Wiring influence on compass

[Norman Colter]

Although I'm specifically interested in my princess, This may need it's own thread.

I am using tinned wire in a paired cable. I'm hoping to cut it long, put each end into a drill chuck and give it a good twist. Being very watchful not to over twist.

Any thoughts?

Thanks, Norm

[Charlie Jones]

I only worry about twisting wires within three feet of a compass. Wires running up the mast are so far away they'd have no effect on a compass, so I wouldn't worry about those.

[PAR]

Charlie has a fair point. Low voltage wiring runs generally don't bother compasses. Large masses of metal do, but you can adjust for this in trials.

In the early days of navigation with the most primitive compasses (magnetic rock, attached to a bit of cork or wood, floating in a bucket), metal objects (mast bands, ships wheel brackets, etc.) caused many a skipper to go bald (hair pulling). In Christopher Columbus's log, during his first voyage to the new world, he noted that he had to send a sailor out on a plank, well off the side of the Santa Maria, to get an accurate heading, as a result of the metals used on the ship affecting the compass. So they've been aware of this, since at least the end of the 15th century, which is pretty amazing to me.

[Charlie Jones]

one other interesting point which really shouldn't affect any of us here ( but it might) is that a compass calibrated for the northern hemisphere won't work well way south of the equator. The "dip" angle becomes too great and the card rubs on the outside. You need it re calibrated or to carry two compasses and use the correct one as needed.

[fatehunter1972]

Norm,

Wiring will affect the compass if you are running large amounts of current through it and it is close to the compass.  Pretty well all electronic equipment stipulates a compass safe distance of 1 meter, or 3 feet.  Twist the wires and keep them away from the compass.  In reality It does not really matter if you compass is affected, i.e. has an error, as long as it is constant and you know the error.  It is the intermittent error, such as the lights on at night that induce an unknown error, that might give you a head ache, as you may not be aware of it.

without the aid of a gyrocompass it will not be easy to determine the error of your compass.  Use range lights and markers and known headings to determine the error.

Michael

[Norman Colter]

Thanks for the prompt replies. I was hoping it would be ok to run the lines up the masts without twisting. I'm only running lights. But I guess I better think about where to place a compass.

Norm

[Joe Nelson CS#35]

What happens when the magnetic poles flip?  2012 or something like that.  Coincidence or not, that coinsides with the end of the Aztec calendar.  Heard a guy on late night talk radio talking about this.  Said it will be an event rather than a process.  Ocean and atmospheric currents reversing and putting massive stress on the fault plates and expect a world wide changing event.  Even if it is not catistrophic, think of the implications of the weather and ocean currents running in reverse.  Worst thing would be your bathtub drain swirl going in the opposite direction   Makes the PNW have an offshore flow rather than onshore.  And we worry about global warming.  Sheesh.  Might be time to buy ocean propert in the new dry oregon climate.  That would also flatten out the ocean too.  Right now when we get a rare east wind, that is the calmest time to be out on the big blue.  Could change the population decities and distribution world wide???

[PAR]

3' is the default answer manufactures provide when they don't want to be making an apology about performance. In reality, 12 VDC for masthead nav lights, draw very little, (90% less if using LED's) and would need to be right next to the compass to cause a problem. Even with a set of 55 watt spreader lights you'd be safe if the light were a foot or more away. Now if you had some trolling motor leads running next to it, you'd see deflection every time you turned on the motor.

[Scott Dunsworth]

I knew metals would screw my compass readings up, but I didn't know about electric current. I am not disagreeing with any of the above comments. But why did the Richie Bulkhead compass I just installed on our Belhaven have wires for the light in the compass? Also the instructions didn't say anything about twisting wires.

Scott

[Frank Hagan]

What happens when the magnetic poles flip?  2012 or something like that.  Coincidence or not, that coinsides with the end of the Aztec calendar.  Heard a guy on late night talk radio talking about this.  Said it will be an event rather than a process.  Ocean and atmospheric currents reversing and putting massive stress on the fault plates and expect a world wide changing event.  Even if it is not catistrophic, think of the implications of the weather and ocean currents running in reverse.  Worst thing would be your bathtub drain swirl going in the opposite direction   Makes the PNW have an offshore flow rather than onshore.  And we worry about global warming.  Sheesh.  Might be time to buy ocean propert in the new dry oregon climate.  That would also flatten out the ocean too.  Right now when we get a rare east wind, that is the calmest time to be out on the big blue.  Could change the population decities and distribution world wide???

Heh ... its the sun, not the earth, that flips the magnetic poles around.  Just happened back in 2001, and will happen again in 2012.  Happens every dozen years or so.  The conspiracy guys only read the headlines and fill in the details later.  See NASAs explanation here: http://science.nasa.gov/headlines/y2001/ast15feb_1.htm

[PAR]

Scott, the compass lamp is a very low wattage, so the draw is quite low and will not affect the reading. Most have bulbs which draw a single amp or now are using LEDs which draw .01 to .02 amps. Now if you have something near by drawing big amps, then it will.

[Ken_Potts]

  Also I think the advice to twist wires is in reference to wires that are single-conductor.  Each conductor creates a magnetic field when current is flowing.  Twisting wires allows the magnetic fields in the two wires to largely cancel each other (current flowing in opposite directions in each conductor).

  Your Ritchie compass likely has wiring that is paired so there wouldn't be a need to twist.

[fatehunter1972]

3' is the default answer manufactures provide when they don't want to be making an apology about performance. In reality, 12 VDC for masthead nav lights, draw very little, (90% less if using LED's) and would need to be right next to the compass to cause a problem. Even with a set of 55 watt spreader lights you'd be safe if the light were a foot or more away. Now if you had some trolling motor leads running next to it, you'd see deflection every time you turned on the motor.

PAR,

You are absolutely correct, particularly in small boats where a little bit of error does not really matter.  Here's a story.  I was leaving Santander in northern Spain for Rotterdam in a 300' coaster.  Lost the Gyro coming out of the harbour but there was a sensor on the Magnetic compass that allowed the autopilot to work of it.  The ship yawed around a bit in the westerly swell off the Atlantic as the magnetic compass tends to be more sluggish but I was sure happy to have it!

Michael

[Greg Luckett]

Heh ... its the sun, not the earth, that flips the magnetic poles around.  Just happened back in 2001, and will happen again in 2012.  Happens every dozen years or so.  The conspiracy guys only read the headlines and fill in the details later.  See NASAs explanation here: http://science.nasa.gov/headlines/y2001/ast15feb_1.htm

Frank, I believe Joe is referring to the Earth's magnetic poles, which do flip also and are expected to again in about 4 years.  This occurs with a time periods in the thousands of years, at least 25000, and maybe more like 40 or 50 thousand....just cannot recall at the moment.  The sun has multiple magnetic fields, the size of the Earth or bigger, which are connected to other solar events, and which affect this planet.  I often wonder how it will affect things like homing pigeons, etc.  We will adapt, but the critters may not have that ability.  When I was in college in the 1960s we were discussing this event.  At that point we were unsure of when the flip would occur next, but estimated sometime in the next 500 years.  Looks like it is zeroed in now.

May I suggest splitting this part of the discussion to its own thread?  It is an interesting subject, but only slightly related to compass interference issues, and it may hijack this thread.