Ocean underdeck trunking/conduit

[Nasher]

A1an

I've thought about this when I first started looking into it.

The trouble with just letting them lay in the hull is that they will jump and move about over the 3m or so length as the boat moves around in a chop. Which over time could lead to fractures in the cables at the end points were they are held more firmly by the witches hat or whatever. A conduit reduces the movement or stops it completely.

All best practice and industry standards specify maximum unsupported cable lengths, which is in the case of a RIB possibly @400mm, but I don't know for sure.
Obviously being in a conduit doesn't create absolute fixed points every 400mm, but the cable is constrained more.

It is VERY tempting to just do it, as it will be a lot less work, but I will know I've not done my best.

Nasher.

[Orwell boy]

Originally Posted by A1an

Just throwing this out there.. Is there a real need for conduit underdeck? I have seen several underdeck solutions from varying manf and some have perforated pipe, some have gutter pipe with holes drilled in and some have fibreglass tray moulded in to hull. All of which let water in and around the cables, if they are going to get wet in the trunking why not let them lie on the hull?

Even the "sealed" trunking has a tendency to let water in if the boat gets a good swamping.

Well i have to share this possibility ! ,when i had my r/c 5.3 re engined i had to have all new front to back cables inc battery cables and even stuff on a frame ,i mean every thing that went thru the ribcraft fitted trunking ,the engine taken off had been in the original profesional owner from new and had done 150 hours ! ,seamark nunn fitted the engine and we had various theories as follows
what came out stunk maybe of fuel ,battery cables were perished ,maybe water and fuel had been frozen in the scottish winter in the hull inside the trunking ? maybe the ribcraft filler had out smarted the operator and overfill went straight down the trunking from inside the console ,maybe a fuel can had split ,who knows but it was very real for my bill when i picked it up ,mind you the fuel fume sensor doesnt go off now every time the sun shines
also must say my nautica has no trunking ,cables just lie against the massive side stringer ,put new wires in as easy as wink !

[Nasher]

Yep, I can understand why it gets done, it's easy, and when you are building a boat or doing it for somebody else it's an easy way out.

But it's just not good enough for me to put my name to it, when I have the ability to do it properly and care about my own boat and the standards to which I work.

And of course the work should include making it impossible , or very difficult, for anything to join the cabling down the hole.

Nasher.

[Orwell boy]

Sorry Nasher i was,nt trying to be critical , but now you say "i have the ability to do it properly " but what is properly ? ,my expierience of the best in this forums reco list was maybe properly failed miserably ,maybe old fashioned or "how we used to do it " has been superseeded by new materials or similar ! ,i have seen several people on here asking how to empty their underdeck trunking ,and a long list of owners of british brands,explaining how they do it , so maybe properly may take a little more thought !
as a complete aside i would say be careful to choose a plastic thats meant to be in the dark because light destroys some very fast

[Nasher]

Wasn't reacting to you Orwell Boy, you've always had nothing but good stuff to say.
Apologies if it appeared that way.

I've seen too many RIBs thrown together by so called professionals with no thought to the state of the boat in 5yrs time when their original customer will have sold the boat to some poor bugger who'll have to deal with their bad workmanship.

For example the amount of ply decks put down with no protection on the underside so they gradually rot is unbelievable.

As you say, there will be lots of argument about the proper way to do it, but my humble opinion is that making no effort to do anything is in this case not good enough.

It would be really good for one of our surveyors on the site to comment if I'm being over the top on this one.

My Ocean, made by Windsor brothers had some great examples of the sort of thing I'm talking about, but I've gradually put them right, sometimes after they've become a real issue.

Using a plastic tube that would age and fall to pieces would appear to be one of them.

Nasher.

[GuyC]

I've put trunking in mine to avoid long unsupported spans of cable and pipework. If you've got a 'natural' place to lay the cables without having to resort to trunking, then I can't think of a reason why you couldn't use it. If the trunking helps to maintain the watertight integrity of the deck it is possibly difficult to stop it collecting water. For mine I've ensured that if water does get into the trunk, it can make its way out of the trunk and into the bilge.

[Nasher]

I just think a 3m or so length of loose cable will flap up and down slapping the hull and work hardening at the ends as you bounce across the Solent chop.

As mentioned I might be going over the top with this, but I suppose it comes down to me feeling confident I know it's been done to my own satisfaction, and others will think differently.

Nasher.

[GuyC]

Originally Posted by Nasher

For example the amount of ply decks put down with no protection on the underside so they gradually rot is unbelievable.

Nasher.

