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Fly Rod Moment of Inertia Calculator


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Rod 2021-07-24
Section Mass (g) Length (m) Mass Center (m) Moment of Inertia (gm2)
7 0
6 0
5 0
4 0
3 0
2 0
1 (butt) 0
Total 0 0
Note: Zero out extra rows for rods with less than 7 sections.

submit to MOI Log
MOI Data Log (right-click to "save target as...", tab delimited text file, can be opened with excel)

Moment of inertia (MOI) is resistance of an object to rotational acceleration. The greater the MOI of a fly rod the more force (torque) is needed to cast that rod. This can be calculated using the rod's total length along with each section's mass, length, and mass center distance (measurement from the section's lower end to the balance point). This calculation is more accurate for multi-piece rods as the data from each section better estimates the mass distribution of the entire rod.

This calculator is based on "Measuring Fly Rod Swingweight" by Grunde Løvoll and Magnus Angus, March 2008.

Eric Mar08