Anyone here with a Physics degree, trolling question !!!

[RandyG]

I have a question regarding line shape during trolling.

Email me if you wish to consider the analysis.

randygardner@chartermi.net

Thanks,

Randy

[ETT]

The pull of the lure varies with your speed. The resistance of the line through the water increases with the amount of line out. Therefore there can not be a constant "line shape during trolling", but rather it is constantly changing. This would be true if you only used one lure and one type and test line. Now add that there are many different lures and a multitude of lines and you see that your best efforts can only derive an estimated shape, subject to many variables. Hope this helps. Good luck.

[Ernie]

Are you talking about the shape of the line (diameter, flat vs. round profile, etc.), or are you talking about the shape that the line takes in the water from the rod tip to the bait/weight (or a combination)?

The friction created by the water on the line will be a function of the diameter and bouancy of the line itself. The shape that the line creates will be parabolic, and would be a function of the length and the friction. Using a bit of numerical analysis (including calculus and differential equations), the shape and the line ( and thus the depth) could probably be estimated, but the bait itself would be a variable that would be necessary for an accurate estimate. (I have a degree in mathematics/computer science from the old days).

A lot of work has been done in this area, and the Precision Trolling Guide has charts for a wide variety of line diameters, line length, and baits.

[Walleye Express]

Ernie.
I think you forgot the water density variable. As waters density is differnet when cold versus warm, thus creating more or excluding the drag ratio and it's effects on both line and lure. 12th grade graduate, 10,000+ hours on the water. Capt: Dan.

[Science Nerd]

I agree with a couple of the previous posts about the fishing line not being a straight line from your rod to the bait. This is very noticeable with heavier line but also happens with lighter or finer diameter line. My best advice...Buy the book (Precision Trolling Guide), follow the directions, and catch the fish. The research you need is already done for you. This question to really be answered would need a lot of research on line type, buoyancy, length, lure type, speed, current, density, and more etc. Each time you changed a variable the whole deal would shift. Probably somewhat predictably but different just the same. Then about when you got it all straight Rapala would buy Storm and screw up the lure action anyway. Wouldn't you really rather spend more time fishing.
Nerdy

[mac]

One of Murphys laws states that all of the above factors plus many more will combine to position your lure out of sight of the fish you may pass by and guide your $10 lure into snags that are in the area.

One of my old teachers said "variation is the rule" and "use what works best for you". (in other words, GOOD LUCK)

[RoyC]

A physicist can't help you, they are too theoretical for musky fishing. You need an engineer. That's what I am! We solve real problems!

I have never tried to analyze a line and lure being trolled in a lake yet, but I have studies and taught the basic concepts. Here are a few observations and comments regarding the other comments.

1. Water density is probably not a significant variable. It only decreases by about 0.3% as water warms from 40 F to 80 F. However, viscosity decreases by about 45% over that same range. So water temperature probably is important, but not because of density effects.

2. Analyzing the line in terms of drag from the water and tension from the lure would probably not be that difficult from an engineering point-of-view, but the geometry is somewhat complicated (2-dimensional) so I doubt that one could solve it mathematically to get a closed form solution. A numerical solution (finite element or finite differnce) would probably be needed. As a result, I doubt that the resulting line shape would be parabolic.

3. Taking line shape (for lines other than round) into account could really make the problem tough. Does anyone use non-circular line any more? I remember a flat line that came out about 10 years ago, but it didn't last long in the market.

4. I haven't looked at the previously mentioned trolling tables in much detail, but a good fundamental analysis of this problem could be interesting in terms of explaining the results in the tables and for extending the tables to conditions not covered by them (e.g., other line sizes and weights, differing water temperatures, etc.).

I used to teach at an engineering university, and if I still did, I would use this as an undergradate independent study or design project just for kicks.

[Walleye Express]

Viscosity (vis-kos'i-te) Resistance to flow.
Density (den-si-ty) The state or quality of being dense or close in parts.
I finally understand why it took the engineers 3 month to plan the renovation, and the maintenance people only 1 month to build it. You weren't in on the Normark Hot-N-Tot redesign were you? Capt: Dan.

