Sloppy Rod

[Graeme H]

Option 2 Merlin. A tired, average caster ...

When we get fatigued, we lose form very easily. Get the timing of the application of power wrong in a cast and it feels like the rod loses power, when in fact it's us that gets sloppy.

If a few glass rods (shown in videos) aren't showing the point where a rod gets sloppy under extreme-ish casting conditions, what will show it?

Cheers,
Graeme

[Merlin]

This is likely the first option Graeme.

I took my old glass rod which was made on a Conolon blank and got its design with my methodology, and it is a really simple one. I am torturing it with a virtual test to see what difference can show up with a modern rod (mapping).

One of these days I shall take it for a casting test outside (no so easy in town). I shall see how bad I am in terms of carry with it by comparison with my favourite rods. I still have the reel and the line.

Merlin

[Merlin]

I mean that the most likely option is the second one in order, in other words I agree.

Merlin

[Torsten]

James,

I've read your FP,

Hopefully it’s obvious that the flexural modulus (stiffness) of a rod changes along its length due to its tapered construction, i.e. the tip will flex deeply before any significant deflection in the section above the handle is noticed.

AFAIK stiffness isn't the same as flexural modulus, first is a object property and thus depends on the dimensions and the second is a material property, independent of the object's dimensions.

I've just measured the broken section for you. The OD was ~8mm. Interestingly the wall thickness varied from 0.45mm to 0.65mm, I wonder if this rod had a distinct 'spine' due to its construction (or whether the 'thin' bit spirals up the blank).
I too was surprised at the failure occurring at such a low deflection. I suspect a 4 point bend test would lessen the localised pressure, however I didn't have that jigging to hand.

I can bend with my hands a rod piece more than these 1-2 mm, so hmm .. I'm wondering if your test jig is suited for thin walled tubes. Is this your test jig?:


I've read in one paper that they inserted rigid rings at the test points to distribute the load along the circumference of the tube.

Maybe a pragmatic test would be to perform a simple load test with a fly rod and measure the ovalisation with calipers.

Anyway, when I look at the graph from Daniel, if it's representative it seems to be an interesting phenomenon but with little relevance and can't be an explanation for the "sloppy" feel.

Paul:

I think it’s a lot harder to break a softer rod than it is a stiffer rod. Same applies to non stretch mono and stretchy mono. That rod that Tim has could very well behave like one of the ones this topic is about.

It's not that simple. It depends on the construction and the used material - e.g. you could build a soft but very fragile rod from very high modulus material or a very stiff and robust rod from a low modulus material like glass fibre. I remember that my club had an old glass fibre T38 rod - that thing was brute, I think you would need to go to the gym before casting it.

I think the other topic (casting sport rules) needs a seperate thread, well tomorrow.

Torsten.

[Paul Arden]

Many years ago, Magnum brought down a bendy 3WT rod with instructions to try to break it with a 10WT line. So we put it in a shootout and threw it for distance. This rod would bend butt to tip, and possibly did when we were casting. We couldn’t break it however – and the way it cast we certainly wanted to! But it just bent and bent and bent some more… it was carbon fibre.

I’ve cast plenty of rods that are complete dogs to cast. Of all materials. For me it’s design. It’s quite possible that a rod ovalises but I imagine that would be a very distinct and immediate feeling. I’ve possibly experienced this but the result has always been a damaged rod that has broken one or two casts later. From the way the fibres are all split (both sides) I assume that this may be what happened (carbon fibre).

Would fibreglass recover from this sort of ovalising? I have had this happen quite a number of times. To ge extent now where I know what it is.

Cheers, Paul

[Bianchetti Ivan]

There are rods that turn while bending, but you should have this feeling with and without transport.

[Merlin]

After some testing I can now compare my 8 foot glass rod (equilibrated cloth) with one of my 9 foot graphite (unidirectional). They are very similar in terms of stiffness curve (deflection versus force at tip) but the graphite one is faster (20% unloaded). The structure of the glass rod is much stronger in terms of hoop strength with its woven structure. Unidirectional fibers are suited for speed, but they lack hoop strength.

If I consider a heavy load deflection, the graphite butt section peaks at 0.2% ovalisation at handle level, whilst the glass one peaks at 0.4% ovalisation at the same location in the same conditions. This is because the glass rod diameter is larger and the wall thinner, which compensates somehow for hoop strength of the rod structure. Diamondback graphite rods were also made from a cloth if you remember this brand, I guess they were unbreakable.

In both cases the critical strain is lower than the maximum compressive strain. Ovalisation reduces the resistance to failure and the more ovalisation there is the lower the strain limit is. At some stage there is a critical ovalisation value leading to failure for hollow beams.

The maximum strain is about 50% of the critical value for the graphite rod and about 20% for the glass rod. No rod is likely to break under casting conditions. Morover ovalisation is small in both cases and does not significantly impact the stiffness of rods (very small effect, nearly invisible on curves).

Consequently I think we can say that the sloppy feel I got from the glass rod (none from the graphite one but maybe I never reached the limit) does not come from some bending weakness. Even if we can imagine more dynamic load by comparison to a static test, what may happen is a failure of the graphite rod if the butt is bent with a small radius of curvature (around one foot) which would be comparable with the tests performed by Tim (mentioned earlier in the thread).

Now I have some questions for competition casters: how do you know that you reach the maximum possible carry for a given rod? How does it feel? What feedback of the rod do you get? Finally how did you succeed in increasing your carry with a given rod (power application I guess)?

Merlin

[Paul Arden]

Hi Ivan, your post is somewhat of a mystery to me

Daniel, good questions. Let me see if I can sum up my opinions. I would say that maximum carry is often dominated by flyline taper. However the rod also plays a part too of course and it’s actually a very rare 90’ line that can’t be carried to the backing knot on just about any 9’ rod. It mostly falls apart when the loop fails to straighten for whatever reason. It could tick the ground, tail, or simply just not fully straighten. Basically it’s that loss of control. If the line isn’t (reasonably) straight at the beginning of the next casting stroke, then it’s going to compound the loss of control.

The usual way to increase carry is with a faster later haul. It’s possible to sometimes even recover from loss of control with an excellent haul on the next cast. It’s definitely not about more force with the rod hand – there obviously is more force but it’s not the dominating factor. The tracking must be straight of course but I think that’s a given with regards this question. Long carry for me is about having a smooth, straight and usually “stopless” casting stroke with a blistering haul that controls the cast. If the tracking is straight then the most effective way to increase carry is to develop the haul.

Cheers, Paul

[James9118]

James,

AFAIK stiffness isn't the same as flexural modulus, first is a object property and thus depends on the dimensions and the second is a material property, independent of the object's dimensions.

Torsten.

Yes I agree, but you have to remember the audience that the FPs are written for, fly fishers not material scientists. That's why I didn't calculate any modulus figure and just spoke of generic stiffness. You're also missing the point that I chose the jigs I did to promote localised stress and ovalisation - I did my best to show that ovalisition could be the cause of the sloppy rod syndrome but I couldn't. It appears that Daniel is now coming to the same conclusion.

James

[James9118]

I can bend with my hands a rod piece more than these 1-2 mm, so hmm .. I'm wondering if your test jig is suited for thin walled tubes.

Torsten.

I've just tried bending some rod sections by hand, gripping them with a spacing equivalent to my test piece :
HT#5 butt - yes I can deflect it.
TCX#10 butt - yes I can deflect it.
AtomSix ST27 butt - no I can't deflect it.
Rod I tested in the Instron - no I can't deflect it.

So you've taken a random rod and decided that because you can bend it by hand my results are somehow invalid, hmm indeed!

James