busy home [deleted] 6:45pm, 24 February 2008
Been up to check out Ians new mooring today, Found it ok but these shackles were only just holding the chain to the bouy .I know they have worn because they cane loose but why did they come loose ..Did the stainless wiremouseing play any part ???
rothwell_neil 11 years ago
A galvanised shackle will corrode faster if in contact with a large area of stainless, from the photos the stainless wire will have had a minimal effect. This looks like nice general corrosion from time and a corrosive environment, the sea. The pin in the shackle has worn at a greater rate through erosion corrosion, the corrosion layer gets removed by rubbing and thus doesn't give any protection. Daft as it seems a layer of rust protects the underlying steel, any wear removes this layer and the corrosion takes place 10 times faster.
busy home [deleted] 11 years ago
What would you use to mouse up your shackles?
rothwell_neil 11 years ago
I would stick with the thin stainless wire as the effect will be minor and at least it will be secure rather than worrying about galvanised wire because when that goes there is nothing left. I guess the best approach is to use as little as is necessary.
busy home [deleted] 11 years ago
Looking at most old chain and shackles they rust together and are inseperable! why did these two side by side undo?
You would love to see the corrosion on our mooring chains that occoured when a local tin mine closed and was flooded a few years back! all the shellfish and marine life died leaving our pier walls BALD! This type of corrosion was to be seen on Ians chain today i.e.
little weed or barnicles black pitting ,not much red rust .When we fit new chain etc i will post photos of it!
Andrew Curry 11 years ago
Were i used to keep the boat there were lots of problems with shackles. Firstly if you look closely at a new one you will find the all the load is being supported by the threads as the hole on the other side is too large. The only shackles i would use on a mooring are the green pin tested ones. I found that after a season they were still in prefect condition. They are more expensive but in my view were worth every penny.
rothwell_neil 11 years ago
There are three types of steel corrosion product, one you can ignore, the other two are red rust, haematite and black rust magnetite. The red rust forms in high oxygen conditions at the surface of water and in the air, the black one forms at low oxygen under deposits and in muds etc. Also can get the black underneath the top layer of red rust. Black magnetite is hard to get off the hands. The probably reason why your shackles weren't a big glob of corrosion products and weed is probably due to movement keeping the surfaces free of product or were they buried in the mud?. Pollutants in the water such as from tin mines have an interesting effect on marine life. Tributyltin is one of the best antifoulants and is still used by the military. It is banned for use by mere mortals as even at the parts per trillion level it turns all female Dog Whelks into male and this is very bad news for Dog Whelk parties and the lack of resultant baby Dog Whelks. Hermaphrodite parties will never catch on.
busy home [deleted] 11 years ago
I have already bought the tested ones for goskars mooring (see my posting to Blue re attaching to cleats ) and decided to get some for Ians on the way home from Falmouth today . Six boats broke moorings at Loe Beach two years ago ,all pulled shackles apart.
Yes this new mooring was left with large bouy still attached on the beach,so has been pounded by wave action all winter ,we were very lucky to find it just attached today.
blueachilles 11 years ago
Ron, I can't find the post you refer to, can you point me in the right direction please?

Groups Beta