Vulnerability of Plastic Through Hulls ?

[Martin&Rene]

In the latest YM, in one of the "Skippers Tips" discussing lightening strikes, there is the statement

Quote
Had she had plastic through hulls they would have melted and she would have sunk
Unquote

Anybody know of any evidence to substantiate or de-bunk that statement?

Is somebody "doing a Macron"?

 

[Frogmogman]

In the latest YM, in one of the "Skippers Tips" discussing lightening strikes, there is the statement

Quote
Had she had plastic through hulls they would have melted and she would have sunk
Unquote

Anybody know of any evidence to substantiate or de-bunk that statement?

Is somebody "doing a Macron"?

I read that too, and wondered about it, so Had a little trawl around the web, and this little piece seems to suggest the exact opposite. I wonder which is right.

Lightning Strike

 

[Slowboat35]

Sounds like dreamland to me.
How can a non-conductor - a perfect insulator melt as it cannot carry any current at all?
How would the current reach it? Via non-conductive plastic/rubber hoses?
Why, in a (presumably) non-conductive plastic hull would lightning choose to exit, of all places, via skin fittings and not via well earthed metallic parts like the propshaft or jump off the chainplates into the sea?
If plastic fittings 'melt' when lightning jumps past it why don't fibreglass hulls 'melt' when this happens? We know they don't.
In a metal hull plastic skin fittings would be the very past places lightning would exit.
Whereas if lightning exits via well-earthed metal seacocks mounted in soggy GRP moisture in the fibreglass or under the sealant might well explosively flash to steam and blow the unit out of the hull as appears to have happened in the Lakes example above but I don't think one would expect lightning to often take such a tortuous path to earth.
The hose in the picture looks as if it might be wire-reinforced. That's a potential lightning conductor!

 

[lustyd]

Composite (they are not plastic!) ones are effectively made of the same stuff the boat is so I can't see why the danger would increase in any way. I guess fire is less likely if your through hull shatters due to dezincification and lets the water in though, so yes composite does pose a greater fire risk overall ?

 

[C08]

I was in my boat on a visitor pontoon when a boat came into the next finger berth to me. A little while later he came around and rather sheepishly asked if I had a spare wooden bung as he had water slowly coming into his boat. . It seeemed coming into the berth he had bumped the pontoon and sheered off a plastic through hull fitting right on the waterline. I found an old bung, said he could whittle it to size and he did a temporary fix. It made me less impressed with plastic (I realise there are lots of different non-metal through hull fittings) fittings.

 

[lustyd]

interesting that a well fitted through hull would break but the boat didn't given they're made of the same stuff. Much more likely it was fitted poorly or it was actually a dezinced metal cock inside which broke with the slightest of taps

 

[Boathook]

It used to be standard, I believe to reinforce the hull within internal piece such as ply where a 'skin fitting' went through the hull. The majority of transducers, logs, etc are plastic and don't normally cause a problem.

 

[Rappey]

Anybody know of any evidence to substantiate or de-bunk that statement?

I can't think of the channel atm but there is an unlucky Australian guy who got hit by lightning and it exited through the grp by the prop shaft leaving holes in his boat !

 

[Slowboat35]

Composite (they are not plastic!) ones are effectively made of the same stuff the boat is so I can't see why the danger would increase in any way. I guess fire is less likely if your through hull shatters due to dezincification and lets the water in though, so yes composite does pose a greater fire risk overall ?

Hoses attached to the skin fittings are plastic or rubber and vastly less substantial. They'll burn through far faster than a seacock will so I can't see any difference fire-wise between the two.

 

[starfire]

But, plastic fittings, plastic hoses, full of conductive sea water ?

 

[lustyd]

Hoses attached to the skin fittings are plastic or rubber and vastly less substantial. They'll burn through far faster than a seacock will so I can't see any difference fire-wise between the two.

My point was that many metal fittings would fail due to lack of zinc and let water in, putting out a fire

 

[James_Calvert]

... sheered off a plastic through hull fitting right on the waterline.

I imagine it was something like what my bilge pump discharges through. People also have them for sinks, cockpit drains and the like.

I recall some warning that they could go brittle with age/uv degradation.

Must check mine. I'll admit I would much rather it was some non rusting metal than plastic.

