Downrigger Blowback

[GeoC]

Just purchased Cannon downriggers for my 21' Key West CC. I love 'em. First time using them was able to hook into some nice Kings off the coast of North Carolina.

Anyway, Cannon provides a chart in the owner's manual that can be used to estimate the depth of a downrigger based on boat speed and downrigger weight. However, I decided to calculate my own set of graphs. The curves shown here are for a 10lb weight. The curves are shown for boat speeds varying from 3kts to 6.75kts in 0.25kt increments.

 

[GeoC]

Re: Downrigger Blowback

I should add that the results are based on solving the second order differential equation that relates the profile of the downrigger line (i.e. how it changes shape with depth in the water) to various parameters of the system (like water density, boat speed, downrigger weight and shape, line diameter and line drag, etc. etc.). The results make qualitative sense, and where comparisons are possible to the results in the Cannon manual the agreement is pretty good.

If someone is interested in a set of numbers for different line (I assumed braided steel cable) or different downrigger weight, please let me know. I'd be happy to run the calculation with a different set of parameters.