Rode

[Neeves]

I did some very simple tests on galvanised chain.

I took a few links of the chains I have and attached to a steel rod. I then suspended the rod between the two transoms of our cat such that the rod would be on the seabed at high or low tide and the movement of the cat (swing mooring) would ensure that the lengths of chain would sweep across the seabed. I monitored weekly, washed the chains in fresh water, air dried them and weighted each piece of chain, to determine wear. I repeated the test a number of times altering the position of the chains on the rod. When we used the cat I simply lifted the rod (with chains) and laid the rod on the trampoline. You can see the wear of the gal, specifically the bottom link on the left hand chain and most of the right hand chain. The fifth from left hand end I'd painted with domestic water based yellow paint for another test. The 6th from the right, 6mm, was an ungalvanised sample - it has a thin and complete layer of rust.



This is a close up of one of the chains. The gal is grey/black, the raw abraded chain is silver, with speckled rust. The wear is not in the crowns but there is no tension in the samples. The wear is in the 'long' of the links abrading on the silica sand seabed.



Both images are after about 4 weeks.

The test seemed to simply accelerate the process of chain abrasion in real life - but it is extraordinary how quickly the gal has been worn. Its also extraordinary how quickly the chain has corroded the brown colouration - underling - wear is both abrasion of the gal and eventually the steel but corrosion is evident as soon as the gal is lost. The idea that galvanising protects areas where a product is damaged - not evident with second image

I cannot measure the gal thickness on curved surfaces and the gal thicknesses will vary. These are all samples of chain from chandlers or chain makers - randomly galvanised - and chain galvanising can vary from 60 to 80 microns. 'Quality' of galvanising, how long the chain is in the zinc kettle will also vary. For my TDG coating I 'produce' a flat surface by slitting the links and then measuring the flat of a number of samples through a batch.

It might be behind a paywall but the testing of gal quality was reported in Practical Sailor

Armorgalv vs. Hot-Dipped - Practical Sailor

Jonathan

 

[noelex]

Thinner, lighter anchor chains corrode significantly more quickly than heavier chains on the same sized boat. I suspect this is because the thinner chain moves around on the seabed more and therefore suffers more abrasion of the galvanising.

The most significant loss of material always seems to occur at the ends of chain links, so make sure you inspect this area well, as it is somewhat hidden underneath the adjoining chain link.

 

[Neeves]

Thinner, lighter anchor chains corrode significantly more quickly than heavier chains on the same sized boat. I suspect this is because the thinner chain moves around on the seabed more and therefore suffers more abrasion of the galvanising.

The most significant loss of material always seems to occur at the ends of chain links, so make sure you inspect this area well, as it is somewhat hidden underneath the adjoining chain link.



View attachment 206398

This is not my experience having commissioned with 8mm chain and then swapped to 6mm.

Its the vessel that makes the chain move on the seabed unless you have been using animated chain. The 8mm corroded more quickly than the 6mm, the 6mm did not lose its TDG coating - maybe because being lighter it does not sit on the seabed as much as the bigger chain.

Of the owners, about 10 and still counting, for whom I have arranged smaller chain from 8mm to 6mm and, the majority, from 10mm to 8mm, not one has complained that the lighter chain wears more quickly.

Jonathan

 

[lustyd]

Next quandry, I now have the new 50m chain fitted in the locker with new shackle. I also have the 50m of 18mm rope ready to splice but it feels unnecessarily bulky and impossible to sensibly manage (especially in our current climate!).

Thinking of cutting the rope to have one 30m and one 20m extension. This will make two just about manageable coils of rope that can be added or used elsewhere. As luck would have it the new chain included some bags I can use to keep this rope in.

Does this seem like a sensible split? I'm choosing to ignore the RYA guidance which suggests that adding 30m of rope to a 50m chain will take our max depth from 12.5m to 13.3m, and 16.6 if I add all 50m of rope.

