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Thread: Determining true depth with downrigger

  1. #1

    Default Determining true depth with downrigger

    So, I lower my downrigger until the counter says 50 feet. The ball is behind the boat and the transducer can't pick it up. How deep am I? That's a question I always ask myself when using the downrigger.

    So how do you use yours? Set it at "50' " (for example), and then if you get a hit you later re-set it to "50", not knowing or caring how many feet deep you really were? Only caring that you got a hit at the "50" on the counter and so that's how you know how much line to let out again?

  2. #2
    Member CanCanCase's Avatar
    Join Date
    Feb 2007
    Bandon, OR


    Back in the Charlie White days, there were many books on the subject. They all included line angle formulas or charts to determine true depth based on line length and angle.

    Just from experience, I've found that at my regular trolling speeds I've got about 10 feet per hundred with my 12# balls and close to 15 feet per hundred with the 10#... ie: If I've got 100' of line out, and I see bottom on the fish finder at 100 feet, I won't drag bottom until the depth rises to around 85' or 90' (depending on which ball I'm using.)

    In the case of my boat fishing 6 lines, your method of "if it said 50' when you hit the last fish, go there!" works great. There are actually only a few different patterns I fish with all 6 lines out and the depths staggered by 15-20' for each rigger.

    M/V CanCan - 34' SeaWolf - Bandon, OR

  3. #3
    Member SoggyMountain's Avatar
    Join Date
    May 2007
    Bait Station, Alaska 99801


    Can Can and I might be on the same page here.... it's possible.

    The one issue you can't escape in Alaska is tide flow. On a flat surface, with no other forces beyond gravity, 50' from the top of the weight would be 50' of line less thne depth of the ball. But, there are other factors. Primarily your troll speed, and the water flow.

    As said in another post somewhere, I don't like downriggers personally. Moreover, I don't like fishing with people who think they need them. This is not to say that they are useless. They aren't. They serve a purpose. If I can't get a 12 oz. weight to depth, then I need a downrigger. I am not willing to pull up more than a 12 oz with a fish attached with my troll gear.

    Too many of my friends try to place their lines on a fish at whatever depth on the recorder. So, they are continually adjusting riggers to what the depth finder says while my herring swims along in his own groove.

    On any given day I can be outfished. But as a rule? Nope. There are too many factors at play.

    Time over target wins. You can't produce that with a downrigger unless you are very familiar with the tides....which no one seems to be as far as I can tell.


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