designing a sub surface jointed fishing lure to glide

Discussion in 'Hydrodynamics and Aerodynamics' started by Basswood, Mar 22, 2013.

  1. Basswood
    Joined: Mar 2013
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    Basswood New Member

    Hello all,

    I have been trying to build various 8-12" jointed subsurface fishing lures that glide. They're made with urethane resin, I mix in microballoons for floatation and keel with lead shot and hooks/spit rings. I've had some success but wanted your guys' input in understanding how shape/mass effects hydrodynamics.

    So far I've discovered near neutrally buoyancy is the sweet spot however many factors come into play. Line tow placement (creates tortional twist), hard/soft tail (rudder), ratio microballoons to lead, hook placement, head shape,etc...

    I'd like to keep the shapes as close to fish as possible, but want as much glide as possible as well. I've looked at various shapes for reference such as mako sharks,barracuda, torpedo's, submarines, etc.. but they seem to contradict each other. Some are skinny and some are bulbous.

    Any help is appreciated!
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    What do you mean by "glide" in this context ?
     
  3. Basswood
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    Basswood New Member

    I'm trying to make my lure continue forward and "glide" the best I can on a slack line. With each lure I've built there seems to be a twist coming from the rear end. I've tried to dampen this with urethane rubber that is pliable, but it isn't enough. I was thinking of maybe placing a few almost a catamaran style fins to get the bait to track better. Lures are 8-12" and 4-8oz.

    Couple of pictures....

    A few different 12" prototypes. The bottom right works the best, but twists at a med/high speed.
    [​IMG]


    Fins to help stabilize, had to be made thicker so hooks wouldn't penetrate. These throw the lure off balance at higher speed and of course kill the glide.
    [​IMG]

    Pic of bait in video. Joint is moved toward the head and not quite at the halfway point. As a result the nose throws sooner. Lure is more mechanical on a straight retrieve.
    [​IMG]


    Here's a video of a few prototypes. Some of them are surface lures, disregard those.
    http://www.youtube.com/watch?v=BlkrLWQcsNk
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Do you mean they don't run straight, but yaw around when the "tug" comes off the nose ? The flexible tail might have something to do with that. I assume you are not trolling them, but jigging ? Only thing I can suggest is that you make them in such a way the tail locks up unless released by tension on the tow-eye, which sounds very difficult to organize ! Failing that, some vertical fins top and bottom at the extreme rear of the forward segment, which will look different to a "real' fish, though.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I probably didn't put that very well, it seems to me the segment behind the hinge is free to swing and therefore cannot contribute to the directional stability of it when not being towed by the nose, it needs to be like an arrow with centre of lateral resistance behind its centre of gravity, or it will veer around.
     
  6. Basswood
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    Basswood New Member

    They are supposed to swim in a "S" pattern on a slow retrieve. The width of the "S" depends on the travel in the hinge. The baits are fished with a slow retrieve then slight twitches to get the lure to change directions and look like a fleeing fish. This is the trigger often for fish to commit.

    The hard tail "locks up" and stays in place. I've noticed changing the firmness of the tail along with thickness of material plays with the action quite a bit.

    So you're suggesting vertical fins on the head section towards the rear? right next to the joint?

    That rear end aids in the "S" action. Watch the lure in this video that trails the pack. This is the action of these baits, however I want them to keep gliding on the pause. I've achieved this to some extent, but want to fully understand the hydrodynamics of it.

    http://www.youtube.com/watch?v=Ji2OPGH7wo8
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    You probably have to factor in the tow line as well, springy nylon might behave differently to braid, e.g. so far as it affects the "glide".
     

  8. Basswood
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    Basswood New Member

    Yes, fluorocarbon has been the most beneficial as it absorbs water and doesn't create a bow or as much friction.

    Line tie position is crucial as well.
     
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