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-   -   Advice, please on crimping wire connections... (http://www.sailnet.com/forums/gear-maintenance/21678-advice-please-crimping-wire-connections.html)

FrankLanger 08-18-2006 12:36 PM

Advice, please on crimping wire connections...
 
I have to make some wire connections this weekend on my boat, and think I know what I'm doing, but would appreciate confirmation or correction. The wires are to the bilge pump, in an inside quarterberth locker. I have bought the right sleeve (blue) for the size 14 wires, and have a crimping tool. I am planning to cut about 3/8" of the insulation off the wire ends then twist a bit to avoid a stray thread of wire, then insert as far as it will go into the sleeve, then squeeze the heck out of it with the crimping tool, then test by pulling firmly on the wire to see if it will hold.

I don't have a soldering iron, and have heard mixed opinions on whether soldering is good on a boat (better connection, but more brittle/prone to breaking with vibration, acid in solder flux not good, etc.).

In one case, I have to add two wires to one end of the sleeve, and only one wire to the other end of the sleeve--any advice? Do I use a larger sleeve to accommodate the two wires and just squeeze harder for the single wire on the other end, or try to force the two wires into the smaller sleeve?

Thanks for any advice--I do need my bilge pump to work.

Frank.

knothead 08-18-2006 12:44 PM

You may want to use heat-shrink butt connectors. Or at least use a piece of shrink tubing over the butt connectors you have already. Especially if the wires are in the bilge.

dave.verry 08-18-2006 02:18 PM

Crimping wire is a fast reliable way to put a removable connection on a wire, or join two wires together. The goal is to squeeze the barrel of the crimp connector around the wire, leaving a gas tight joint.

Unfortunately, these connections are often done incorrectly or using the wrong tools and leave a connection that can corrode and fail in a moist environment.

The first item is to use the correct tool. Unless you have done a lot of crimp connections the tool should have a ratchet to prevent you from opening the jaws until enough force, or a small enough diameter, is put on the connection. Most tools you can buy from the local hardware store are just cheep toys and will not do the job.

Some try to get around this by soldering the joint. This leaves the end of the wire leaving the crimp barrel brittle and susceptible to breakage. Also a bad crimp leaves voids that trap solder flux. Solder flux is an agent, usually in the solder, that cleans the metal surface to allow the solder to stick. What’s wrong with that, you ask. Flux is a corrosive and will degrade the joint over time, exactly what soldering was supposed to prevent. So the long and short, never solder crimp connections.

One option I have used on large crimp connections is to coat the inside of the connector barrel with an anti oxidation compound such as No-OX. This compound is made for electrical connections and can sometimes protect marginal joints from oxidizing and failing.

Ok, so you have the correct tool and you need to crimp more then one wire in the barrel. Two wires having the same diameter as one of another gauge can be crimped into a connector of the larger gauge. Two 14 AWG have the same diameter as an 8 AWG wire but might fit into a 10 AWG connector, or might not, depends on the stranding. But as long as the wire combination fits into the barrel AND the crimper for the gauge of the connector, not the wire, is used, the crimp should be good.

Let me put in a small word or two on stripping wire. Strip wire so there are no nicks or broken strands. A thermal stripper, one that melts off the PVC insulator is the only sure way of doing this, but a good mechanical stripper in good repair will also do good strips. Avoid the combination stripper/crimper as it will do neither well. I also strip one size larger then the wire, i.e. use the 12 AWG position to strip 14 AWG wire, to help prevent nicks. Inspect the strip after you do in, if there are broken strands at the point of the strip, do it again.

The strip length of the wire depends on the connector barrel length. The wire should go completely through the barrel and be visible on the non-insertion side of connector barrel. Don’t leave too much wire since it might interfere with the screw or fast-on and don’t leave to little. On a good joint the wire insulation should touch or almost touch the barrel, or be covered by the connectors insulator.

Some crimp connector barrels (the good ones) don’t have a seam in the barrel, some do. If there is a seam, make sure the crimp nipple of the tool (if your tool has one) compresses the side of the barrel WITHOUT the seam. The other side should have a concave area to protect the seam from opening. Doing it the other way will leave your joints loose and prone to failure.

One last thing I do is to use heat-shrink on each connection. Put a length of heat-shrink tubing on the wire(s) before the crimp is made and shrink the tubing over the connector barrel and wire. I like to have the tubing at least twice as long as the connector barrel to act like a small strain relief on the wire to help eliminate sharp bends just at the barrel and thus, wire strand breakage. Since I always do this, I prefer the non-insulate crimp connectors to make it easier. These non-insulated types also make it easy to inspect the crimp after it is done. It’s just as easy t place heat-shrink over insulated connectors, just make sure the tubing will go over the insulator, not just the wire.

FrankLanger 08-18-2006 03:08 PM

Thanks for your detailed description!
Frank.

sailingdog 08-19-2006 12:20 AM

Generally, you don't want to cut the insulation to expose more than 1/32" beyond the crimping barrel of the connector.

