I finally get to disagree with Wheels, well a little anyway.
to chain connections are one of our specialties. We have been doing them since Maxwell
first came up with the auto rope
to chain winch concept
. We have done literally thousands of these and do a lot of test work
and a couple of others. This is fun, they pay us to build the latest cunning plan from their engineers and then they pay us again to find out whats wrong with the concept
... very cool fondling and busting other peoples stuff.
There is 3 basic methods of joining rope to chain in a anchor rode
situation. All are equally as strong as each other give or take a few %. Mind you nobody should put themselves into the position they find out. If they do they are using all the gear
at loads massively above manufacturers recommendations, it is one very extreme bit of weather
and the rode coming apart just adds to all the other failures that will happen first.
We have 'straight pulled' and cyclic loaded many of these over the years. Not to mention seeing hundreds of used ones.
1, A thimble - works fine apart from the fitting the bugger down the chain pipe and on Auto Rope to Chain winches. Maximum strength will be the rope break load less 15%. The 15% is the standard deduction for a good splice be it 3 strand or 8 braid (octiplait). In real life the shackle will probably be the weak spot. Don't be cheap
always use a Stainless thimble.
2, Around the last link and backspliced. Note this is not an eye splice around the end link, that is just asking for chafe and the most common we replace. Done right rope chafe is a none issue and the strength is no more or less than a thimble. The problem that 'can' occur with this splice is the chain link eroding under the rope. We have noticed 'in the odd' old one the chain itself is quite corroded. This is why we always cut the end link off when we redo one. All of the rodes we have seen this in are heavily used (usually off charter
boats or the extreme fisho's) and at least 3 years old. Notice the use of 'in the odd one' meaning it is not common but has been seen to happen. Issues with the rope are in the less than 1% area.
This splice is easy for the average boaty with a few clues to do well. It is also easy to see problems if they occur.
The key thing is to get the splice as tight as possible onto the end link this way there is no movement between the chain and rope hence no chafe. All the movement is between the 1st and 2nd links of chain.
3, The down the chain splice. A smidgen stronger that the other 2 if done very correctly which is not that easy. In actual use there is no strength differance than the other 2 ways. The problems with this splice are it is not easy to do correctly, you run a high risk of damaging your winch
and issues are not as easy to pick up. They should be but it don't seem to happen.
To get this right all the fibres must take equal load or just part of the rope does the work
with the possible big decrease in load carrying. This method also has issues when cheaper ropes are used and when they go hard. This makes the splice too long and stiff to work around a winch well. There is the problem with the 'odd' link rotating in the splice and if one rotates enough it could hit your gypsy
'on end' which has blown some gypsies apart, usually causing gearbox
damage. On smaller 7/8mm winches repair
bills have hit US$700 odd. This method is also a bit visually busy and we have seen the odd one with broken strands which are not easy to pick up from a casual glance. Winch manufacturers are not great fans of this splice due to their products getting beaten up.
In real life all 3 options are viable and can be regarded as equally strong. Anyway the splice is not the weakest part of an average well matched (rope and chain sizing) rode, the chain is.
A common match is 10mm chain to 20mm rope. Break load of the rope 9000kg (average) less 15% for the splice makes it 7650kg. Grade 30 10mm chain (the most common in use) break load 5000kg or on a Grade M (the US call it 'HT') 6500kg, both still below the spliced rope load.
In all the testing we have seen the rodes break at the back of the splice as would be expected with any spliced rope. We have yet to see one rope spliced directly to the chain rode fail due to the connection between them. This excludes rusty thimbles cutting thru the rope, shackles busting or poor splices which just fall out - in that order. Talk chafe in other parts
of the rope or knives due to rock grabbing anchors and the list is huge.
In reality any rope to chain connection will still take far larger loads than your anchor will hold, the winch will hold, snubbers will hold, a lot of decks will hold (don't laugh we have seen a deck
torn open) and most boaties will allow before they bail out of a nasty spot.
Rick - sexy looking set up but watch your double braid. 1/2 of double braids loads are carried by the cover and the other by the core
. As soon as the cover is cut you have a sudden (possibly big) strength loss. Polyester was a better choice than Nylon though, good call.
Gezz another novel but I hope it is of some use to someone.