Standing Rigging Testing

[alan]

I have seen recent articles about 'electronic' means of standing rigging testing.
Can anyone tell me where one can purchase one of these meters? and how much they cost?
I'd like to test my own rigging annually and keep a record, and try and identify any problems.

I guess these instruments work like a four probe earth ground test set as used on electrical installations ??

Can anyone out there help???

Thanks,
Alan.
Italy.

Alan Cloke

 

[DoctorD]

Unless you are an expert - I would get rigging checked professionally. Non-destrucive testing is very hard to do reliably. You can visibly check rigging but it is very very difficult to know when it is going to fail if it looks alright. It is why insurance companies often insist you change your standing rigging at ten year intervals.

 

[vyv_cox]

I don't think you can do this yourself. It's a service offered by one or two companies in UK. I've read about it in (probably) YM or (possibly) PBO in the past few months.

 

[Plum]

Non-distructive testing on rigging is very controversial subject as although, in the right hands, may indicate that there are cracks or wire-strand breakages that were not there on a prior test, this in fact gives you very little information about the rig. Stanless steel rigging fatigues over time in use. There is no test available that will tell you the residual life of the wire or the fitting. The sort of defects that non-distructive testing will reveal will be those that start right at the end of the fatigue life where the onset of identifiable cracks is rapid and failure is imminent. So, doing a non-distructive test once per year is a waste of time. Getting a good result from such a test will NOT tell you that the rig will be OK for another season. It may not even tell you it will be good for another month. All the non-distructive test will tell you is whether failure is imminent or not.

 

[Boathook]

There was an article in PBO last month about testing rigging by Maidment?. I belive it's the same idea as used by National Grid for the power lines and how many of those do you see down!. Like most things the skill is understanding the results and what the difference means to each fitting.
I had the tests done many years ago when first started & the insurance company accepted the results. In the end you do have to renew rigging but not every 10 years

 

[paulstevens]

Wrong!

Plum your analysis holds good for a solid rod but not a wire containing 19 individual strands. Broken strands due to fatigue typically occur just inside the terminal and one at a time. This may happen over a season or two without catastrophic failure. The time to discover fatigue is when just one strand is broken not when your mast goes by the board and this equipment can do that.
It is also important to remember that one is not measuring absolute values, one is comparing a number of identical terminals on the same boat.
I use this equipment on a daily basis and certainly do not believe it is a waste of time. I have also identified terminals where the wire has been cut too short and not fully inserted into the terminal, an accident waiting to happen.

The equipment is called Maidsure Rigtester and it was pioneered by Dennis Maidmant of Southampton. It is basically a resistance test using the four wire Kelvin method.

 

[Plum]

Wrong?

You put forward a good counter-argument, Paul, and I agree that such equipment used in the right hands will pick up significant defects. If, as a result of you finding a defect, it results in someone renewing their rigging before it fails at sea, then I can't argue, you have done good work.
But my point is that we should not lead people to believe that a "no defects" result from such a test means that the rig has lots of life left in it, even with multi-strand wire. I strongly believe that in the absense of a residual-life test, resistance testing/comparison should not be used as a substitute for periodic renewal of stainless steel wire as a precausion against fatigue failure.

 

[AndrewB]

Maidsure

We have our wire rigging electronically tested every three years by Dennis Maidment in Southampton (sorry, don't have address to hand, but small-ads in YM/PBO).

This is quite definitely something that requires expertise, and is not a DIY job. If you can get your rigging to Southampton though its fairly cheap (from memory, approx £60 for ten wires, 20 terminals, last time I went). Rigging needs to be tested regularly since it is a RISE in resistance that indicates swage failure.

Like others, I'm not 100% convinced of this method's reliability. But my insurance company seems prepared to accept it. Its much cheaper than new rigging every 10 years. And so far I've had no rigging failures.

 

[paulstevens]

better than doing nothingg

No test is 100% and it is not meant to be a substitute for regular replacement. But in reality few yacht owners renew their rigging regularly although many claim to particularly when the boat is changing hands. I have used this equipment as routine in surveys for about 2 years and have found enough defects to be totally convinced.
The irony of course is that most pre purchase surveys are carried out with masts standing and very few buyers or vendors are interested in paying to have the mast unstepped. Even stranger is that most insurance companies require a survey every five years once a boat is 20 years old, but not one insists that the mast be unstepped! Resistiance testing often shows up a suspected defect in the terminals at deck level resulting in the mast being unstepped and in my opinion that alone justifies the test.
With the proliferation of highly stressed fractional rigs and all the gear getting lighter we are in for increasing numbers of rig failures as these boats get older.
The moral of the tale is stick to a good solid masthead rig with a large safety margin. Sorry to be so boring but speed isn't everything.