Also, in a marine environment, you really need to use ADHESIVE-LINED heat shrink tubing, not plain heat shrink tubing.

jorjo 08-19-2006 11:55 AM

DO NOT CRIMP !

End of story, crimping on a boat is a no no. crimping to a bilge pump is lunacy.

Crimping is a cheap and cheerfull method of making a terminal connection.

Solder. JUST LIKE the MANUFACTURER OF YOUR BILGE PUMP did when making it.

There is NO argument between solder or crimp. There is nothing brittle about a soldered joint IF Its been made correctly and the cables dressed accordingly (hellerman sleeved etc)

When it comes to critical systems YOU solder OR you get someone in who knows what they are doing to solder it for you.

DICKWATERS 08-19-2006 12:40 PM

ABYC Standards

11.16.3.7. Solder shall not be the sole means of
mechanical connection in any circuit. If soldered, the
connection shall be so located or supported as to
minimize flexing of the conductor where the solder
changes the flexible conductor into a solid conductor.
EXCEPTION: Battery lugs with a solder contact
length of not less than 1.5 times the diameter of the
conductor.
NOTE: When a stranded conductor is soldered, the
soldered portion of the conductor becomes a solid
strand conductor, and flexing can cause the
conductor to break at the end of the solder joint
unless adequate additional support is provided.

hellosailor 08-19-2006 12:56 PM

Frank, I'm with d.verry on this one, crimp is usually the better way to go. But offhand, I'd usually take two 14g wires and treat them as one 12g wire (just moving up one gauge size) and then crimp them in a 12g (yellow) crimp.

There ARE special crimp fittings that are actually 12g in one side and 14g or 16g in the other...but don't worry about that. Instead, use the 12g fitting to accomodate the two 14g wires. Then on the other side...either fold over the single wire, or insert a second dummy, so again you've filled the crimp fitting "mormally" with the amount of wire it expects.

The Ancor type adhesive lined shrink wrap crimp fittings are the way to go in the bilge. After heating them, they shrink down and the adhesive flows and you literally will get a waterproof connection. They also are long enough so that you can see they fit well over the insulated part of the wire, just strip enough so the bare portion fills the correct half of the crimp fitting. (Half only, it takes two crimps to seat the two wires, one from each end.)

Pulling on the crimp to test it IS the right way to do it, if you can pull it apart, it was no good anyway. Those cheap hand crimp tools (without the ratchet) can make a workable crimp if you have good hands or you test them. The $50 ratcheting tool is really better--but for one crimp I can understand not buying one.<G>

In our bilge wiring, after I made the heat-sealed crimp AND tested the pump function, I also overwrapped the splice with butyl tape, aka "self amalgamting tape" or "silicon tape" which is a rubbery tape that fuses to itself in 24 hours, forming a second waterproof coating over the splice.

Solder works...but long term testing shows it isn't the best solution even though it "seems" like it should be. Among other things it sets you up for galvanic problems because now there are more metals in the joint, unmatched, and creating a stiff point to work harden the stranded wires.

Take up whatever slack you have from the bilge pump to the splice, and try to hang/screw/whatever that joint as high up as you can. That way, even if the waterproofing fails, less chance of it getting wet.

sailingdog 08-19-2006 02:38 PM

The other real problem with soldering is that the solder moves along the wire via capilliary action and can cause the wire to become rigid...so you're defeating the purpose of getting good marine-grade wire in the first place. Where the solder creeps along the wire, it will fatigue and break much more readily than unsoldered wire of the same size and type. Also, the real problem is that the heat that can occur in a boat's electrical system can cause the solder to melt and then the wire may fall free and short out on something more dangerous...

hellosailor 08-19-2006 06:13 PM

The fatigue (hard spot) problem can be solved, and is covered in various specs that require a soldered splice to be firmly affixed to something else, i.e. with an attachment to the bulkhead or firmly taped into a wire harness so it is supported and can't flex at the solder joint.

With a crimp...I still like to do the same thing, make sure the xtra mass of the splice is attached to SOMEthing so it can't work the wires.

But on the heat...for routine connections if you can generate that much heat, you're in trouble anyway. A fuse should blow long before the solder can melt. For *cable* lugs, which are carrying high current normally and can carry 1000-4000+ amps during a short, I'll agree with you that solder melting and releasing a connection is more of a real concern. Oddly enough....in the elevator industry, where they use "the same" heavy cables and lugs, the standard used to be SOLDER into the lugs. I've used "elevator solder" and have no idea why it was supposed to be special, just proves that it takes all types, I suppose.<G>

Personally, I swage battery lug fittings--but only after I've placed solder paste ("Solder-It") inside the cable. After the swage is made, I heat the lug enough so the solder paste flows and the resin bleeds out. I'm sure that's "wrong" but in my book, it guarantees the physical crimp has been made, AND an airtight solder connection is in there as well to exclude moisture. I guess in ten or twenty more years I'll find out just how well that's been aging.<G>


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