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Verification fly rod

Purpose

The purpose of this section is to demonstrate how the rod input into the simulation model is verified.

Method

Each rod is specified by distributions of:

· Outer diameter. The outer diameter is used to calculate air drag.

· Bending stiffness. The bending stiffness gives the relation between bending moment and curvature in static bending. The bending stiffness distribution determines the rod deflection profile when subject to applied static loads (in zero gravity).

· Mass density i.e., mass per unit length. The mass density distribution with the bending stiffness distribution gives dynamic rod properties e.g., eigenfrequencies.

Here, the method used to verify the rod distributions is shown with the rod distributions for the 50ft oh ref. cast as an example. The fly rod blank is modeled for each rod section as a hollow tapered tube with a Young’s modulus and density varying linearly along the section. The outer diameter is measured but the inner diameter, Young’s modulus and density are treated as unknown. The unknowns are varied until acceptable agreement with experiments is obtained.

Each ferrule gives an increase in local bending stiffness and mass density.

The guides (including wrapping) give additions to the mass density with the relative additions being largest for the tip section. The guides are modeled using a mass density distribution giving an addition centered at the position of each guide.

The rod verification method includes the following measurements:

1. Rod tip deflection for applied loads.

2. Mass for rod sections (zero moment mass distribution).

3. Position for center of mass for rod sections (first moment mass distribution).

4. Frequency of small amplitude physical pendulum oscillations (second moment mass distribution).

5. First eigenfrequency for clamped rod vibrations.

The measurements listed above were made for:

· the rod top section only.

· The rod top section + 1 section.

· The rod top section + 2 sections.

· The complete blank above the handle (measurements 2, 3 and 4 not applicable/possible).

Mass measurements were made using a precision gauge, resolution 0.001 g, accuracy 0.01 g.

Deflections mere measured using a digital caliper, resolution 0.01 mm, estimated accuracy 0.2 mm.

Eigenfrequencies were measured using video (240 frames per second) counting 30 cycles.

Physical pendulum frequencies were measured using video (60 frames per second) counting 10 cycles.

Results:

The outer diameter comparisons are trivial and are not presented here.

The results comparing experimental data and input to the simulation model for the mass distributions are shown in the table below:

The results comparing experimental data and results from the simulation model for static deflections and eigenfrequencies are shown in the table below:

Conclusions:

· The agreement for mass distribution, presented in the first table, shows that it agrees with measurements within about 0.2%.

· The agreement between experiments and simulations for static deflections shows agreement within about 0.2%.

· The measured eigenfrequencies are 0.2-4.0% lower than the calculated eigenfrequencies. A likely explanation for the deviations is that clamping in the experiments is not perfectly rigid.

· To summarize, the agreement between experiment and the simulation model shows that the rod properties are accurately modeled.