Missing fuse or link?

[chris-s]

Whilst exploring the depths of one of the lockers on our new-to-us boat, we came across what looks like some sort of on-line fuse holder in some heavy copper braid connecting a chain plate to a keel bolt, presumably some form of lightning conductor. Leaving aside the effectiveness or lack there-of of such a system, I’m puzzled at why it would appear to have been fused? What sort of fuse could you use?

 

[[194224]]

A bit of a puzzle but I would be surprised if it were a fuse. Perhaps it is just a device to splice those two cables together but removing the centre screw breaks the connection for some reason?

EDIT
Presumably there is continuity between the two terminals?

 

[Poey50]

It would be quite some fuse to stop 300 million volts.

 

[chris-s]

It would be quite some fuse to stop 300 million volts.

Exactly what I was thinking!

Looking at the photo again, it looks like that rusty bit is/was a link of some sort. I’ll give it a poke and prod next time.

 

[billskip]

It would be quite some fuse to stop 300 million volts.

Why would you want to stop it, if it's got that far its already done any damage.
I seem to remember years ago a device that looked like a short small gas filled neon tube and was claimed to take a lightening strike to ground quicker than the spike could damage the electrical components....just a guess....

 

[Poey50]

Why would you want to stop it, if it's got that far its already done any damage.

My point is that a fuse is pointless, not that it should stop a lightning surge.

 

[Martin_J]

Hard to tell from the photo. If it's in the braid close to the keel, could it be a capacitor?

It could be used if the previous owner was using the keel as a ground for an HF radio. It would allow the keel to act as ground for AC but would block undesirable DC currents.

 

[chris-s]

Hard to tell from the photo. If it's in the braid close to the keel, could it be a capacitor?

It could be used if the previous owner was using the keel as a ground for an HF radio. It would allow the keel to act as ground for AC but would block undesirable DC currents.

Would that be likely if connected between a shroud chain plate and the keel?

Oh the puzzles of a new boat!

 

[[194224]]

Would that be likely if connected between a shroud chain plate and the keel?

I wouldn't have thought that likely but who knows, we're all flummoxed at the moment. You must tell us when you get to the bottom of it.

 

[William_H]

Long a go in telephone lines it was common to fit a lightning protection device in the form of plates very close together often with a sharp point at the 2 proximate ends. This was connected between lines and ground. So no electrical connection but a gap easily jumped by high voltage from lightning strike or induction into (aerial) wires.
It could conceivably be a similar device. (works a bit like gas dis charged tube previously mentioned. Check for conductivity between bolts.
Or as said may be a capacitor for HF radio grounding or a place to mount a capacitor. Doesn't look like a C to me.
Regarding lightning protection I would remove connection to shrouds. Move it to connection to base of mast itself. Stainless steel wire has a quite high electrical resistance and so with high current will fuse or at least get hot enough to lose temper. By comparison the ali mast can conduct huge currents without a problem because of large cross section area and low electrical resistance. ol'will

 

[Spirit (of Glenans)]

Long a go in telephone lines it was common to fit a lightning protection device in the form of plates very close together often with a sharp point at the 2 proximate ends. This was connected between lines and ground. So no electrical connection but a gap easily jumped by high voltage from lightning strike or induction into (aerial) wires.
It could conceivably be a similar device. (works a bit like gas dis charged tube previously mentioned. Check for conductivity between bolts.
Or as said may be a capacitor for HF radio grounding or a place to mount a capacitor. Doesn't look like a C to me.
Regarding lightning protection I would remove connection to shrouds. Move it to connection to base of mast itself. Stainless steel wire has a quite high electrical resistance and so with high current will fuse or at least get hot enough to lose temper. By comparison the ali mast can conduct huge currents without a problem because of large cross section area and low electrical resistance. ol'will

It's my impression that lightning is composed of static electricity, which is conducted only on the surfaces of structures/objects, hence the composition of the rigging would not be affected, nor have any effect, one way or another, but the mast, with its greater cross-section would be its more likely path to earth, in any event.

 

[billskip]

It's my impression that lightning is composed of static electricity, which is conducted only on the surfaces of structures/objects, hence the composition of the rigging would not be affected, nor have any effect, one way or another, but the mast, with its greater cross-section would be its more likely path to earth, in any event.

If .. and as said it's a guess...if the remains which the OP has, which looks like a cartridge holder, is in fact a device for lightning protection, it just maybe that whoever connected it may have thought or been advised at the time its installation was ok as there was no convenient connection directly to the mast.
You may be correct in your theory regarding static electrical energy, but I have been sitting in a house that was struck by lightning and can assure you it seems to do exactly what it wants.
There are also many YouTube showing what happens to trees (wooden ones) when struck, so anyone trying to determine the path it takes is a gamble.
It is also thought that lightning can in fact go from the ground/sea upwards.

 

[William_H]

If .. and as said it's a guess...if the remains which the OP has, which looks like a cartridge holder, is in fact a device for lightning protection, it just maybe that whoever connected it may have thought or been advised at the time its installation was ok as there was no convenient connection directly to the mast.
You may be correct in your theory regarding static electrical energy, but I have been sitting in a house that was struck by lightning and can assure you it seems to do exactly what it wants.
There are also many YouTube showing what happens to trees (wooden ones) when struck, so anyone trying to determine the path it takes is a gamble.
It is also thought that lightning can in fact go from the ground/sea upwards.

I think it is fairly well understood that a lightning strike cloud to ground starts with a leader from ground up to the high voltage static charge which then comes down the ionised air from the leader. Leader is so fine and fast almost impossible to see with naked eye.
Any lightning strike involves huge currents which can induce voltage/current into nearby conductors which becomes another problem of lightning damage.
However protection of buildings from damage by direct strike seems to be settled on a top spike conductor connected by a low resistance (copper often) conductor to ground. The lower the electrical resistance the happier the current is to follow that path. Any resistance or break in the path causes either arcing across the gap or a high voltage drop which seeks a path nearby. The problem is that the leader can go through relatively high resistance like a tree but the main current flow down will overload the resistance ie vaporise the moisture in the tree. or in the case of sail boat try to lead the current away from shrouds by taking current via low resistance mast to water. ol'will

 

[Spirit (of Glenans)]

My boat has, installed by the previous owners, a heavy braid connection , similar to the braid shown in the OP's photo, between the base of the pole supporting the mast and a keel bolt.

 

[chris-s]

To follow up on this, I had a closer look at the ‘thing’ and it is definitely something that should be fitted with a link between the two clips. There was some rusted remains of something in each clip, which seems strange to use something made of a material that is just going to rust away. Maybe the fuse kept blowing so they stuck a nail in it ?

 

[Spirit (of Glenans)]

My boat has, installed by the previous owners, a heavy braid connection , similar to the braid shown in the OP's photo, between the base of the pole supporting the mast and a keel bolt.

"Compression Post" -couldn't think of the word at the time?