Hull vs. line voltage

[lone eagle]

Talking about current leakage, I stuck my voltmeter in some damp wood not far from my battery bank. To keep the story short, I found voltage but not from poor wiring but from the batteries themselves. I never thought that voltage would travel across a fairly clean plastic casing let alone in and out of a plastic battery case and beyond. Much cleaning of acid residues got the 8Ds to zero leakage but still working on a pair of "sealed" batteries that actually leak out of a plugged orifice where a charge window is situated. Conumdrum..I caught quite well last year

[Lulu]

I've read the series of responses. What I noticed is everyone is looking at the trees without seeing the forest, or even the entire view. First, one needs to know why fish respond to electrical current, second what causes the current, and third how to manage the current.

Number 1: A little anatomy lesson. Fish sense their surroundings and find their food using their senses as we do. But, we think in terms of our natural environment, not the fish. Salmon's primary sense is feel, i.e. the lateral lines down their sides. These touch cells detect vibration and electrical current far better that we do. They smell 100Xs better than we do. And, their eye sight in general is worst than ours. We have 4Xs the number of cones (which see color) than a salmon; however, they have 10X the number of rods (black/white receptors). What that means is salmon don't see color well, but they do see variations in gray tones better than what we can imagine. Also, rods are the primary sensory for spatial acuity. Meaning, salmon have better depth perception which allows them to judge distance; import feature for striking a bait fish or hoochie, but they can't see a long distance very well. They have to be close to their target for sight to help in their survival.

The lateral line sensing touch (vibration) also senses electrical current. Don't think in terms of volts. Think in terms of millivolts (very small voltage). Another anatomy lesson: an electrical discharge is fired between the neuron and muscle to make it contract. As bait fish swim, their collective electrical discharge creates a current (though very small). Predatory fish learn this current is (which they sense in their lateral lines) a possible dinner; which they will divert their direction and investigate.

The point is: Salmon are attracted to a boat with a high "boat potential." They're investigating the possibility that the boat's ionic discharge is a school of bait fish. But, that doesn't mean they will bite. I know I have a school following the boat when the snooter's top leaders are producing. Also know the boat is not dialed in if the floats aren't catching at the same time. The reason salmon (or tuna) are attached to the boat's hull potential (ionic discharge from the dis-similar metals which creates an electrical foot print) is THEY THINK THE BOAT IS A SCHOOL OF BAIT.

Number 2: What causes the boat's current (hull potential)? The primary source of current is the zincs sacrificing to the other metals; i.e. the prop, shaft, through hull fittings, keel cooler(s), etc. Every boat is different. The only thing you need to know is your boat's optimal hull potential. In other words, when the bonding system is clean and water tight, all metals in the water are grounded (including the shaft) what is your hull potential? There are three measurements: at the dock, at the dock with the motor running, and at the dock with the transmission engaged. I won't get into what each measurement means, but I will add that these are base line measurements. They will NOT mimic what you see trolling, but they are indicators of what you should expect. Natural line voltage while trolling will be lower.

Bottom paint: the copper in bottom paint reacts with the zincs adding to the ionic dis-charge. A newly painted bottom will have a higher hull potential than six month later, but by a very small amount (.1-.2 millivolts. Sacrificing of the zincs adds to this decline in hull potential). Know there are big differences between ablative paint and hard fouling paint. I learned this lesson the hard way. You want hard fouling paint with a cuperous oxide content of at least 40%. Also, use the bottom of the can on the back of the boat. The back of the boat has the biggest and last presents in the water. You can never get the copper fully (homogenously) suspended in the paint, it is too heavy and falls out of suspension quickly.

Things that you have to watch is stray current. The first source is typically a bad wire in the bilge (bilge pump). Could be a nav light, radio connection, the list goes on and gives you brain snakes. Start with the obvious and easiest to access (bilge, nav lights for instance) and work towards the least obvious.

Number 3. How to manage the current (hull potential)? A number of things can be done to increase or decrease (manage) hull potential. For example, adding zincs, adding aluminum anodes, adding bonding plates (usually steel but I've seen copper used), adding a K-pact system. My warning is be careful. Wood boats can not have the hull potential of a steel boat unless ample sacrificial metal is added to protect the plank screws. There is a balance that is specific to the boat's below-the-water-line metals, the types of metals and their mass, and the boat's construction (wood, fiberglass, steel, or Al). The target boat potential range at the dock for salmon is .8 to 1.1 millivolts.

