Electrical problem corroding massive holes into anchor!

Discussion in 'OnBoard Electronics & Controls' started by DennisRB, Nov 14, 2010.

  1. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    We fitted a large bugle anchor to my mates Duncanson 35 before our trip to Brisbane from Adelaide. We are half way now. I'm not sure the boat had seen much rough weather for a long time, but in short the anchor well filled up to the level of the internal hatch spilling muddy water into my bed. To my surprise I could not find a drain hole!

    Now the whole windlass has a green corrosion look to it and when you touch it or the bow railing you get a tingle from the batteries. I think it got salt water splashed all over the internals when the anchor well filled up. Where the anchor touches the anchor roller the stainless fitting almost melted a hole through the anchor from electrolysis in one week.

    I took a look at the wiring and it appears they have run 12V+ straight to the winch then the foot switch is joined on the cable which joins the earth strap (which runs through the bilge essentially joining the negative terminal of the batteries to sea water). I'm not sure if this is the way its usually done. I have disconnected the positive cable for now.

    The way it is, the windlass always has a positive at the motor, and the negative is made when you hit the foot switch, but the chain also has reference to negative as it is sitting on a uninsulated copper earth strap. So I think the salt water or other prob as allowing some current to flow from the constant positive through the earthed chain or bow roller etc. Anyhow I was thinking of connecting the negative straight up to the winch and fitting the switch to the positive so that the winch does not have a positive reference until you hit the foot switch?

    Good or bad idea?
     
  2. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    Anyway. I just swapped it over. Seems to have fixed the prob. I was just wondering if anyone had any ideas why it might have been like that? Or what about a uninsulated earth strap for terminating all negatives to?
     
  3. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    This sounds like an installer screwed up. The switch should always be in the + side of a line, as early in the circuit as possible, to prevent exacally this type of problem. I would contact the installer and demand compensation for any damage.
     
  4. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    The boat was purchased as is recently by my mate. Just about everything on it is back to front.
     
  5. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    This must be a very peculiar boat, we all know an anchor well without drain quickly turns into an aquarium. Even without electricity being present, that is asking for trouble.

    I can understand the reasoning for switching the negative wire: somebody had doubts about connecting a switch on a wet deck to 12V. But it is still wrong of course.
     
  6. DennisRB
    Joined: Sep 2004
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    Location: Brisbane

    DennisRB Senior Member

    It filled up to the interior door above my pillow where it drained into my birth. I found this out after 2 days of sailing to windward (where I slept in another crew members bunk while he was on watch). As anyone that has done ocean sailing knows its pretty uncomfortable to sleep in the front when going to windward through chop. The well had all sorts of crap in it and i ended up with mud on my bed!

    I cleaned it all out and I could not find a drain hole. I think the well goes under the waterline. The Duncanson 35 does not have a lot of freeboard. It has a separate rope locker to one side of the well and it has a drain hole. I think there is meant to be an automatic bilge pump that drains to the rope well or something?

    Re the 12V on deck. There was still a measured 12V at the switch. There always will be. Its just that the 12v gets there through the electric motor rather than right from the battery. I think someone just screwed up. The electric motor also has the brush cover missing so all the commutator and brush gear was free to get soaked when the well filled up and splashed around.

    What are peoples thoughts on a bare earth system (similar to a car) on boats?
     
  7. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Best way to solve the anchor winch problem is to remove all electricity to the winch by using a two pole solenoid. Relay. Many winches are set up that way. The typical 2 pole relay, breaking plus and minus, I see is make by Albright.

    www.albrightinternational.com/
     
  8. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    ...no way that you can run what you call a bare earth system on a boat...No hull earth bonding should ever be a source of electrical current, you will destroy the skin fittings and all underwater metals very fast. The battery negatives do in fact also join the boats bonding system, but they are not current carrying wires.
    Install a battery switch at the battery source for the anchor winch, and also a fuse as close to the batteries as possible too. That way you only have power to the winch when needed.
     

  9. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    I agree with landlubber and other posters. You can not bare earth a DC electrical system on a boat. It will lead to all kinds of Electrical and galvanic corrosion problems. Moving the switch was a good move. Whoever installed this did not know what they were doing. 12V may not zap you to death but it can cause serious problems with all the metal fittings on your boat that are in contact with water. Wires should never be in the bilge. Again this leads to galvanic corrosion and is really bad for the wire it self. I would suggest that when you get to port you rewire it. And you need a cover for the brushes. You are getting water inside the motor which can't be good for it.
     
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