Rigging Test - Maidsure - Interpreting Results

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rodsuter

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I have just had my rigging undergo a 'Maidsure' resistance test.

I also have results from a test carried out 5 years ago (not the same company), and had hoped to be able to make a comparison and so detect any deterioration.

Both tests were reported as indicating that the rig is OK, but I am having difficulty in interpreting the results for comparison purposes. The actual individual resistance readings vary significantly between the two tests.

Can anyone assist in this regard ?
 
rodsuter said:
I have just had my rigging undergo a 'Maidsure' resistance test.

I also have results from a test carried out 5 years ago (not the same company), and had hoped to be able to make a comparison and so detect any deterioration.

Both tests were reported as indicating that the rig is OK, but I am having difficulty in interpreting the results for comparison purposes. The actual individual resistance readings vary significantly between the two tests.

Can anyone assist in this regard ?
Click to expand...

A general increase in the readings, a decrease or purely random ?
 
VicS said:
A general increase in the readings, a decrease or purely random ?
Click to expand...
Maidsure did my rigging every three years for a good many years. The measurement is of such sensitivity that only a comparative test using the same equipment is likely to be useful. Even then, I had my doubts about its validity, but my insurers were prepared to accept it in lieu of complete rigging replacement, and it was certainly a lot cheaper.
 
I have the measurements made in both tests, 5 years apart. For each shroud there are two measurements but I am not sure whether they are repeats of resistance measurement of one terminal or of the upper and lower. Further confusion exists in my mind because the two companies who have carried out the measurements do not use the same nomenclature for the shrouds, which are not for a straightforward masthead rig. I have asked Rod for clarification.

The technique used is described here http://www.allaboutcircuits.com/vol_1/chpt_8/9.html Apparently it is widely used for power transmission lines where it can predict broken wire strands and similar defects.
 
I would suggest that OP has wasted money on resistance test of rigging wire which could have been put towards replacing the wire. It seems to me that the wire will seem totally OK both resistance and visual until at some point the internal structure of the SS especially near the lower swage lets go. You get a sudden failure of the wire. I have seen it at our club 4 or 5 times. It is just not worth sailing with old rigging wire. all IMHO olewill
 
I know nothing about the Maidsure test, but a resistance test might give a little information about the state of the terminal, in particular if you are talking about Talurit splices. The test for a fatigue failure in the wire would be an eddy current test. Maybe that's what your two readings are?
 
William_H said:
I would suggest that OP has wasted money on resistance test of rigging wire which could have been put towards replacing the wire. It seems to me that the wire will seem totally OK both resistance and visual until at some point the internal structure of the SS especially near the lower swage lets go. You get a sudden failure of the wire. I have seen it at our club 4 or 5 times. It is just not worth sailing with old rigging wire. all IMHO olewill
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All my observations show the opposite. Fatigue failures in 1 x 19 wire take place strand by strand until the remainder have insufficient strength to support the load, upon which it fails. This is characteristic of almost all fatigue failures, usually described as 'broke without warning' or 'sudden fracture'. The reality is that the crack(s) may have been growing for years. Several examples at http://coxengineering.sharepoint.com/Pages/Fatigue.aspx

Yacht owners may be more suspicious of such techniques but the power transmission industry has been using resistance measurements of terminals for years, with great success. If yacht insurance companies accept the results I suspect we can assume that there is some truth in the claims for them.
 
William_H said:
I would suggest that OP has wasted money on resistance test of rigging wire which could have been put towards replacing the wire. It seems to me that the wire will seem totally OK both resistance and visual until at some point the internal structure of the SS especially near the lower swage lets go. You get a sudden failure of the wire. I have seen it at our club 4 or 5 times. It is just not worth sailing with old rigging wire. all IMHO olewill
Click to expand...

How old is "old"?
 
vyv_cox said:
All my observations show the opposite. Fatigue failures in 1 x 19 wire take place strand by strand until the remainder have insufficient strength to support the load, upon which it fails. This is characteristic of almost all fatigue failures, usually described as 'broke without warning' or 'sudden fracture'. The reality is that the crack(s) may have been growing for years. Several examples at http://coxengineering.sharepoint.com/Pages/Fatigue.aspx

Yacht owners may be more suspicious of such techniques but the power transmission industry has been using resistance measurements of terminals for years, with great success. If yacht insurance companies accept the results I suspect we can assume that there is some truth in the claims for them.
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Rigging is more than 1x19 wire though. I accept what you say about strands failing, but these measurements are taking account of the swages and terminal fittings. You must compare like with like.

Regards

Donald
 
Aja said:
You must compare like with like.
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Which is why they suggest that the best regime is to take regular measurements. In the real world that is nigh on impossible for most of us and in the case of the OP, who I know well, the earlier measurements were made in UK and the latest in Greece. There seems to be considerable variation across the results of each company and between the two. However, the maximum figure is less than 1 ohm, most a lot less, and both companies consider them to be satisfactory. I can find no guidelines to suggest what is good and what is not, hence the OP question.
 
Hello Viv. Yes I do understand what you are saying about fatigue failure of the SS in the 1X19 wire. Fatigue in metals is well documented and understood. You have my highest respect regarding metalurgy. My claims come from friend's experiences. In each case buying an old hardly used smaller keel boat around the 21ft size so 3/16 inch SS wire. The rigging in each case looking fine until it let go. These wires were 25 + years old. Very scary. This experience seems to contradict what we might expect from SS wire. One 32ft racing boat also suffered a similar failure of rigging. Of course mast was demolished in every case.
My other experience was with a fleet of 10 off ten ft training dinghies. These each had about 30 hrs use per year all the rest of the time being unrigged and stored in a shed. Yet over about 15 years all of the rigging wires showed individual strands breaking at the swage. I would not think fatigue related so much as calender time. I guess due to lower loads thse did not actually let go completely.
I have never seen or had reason to be concerned with the other elements of the rigging. usually thse parts in SS are several times larger in load cross section that the wire.
I reckon that 15 years is a good time to replace rigging wire for safety. Especially on the samller KBs.
So problems seem to be worse with smaller wire size. (Corrosion or similar would be worse.) but mostly related to calender time. olewill
 
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