Sunday, March 20, 2016

50 Shades of Grey Wiring

Bondage was the first thing I thought of when I saw this. By this I don't mean with soft silk scarves, but more akin to being stuffed into an iron maiden. There is some minor good news here. These fuses would stay in place if this boat was was struck by a tsunami. The bad news should be apparent to you by now. How do you replace or even check these fuses? The answer is with difficulty and tools. There are fourteen tie wraps and 6 wire clamps securing two tiny, but important fuses.


Let's look at changing or checking these fuses. We need a screwdriver to release the clamps, and not just any old wire cutters to snip off the small tie wraps, but a smaller and sharp one. It's easier than you think to inadvertently cut or damage the wires themselves if you're not very careful.

Now imagine you have to do this in dim lighting inside a cramped console on a boat bouncing around in three foot seas with a nonoperational MFD.

Although this isn't a boat I would buy there is no denying that the fit and finish of this vessel is at a very high level. At a first glance the wiring is beautiful. Every wire is perfectly aligned. Copious quantities of tie wraps and clamps were used to secure it rigidly in place.

Unfortunately somewhere along the way OCD and anal driven appearance became more important than functionality. Can you over do wiring bondage? You betcha and it becomes more expensive, and difficult to do repairs. Trouble shooting, and chasing down wires is tedious and time consuming. Finally overly tight restraints can damage connectors and wiring over time and in some cases can create induction issues with communication cabling.

The little picture to the right is from a NASA discussion on wire distortion caused by tie wraps. Although the wire looks okay albeit bent out of shape, it has failed.

Another cause of wire distortion is bending wiring into sharp turns. This causes the outer curve of the wire to be put into tension, and inside curve goes into compression causing strands to separate. Really tight and precise bends makes the wring look chic, but it's not good technical practice. A quick rule of thumb is the wire's bend radius should be about 10 times the wire's outside diameter.

The MFD's were installed by the dealer, and I'm installing the autopilot after the fact. The builder had installed two power posts in the console. The one you can't see is on the left side of the console and it's packed with ring terminals feeding power to unidentified devices. The one on the right has only one wire attached, and that where I'm getting power for the auto pilot. Forty amps worth of power is needed.

What do I know about these posts. Zip is what I know. I don't know the power source, but I can surmise from the feed wire size it will support the load, I think, sort of. The wiring is so constrained I can't easily trace it back.

This all begs the question why a fuse block wasn't installed in the first place. A common power source location that could be easily accessed and labeled. In this scenario only one style of fuse (ATC) would be needed. As it is there's a hodgepodge mix of small ATM, regular ATC, and glass fuses of unknown sizes all aggressively tie wrap handcuffed to something.

I'm switching to another boat in which this builder has both a bondage and rubber fetish. To provide some perspective, this up tube view you're looking up at is a pull coming down from the bridge into a cabinet containing  the power panels and switching gear.

What's up with this spurted spooge stuff? This is a bone dry area. There are no fumes other than stale coaming air from the bridge. It didn't completely seal anything, but it did a great job of making it very difficult to pull additional wires to the panel.

It gets worse, its nearly four feet away from me. This means I can't reach it from below. Using some interesting and pejorative jargon, coupled with a dowel being shoved into the orifice from up top resulted in a portion of the goo being displaced enough allowing a few wires to sneak through.

For the record, I think neat and organized wiring reflects the skills and pride of the installers and builders. But it's easy to get carried away. Because it looks good doesn't automatically imply that it's great work. You can have too much of a good thing. You want it impress me do a reasonably neat professional job. Put labels on each end of the wires, and provide a real wiring diagram. I haven't seen one of these delivered with most boats in years that meant anything. Don't make me find my riding crop and teach you a lesson.

5 comments:

  1. Yes.. I was worried about you Mr. Bill.. Glad to see your back. CHEERS!

    ReplyDelete
  2. We missed you for over a month Bill... I was starting to show signs of withdrawal.

    ReplyDelete
  3. Welcome back, Bill! I hate small tubular fuses - finicky things, fragile, and sensitive to positioning (in smaller sizes) for their performance. AGC is the way to go if you gotta have fuses (though the mini versions are OK for small stuff like you have here). Preaching to the choir, I know..;)
    Our Tayana 48 has every wire labelled with a number on both ends) - but there is no vestige of a diagram or list of what number goes to what. Maybe the OO had it and lost it, I don't know.

    ReplyDelete
  4. Things were better before Panduit's patent expired, when tie wraps cost $0.25 each in 1975 dollars.

    ReplyDelete