Friday, 25 September 2009

Looming Large

Since I mentioned in passing, the other day, that some of my "large ship" work was drying up as a result of the global downturn in trade, I have had several people ask me about making wiring looms for their new boats.

For those of you that haven't come across this concept, its a spin-off from the wiring looms that are now standard in cars and production boats.

Like cars, production motor cruisers such as Princess, Sunseeker etc are not wired one wire at a time, as this would be too time consuming and therefore expensive.

The cabling for these type of boats is made to pattern and length, so that the boatbuilder can just clip one loom into place and connect-up all the loose ends.

Visually, a wiring loom resembles a fish bone, with a main spine and various offshoots coming off.

This practise has now caught on in the narrow-boating world.

Its very useful for people fitting out their own hulls or sailaways, as it saves a lot of fitting-out time, time wasted sourcing small quantities of materials and specification guesswork.

The cables can be made to order as a bespoke loom and delivered to the boat in one or more pieces, subject to complexity.

It means that the person doing the fitting out can spend less time working in a cramped hull (which is no fun in winter) or more time doing some other form of fitting out, like the plumbing or tiling the shower.

Normally, I either start off by visiting the boat to discuss the layout with the owner and make a pattern, or if the boats physically too far away, the owner can complete a diagram by adding dimensions and a few other necessary details.

I can then make the loom in my workshop at home (not on our boat - not enough room !! ).

The loom is made up of correctly dimensioned cables for the current it will need to carry and is supplied as a finished product with marked cables within the loom, a wiring diagram and a list of the conductors used and their specification.
Looms are cable tied and heat-shrink sleeve wrapped for strength.

When the loom gets to the boat, the spine has to be fitted into place (usually alone the centre of the deckhead or under the gunwhale) and the dimensioned tails then fall into place to line up with the switches and light fittings. The person doing the fitting-out then has to connect the 2-wire connections on the loose tails to the light fittings and switches and the other end of the spine is connected to the outputs of the DC fuse box or distribution panel.

Its also possible to split the lighting circuit so that a failure on one circuit (e.g. blown breaker or fuse) doesn't plunge the whole boat into darkness or even one end of the boat. The loom allows lights to be interleaved, so that every second light would stay on, etc.

I can also make up heavy duty battery cables (up to 70mm2), which can be supplied to length, for new inverters, battery chargers, etc.

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