View Poll Results: What is the optimal method for joining untinned copper wires on a boat?

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  • Chocolate box connector - untreated copper ends to wires

    4 3.13%
  • Tin the ends, then use a chocolate box connector

    2 1.56%
  • Crimp connectors - untreated copper ends

    21 16.41%
  • Crimp connectors - tinned ends

    12 9.38%
  • Waterproof junction box

    3 2.34%
  • Soldered joints protected by heat shrink

    79 61.72%
  • Chocolate/junction box set in epoxy

    0 0%
  • Other - please specify

    7 5.47%
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  1. #11
    Coaster is offline Registered User
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    There is no one optimal method. In each case the right choice will depend on location, size and type of wire, size and type of boat, required durability and other factors.

    For example joints in permanent external lighting cabling on a 30' seagoing cruising sailing boat will be best dealt with differently to a temporary CD player connection inside a 60' inland waterways boat.

    I find it hard to understand the rationale for tinning the ends of copper wire before making a crimped or other mechanical connection. Presumably the intention is to deter corrosion. But the tinning only protects the part of the wire from which insulation sheathing has been stripped. Moisture and oxygen will still cause the copper to corrode in the unstripped part of the cable adjacent to the joint. That's why I use tinned cable for most of my wiring.

    Of course, adhesive heat shrink can be used to protect the joint, using different sizes as necessary to step up or down to ensure proper sealing where there is large variation in diameter. But if heat shrink is used properly there seems to be no good reason for tinning the end of otherwise untinned wire.

  2. #12
    Scotty_Tradewind's Avatar
    Scotty_Tradewind is offline Registered User
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    When an apprentice in the 60's, we were encouraged to wire anything that may vibrate with a single coil/loop of wire just after the connection and before any loom. This I suppose was an attempt to get the loop to absorb some of the vibration.
    I must admit that in some of my recent soldered connections I've failed to do that.

    Quote/Coaster....But if heat shrink is used properly there seems to be no good reason for tinning the end of otherwise untinned wire. ....end Quote
    Doesnt a solder tinned end 'grip' better in a connection and prevent some of the cabling from fracturing when tightened in certaian connectors?

    Danny Jo.....sounds a dream boat?
    Last edited by Scotty_Tradewind; 09-09-10 at 10:59.
    You never get to where you want to go if you only travel on sunny days.

  3. #13
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    I voted soldered joint but I would say it depends on whether you would need to undo the connection again if so I would solder the ends and use a choc box. Great for future testing and easily replaced if need be, though I've never had to.
    Last edited by Spyro; 09-09-10 at 11:01.

  4. #14
    Coaster is offline Registered User
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    Quote Originally Posted by Scotty_Twister View Post
    Doesnt a solder tinned end 'grip' better in a connection and prevent some of the cabling from fracturing when tightened in certaian connectors?
    Good point.

    When putting very small wires into screw-type connectors I twist the exposed strands then bend the end over to double the cross section. That arrangement seems to hold better. Is there a downside to that arrangement?

  5. #15
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    Quote Originally Posted by Coaster View Post
    I find it hard to understand the rationale for tinning the ends of copper wire before making a crimped or other mechanical connection. Presumably the intention is to deter corrosion. But the tinning only protects the part of the wire from which insulation sheathing has been stripped. Moisture and oxygen will still cause the copper to corrode in the unstripped part of the cable adjacent to the joint. That's why I use tinned cable for most of my wiring.
    The intention is partly to deter corrosion, but I wouldn't expect it to be particularly effective in conditions severe enough to corrode right through the adjacent unprotected copper wire. Rather, I am concerned about an increase in resistance due to build-up of an oxide layer between the contact surfaces. The second reason for tinning the ends with solder before making a chocolate box joint is to increase the rigidity of the wire in the terminal - then, when you screw the connector up tight it creates a dimple and makes it much harder to pull out. On the other hand, solder-tinning the ends before crimping on a connector may cause more problems than it cures, because perhaps (and I speculate here) crimping may work better if the substrate conforms to the shape of the crimp.

    I agree that pre-tinned wire is the best option. Pre-tinned wire and the sort of chocolate box connector that uses tinned brass (or similar) with a plate between the screw and the contact point takes a lot of beating. But this thread is about the best way to join copper cable that is not pre-tinned. There is a place for non-pre-tinned wire on boats, I think, unless you want to spend loads of money when running 12v supply cables around the boat - to the masthead light, the fridge, the hydraulic pump for the autopilot, etc.
    Last edited by Danny Jo; 09-09-10 at 11:36.

  6. #16
    markdj is offline Registered User
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    Soldering the ends before crimping heats the outer plastic sheath which in turn melts slightly causing a better seal to the untinned copper and crimping with a ratchet crimper is a very strong joint. Preferable to use tinned cable of course which is cheap from furneaux riddall.

  7. #17
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    Quote Originally Posted by markdj View Post
    Soldering the ends before crimping heats the outer plastic sheath which in turn melts slightly causing a better seal to the untinned copper and crimping with a ratchet crimper is a very strong joint. Preferable to use tinned cable of course which is cheap from furneaux riddall.
    Thanks for the name - http://www.furneauxriddall.com/shop/index.html - now bookmarked.

    It's interesting that their price for tinned cable is only approximately 10% more than for untinned. When I think of the time I have spent tinning ends, I am forced to conclude that using untinned cable may be a false economy.

  8. #18
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    The most important things to me , after the integrity of the initial joint are to keep it sealed to prevent oxidation and water / moisture ingress, and to be able to re-make or at least inspect the joint at some time in the future. All joints are high on the suspect list when fault finding, so if it's totally sealed in resin or something you just don't know what's going on underneath.

    So whether I've crimped or chocolate boxed it, I always tape it up tight with insulating tape afterwards. I reckon heat shrink would be equally as good or better. The other advantage is that it provides additional support to the joint and prevents movement or fatiguing, hence improving reliability that way too.

  9. #19
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    Quote Originally Posted by Trundlebug View Post
    So whether I've crimped or chocolate boxed it, I always tape it up tight with insulating tape afterwards. I reckon heat shrink would be equally as good or better.
    I have two issues with insulating tape. Firstly it's messy and a pig to remove. Secondly it's ugly (and might make a future potential buyer/surveyor surmise, albeit correctly, that an amateur had been at work).

    The main limitation with heat shrink tubing is that it will only reduce it's diameter by about 60-70%. So if it's big enough to go over the choc box, it'll be too big to make a good seal on the cable.

    I quite like http://www.furneauxriddall.com/shop/...ink_Butts.html, but they are quite pricey.

  10. #20
    Ubergeekian's Avatar
    Ubergeekian is offline Registered User
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    Quote Originally Posted by markdj View Post
    Soldering the ends before crimping heats the outer plastic sheath which in turn melts slightly causing a better seal to the untinned copper and crimping with a ratchet crimper is a very strong joint. Preferable to use tinned cable of course which is cheap from furneaux riddall.
    Aluminium crimps to copper wire, if properly done, form a cold welded intermetallic bond between the two metals. In other words they aren't just touching, but form a continuous metallic structure.

    Does this happen when there's tin in the way? I dunno.

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