Jury rig 4amp fuse mid Atlantic?

jeremyshaw

jeremyshaw

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My boat is currently about 300m SE of Bermuda on passage from Grenada to Horta with a delivery crew on board.

They email that the watermaker has failed and it seems a 4amp glass type fuse is the culprit. It's undocumented so we don't have a spare, though I'm hopeful the crew can cannibalise one from something else or jury rig some of the other spare fuses we have.

BUT if that's not possible, would it make any sense to solder in a thread of wire from a multistrand piece and if so what size? I suspect not as I'm always surprised how tiny those fuse wires are and obviously we don't want to fry the machine (nor do we know why the fuse went).

There is plenty of water to get them to Horta safely if unwashed, and I'm contacting Sea Recovery for advice but what would you do?
Thanks
 
If you google "fusing current of copper wire" you will get several links with tables showing fusing current of various thicknesses of copper wire. The next problem will be estimating the guage of individual strands of a mult-strand wire so you can look it up!
 
jeremyshaw said:
My boat is currently about 300m SE of Bermuda on passage from Grenada to Horta with a delivery crew on board.

They email that the watermaker has failed and it seems a 4amp glass type fuse is the culprit. It's undocumented so we don't have a spare, though I'm hopeful the crew can cannibalise one from something else or jury rig some of the other spare fuses we have.

BUT if that's not possible, would it make any sense to solder in a thread of wire from a multistrand piece and if so what size? I suspect not as I'm always surprised how tiny those fuse wires are and obviously we don't want to fry the machine (nor do we know why the fuse went).

There is plenty of water to get them to Horta safely if unwashed, and I'm contacting Sea Recovery for advice but what would you do?
Thanks
Click to expand...
I wouldnt even worry about the thickness that much, I would experiment with a a couple of strands of wire stripped from a piece of cable, wrapped around the fuse. If that blows then there is something more serious going on. Think back to when we were kids, the piece of cardboard with 3 sets of fuse wire wrapped around it, ready to change the fuse. 15 amp was about as thick as the strand from ordinary stiff household wiring.
Stu
 
Great suggestion. I've found that and emailed the crew. For anyone curious the fusing rating of copper wire is:
.152mm 3amps
.213mm 5amps

Not sure the micrometer will measure that small, but there are ways round that.
Many thanks
 
jeremyshaw said:
My boat is currently about 300m SE of Bermuda on passage . . . a 4amp glass type fuse is the culprit. . . . . would it make any sense to solder in a thread of wire from a multistrand piece and if so what size? . .
Click to expand...

Just looked in my Radio Reference Data Tables and a 4 amp fuse would require a strand of copper wire 0.0053 inch or 39SWG (very thin). :eek:

I cannot think why such a low value or the cause of failure. This size of fuse is usually used in microprocessor control circuits and probably non-inductive loads inside the water-maker.

The standard copper multi-strand wire is 7/010 (ie 7 strands of 0.010 inch. Where one strand has a current rating of about 10 amps. (10 amps is 33 SWG, 0.0098 inch).

Personally, I would suggest they run with the supply of water they are carrying and only risk a single strand of 7/010 if they become short of water to the point of dehydration.

Get back to me if you require any further help.
 
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suggest you find the model and confirm power/current rating of water maker. Inductive load is one issue, the fuse needed to be a slow blow or time delay type. There will be a letter next to the current rating denoting the type, it would be useful to know if the fuse was the correct type and rating for obvious reasons. If you jury rig a fuse, you need to try to be entirely sure the water maker isn't faulty and the wiring isn't either. I would only run under constant observation in good weather and daylight hours until absolutely confident.
 
Thanks for the replies. I'm pretty sure the fuse is related to the control panel which operates switches for the pumps and the salinity meter (which has automatic switchover). I've emailed the maker for more info which should help, and in a pinch I think the crew can bypass the electronics and manually operate the whole thing to power the two pumps and use good old taste testing to replace the salinity meter!
 
jeremyshaw said:
Not sure the micrometer will measure that small, but there are ways round that.
Many thanks
Click to expand...

Wind between a few and lots of turns onto a pencil. Count turns, measure length of pencil covered by turns. Divide this length by number of turns to get thickness of one turn.
 
Mmmmm...........

If my delivery crew had to ask for direction regarding the repair of a failed fuse mid ocean I think I would be worried about how good my delivery crew are.

It's a bit like arguing about the salt and vinegar on your chips while the chip pan is on fire!

Just FIX the fuse.

73s de

Johnth
 
fuse

You might want to ask them to inspect the blown fuse before jury rigging one.

They need to look very close up! if a short has caused the fuse to blow, they blow very quickly and small blobs of the fuse are scattered on to the glass.

Overheating of the fuse will cause the old small piece of wire to be in place but 'sagging', brown and if in place the small bit of paper within the fuse is scorched also.

Not always but it can be a clue.
 
Whatever happened to the bit of cooking foil or silver paper from the cigarette packet wrapped around the blown one..........certainly kept my old Mini running in times of trouble.........................
 
NDH said:
Whatever happened to the bit of cooking foil or silver paper from the cigarette packet wrapped around the blown one..........certainly kept my old Mini running in times of trouble.........................
Click to expand...

You can get out of the Mini when it catches fire and phone the fire brigade. You wouldn't normally sleep in a Mini either.
 
NDH said:
Whatever happened to the bit of cooking foil or silver paper from the cigarette packet wrapped around the blown one..........certainly kept my old Mini running in times of trouble.........................
Click to expand...

I have seen 6" steel nails cut down to replace fuses, and it wasn't even a (bad) temporary fix, they had eventually gone rusty and failed; and that was on a boat not a car!

Ants
 
Sailors

lenseman said:
They haven't got a spare or knowledge of the correct wire to use, they are sailors not electronics engineers!

Oh and BTW, it is 73 not 73's

73 de G6UXD/MM
Click to expand...

It is an interesting statement that they are sailors and not electronics engineers. It seems to me that in this age of gadgets seamanship is less important than engineering skill in managing and maintaining systems.
As electronics are the trickiest and we depend on them so much then that is where the skills are needed.
Joshua Slocum didn't need an electronics engineer but it sure would be useful skill in any long voyage today.
We have a 16yo girl close to completing a round the world non stop trip. The gadgets made the trip easier (GPS and roller jib reefing) being the main ones. It is more a question of personal courage than seamanship even then sat communications and internet have changed all that. Providing it continues to work of course. olewill

olewill
 
On the basis they seem incapable of dealing with a blown fuse, it seems safe to assume they would be incapable of discovering why the fuse blew in the first place. On that basis replacing the fuse with a fuse other than one you are quite sure will not be required before reaching port would be foolish as it may well blow again.

Using a larger fuse may work, but the concern would be that a partial short causes a fire. In desperation running the watermaker under constant observation in case of fire may be an option, but of course the reason the fuse blew could be the watermaker is goosed any way.
 
maxi77 said:
On the basis they seem incapable of dealing with a blown fuse
Click to expand...

This may be a bit harsh. I am quite capable of dealing with such a situation (given access to a "copper wire fusing current" table. Given a micrometer I think I could draw out a slightly oversize strand to somewhere near the right size (although ipod headphone leads are a good source of tiny wire and in a family-used boat can be found under almost every berth).

However, I think I would still involve the owner in the way this crew have done. This is not the 19th century where communication with owners was only possible within sight of land. A better solution usually emerges from consultation, and asking for help is not a weakness!

Isn't this rather like the way the skipper sleeps better if she/he knows the crew will wake her/him if they feel there is a need.
 
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