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#1
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
Are solid stainless steel rods any less vulnerable?
What alloy is used for major standing rigging; there must be some less prone to chloride/stress attack, or? I worked with some higher than 316 plus extra titanium alloy(32?) for seawater boiler; it was a much better choice than regular 316. I am not sure if this alloy is being offered in steel rope shape. Any one knows more about it? thanks |
#2
posted to rec.boats.building
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Inspecting Standing Rigging
noexpert wrote:
Are solid stainless steel rods any less vulnerable? What alloy is used for major standing rigging; there must be some less prone to chloride/stress attack, or? I worked with some higher than 316 plus extra titanium alloy(32?) for seawater boiler; it was a much better choice than regular 316. I am not sure if this alloy is being offered in steel rope shape. Any one knows more about it? thanks Most sailboat rigging is 304. Some is 316 but it's a bit weaker than 304 (about 10%). Rod rigging is usually Nitronic 50. More corrosion resistance but no warning of failure like broken strands. About twice the cost of wire rope so it's restricted to racing boats Evan Gatehouse |
#3
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
noexpert wrote:
Are solid stainless steel rods any less vulnerable? What alloy is used for major standing rigging; there must be some less prone to chloride/stress attack, or? I worked with some higher than 316 plus extra titanium alloy(32?) for seawater boiler; it was a much better choice than regular 316. I am not sure if this alloy is being offered in steel rope shape. Any one knows more about it? thanks Just a suspicion, but it seems to me that the problem here is a result of the swaging process itself. When the swage is squeezed, there should be uneven compression which would cause the material to yield unevenly - leading to rather high localized stress concentrations. In-service vibration, over time, should lead to exactly the kind of cracks described by GBM. FWIW, for highly stressed aircraft cables, the terminals (ends) are *Rolled* rather than squoze... Richard |
#4
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
"cavelamb" wrote Just a suspicion, but it seems to me that the problem here is a result of the swaging process itself. When the swage is squeezed, there should be uneven compression which would cause the material to yield unevenly - leading to rather high localized stress concentrations. In-service vibration, over time, should lead to exactly the kind of cracks described by GBM. FWIW, for highly stressed aircraft cables, the terminals (ends) are *Rolled* rather than squoze... Richard Could be, but experience shows that this type of failure does not occur in fresh water. The experts advise that it is the presence of chlorides in crevices with an oxygen deficient atmosphere and stress that cause the failure. The whole swage and the wire strands are stressed to various degrees. GBM |
#5
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
GBM wrote:
"cavelamb" wrote Just a suspicion, but it seems to me that the problem here is a result of the swaging process itself. When the swage is squeezed, there should be uneven compression which would cause the material to yield unevenly - leading to rather high localized stress concentrations. In-service vibration, over time, should lead to exactly the kind of cracks described by GBM. FWIW, for highly stressed aircraft cables, the terminals (ends) are *Rolled* rather than squoze... Richard Could be, but experience shows that this type of failure does not occur in fresh water. The experts advise that it is the presence of chlorides in crevices with an oxygen deficient atmosphere and stress that cause the failure. The whole swage and the wire strands are stressed to various degrees. GBM Capillary action would draw water up the wires and into the fittings. Sea water there would be a bad thing (tm) that would aggressively attack the small surface fractures in the fitting. Your point about sealing the swedged fitting with epoxy should reduce the susceptibility quite nicely just by sealing the open end of the wire and fitting. Keep the nasty old sea water out of those tender places... Richard |
#6
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
"noexpert" wrote in message ... Are solid stainless steel rods any less vulnerable? What alloy is used for major standing rigging; there must be some less prone to chloride/stress attack, or? I worked with some higher than 316 plus extra titanium alloy(32?) for seawater boiler; it was a much better choice than regular 316. I am not sure if this alloy is being offered in steel rope shape. Any one knows more about it? thanks Navtec rod rigging uses an alloy they call "Nitronic". It is supposed to be much more resistant to corrosion than the alloys commonly used in wire rigging and turnbuckles. |
#7
posted to rec.boats.building,rec.boats.cruising
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Inspecting Standing Rigging
I remember the collapse of a public pool ceiling killing a number of peoples
in switzerland some years ago. The hang up ceiling was supported by hidden 304 type (18-8) S-hooks behind and out of sight for inspection. I recall the report stating that the chloride laden pool air and humidity exposed the hooks causing this intercristaline corrosion leading to sudden failure to support loads. As I understand the engineering world in Europe took note and better suited s/s alloys are utilised now. If rigging for ocean going boats is still made from 304, I think it amounts to criminal negligence to continue to equip boots with these essential structural members in a maritime environment where plenty of chloride (salt) are present. Having worked with both 304 , 316 and others the price difference of those different alloys were not really the mainconcern but mainly to get the right stock for the task on hand. I am not clear what the nitronic s/s alloy is made of, but if it is more suitable why bother with 304 at all. |
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