Compasses Magnetism Electrical Panel

[Sprite]

Has any body got a compass on the portside of the companion way. Mine is
mounted to the aft of the cabin roof. (That would be the back wall of the cabin roof, just forward of the cockpit). My electrical panel is on the same side except it is on the inside. What I would like to know is what is the best way to shield the compass from the panel.

John

[Mike Goodwin]

Move it to the STBD side!

[Sprite]

OOOKAY

John

[Bill]

Use the hole on the port side for a knot meter.

[Tony G]

Maybe one of you can substantiate this. I recall reading, and I can't remember where, that one should twist the wires around each other when wiring a boat. That way they 'cancel out' or shield the rest of the electrical components from interference caused by electricity flowing through the power feeds.

Anybody else hear of this? Did I imagine the whole thing? :confused:Would it even apply to a situation like this where you have terminals or a buss bar in a row?

[CapnK]

Tony -

Don Casey, in his great (for electrically challenged people like me) "Sailboat Electrics Simplified", says to twist wires whenever you are running a pair to cut down on stray fields.

But I think that has more to do with RF interference than with magnetism.

Compass next to electrical box = Bad. I don't know if you even could shield it, at least properly & without a lot of fuss. Easier to move it and put a knotmeter or depth gauge there. Katie's compass is mounted on it's own companionway drop board, which is still too close to the electrical stuff IMO. Wouldn't the turning on of circuits create magnetic fields, thus making it impossible to properly swing the compass? Unless you were to keep track of all the possible deviations for every possible switch setting. On Katie, those 5 switches would make for how many different possibles? I'm math challenged, too, but it's too many more than I'd care to keep track of...

Compasses are solitary instruments which need, even demand, their own space. :D

[eric (deceased)]

Dont Keep It Near Speakers,microphones And Ferrous Metals And The Like.3 Or 4 Feet Away And Any Stray Currents From Electrical Feilds Wont Be Enough For You To Tell The Difference.besides Most People Cant Hold A Course Within 5 Or Ten Degrees Continuosly Especially In A Quartering Sea.When running downwind on starcrest under twin headsails even with the monitor vane steering,it fishtailed 15 -20 degrees each way.and now with the advent of gps all my course headings are measured in true headings.besides,dont you know that DEAD MEN REALLY CANT VOTE TWICE????AND TIMID VIRGINS DONT MAKE DULL COMPANIONS.....(A REAL NAVIGATOR KNOWS WHAT THAT MEANS)

[Mike Goodwin]

............If you add whiskey .
My Grandad would always add that to that little memory aid .

Dead Men Can't Vote Twice, the "really" confuses the issue and has no place or column .

Also heard ;
Dead Men Can't Touch Virgins
Dead Men Can't tickle Virgins
Two Virgins Did Call Me

And after much rum;

Dead Virgins Can't Trust Most ................Men

You see folks the secret here is in the letters T,V,M,C, D and how it all relates to compasses and Navigating .

[Sprite]

I thought if you twisted the wires the field would cancel. To clarify another
point. My compass was mounted on a block of wood which then was screwed
into the aft portside wall of the cabin. So there is wood plus the wall itself blocking the fuse box is this adequate shielding. Does anyone know whether
there are marine junction boxes available anywhere?


John

[Mike Goodwin]

Every decent marine store carries them and some of the indecent ones too .

[Sprite]

I checked out West's but did not see them any suggestions.

John :confused:

[Bill]

I checked out West's but did not see them any suggestions. :confused:

Check out Defender's panels:

http://www.defender.com/category.jsp?path=-1|328&id=299263

[Jack]

............If you add whiskey .
My Grandad would always add that to that little memory aid .

Dead Men Can't Vote Twice, the "really" confuses the issue and has no place or column .

Also heard ;
Dead Men Can't Touch Virgins
Dead Men Can't tickle Virgins
Two Virgins Did Call Me

And after much rum;

Dead Virgins Can't Trust Most ................Men

You see folks the secret here is in the letters T,V,M,C, D and how it all relates to compasses and Navigating .

These memory aids are to remember how to convert from true to magnetic compass readings. Unless you have a gyro compass onboard, they are just ways to sound salty. They are cool though.

[Theis]

Twisting wires does cancel out the electromagnetic field. with regard to the illuminating light (assuming you have one) it is particularly important that the wires leading to the light are twisted.

What you should be concerned with is the electromagnetic field (which the twisted pair cancels out. Electromagnetism and magnetism are the same. This has nothing to do with RF radiation.

My suggestion is that you set the compass to go each of the four ways, and then turn on the switches, one by one, and see if any of them make any difference. If not, you are in good shape. If they all do, you are in terrible shape, and if only a couple do, you can do more to twist wires in the box, or alternatively, not turn on those switches.

Keep in mind that it is the flowing current that creates electromagnetic fields, not voltage. Also, the strength of the electromagnetic field is a function of the amount of current, and is not a function of the the voltage. No current flowing, no electromagnetic field.

Hope this helps.

[Sprite]

Theis,

That is something Im glad you brought up. The wires to the socket for the light
to illuminate the compass weren't twisted. I pulled it out because it was completely corroded. I bought a new perko socket to replace it. Now I will twist the new wire.

Thanks

John

[Theis]

I had somewhat a similar experience, even though my compass is mounted on the starboard side.

The manufacturer blamed it on other "iron" in the vicinity - up to two feet or more away. That took in the fire extinguisher over the counter (although I believe that is all aluminum), perhaps the outboard motor (although that too is also mostly and perhaps all aluminum, and the two anchors at the bottom of the starboard lazarette, bottle caps on the beer in the icebox (although I think they two are mostly aluminum as well) and who knows what else.

After painstakingly surveying the area, I came to the conclusion the manufacturer didn't have clue what it was talking about and had given me a cop out answer to get rid of me as an inquiry.

The issue did get resolved but not because of anything the manufacturer's told me, as I recall.

[CapnK]

I saw an interesting mount on a Whidby 30, a Canadian-built Alberg-drawn boat that came through the marina a few weeks back. I believe it was built into the boat by the manufacturer.

Kind of hard to describe, it was in the middle of the upper aft edge of the bridgedeck. Imagine if you put a box against the bridgedeck there *on the inside of the boat*, and then removed the top and aft parts of that box, so that you'd be looking into the box if you were in the cockpit. The compass was mounted there.

I can draw it, if anyone is interested and my description is as confusing to you as it is to me. :)

In that spot it would be away from any electronics you mounted internally or externally on the after part of the doghouse.

[ebb]

Kurt,
Geoff has his up there at the end of the seahood, tucked in under the dodger.
It definitely would be best to have only the compass there and place the other readouts on the sides of the companionway.

338 is going to have a Contest 130 over the hatch. It's big, over 5", but actually less bulky than the Contest 100. Gonna look like the eyeball of the Cyclops sitting there. Plastimo is non-repairable, but has a five year warranty. It is imco fine looking and absolutely the best direct reading (conical card) 'steering' compass out there. Haven't sailed with one. Yet.

If there's a problem with this, it is the size of the compass and perhaps the fairing around the compass you have to build. And the lead of the nightlight wire. But at the end of the seahood there it would be designed as a splash dash :rolleyes: with fastenings for the bottom of the dodger.

This compass with its lubber lines would make it real easy to read anywhere in the cockpit. Unavoidable, I think. Probably see the numbers from out in the trailing dinghy. Mounted high up, on the centerline and protected from the elements by design of the dash and by a hard or soft dodger the compass is exactly where it should have been all along.