Question about physical wiring arrangements

I was rather lucky this past weekend to see two very different approaches to wiring.

The first boat was having a python like wiring loom fitted. It was a thick bundle of wires built outside of the boat. Various smaller bundles and even single pairs of wires of various lengths and colours dangled from the length of the loom.

It looked impressive and I watched amazed for all of the half hour it took two men to fit it to the boat. I kid you not, about a half hour after the loom disappeared down below, they were testing the anchor winch.

The second boat was impressive for all together different reasons. I was invited aboard to get a good look at what this builder was doing. His boat had all positive supply wires to various devices running fore and aft from the switch panel along the left side of the boat. Probably because the nav station where the switch panel was located happened to be to the left.

Insulation colour and little coded tags at intervals could be looked up to identify the wires use and purpose.

All the negative return lines ran along the right side of the boat.

I wonder which might be the better arrangement as both are elegant but very different?

 

A wiring bundle is really only practicle with a production boat. Normally you make a jig to form the bundle into the correct shape.

Seperating positive from negative has the advantage of minimizing fire risk. Positive cant touch negative.. Copper is expensive . If extra meters of wire are needed for this layout, its an issue. Always separate AC for DC in bundles.

Colour code is OK. I prefer numbered wire and multicore cables. Most of the wiring in a boat are positive control wires.

Marine grade wire is hard to find and expensive. Now is the time to look. Ask a professional electrical engineering company . Use professional components...juction boxs, terminal strips.... The electric company will have a catalouge. When you see the price you may modify your technique.

Very good idea to examine the system used by quality production boats. They dont fool around and choose the best bang for the buck.

Always lay additional cables and leave them blank....particularly nav station service. You will be happy in the future when you add new gear. I recently added an anchor chain counter to a boat. It took 9 hours to route one cable.

 

The wiring loom solution requires a detailed design stage and is seldom used for a single boat. A lot of wires are added for functions that can be implemented later and may in fact never be used at all. Inevitably sooner or later a new application emerges requiring a special cable that is not part of the loom so it has to be added.
The good thing is that there is a complete set of drawings.
What you saw was probably just the DC wiring, no sane designer would mix AC and DC wiring in one loom.

The guys who keep positive and negative wiring on opposite sides make one grave mistake they will later regret. They created a large single turn coil that offsets any type of compass and cannot be compensated because the deviation depends on the current flowing through the loop. It also causes electrical noise to be radiated freely.

 

A technically correct wiring diagram is critical. It will last the life of the boat.

The way I do it is to first gather all electrical diagrams for your choosen systems.

I then make a crude sketch of the systems layout, with measurements of the cable runs , then hand this crude
wiring diagram and equipment wiring diagrams over to a professional to proof read and make technically correct.

You then electrify the boat with this technically correct diagram, making notes...as designed, as built..... and return it to the Pro for an as built diagram

 

I wondered if that was the case. It looks tidy, but I'd rather not build a jig just to construct a loom.

I've found marine grade coloured wire readily available, but costly, just as you suggest. Oddly, wire, with major and minor colour striping does not seem to be available here.

I quite like the Blue Sea Systems 360 panel and wiring stuff. It's tidy, cleverly designed and well thought out.

Hmm, a very good idea, that would not have occurred to me. A few extra unused cable pairs won't bankrupt me.

 

For wire and components stay away from the Yacht stuff. Expensive and limited.

Contact an eletrical engineering company. The type of company who electrifies commercial craft. They can give you sources

 

Looms are nice, but only practical as noted. Wiring up a boat isn't hard, if you have a clue. You do one circuit at a time, pulling wire as you go, maybe bundling them as you complete sections. Some forethought and planning goes a long way, such as wire chases and access ways, though this usually isn't something seen in back yard builds.

 

Precisely why I had a look around and asked these questions.

I suppose my vanity insists that at some future time the current owner or his trades people take a good look and be impressed.

I've printed large scale pages of the relevant drawings upon which I can lay lines and take measurements.

Likewise I did the same for the electrician that will be installing the AC system and battery chargers.

Just a matter of now how best to arrange the wiring.

I visited a gentleman yesterday who had an aluminium sports fishing boat hull built by pro's which he then finished himself.

On his back fence was a peg board arrangements of sorts. He build his wiring loom vertically upon the face of the fence. I smart idea, I thought. Perhaps a loom is not difficult as I first thought. He went on to explain that he penciled out upon the plans his wiring arrangement. He then lay this on the fence and ran wires held in place with dowels.

