Two bits of bad design.

[Norman_E]

I have just had to do some work on the boat and found two horrors.

Number One: I have two large filters, one filters the grey water from the galley sinks to prevent debris entering the pump that directs the water into the grey water holding tank. The other filters seawater to protect the fridge compressor cooling pump. Both have clear plastic domes over the stainless steel mesh and cream plastic bodies. They bear the logo of an American maker, but are made in China. They also say, not for use with alcohol. They should say not for use with water, because both proved hard to unscrew to clean the mesh, and completely impossible to screw back together. The reason: The cream plastic swells when wet! After two days drying out the diameter of the male threaded cream part has reduced by 2mm, and the two parts can now just be screwed together.

Number Two: The Vetus bow-thruster worked intermittently during our month long cruise, and finally failed altogether. The Reason: The Vetus supplied cables to the remote switch are made of domestic copper wire which has all gone black and no longer makes good contact at any of its connections. With 13.28 volts at the thruster end, I measured 10.9 volts at the helm switch end of the cable and less than one volt at the switch itself.
I spent a wearisome day getting some proper tinned cable through various ducts to get it working again. Really Vetus should no better than to supply ordinary copper four core cable.

 

[AllanG]

Regarding your bow thruster cable, I very much doubt if Vetus actually supplied your cable, more likely, this was used by the company that fitted your bow thruster.

 

[Norman_E]

The cable has Vetus lables on it! It is fitted with 4 pin plugs and the online page for the current model shows the very same cable and plugs, so definitely Vetus supplied. https://www.vetus.com/en/vetus-connection-cable-control-panel-bow-thruster-10-meter.html

 

[lw395]

Proper electrical contacts are not reliant on plating. If the copper wire has corroded under the connections, they were never good enough. Were the connections crimps or what?

 

[Norman_E]

Mostly crimps, but that is irrelevant because the whole length of cable has turned black. Despite careful cleaning of the ends after cutting them back by a foot at the helm end to try and find untarnished copper I still had a voltage drop of over two volts due to the corroded wire and the impossibility of getting a clean connection.
Marine cable should be tinned, not just plain copper. The stuff supplied by Vetus is just domestic four core wire as used in central heating controls, with Vetus' own plugs added and is not suitable for marine use particularly connected to a device that has perforce to be fitted into the bilge.

 

[lw395]

The problem is not so much the wire, as the connectors.
These things are just not intended for anything other than a dry environment.
There are plenty of connector which have a backshell sealed to the cable outer sheath.
With what you have, all you can do is either keep it dry or rely on some kind of grease/oil.
Plating will help, but it's still poor.

 

[Norman_E]

I prefer soldered joints to crimps, but in some places its not possible, and I have never had a crimped joint fail using proper tinned cable because the tin does not corrode like copper.
EDIT. I did put Vaseline on some joints made with copper wire that came out of an old depth transducer, but I am not sure if it helped or not, because the wires were already black and probably only made contact where I had scraped them. Once copper wire goes black you cannot solder it. I scrapped that system a few years ago when the LCD screens in the displays failed.

 

[jamie N]

On many ROV, the cabling is just plain copper. The cable will only turn black with moisture and current present. You might elect to use only stainless steel cabling perhaps?

 

[Norman_E]

Hmmm... Moisture & current present? That would be just about any bit of electric cable on a yacht!

Of course the worst and most stupid bit of design is the filters where normal use to filter water makes it impossible to clean the filter mesh without waiting two days for the filter body to dry out and shrink back to size before re-assembly, even if you can actually unscrew the dome in the first place.

 

[ronsurf]

Regarding the filters - it could be argued that the plastic swelling when it's wet ensures it won't leak, which then makes it a clever design.

However, it is American designed.

 

[jamie N]

Hmmm... Moisture & current present? That would be just about any bit of electric cable on a yacht!

Of course the worst and most stupid bit of design is the filters where normal use to filter water makes it impossible to clean the filter mesh without waiting two days for the filter body to dry out and shrink back to size before re-assembly, even if you can actually unscrew the dome in the first place.

Absolutely right; that's why we insulate the cables!!
Seriously, is there another supplier of the filter dome, which is more stable, or even to make your own using 'Polymorph'? I'm unaware of the size of course.

 

[Norman_E]

Absolutely right; that's why we insulate the cables!!
Seriously, is there another supplier of the filter dome, which is more stable, or even to make your own using 'Polymorph'? I'm unaware of the size of course.

The dome is fine, made of clear plastic that seems dimension-ally stable. Its the much more complicated part with the inlet and outlet ports that swells up. I sent the filters home with my wife when she flew back, and will be contacting the U.S. "manufacturers" who put their name onto Chinese rubbish when I return. I suspect the Chinese factory just changed the plastic specification to suit what the had, or what was cheapest.