 

[doug748]

Having two good lengths of rope in the cockpit locker can be useful in big rafts of alongside boats but arguably less so if you want a seriously big, long towline.
On balance I might have the 50m chain in the chain locker and two 25m lengths in the cockpit ready to go - though 20 and 30m has it's advantages.

.

 

[RunAgroundHard]

As long as you have a worked out method for joining when you need the extra length. If using for towing and the two lengths are joined there will be a weakness at that join. How often do you tow though!

 

[lustyd]

I doubt we’ll ever tow so not something I’d plan for specifically. Joining them will just be another shackle I think, although even using one will be rare I imagine. Even in Jersey with huge tides we only put about 40m out

 

[noelex]

Thinking of cutting the rope to have one 30m and one 20m extension. This will make two just about manageable coils of rope that can be added or used elsewhere. As luck would have it the new chain included some bags I can use to keep this rope in.

Does this seem like a sensible split?

This is a sensible split .

I'm choosing to ignore the RYA guidance which suggests that adding 30m of rope to a 50m chain will take our max depth from 12.5m to 13.3m, and 16.6 if I add all 50m of rope.

The RYA guidance suggests the scope required for rope rode is much longer than chain rode.

It is often suggested in this forum that the weight of the rode has no effect on the required scope. Personally, I think that neither of the extreme positions is accurate, and the truth lies somewhere in between.

 

[lustyd]

Yes I agree the guidance is massively oversimplified and poorly thought out. It makes me chuckle that my 50m of chain allows me to anchor in 12.5m but apparently adding one metre of rope would reduce that to 8.5m.
That said, I couldn't write a better recommendation, nor explain why I put out what I put out. I generally keep putting out chain until there's enough

 

[Supertramp]

Provided you are happy with joining shorter lengths when needed then ok.

I have kept two long lines of over 50m on board - one (Octoplait 14mm) is for the main anchor or kedge rode, one (braided, 14mm) is for mooring/towing. I'm sure joining ropes does not create enough weakness to worry about although I might worry if using it in extreme winds. Its better to have something accessible and easily used than inaccessible and hard to manage.

The day you want a really long line it will never be long enough!

 

[lustyd]

I'd love to keep it as 50m but with 18mm octoplait it's impossible to manage sensibly, and when it's wet I can't even lift it easily!

I'm going to have one join anyway from the chain to rope and I can't imagine rope to rope being worse

 

[doug748]

A 50metre line would be good but two 25m lines are likely to find a bit more use. Alongside a harbour wall would be one occasion. Passing a long line up in sea locks as well, not an everyday thing for most but you need to tackle it if you want to go inside at St Malo, for example.
Regattas and rallies are well known for large rafts of boats calling for lines ashore. Waiting for rise of tide in places like St Helier you tend to see even large expensive boats scratching for lines to take ashore in rafts of ten or more.

.

 

[lustyd]

Unfortunately (or fortunately, depends on how you look at it) we also have some huge mooring warps having been through the Crinan last year so we're all set for crazy big ropes
It's not a popular opinion but I'm not a fan of shore lines in rafts, they don't add much in terms of security but they absolutely add to the nightmare of rafting!

 

[SaltyC]

Unfortunately (or fortunately, depends on how you look at it) we also have some huge mooring warps having been through the Crinan last year so we're all set for crazy big ropes
It's not a popular opinion but I'm not a fan of shore lines in rafts, they don't add much in terms of security but they absolutely add to the nightmare of rafting!

Agreed shore lines add complexity, especially if an inner boat wants to depart.
However, if you were the inside boat on a raft of 4 boats would you be happy to take the strain of all?
Also if in a tidal stream eg estuary, think of the distortion on the outer boat on tidal change, if the other rafts had shore lines and one not.........

 

[lustyd]

In reality the angle of shorelines just isn’t going to help in a tidal stream. If there are cleats further down the pontoon to tie to you’d just split the raft! Rope that’s almost perpendicular to the pontoon offers nothing for fore/aft movement.