There is history to these numbers. Don't jones if you're not in the range. The point is the fish will find you, but they may be attracted to another boat with a higher hull potential. What needs to be certain is all electrical connections are clean and dry. All in-water metals are bonded, typically to the engine because that is the biggest piece of metal on the boat.

Note: I have not address line voltage. That is a subject for another posting. Know this, line voltage and hull potential are different but are inter-related. The proper line voltage will insight the strike from the school following the boat's hull potential. An in-proper line voltage will discourage the strike and loose the school. BRAIN SNAKES!!!???

You have five choices to manage line voltage if you know your boat's hull potential is good. Wait for your line voltage to be attractive, change the black box setting, add or delete line zincs, make certain the leads are pure lead and clean, and/or change the length of the breakaways to the leads.

One other take away is this, we work in an ever changing environment. You have to have base lines so you know how your boat has changed. You have to be willing to make changes. Keep it simple or you'll go crazy. If you don't want to change, be content to be average.

[Crawfish]

Talking about current leakage, I stuck my voltmeter in some damp wood not far from my battery bank. To keep the story short, I found voltage but not from poor wiring but from the batteries themselves. I never thought that voltage would travel across a fairly clean plastic casing let alone in and out of a plastic battery case and beyond. Much cleaning of acid residues got the 8Ds to zero leakage but still working on a pair of "sealed" batteries that actually leak out of a plugged orifice where a charge window is situated. Conumdrum..I caught quite well last year

Once,
I touched the positive side of my multi meter in the wood the batteries were sitting on and grounded the other probe. I got twelve volts! Not sure how many amps?
I was amazed to say the least. Ever put your hand into the bilge to grab something that fell in and get burnt by voltage. If you have you won't forget it. That boat still fished well with all of that going on.
The zinc's ate normally as well. Its always been puzzling. I love fishing because of the constant mystery or maybe it's constant misery?

[Salty]

Great post Crawfish. Pretty much sums up all I know plus quite a bit.

[Once and Future]

Lulu: Thanks for all that food for thought. In depth analysis! I'm not going to obsess about which part of the bottom paint can goes on the back of my boat though. (However, I often store my paint cans upside down just to keep the particulates moving. So I do think about stuff. Way too much, maybe.)

I never would have thought about a school of fish having a collective charge, and similar to a boat. However, I am in doubt about how far a charge or current could be felt in a conductive medium like salt water, even by a sensitive organism. It seems apparent to me that even a faint scent would carry much further than an electrical charge.

I have heard talk of "ion wash" plates that some are attaching to boats. But I just think that could travel very deep in the water. Mind is not totally closed, though.

As it gets complicated, I still the think the medical oath comparison of "do no harm" is apt. Eliminate obvious leakage currents, have good zincs, and you're most of the way there.

Now I'm thinking about how I switched bottom paints, though...

Ha! I just thought of something else! I once put the leads of a 200 mile electrical fencer to in a fresh water irrigation ditch to keep fish away from a pump inlet. (30,000 volts or something.) And there was a school of minnows right there. Instead of swimming away, the school just stayed right by the leads and collectively twitched each time the fencer fired.

[Crawfish]

Lulu,

I was actually citing one of your experiences about voltage earlier in a post.
Good to see you here. Keep posting. I want all of your secrets.

[Lulu]

Nice to see so many interested. Over 20 years of dragging my balls around, I've had similar experiences and had the same questions.

Voltage from the batteries: Depending on the boat's construction and location to the bonding system, current created from the battery may or may not effect the boats potential. A tight wood boat were the bonding system is not near the battery spill conceivably could isolate the charge. I have a steel boat. Any charge (stray current) is going to effect the boat's hull potential. I always have two boxes of baking soda in the engine room. I'd like to make a note about negative grounds. There are so many variables it is impossible to eliminate everything without spending days. Suggestion: Always use a single common ground from the engine when using the volt meter. It eliminates one possible difference in your readings.

