Date post: | 21-Dec-2015 |
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Measurement of Fly Rod Spines
Graig Spolek
Modern fly rods
• Hollow, tubular, and tapered
• Manufactured of carbon fiber reinforced plastic
• Formed by layering pre-preg (graphite imbedded cloth) around a mandrel
Mandrel
Pre-Preg
Finished Rod Exhibits:
•Variable Diameter
•Variable Wall Thickness
Increasing Wall Thickness
Wall thickness adjusted by varying overlap of pre-preg
3 wraps 3 ¼ wraps 3 ½ wraps
Rod Spine
• Preferential plane of bending
• Align rod hardware to maintain bending during fish fighting that causes static bend in rod.
Rod Resists Bending in this Direction
Rod Freely Bends in this Direction
Increasing Wall Thickness
NoSpine
IncreasingSpine
MaximumSpine
DecreasingSpine
NoSpine
3 wraps 3 ¼ wraps 3 ½ wraps
Push Down Here
Hold Tip
Rotate Rod
Rest Rod Butt on Floor
Method for Location of Rod Spine
Method for Location of Rod Spine
• Static test
• Yields average spine orientation over whole rod
• Maximum influence of spine orientation at point of maximum deflection
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
F
L
AxialRotation
Rod
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
Model Inputs
• Measured from actual production rods
• Outside diameter - DO
• Wall Thickness - t
• Angle of Layer Overlap - θ
Do
θ t
Outside diameter - DO
Wall Thickness - t
Angle of Layer Overlap - θ
Comparison of rod section to model
yi
dAi
dAyI 2
yi
dAi
ii dAyI 2
MODEL RESULTS
F
L
3L
IECF
MODEL RESULTS
min
max
min
max
I
I
F
F
C, δ, E, L = constant
COMPARISON: MODEL & EXPERIMENT
min
max
I
I
Experiment measures:
Model predicts:
min
max
F
F
RESULTS
1 2 3 4
Point Rod 123 Rod 114 Rod 117 Rod 118 Rod 122
Expt Model Overlap Expt Model Overlap Expt Model Overlap Expt Model Overlap Expt Model Overlap
1 1.20 1.11 120 1.14 1.08 45 1.04 Missing Missing 1.11 1.07 120 1.13 1.10 80
2 1.13 1.14 90 1.16 1.10 60 1.15 1.05 150 1.18 1.11 90 1.10 1.12 105
3 1.10 1.13 60 1.14 1.09 75 1.06 1.00 180 1.06 1.09 50 1.11 1.09 245
4 1.10 1.09 30 1.12 1.12 120 1.08 1.05 150 1.04 1.04 15 1.06 Missing Missing
QUESTION: Do these agree?
Can the differences be attributed to measurement uncertainty or is the model incorrect?
,, tDfI o
21
222
I
t
I
D
ItD
oI o
Uncertainty in Moment of Inertia
Estimate for Partial Derivative
ii X
R
X
R
For small individual uncertainties
iXiX
iii XXi
Xi
RX
R
X
R
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
21222
IIItDoI
Do
θ t
Outside diameter - DO = 0.350” ± 0.003”
Wall Thickness - t = 0.028” ± 0.004”
Angle of Layer Overlap - θ = 90º ± 5º
Estimate of ΔImax
DO t (n=4) θ Imax (*10-5) ΔI
0.350” 0.028” 90º 1791 0
0.347” 0.028” 90º 1741 50
0.350” 0.028” 85º 1790 1
0.350” 0.032” 90º 1855 64
8164150 21
222
maxI
Estimate of ΔImin
DO t (n=4) θ Imin (*10-5) ΔI
0.350” 0.028” 90º 1623 0
0.347” 0.028” 90º 1577 46
0.350” 0.028” 85º 1615 8
0.350” 0.032” 90º 1675 52
7052846 21
222
maxI
The final result is the ratio of the inertia values
21
2
min
2
max
min
max
minmax
IIRatio
I
IRatio
IIRatio
Substituting values
0625.01623
70
1791
81
10.11623
1791
21
22
Ratio
Ratio
Ratio
Final value for ωRatio
069.010.1
069.00625.0*10.1
Ratio
Ratio
Comparison of Model and Experiment
Model Uncertainty: ± 6.26%
Experimental Uncertainty: ± 5%
ROD 114
1.00
1.05
1.10
1.15
1.20
1.25
0 1 2 3 4 5
Expt
Model
END