His only difficulty was the size of through bulkhead holes which he said made feeding the loom through them, at times frustratingly difficult.

I'm better informed but still have no clearly superior way of going about this task.

 

Wires and pipework, on a pro build boat, pass thru bulkhead waterproof and chafe proof glands. Ask your supplier.

 

Wires are layed flat in a tray and secured every 150mm with a ss tarap that is molded around the wires with a hammer stiking a soft former...wood or plastic.

These flat run penatrate the bulhead thru a rectangular thru bulkhead gland. This gland is then packed with rubber shims.

 

I think making a loom is a waste of time on a one off build. If you know what you need and where it needs to be, you just pull the wires through, cut to length, attach the terminals and call it a day. It seems a waste of time to fool with it twice. For example, you might need a bow light, cabin light(s), speaker leads and a windlass feed in the forward sections. Knowing this you pull (from a spool) the 16/2 duplex, plus whatever else the devices might call for and put ends on each as the devices require. You can "loom" them in a convoluted sheath or use an auto looming wrap or simply zip tie them or place them in a conduit or under clamps. The device end is attached, so just lead them back to where they need to be (panel, instrument cluster, whatever) and clip the ends to fit. Personally, I like to work the other way around, from the panel out to the devices, so the first fittings installed are at the panel (switches, controls, etc.), then the wires are fed to their respective locations, through whatever means or conveyance. Then these are cut to length and the fittings attached.

When you have a bunch of wires, all going to the same place, such as an engine box or splash well, then a loom of sorts can be made, but it's still just a bundle of wires, cut a little long, then custom fitted at each end, literally "on site" as required. Under the instrument panel you can show some organization and planning, but this is really just a personal thing.

Again it would be nice to have enough forethought and planning to figure all this out in advance, but frankly, there's enough stuff to do, on the average back yard build that this level of prep is way over the top. This said, I would look at situations where you might need 5 - 16's, 4 - 12's, 6 - 14's, all in the same location. It would make sense to cut up and bundle this combination, say a foot too long on each end, just so you don't have to pull 15 wires separately, but this is about as far as you might want to take it. In this vain, you could take it slightly further, by putting the fittings on one end of this bundle and looming it loosely. When you've installed the fittings at one end, you can pull the slack to the other end and tighten up your looming, with the advantage of having a little extra wire to clip off, if necessary.

Lastly, building a loom suggests you're absolutely sure you know how everything is going to run, which I find an impractical proposition. I've done countless wiring jobs and I've "changed my mind" as to the way I wired things up on just about every job. Simply put, the finished job ended up being different compared to how I envisioned it initially. You're ready made loom doesn't permit this and there's nothing that'll piss you off more then coming up 6" short on something, because you forgot to account for something, while making up the loom.

 

Since I'm an amateur like you James, who's actually doing this I thought I'd add some thoughts.

1. I enjoy planning and installing my electrical system but only work on it for a few hours on any one day. I find that if you do a little and walk away you'll think about things and perhaps make positive adjustments going forward that you would not think of if you just did it all at once. I'm sure you have lots to do aside from electrical, take time to "ponder".

2. Access. For me this is as important as the wiring itself. Always consider what you will do if maintenance is required. I'm not a big fan of disconnects but find them a necessary evil, especially with respect to things like navigation lights where the manufacturer makes a beautiful light and ships it with a pig tail maybe 20 centimeters long.

Think....what will I do if I have to replace or repair? Can I get at this light, fan or whatever? An inspection port or even a hatch in a strategic area might be a little extra work now but it could save you a lot of headaches later.

3. AC is convenient and now is the time to install it. I'm doing a small cruiser only 27' with 10.5' beam. I've installed AC outlets on the flybridge, the rear cockpit, in the v-berth, the head and the main cabin. For me extension cords and boats are a bad combination.

4. Consider ventilation. As I restored this boat I always kept a couple of AC fans in there on a timer. They ran a few times a day and kept the boat condensation and odor free. As part of the electrical system I installed some 140mm computer case fans (inexpensive, 12 volt and low power consumption). I ran these fans through switches but also incorporated a small DC timer. Like this one:

http://www.amazon.com/Amico-Digital-Power-Programmable-Switch/dp/B008999RYY/ref=cm_cr_pr_product_top

These fans run on a 24 hour breaker such as you use for bilge pumps.

One last thing. You're absolutely right to use high quality components like Blue Sea. You won't be disappointed.

Good Luck,

MIA