The paint is a long story. I got the bottom of the can on the back of the boat idea from a chemist at Pettite. I had ablative paint on the bottom after sanding blasting 10+ years ago. I noticed production was declining a small amount every year to the point that I knew there was a problem. I pulled the boat (which was not fishing average to the rest of the fleet), hard sanded the ablative paint almost to the barrier coat, and painted 3 coats of Trinidad pro. First trip out, first tack!, was for 40 (by myself) and ended the day with 102. (I hadn't had 20 in a day to this point of the season) The fleet found me by mid day and only scratched a few. I was still catching. I was told I was nuts by everyone, including my wife. And honestly, thought I was completely mad and ready to sell the boat. But, after trying everything else (including new leads) this was the last resort and it worked. I'm blasting the hull in 4 weeks and starting over with hard fouling paint.

How far does the hull potential current extend from the boat and how deep does it go? I've had some long conversations on this subject and still can't answer the question with certainty. I know three things: 1.) The kinetic energy from the boat's forward progress will force the field out and away from the boat, similar to the boat's wash. 2.) the prop wash will distribute the ions in a down ward spiral like campfire smoke on a windy day. And 3.) salt water is more electrically conductive that copper. (I'm told, but not sure I believe, the hull potential can extend over 300 feet behind the boat given water temperature and salinity) A deep and wide boat (lets say 7`deep and 15` wide) is going to disperse the current and ions farther and deeper than a boat with a 4` draft and 10`stern. The bigger boat is also going to have more active surface area. I stay away from the slammers so they don't steel my fish.

What I tell people who want to improve their fishing and seem to be sincere is: Don't buy a black box until you've got your boat squared away. The box adds another level of complexity that WILL drive you nuts. If the boat fishes to your satisfaction, don't change anything. The black box only has the potential to improve fishing in a slow or scratch bite. Or, when your exploring unfished water. If it is a full on bite and everyone is catching, the box is not going to improve production. The black box can make a 10 fish day into a 20 fish day. Unfortunately, I have more slow days than 100 fish days.

[SilverT]

Lulu,

Thanks for taking the time to be so thorough in your explanation. It's extremely helpful and I'm forwarding a link to this to a friend struggling with the issue.

Lane

[Salty]

Then there is the recent science indicating seabirds find their prey fish by smelling their excretement. Wonder if salmon do the same.

[Crawfish]

Then there is the recent science indicating seabirds find their prey fish by smelling their excretement. Wonder if salmon do the same.

Boy do I have a story for you guys about smelling the fish. But its got to wait until later.

[Lulu]

Salmon's sense of smell is single parts per Billion; better than a bloodhound. It's more than reasonable to think fish follow a sent trail; regardless of what it smells like, even dinner. That's why I use gloves with bait. Not to keep the scent off me, but to keep my scent off the bait.

[Lulu]

I indicated I would address line voltage separate from hull potential. Here it goes. And trust me, this is the conversation creates the most confusion, differences of opinion, and doubt.

I'll touch on fishing with a black box, with out a black box, and the common denominators. Those common denominators are the gurdies, wire, and leads. The gurdies are made of brass which are roughly 80-90% copper with some zinc or other metal thrown in. The copper is highly electrically active which means it has electrons to sacrifice which creates current. The wire is generally stainless and will accept the electrons passing them down to the lead. Lead is a noble element which means it is real happy all by itself and makes a great ground for the gurdies' copper. You probably starting to think, "Oh!! I have a battery on the back deck and didn't know it." The natural line voltage will depend on how pure the lead is, how long the ganions (breakaways) are, how many splices in the wire, and how clean the gurdies spool is. Ganion length will increase the wire's potential (make it hotter) because the electrical potential has to build up to make the jump to the lead. Rule of thumb is longer in the spring and shorter in the late summer/early fall. Line voltage can be increased by adding brass breakaways at the end of the wire tying the ganions to the breakaways. Line voltage can be decreased by adding line zincs. The zinc is negatively charged accepting the electrons from the gurdies so there are fewer electons jumping to the lead. (less current on the wire)

The number one thing that inhibits the line voltage is scaling. That's the green stuff on your gurdies and the chaulky white stuff that builds up on the lead. Scaling is less electrically conductive. The line voltage will degrade as the scale builds up. Start the season with clean gurdies, new wire, and new leads and the line voltage will not be the same in a month, and certainly not at the end of the season. If you notice a difference in voltage on each wire, it can be traced back to something not being as clean as the other wire(s). Another thing that inhibits current is an old ganion. The ganion will take up salt creating a direct pathway to the leads. (my experience is nylon cord is better than tuna cord, but all need to be changed periodically)

