those two rods will not cast or feel at all alike. I tend to like faster, tip action rods, but I am amazed how well a slower butt action rod can cast when you let the rod do its thing. I know the spring effect only accounts for something like 20% of the power but it feels to me like slower butt action rods (the bamboo rod makers call these type of actions parabolic) store more power than stiffer, faster, tip action rods. It’s not scientific at all — it just feels like the rod does more of casting and that might just be that everything happens slower…

-Ron

[Paul Arden]

Hi Ron,

Action Angle in the CCS system addresses that.

I tend to think of a rod as having “gears”. 1st gear, 2nd gear etc.. and it’s where those gear changes occur that I find most interesting. A short stream rod for example might be best tuned to very short casts of around 20’. An all round 5 or 6WT is for everything from leader-only to distance, but mostly somewhere in the middle. A 7WT might be skewed towards distance. It’s the variable/progressive bend that allows us to do this.

Cheers, Paul

[Merlin]

Hi Ron

It makes more sense to measure the amount of weight required to bend the rod 15%.

If you use that kind of relative scale, you have the same problem than the CCS: you overline short rods and underline long rods. The stiffness scale must be absolute to match line weights. In other words, a given line number is characterized by the deflection amount at tip which has to be the same whatever the rod length for a given weight.

The only thing these static bend tests don’t take into consideration is where the rod is bending.

You can opt in for the Orvis rating system which does that, the difficulty being to identify the location of the maximum rod section rotation. Nobody but Orvis uses it, every rod manufacturer use his own scales.

I know the spring effect only accounts for something like 20% of the power but it feels to me like slower butt action rods (the bamboo rod makers call these type of actions parabolic) store more power than stiffer, faster, tip action rods. It’s not scientific at all

I confirm that it is not scientific. The “20% share” relates to elastic energy versus total line kinetic energy, on the average. Sometimes the same figure is related to speed (Grunde & Jason paper), and here you relate it to power (which is the variation of energy over time, again something different). If I consider a parabolic rod this share can go up to 35% with a high load /long carry. There is no simple calculation allowing to say that there is more elastic energy (and not power) stored in a bendy rod by comparison to a stiff one. You can store a large amount of energy in a stiff rod with little deflection. The deflection in itself is not a sufficient indicator; you need to know the (absolute) stiffness of the rod to draw a conclusion. To make a comparison you have to define the conditions, and there is little straightforward here. For sure a rod bending deep into the butt does not give the same feel than a rod bending from the tip: it has a significant inertial effect which is advantageous when lifting off a long line from water. And on top of that it is pretty stable (little wobble, if any).

One can create his own scale for his rods, I prefer using something relevant of the physics of the cast, and unfortunately, there is no universal rule valid for anyone but a general trend with fuzzy limits.

Merlin

[RSalar]

One can create his own scale for his rods, I prefer using something relevant of the physics of the cast, and unfortunately, there is no universal rule valid for anyone but a general trend with fuzzy limits.

Merlin

Hi Merlin,

If we think of the fly rod as a spring, which I suppose it is. It would be somewhat like a leaf spring or flat spring. So lets say you were designing a 9 foot long flat spring that would be used to launch cannon balls. One end is anchored in concrete, the other end is free to flex. The flexible end is drawn back under tension and the cannon ball is placed in a cup or recess. Then the spring is released and it throws the cannon ball. To maximize the distance that the spring throws the ball, wouldn’t you match the flexibility of the spring to the weight of the ball? Or would you maximize the stiffness — assuming the stiffer the spring the stronger it will be, and the more force it takes to bend the spring the faster and farther if will throw the ball? Would you ever taper the spring? Why are fly rods tapered? What if the fly rod had a constant diameter and the flexibility was the same from butt to tip? I suppose you could cast it …. Is the more flexible tip there strictly for the sensitivity it provides when hooking and playing a fish … or does it serve a purpose when casting a fly line?

Thanks,

Ron

[RSalar]

Hi Ron,

Action Angle in the CCS system addresses that.

I tend to think of a rod as having “gears”. 1st gear, 2nd gear etc.. and it’s where those gear changes occur that I find most interesting. A short stream rod for example might be best tuned to very short casts of around 20’. An all round 5 or 6WT is for everything from leader-only to distance, but mostly somewhere in the middle. A 7WT might be skewed towards distance. It’s the variable/progressive bend that allows us to do this.

Cheers, Paul

Hi Paul — I think you just answered my question to Merlin (at least partially). So the tip, because it is the thinest and most flexible part is used to make short casts — it’s like having having a 2 foot long fly rod attached to the end of a 7 foot long broom stick. Then as you shift gears you start to employ more of the rod — maybe now you are using 6 feet of the rod. Then as you lengthen the line you shift to third and now the entire rod is bending or most of it. There could be a 4th gear for the really long casts when the rod is bending all the way down to the grip. The analogy is a good one.

