A-frame wire failing again

[Jef & Marin, Netherlands]

Our catamaran has a 14mm 1*19 wire over the crossbeam's A-frame.
For the 3rd time in 9 years / 50,000nm it failed and has to be replaced. This time 3 strands have broken just outside the toggle swage. The other side of the wire has a turnbuckle thread swage.
I tension the wire such that with tensioned rig the crossbeam is straight.
I will change the wire for 14mm compact strand with Petersen Hi-Mods, hoping that the increased strength and the lack of swages will prevent this happening again.
The groove in the top of the A-frame prevents use of bigger wire.


Is this a known problem amongst catamaran sailors or riggers? What could be the cause?

[massnspace]

Originally Posted by Jef & Marin, Netherlands

Our catamaran has a 14mm 1*19 wire over the crossbeam's A-frame.
For the 3rd time in 9 years / 50,000nm it failed and has to be replaced. This time 3 strands have broken just outside the toggle swage. The other side of the wire has a turnbuckle thread swage.
I tension the wire such that with tensioned rig the crossbeam is straight.
I will change the wire for 14mm compact strand with Petersen Hi-Mods, hoping that the increased strength and the lack of swages will prevent this happening again.
The groove in the top of the A-frame prevents use of bigger wire.


Is this a known problem amongst catamaran sailors or riggers? What could be the cause?

What happened the FIRST TWO times? Where did it break?

[Jef & Marin, Netherlands]

Maybe the pictures help

[Alan Mighty]

Originally Posted by Jef & Marin, Netherlands

Is this a known problem amongst catamaran sailors or riggers? What could be the cause?

Did you measure the tension that was in that wire rope? Is that different from the rated tensile strength of 14 mm wire rope?

Breakage of the wire at or near the swage fitting always suggests that the swaging process may have contributed to the failure.

In the recent past, meaning about 2019, the master rigger Brion Toss suggested that over-compression of the swage fitting, compressing it more than specified, can contribute to failure of the wire. The way to check that is to know the specified (by the swage manufacturer) outside diameter of the swage fitting after the swaging process.

Have you measured the outside diameter of the swage?

[Alan Mighty]

Originally Posted by Alan Mighty

The way to check that is to know the specified (by the swage manufacturer) outside diameter of the swage fitting after the swaging process.

Have you measured the outside diameter of the swage?

For example: https://www.ronstan.com/us/rigging-r...specifications

[Alan Mighty]

Originally Posted by Alan Mighty

In the recent past, meaning about 2019, the master rigger Brion Toss suggested that over-compression of the swage fitting, compressing it more than specified, can contribute to failure of the wire. The way to check that is to know the specified (by the swage manufacturer) outside diameter of the swage fitting after the swaging process.

See: https://www.practical-sailor.com/blo...-raise-concern

[skipperpete]

I don’t know why those cables have failed, but if thats a Knysna 44, I’m going to take a very close look at the ones on the boat that I’m working on right now, it has an identical A frame and is not a young boat, I think this boat has dieform, I’ll report back after I do an inspection
Are they stainless steel slides that hold the trampoline tensioners?… Aluminium? I just replaced all the slides but could only get black plastic ones that fit very badly, yours look excellent.

[Nekton73]

I echo the question, where did it break the first two times? If it broke at the same place, at the toggle swage, then I would suspect uneven loading in the a-frame cable. This could result from it being prevented from equalizing load across the apex of the bridle as it passes over/through the groove in the frame.

[skipperpete]

Originally Posted by skipperpete

I don’t know why those cables have failed, but if thats a Knysna 44, I’m going to take a very close look at the ones on the boat that I’m working on right now, it has an identical A frame and is not a young boat, I think this boat has dieform, I’ll report back after I do an inspection
Are they stainless steel slides that hold the trampoline tensioners?… Aluminium? I just replaced all the slides but could only get black plastic ones that fit very badly, yours look excellent.

Ok, inspection done and no broken wires, a tiny bit of red stain and all the swage entry points appear to be sealed with some sort of white stuff, maybe 5200 or similar. That A frame cable is ultra tight ( bar tight).
Hope you track down the cause, are you going to do a post mortem on these swages with an angle grinder ?

[Jef & Marin, Netherlands]

Thanks for your help.
All 3 times, the the breaking wires were at the end of the toggle swage, never at the turnbuckle side.
I have already replaced it with old 1*19 shroud wire, using a Petersen Hi-Mod turnbuckle CTT14 and stud CTS14. I am ordering Compact Strand cones and crowns to replace the wire with Compact Strand in less than one year.
Regretfully I have put the old wire and terminals in the bin, and then left Dutch Harbor in the Aleuthians, so I can not postmortem the swages. However the fact that this happened 3 times, swaged on different locations, makes it improbable incorrect swaging was the cause.
Nekton73, at the A-frame, the stainless wire has to slide over corroded aluminium; this might cause an uneven load, but the turnbuckle side would be tighter. I have put Duralac on the aluminium to stop further oxydation a few years ago. Putting a nylon slider below it might not be strong enough. Notice it is a toggle and not an eye, so the force on the wire should be central.
So he cause is still a mystery.

The sliders on the trampoline are indeed stainless steel, so probably sources from France in 2003. The boat is our Switch 51 from Sud Composites, in the south of France. This boatyard has later been sold to Swiss Catamarans. The trampoline is very durable PVC, brand Ferrari from France. When we bought the boat in 2014 the trampoline was already old, and still doing well after reversing and stitching with Tenara.