# Force on a Fishing Rod

1. Jul 29, 2014

### stuhr727

I am looking into building my own fishing rod and am really lost on how to measure force exerted strictly on a pole as it bends. I think I'll have to use a strain gauge but I cant even find an equation to measure the force.

Can anyone provide the equation, variables, and sample problem? I'd like to solve for force, ill have the Modulus of Elasticity ε.

Ideally solve from the output of the strain gauge.

2. Jul 30, 2014

### SteamKing

Staff Emeritus
If you want to measure the force applied to the pole, put a dynamometer (force gauge) in the fishing line and pull.

Strain gauges measure strain, not force.

3. Jul 31, 2014

### stuhr727

A dynamometer won't account for the force being distributed across the pole. All of the guides and the bend will make the force gauge reading on the line less than what it really is.

Understand strain gauges measure strain...but you can use strain to calculate force. Can someone smart reply.

4. Aug 1, 2014

### Oxvillian

Euler (who was fairly smart by most accounts ) worked out the mathematics of bent rods about 250 years ago, if that's what you're looking for. It's quite involved - lots of nasty elliptical integrals

I think you might be confused about the forces involved here. SteamKing is correct - a force gauge in the fishing line will tell you exactly the force exerted on the rod by the line. Inside the rod, life is complicated because various bits of the rod exert different forces on various other bits of the rod. It's not like there's one force "all the way through the rod". Instead, there's a continuously varying stress field.