[RandyG]

I still need a Physicist. If you would like to help with the dynamics
of fishing line while trolling please email me.

randygardner@chartermi.net

Thanks,

Randy

[RoyC]

I am purely a spectator when it comes to fishing, my work life has nothing to do with it. I think I like it that way, but if somebody would pay me as much to go fishing . . .

[Walleye Express]

Sorry Roy.
Sarcasim was my minor in school. I was the only one who made the school phycologist cry. Capt: dan.

[RoyC]

I guess that I should clarify a previous comment about density effects. Density is very important in terms of line and lure drag, it just doesn't vary much for the range of temperatures or depths that you would encounter when fishing.

[RoyC]

I didn't even notice the sarcasm about being an engineer. We get that all of the time, especially blame when something goes wrong!

But the next time you get in your boat with all of your equipment, think about how much engineering was involved. Even I can't figure out how such good stuff gets designed and built for so little money. But there are a few engineering details that are just so stupid that . . . .

[Beer Boy]

This dencity thing has got me cofused. All I know is that beer disappears quicker when its cold than when its warm. It flows easier.....I know that and I have a Grade 6 education

[RoyC]

Yea, that's one of the mysteries of science. Beer flows faster when the beer is cold, and the weather is warm. But some things even engineers just take for granted. ;-)

[SUPERTROLLER]

RandyG, the one thing I see in this discussion so far that nobody stated was that the curvature of the line (or bow) will be the opposite of the dive curve. The line will be running nearer the surface and the parabolic swing to the lure is going to be steeper as you near the lure. The bowing of the line will be held towards the top of the water by the water pressure created from the drag on the line. The lures diving bill finally exerts enough pressure to cause the lure to pull towards the bottom and overcome the water drag on the line. This would be true for mono and superlines with the superline having less stretch though the curve in the line is much less. Leadcore has it's own weight to pull the line down along it's entire length and therefore probably is straighter than mono or superline even though it has a higher drag coefficient. I'm guessing on the leadcore but remember Mark Romanack discussing this at a seminar one time on the mono. He's the precision trolling guru so I'll believe him when he says it works this way.

[Dave in Mpls]

Supertroller is right on regarding the "shape" of the line from the water surface to the lure. The effect will be less pronounced for superlines vs mono, assuming same lb test line, as the superlines will be thinner, thus having less resistance. A downrigger ball will impart the opposite curve on the wire from the downrigger to the ball.

Regards

[Ernie]

The point of my response is trying to get at what Randy is looking for. Don't know much based on his short post(s). Hope he can shed some light on this.

Many variables (did not intend to list them all) to consider if attempting to do something with the physics and some thorough analysis of all of them would be required for a level of accuracy that he may (or may not) be looking for.

Did not intend on an education vs experience debate. I thank God that I have had a good measure of both, and always on the lookout for more.

[KevinA]

Randy,
I'm still interested in why you think you need a physicist? This is a physics question (Newtonian Mechanics), but what is it you're trying to figure out?

The shape the line will attain as you follow it from the boat to the lure could be well described with a quadric (x ^ 4) equation. I'm running on instinct here as much as anything, but if you take a sample curve from Precision Trolling (for example the 3/8th oz Hot-n-Tot dive curve), and fit this equation with a quadric polynomial, then take the first derivative of this equation(curve) you end up with a curve like the one at the link below. This is essentially what a typical mono line would look like if you could see someone dragging a 3/8ths oz Hot-n-Tot by you as you sit underwater.

OK, now what? If you want to predict depth as a function of line out that wouldn't be too hard from the inital dive curve, or a fit of the curve as long as you don't extrapolate too far. If you wanted to calculate the maximum depth of a lure you might be able to achieve set the derivative equation equal to zero & solve for x(it's been a dozen years since calculus & analytic geometry, I'm blowing some dust out here). Again Randy, what do you want to know?

http://users.wi.net/~datuboat/images/image5.gif

[KevinA]

That rather frustrated little face above is supposed to be "solve for x", great little face though