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Measurement of Fly Rod Spines Graig Spolek
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Modern fly rods Hollow, tubular, and tapered Manufactured of carbon fiber reinforced plastic Formed by layering pre-preg (graphite imbedded cloth) around a mandrel
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Mandrel Pre-Preg
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Finished Rod Exhibits: Variable Diameter Variable Wall Thickness
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Increasing Wall Thickness Wall thickness adjusted by varying overlap of pre-preg 3 wraps3 ¼ wraps 3 ½ wraps
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Rod Spine Preferential plane of bending Align rod hardware to maintain bending during fish fighting that causes static bend in rod.
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Rod Resists Bending in this Direction Rod Freely Bends in this Direction
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Increasing Wall Thickness No Spine Increasing Spine Maximum Spine Decreasing Spine No Spine 3 wraps3 ¼ wraps 3 ½ wraps
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Push Down Here Hold Tip Rotate Rod Rest Rod Butt on Floor Method for Location of Rod Spine
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Static test Yields average spine orientation over whole rod Maximum influence of spine orientation at point of maximum deflection
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Measurement of Rod Spines Measures local spine Measures magnitude of spine by comparing maximum and minimum force required for specified deflection Allows location of spine orientation
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F L Axial Rotation Rod
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Model of Spine Due to Pre-Preg Overlap Develop model of material distribution Calculate Moment of Inertia (I) due to distribution of material Accommodate different orientation
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Model Inputs Measured from actual production rods Outside diameter - D O Wall Thickness - t Angle of Layer Overlap - θ
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DoDo θ t Outside diameter - D O Wall Thickness - t Angle of Layer Overlap - θ
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Comparison of rod section to model
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yiyi dA i
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yiyi
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MODEL RESULTS F L
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C, δ, E, L = constant
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COMPARISON: MODEL & EXPERIMENT Experiment measures: Model predicts:
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RESULTS 1234 PointRod 123Rod 114Rod 117Rod 118Rod 122 ExptModelOverlapExptModelOverlapExptModelOverlapExptModelOverlapExptModelOverlap 11.201.111201.141.08451.04 Missing 1.111.071201.131.1080 21.131.14901.161.10601.151.051501.181.11901.101.12105 31.101.13601.141.09751.061.001801.061.09501.111.09245 41.101.09301.12 1201.081.051501.04 151.06 Missing
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QUESTION: Do these agree? Can the differences be attributed to measurement uncertainty or is the model incorrect?
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Uncertainty in Moment of Inertia
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Estimate for Partial Derivative
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For small individual uncertainties
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So the uncertainty in I can be estimated by the root mean square of the finite perturbations in I, ΔI, due to the measurement uncertainties
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DoDo θ t Outside diameter - D O = 0.350” ± 0.003” Wall Thickness - t = 0.028” ± 0.004” Angle of Layer Overlap - θ = 90º ± 5º
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Estimate of ΔI max DODO t (n=4)θI max (*10 -5 )ΔI 0.350”0.028”90º17910 0.347”0.028”90º174150 0.350”0.028”85º17901 0.350”0.032”90º185564
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Estimate of ΔI min DODO t (n=4)θI min (*10 -5 )ΔI 0.350”0.028”90º16230 0.347”0.028”90º157746 0.350”0.028”85º16158 0.350”0.032”90º167552
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The final result is the ratio of the inertia values
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Substituting values
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Final value for ω Ratio
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Comparison of Model and Experiment Model Uncertainty:± 6.26% Experimental Uncertainty: ± 5%
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END
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