These various composite seacocks will be far more robust, and shouldn't be exposed to uv damage under the waterline.

But how robustly will their seals last? What happens over time when barnacles get attached to the working bits and then their cement gets ground in?

 

[Bobc]

In the latest YM, in one of the "Skippers Tips" discussing lightening strikes, there is the statement

Quote
Had she had plastic through hulls they would have melted and she would have sunk
Unquote

Anybody know of any evidence to substantiate or de-bunk that statement?

Is somebody "doing a Macron"?

Utter rubbish.

Firstly they are made of a glass-filled thermo-set composite plastic (i.e. it won't turn back to liquid if you heat it up again), and secondly, if they caught fire, so would a grp hull.

 

[lustyd]

But how robustly will their seals last? What happens over time when barnacles get attached to the working bits and then their cement gets ground in?

Every report I’ve seen from someone who owns them has said they never get stiff and work fine year after year. Contrast that with metal ones which work smoothly for maybe two days.

 

[pvb]

Sadly, it's a reflection of minimal journalistic input by people who don't know which way is up. Magazines are struggling to survive, and hiring and paying good people must be difficult.

 

[geem]

One of the theories with regard to lightning strikes is that the lightning tries to get to the seas surface and not below. A keel stepped mast or a deck stepped mast sat on a steel mast post doesnt provide a direct route for lightning to get back to the surface. Lightning leaving the mast or mast post is heading for the surface of the sea so will ‘escape’ the hull at or near to the sea surface level external to the hull. It will either jump directly from the mast or post straight through the grp hull or go via a metallic fitting close to the sea surface as its an easier jump. A number of yachts that have had lightning strikes in the US have been left with holes at the waterline. I cant see why a plastic skin fitting would give an easier route unless the closer proximity of sea water in the connected pipe eases the escape route. An America friend who was hit by lightning in Florida (a very common occurrence) had his bronze skin fitting blown out. He was onboard at the time so managed to deal with the leak.

 

[RJJ]

I was in my boat on a visitor pontoon when a boat came into the next finger berth to me. A little while later he came around and rather sheepishly asked if I had a spare wooden bung as he had water slowly coming into his boat. . It seeemed coming into the berth he had bumped the pontoon and sheered off a plastic through hull fitting right on the waterline. I found an old bung, said he could whittle it to size and he did a temporary fix. It made me less impressed with plastic (I realise there are lots of different non-metal through hull fittings) fittings.

I should think that's a PVC one. My boat has PVC fittings for bilge pump exits above the waterline. I can't imagine how an FRP trudesign or Marelon one would break.

 

[dgadee]

I have had to remove a marelon seacock (don't ask) and it was not easy. I ended up grinding away the through hull. It is pretty substantial and certainly not fragile nor likely to go brittle. The real difficulty was getting my hands on a new through hull part. The seacock supplier told me that it was not possible to get a replacement, Forespar in the US told me that it would have to come from them, but the importer told me that it could be purchased via a local chandlery. Here's waiting to see if it turns up. Forespar seem to use some odd semi-BSP thread - on the 38mm seacock it is 1 3/4" BSP but with a different thread form.

 

[Plum]

Utter rubbish.

Firstly they are made of a glass-filled thermo-set composite plastic (i.e. it won't turn back to liquid if you heat it up again), and secondly, if they caught fire, so would a grp hull.

Actually, the TruDesign ones are a galss filled thermoplastic, but you are still right "utter rubbish"

 

[TSB240]

Slight thread diversion but a real life experience.

Many moons ago.....
On a hot summers evening I was packing our lark sailing dinghy away with my brother. We both experienced and watched each others hair literally starting to stand on end due to static charge in the air.
We rapidly grabbed our gear and dived for cover in his car and drove away from the storm.
I found out later that an adjacent boat had taken a direct strike. This melted the mast and vapourized a hole about 1M out of the GRP bottom. There were no signs of fire. We think the boat may have had a few gallons of water in the bottom by the mast as it had no cover and had been left bow down on its trolley.

Maybe there is an argument for disconnecting the thin multicore wires connected to your echo sounder and log in a thunderstorm. I suspect they would be vapourized like a half amp fuse before any possible damage could be caused to the plastic through hulls!