Something that looks like a fuse

wernervdw · #1 03-09-2003

Last summer I bought a Dufour 2800. At the moment I am cleaning my boat and found something I do not recognize and seems to be damaged.

In the bilge I saw, connected to 2 thick flat ''earth-cables'', a glass tube that looks like a very thick fuse. Looking through the glass I do not recognize the structure of a fuse. One side of the cables goes down to the keel, the other side goes up... somewhere...

Does anyone know what this ?

thanks

Werner

kmeeks · #2 03-10-2003

Just a wild guess - but could it be some kind of ground for lightning strikes?

wernervdw · #3 03-11-2003

Might very well be.. so far it''s my only hypothesis that would somehow fit also.

But still I cannot figure out where the lightnin would be directed to.. It is a polyester boat and I don''t see a metallic part on my keel.

thanks
Werner

cysltd · #4 03-11-2003

The wire sounds like it runs to the keel for grounding purposes. There is lead in the keel even though you may not see it - likely encapsulated.

The wire that appears to go up is probably going to a chainplate or mast step.

The fuse like thing may be someone''s add on as an attempt to discern whether current has travelled through that wire .... just a guess as I have not seen anything of that description in that area before.
Liz

DelmarRey · #5 03-11-2003

Where does the other end of the wire lead to. Is it connected to thru hull fittings, prop. shaft packing and engine. It could just be a grounding system for electrolysis. A fuse in a lighting strike would be useless to the system. That surge of power needs to go to the water. Find out where the other end goes and you''ll find out more about your vessel. You might even find stuff that could save your boat in an emergancy. Or even prevent an emergancy. Explore become a amature surveyor.

wernervdw · #6 03-11-2003

Next weekend I’ll have a thorough look where the leads go to (will take a multimeter with me to measure). I am really intrigued by it.

thanks for the tips so far

regards
Werner

wernervdw · #7 03-17-2003

I''ve checked where the lead is going to this weekend. What I saw makes it, to me, more confusing. The lead that goes via the fuselike thing to the bow of the ship. There it''s moulded into the Polyester (so it must be original) where it ends at a metal noseplate (bowplate). On this plate the forestay is connect to...

This is my hypotheses :
Maybe the lead is intended to direct lightning, coming from the mast, through the forestay to the metal plate. From here to the keel (but via the fuse). My gues is now that the fuse only conducts above certain voltages. When the ship would be in contact with a conductive thing (maybe other ship) the fuse will not conduct (since too low voltages) and will not cause electrolysis. Lightning would be enough to trip the thing and the current would be going to the keel.

Could this be it ??

best regards
Werner

tsenator · #8 03-17-2003

Werner good guess.

Can you take a picture of it and post it somewhere? I bet we all are very curious as to what it is or where it came from.

Did you try contacting Dufour?

jparker11 · #9 03-17-2003

Werner

Sounds like a lightning protection system to me. The fuse like element sounds like a cad welded cable splice (often looks like a fuse assembly).

Lightning protection systems are intended to dissipate build ups of static electricity BEFORE a strike can occur. Even the best LP systems involve crossed fingers and a prayer when a strike occurs. I am unaware of any fusible link that can handle such high voltage/current loads?? And, if someone thinks a little fuse is going to stop a strike from blowing a hole in the boat once it has traveled down the forestay and into this conductor, they are deluding themselves.

You might check electrical conductivity between the forestay and the ground plate. Admittedly, my experience is with LP systems on tall structures (several hundred feet), but marine systems should follow the same guidelines.

GordMay · #10 03-17-2003

Werner:
I think your hypothethis is exactly backwards. As Delmarey suggested, were it a FUSE, it would only conduct at low currents, opening at high (lightning) currents. Not what you want!
John Parker (jparker11) is more likely correct in suspecting that it is a thermal weld (cadweld).
Further to John Parker (& others): I have been unable to locate ANY INDEPENDANT data suggesting that "Dissipation" systems actually "neutralize" the vessell''s static charge before lightning strikes. Most "Dissipators" (I''ve seen) will make less than ideal Air Terminals (Franklin Rods), which (unlike dissipators) would best present a ROUNDED end (3/8" - 1/2" diameter) to the leader/strike.
Would greatly appreciate direction to any independant research on the effectiveness of dissipators..
In actuality, I belive that lightning mitigation systems merely provide a prefered path to ground for any lightning currents. They are properly installed to minimize the likelyhood of side flashes, and induced currents.
It''s a complex issue, with much misinformation out there (incomplete and/or wronge).
As previously stated, pictures might help identify this "fuse-like" item.