Mooring chain covered with firehouse

[Djarraluda]

Corrosion needs oxygen, so the wrapping of chain will limit water flushing, thus limit oxygen replacement and corrosion will be minimised.
Erosion will occur with the sand etc, so protecting the surface from abrasion will reduce wear.
As noted above, the hose will wear, but then that is easily (and cheaply replaced each year. Even if it only lasts 6 months, that is a 50% reduction.
I would be inclined to use cable ties top and bottom to keep the hose in place, they can then be removed and hose slid up for inspection.
Above all, do not forget to inspect and replace the swivel as necessary though.

I used to end-for-end the riding scope each year to even out wear and corrosion. The whole length then needed replacement at same time. Others used to add a few metres of extra length then shorten it, cut the lower part away, as it wore.

[adlib2]

Originally Posted by Jack Lahr

FYI a great source for firehose is EBay

Thanks for that. I used fire hose for chaffing for years from the local fire house, but once I started cruising I couldn't get it.

[Mossy Man]

Jim,

Maybe Sponge Bob lives at the base of this mooring. He is a good dude and surely would not mind a chain through his firehouse.

[admiralslater]

Our club (Toronto Multihull Cruising Club) has about 50 moorings. They are large poured concrete blocks with 5\8 chain with a car wheel and tire (tyre) at the surface. All the chain wear is about 3 ft up from the bottom where the slack chain swishes in the mud. We are attempting to deal with this by shortening the chain so the chain does not drag. The scope is achieved by lengthening the the mooring lines. In the Caribbean I saw mooring s where the pennant is suspended under water so it does not touch the bottom.
This has the added benefit of not damaging the seabed environment.
I wonder if we might see Dynema or similar start to be used in this application.

[Franziska]

@Djarraluda

Sorry, but I beg to differ.
Corrosion does not necessarily need Oxygen.
Google "crevice corrosion on stainless steel" and you will be surprised...

Not sure what this means for firehose over stainless chain though.
Guess a test would be worth it.
Might be also worth testing dyneema with firehose cover.

N8N8,

Franziska

www.ladyrover.com

[jimbunyard]

Originally Posted by Djarraluda

Corrosion needs oxygen, so the wrapping of chain will limit water flushing, thus limit oxygen replacement and corrosion will be minimised.
Erosion will occur with the sand etc, so protecting the surface from abrasion will reduce wear.
As noted above, the hose will wear, but then that is easily (and cheaply replaced each year. Even if it only lasts 6 months, that is a 50% reduction.
I would be inclined to use cable ties top and bottom to keep the hose in place, they can then be removed and hose slid up for inspection.
Above all, do not forget to inspect and replace the swivel as necessary though.

I used to end-for-end the riding scope each year to even out wear and corrosion. The whole length then needed replacement at same time. Others used to add a few metres of extra length then shorten it, cut the lower part away, as it wore.

I was thinking along the same lines but came up with a different conclusion.

Since fire hose is mean to be impermeable, there will be little to no exchange between the trapped water and the surrounding water. We all know what generally happens when stainless is used in anoxic conditions; crevice corrosion.

Not being a chemist, I've no idea what would happen with galvanized chain used in an anoxic environment. About four years ago, though, I made a mooring in a dead end canal that had an underwater ledge at the entrance that caused the bottom six feet or so to be anoxic. (That is an assumption; live bait put on the bottom died immediately, land vegetation (branches and such) did not rot, etc.)

When I pulled the chain and anchor a year later, most of the links in the last 15 feet of 1/2 galvanized chain were reduced to black scale with a core of, at most, 1/8" unaffected steel. Some of the links had areas that were all scale. The threads on a 5/8" heavily galvanized shackle wouldn't engage after I took it apart and cleaned the scale off them. Probably the only reason I got the anchor back (without diving for it) was because I pulled it with the trip line I had attached to the nylon rode.

Given this experience, I would say punch some holes every foot or so to let the water circulate, but who knows?


It's a good question, though the answer may best be had by trial and error...

[Jim Cate]

Just a offhand thought: are we sure that the wasting of the mooring chain that is reported is due to abrasion? Frankly, that seems unlikely to me, for steel is pretty resistant to abrasive wear, especially when there is little pressure between steel and the abrasive, and the speed is low... the situation of a chain being dragged about lying on the bottom, with only its weight pressing it against the soil. We have lived mostly at anchor for thirty years now. OUr anchor chain is dragged about far more than that on a mooring, and we've seen the galvo gradually disappearing, but never any observable wear on the steel. The only wear observed is where the links bear against each other; this is a high pressure situation, with lots of load on a very small area, and the wear is in thousandths of inches over years of usage.

I would think that corrosion is a more likely source of metal loss in many situations. I've seen too many mooring tackle bits that were obviously wasted due to corrosion to believe otherwise. How enclosing the chain with hose would affect this is an unknown, and might well vary depending upon the chemistry of a specific bottom... I dunno.

Jim

[admiralslater]

Originally Posted by Jim Cate

Just a offhand thought: are we sure that the wasting of the mooring chain that is reported is due to abrasion? Frankly, that seems unlikely to me, for steel is pretty resistant to abrasive wear, especially when there is little pressure between steel and the abrasive, and the speed is low... the situation of a chain being dragged about lying on the bottom, with only its weight pressing it against the soil. We have lived mostly at anchor for thirty years now. OUr anchor chain is dragged about far more than that on a mooring, and we've seen the galvo gradually disappearing, but never any observable wear on the steel. The only wear observed is where the links bear against each other; this is a high pressure situation, with lots of load on a very small area, and the wear is in thousandths of inches over years of usage.

I would think that corrosion is a more likely source of metal loss in many situations. I've seen too many mooring tackle bits that were obviously wasted due to corrosion to believe otherwise. How enclosing the chain with hose would affect this is an unknown, and might well vary depending upon the chemistry of a specific bottom... I dunno.

Jim

I would agree except that the wear on our moorings is always in the same location ie.where there is bottom contact the rest of the chain is fine . as we are in fresh water we dont even use galvanized chain and it can last years and years .

[Franziska]

Ahh, Freshwater, might have overread that.
This is making this very different.
Seawater corrosion is a different beast due to the salt influence.

[Sailmonkey]

I would swear at one point the OP said all the corrosion problems
were in the top 3' of chain.


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[admiralslater]

Any bites on using fancy rope for this job. I have personally seen huge marina docks (Red FrOg in Panama) held in place with rope. I thought I heard that Dynema floats which would solve the problem.

[Franziska]

I think dyneema could be great, especially in a freshwater environment.

In seawater I'd be hesitant due to sharp marine growth.

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[Cadence]

Just a wild ass question. Is there anything nearby that may be causing electrolysis. As I said wild.

[capt-couillon]

Re: Using line instead of chain for "downline"...

Our moorings here in Boot Key all use synthetic line for downlines rather than chain. Plenty of stretch without having a chain cantenary dragging on the bottom. Inspected 3 times a year and replaced as required. Latest replacements have a cover on the downlines and pennants to reduce marine growth and associated abrasion within the lay of the line.

[admiralslater]

Originally Posted by capt-couillon

Re: Using line instead of chain for "downline"...

Our moorings here in Boot Key all use synthetic line for downlines rather than chain. Plenty of stretch without having a chain cantenary dragging on the bottom. Inspected 3 times a year and replaced as required. Latest replacements have a cover on the downlines and pennants to reduce marine growth and associated abrasion within the lay of the line.

that is very interesting . How long are the down lines lasting .and are you using a heat strink type covering on the rope