I still want to know what the effect would be of having a constant diameter fly rod. I have a feeling that for maximum distance it might be just the ticket — after all when you are throwing a really long line the tip of the normal tapered rod isn’t doing much (or is it)? It seems like a very light tip would just bend completely in line with the fly line and all of the spring power is coming form the resisting part of the rod. If the rod had no taper or just a very little taper then the tip would add a more beneficial share of the power to the cast. Do completion distance rods have more powerful tips than regular fishing rods?

Cheers,

Ron

[Paul Arden]

Hi Ron,

The taper also adds another dimension to the rod because it unloads butt to tip (not always strictly true, but pretty close) and this results in higher line speed with the “whip effect”, as well as allowing us to stop it incrementally. But there must be other advantages: lighter swing weight, better damping, more pleasant feel and so on. I think it probably also makes it easier to draw a straight line with the rod tip.

I once cast a bendy ruler with a tip ring attached for demos when I first started teaching. It was ugly to cast but certainly had no taper and was possible until I broke it

Cheers, Paul

[Merlin]

A fly rod is not a bow, Ron. In your example there is no need for tapering anything if there is no constrain on the way the bow is loaded. There is no need for tuning either, take the stiffest bow you can bend to throw your cannon ball (at the right angle with horizontal).

I guess the first anglers found the branches they used rather practical, with their tapered shaft. A uniform taper is a stick, something useful for apple casting, for a given range of apple size (the stiffness of the stick has to be tuned to the mass of the apple). For fly casting it is inappropriate for achieving a rather straight line path, it works like a hinge and would give a typical domed tip path, not a straight one. It is the ultimate butt action rod. For a large bend the tip would point backwards on a rather long piece of shaft.

Good common sense says that rod must be tapered to offer a casting range, but it looks more like an automatic transmission than a gear box. The taper determines the casting range, in other words one designs differently a rod for close fishing by comparison to a pure distance competition one. The flat taper is at odds with distance, for which an Eiffel tower taper is better suited.

Merlin

[RSalar]

When I think of “taper” in terms of a fly rod, to me it means the rate of change in diameter from butt to tip. I’ve never measured fiberglass or graphite fly rods (I suppose I should) but a typical bamboo fly rod’s diameter changes from around 0.003”/inch to as much as 0.004”/inch. This diameter change is called the “rise” or “slope” and is normally measured from the tip to the butt in 5” increments (.015”/5” to .020”/5”). A 5wt rod would have a tip diameter of about .070” and if it was 7 1/2 feet long the diameter of the butt would be around 0.385” in diameter. The faster the rise the faster the action — but it’s the tip diameter (or more accurately the intercept point indicated by a straight line that extends from 60% to 10% of the rod’s length) that determines the indicated line weight, not the slope of the taper.

The Eiffel Tower would be a very fast action as compared to say a modern radio tower. Obviously a rapid change in diameter will cause the tip diameter to be a lot smaller than the butt making it a tip action rod. The tip bends a lot and the butt very little. A slower change in diameter means the butt will bend more — the old bamboo rod makers called that a parabolic action. My question would be: In terms of a spring — which stores more energy? The tip action rod/spring or the full flex rod/spring. Just thinking about it I would guess the more of the rod that bends the more energy it can store. What is the real answer?

-Ron

[Merlin]

Ron

The faster the rise the faster the action — but it’s the tip diameter (or more accurately the intercept point indicated by a straight line that extends from 60% to 10% of the rod’s length) that determines the indicated line weight, not the slope of the taper.

Agree up to some point. The tip diameter is loosely related to line size. I guess you refer to RodDNA or Letcher Lambuth’s book here. You can make a rod for a given line with various slopes (or “action”).

In terms of a spring — which stores more energy? The tip action rod/spring or the full flex rod/spring. Just thinking about it I would guess the more of the rod that bends the more energy it can store. What is the real answer?

It appears to be paradoxal but if I compare two graphite rods (same length, same line, similar MOI), the “tippest” one stores more elastic energy than the other one for the same series of ”virtual” casts with my 2D casting model. It might be due to the “hardness” of the spring(s). As rod deflects they deflect less for a given load increase, and if I consider a parabolic rod I may end up with a pretty linear rod, whilst on the other hand, a tip action rod is typically non linear. Let’s say K is the stiffness and x is the deflection, a typical non linear rod would correspond to a force applied F:
F= K1*x+K2*x^3
Consequently, even if x is limited because of the stiffness level of the rod, the non linear term (K2) contributes significantly to the elastic energy stored into the rod if it is large enough. If the rod is linear (K2=0), this does not happen.

Merlin