It's a bit of thread creep but my Pac 22 had exactly this and the original deck was still intact 25 years after she was built.

[Nasher]

I had a quick google

From:
electric cables | Boat Safety Scheme | Go Boating - Stay Safe

To prevent damage caused by vibration, cables must be securely fixed at approximately 300mm (12ins) intervals, or run in a pipe or trunking which is adequately supported.

[jakew009]

Originally Posted by Nasher

I just think a 3m or so length of loose cable will flap up and down slapping the hull and work hardening at the ends as you bounce across the Solent chop.

As mentioned I might be going over the top with this, but I suppose it comes down to me feeling confident I know it's been done to my own satisfaction, and others will think differently.

Nasher.

I’m in the process of refurbing a Cobra 7.5m rib at the moment and have a similar dilemma.

The original fit out was basically a 6” length of 4 inch drain pipe going through the deck under the console and near the engine. Cables were threaded through the bit of pipe, ran along the bottom of the boat, and came back up at the other end.

In a Cobra, the under deck all drains to the bilge, so any water that goes down the pipe ends up in the bilge anyway.

Apart from the fact that the cables were all covered in a mucky greasy filth, I could see no damage from 15 years and 800 hours worth of rubbing and slapping when I pulled all the cables out.

I was thinking of threading some conduit through, for all the same reasons you were, but now I’m wondering whether it’s really worth it.

The main con as far as I can see is that water could get into the conduit and be really stinky. I could try to seal the ends of the conduit, but in reality you’re always going to get some water tracking down the wires / pipes and into the conduit. I don’t think there’s any good answer to this.

The benefit of the conduit is that the cables are less likely to ‘rub’ and get damaged. But I think this is a bit of a moot point.

So I think I’m just going to chuck them back in the bottom of the hull.

In the list of a million ways to breakdown at sea, I think a damaged under deck cable as a result of not being in a 5 inch conduit is pretty low down.

[jakew009]

Originally Posted by Nasher

I had a quick google

From:
electric cables | Boat Safety Scheme | Go Boating - Stay Safe

To prevent damage caused by vibration, cables must be securely fixed at approximately 300mm (12ins) intervals, or run in a pipe or trunking which is adequately supported.

Thing is unless you’re going to size the cable to the conduit so there’s not loads of slop inside, and then somehow fix the conduit down to stop it moving around, your potentially introducing more abrasion points inside a big conduit than you would be if you just chucked the cable in the bottom of the boat..!

[Orwell boy]

Just trying to think outside the box here as you want it so good (which i agree) what about a 6" heatshrink sleeve or similar to whats used on machining centre doors etc ,it could stand 6" higher than floor level at each end ,but you best put some spares for future add ons before you shrink ,some of those products are bulletproof nowadays .

[xpertski]

Originally Posted by jakew009

I’m in the process of refurbing a Cobra 7.5m rib at the moment and have a similar dilemma.



The original fit out was basically a 6” length of 4 inch drain pipe going through the deck under the console and near the engine. Cables were threaded through the bit of pipe, ran along the bottom of the boat, and came back up at the other end.



In a Cobra, the under deck all drains to the bilge, so any water that goes down the pipe ends up in the bilge anyway.



Apart from the fact that the cables were all covered in a mucky greasy filth, I could see no damage from 15 years and 800 hours worth of rubbing and slapping when I pulled all the cables out.



I was thinking of threading some conduit through, for all the same reasons you were, but now I’m wondering whether it’s really worth it.



The main con as far as I can see is that water could get into the conduit and be really stinky. I could try to seal the ends of the conduit, but in reality you’re always going to get some water tracking down the wires / pipes and into the conduit. I don’t think there’s any good answer to this.



The benefit of the conduit is that the cables are less likely to ‘rub’ and get damaged. But I think this is a bit of a moot point.



So I think I’m just going to chuck them back in the bottom of the hull.



In the list of a million ways to breakdown at sea, I think a damaged under deck cable as a result of not being in a 5 inch conduit is pretty low down.

Lots of dilemmas. I guess it’s personal preference with everyone trying to do what they think is best. I went with the same approach Nasher is and the way I arrived at stopping water entering the conduit was two fold, first getting the engine cables etc to enter the rear bench seat, where the conduit then starts with a fibreglass cuff at the deck to stop any water getting in if it found its way into the bench seat and a witches hat on top. The conduit then runs under deck and comes up inside the console so is never outside, this to my mind minimised the risk of water ingress and also doesn’t expose the conduit to the sun. Don’t know if it’s ‘the’ best way, but after research and lots of thought it was the best I could come up with.