Fishing without a black box: The gurdie base should be non-conductive and isolated from the boat. You want the line voltage to encourage the strike (verses the hull potential to attract the fish). The natural difference between the hull and the wire is going to be around .2 volts. Don't get hung up on a number. There are some many things that can change the ratio on any given day i.e. surface temp, the boats zincs scaling, troll speed, etc. What does need to be noted is what the line voltage is at the dock. And especially when you're fishing well. These are your base lines to make adjustments when your not fishing as well as you know you can. Before we get too far. Line voltage while trolling will be less than at the dock. The reason is the forward progress of the boat creates resistance in the water. The water molecules mechanically knock of some of the electrons as the wire cuts through the water. The mechanical energy is different than the electrical energy which is a chemical reaction. Knowing your boat and what the readings should be helps make decisions on what can be done to improve productivity. No two boats will be the same.

Fishing with a black box:

This gets complicated and I'll try to keep it simple. The box will drive current or take away current as it is dialed. Usually you're taking current out of the wire because (in a perfect world) the line voltage while trolling will be ~.6 volts. What the box is doing is stabilizing the current so it is the same on all wires. It allows for changes in line voltage without hit-and-miss on the other stuff that effect line voltage. BUT, all the common denominators have to be the same and clean. (no variables!!!!) That means the leads should be scrubbed routinely, the ganions replaced, and the spools kept clean. Last year I found the gurdies handles (Hasbro) had worn down (the little ear on the handle that fits into the bullet which engages the spool brake) and made intermittent contact making the wire voltage jump when the brake was engaged or dis-engaged. I replaced the handles and life was good. (By the way, this was no easy fix. It took days to diagnose the problem)

Conclusion: Know your boat. Keep stuff clean. Make small changes. Try to make everything the same. ( A point here about keeping things the same. My belief is fish are wary of things that are different. If two wires have different voltage, they may hit one and not as well on the other for instance. They hit the heavies better than the floats, How many splices are in the float wire(s)?)

Good fishing, may the seas be calm, and be safe.

[Kelper]

Salmon's sense of smell is single parts per Billion; better than a bloodhound. It's more than reasonable to think fish follow a sent trail; regardless of what it smells like, even dinner. That's why I use gloves with bait. Not to keep the scent off me, but to keep my scent off the bait.

Thanks for the posts Lulu.

I have something to add to the above statement. I believe salmon travel in schools and are very eager to follow a scent trail. It's the reason you are seeing charter boats now anchoring when mooching herring for salmon, versus drifting for salmon. It's not to save fuel. It's much easier for a school of salmon to follow a scent trail from an anchored vessel back to the source, than for the salmon to home in on a drifting boat. Mooching herring is extremely effective on anchor particularly off the beach a bit, and often you are swarmed with salmon while boats drifting nearby are only catching a few. Cohos can really show up in full force once you get that herring scent in the water and you are stationary for them to home in on.

[Crawfish]

And then you have the other side of the story.
The guys who fish old worn out wood boats with no nails left in them, zinc's that are completely missing, no bottom paint left and props that are pink. These are the same guys who bolt their gurdies straight down to the deck,have their davits tied on with seine twine because the bulwarks are rotting off and catch so many fish they have to stay up till 1 AM all the time to belly ice them.
I truly wonder. I truly wonder.

[Salty]

I wonder too. But, great posts. lulu. I hadn't thought about the splices.

[Once and Future]

I can't handle the truth.

[Jackson]

Great posts, lulu. Some things to think about.

[Lulu]

I understand the responses. I have been on the back deck with my head in my hands pulling my hair trying to figure out what's wrong, thinking "I quit." And, I know boats who catch and wonder why. I know this, when you look at the boats that consistently catch and finish in the top 5% of the fleet every year, you will find most of them are tuning their boats and using a black box. I don't know the number, but from my perspective of the troll fleet fishing my waters, 90% are scrubbing their leads, changing zincs every year, isolating the gurdies, etc. I just can't argue with success.

[Salty]

I change the aluminum anodes every 6 months. Replace zincs every year. Scrub them up after 6 months.

[Scotthmt]

Great post, I keep reading over and over.