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inf2003
Joined: 15 Jan 2009 Posts: 148
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Posted: Tue Jul 23, 2013 10:14 am Post subject: |
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Thank you , Good explanation. |
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rigitrite
Joined: 19 Sep 2007 Posts: 520 Location: Kansas City
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Posted: Tue Jul 23, 2013 10:16 am Post subject: |
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A good way to prevent this kind of crevice corrosion from ruining your day (you can imagine how unhappy you’d be if that bolt failed at the furthest point from your launch: you lose a $100+ fin and have a nice long body drag back to shore), is to use a little anti-seize compound on the threads. That’s what I do, and just inspect your stainless hardware from time to time. If you see some corrosion in the thread valleys, just get a wire brush and clean it off really well. Fixed! _________________ Kansas City |
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andydavis
Joined: 11 Apr 1999 Posts: 319 Location: Point Isabel
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Posted: Tue Jul 23, 2013 10:37 am Post subject: |
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rigitrite wrote: | A good way to prevent this kind of crevice corrosion from ruining your day... |
what about the embedded nut? seems more vulnerable. |
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spennie
Joined: 13 Oct 1995 Posts: 975 Location: Thousand Oaks, CA
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Posted: Tue Jul 23, 2013 10:41 am Post subject: |
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Interesting. That must be why they need to use aluminum nails on a pool deck. Not much fun to hammer in, but I guess they don't corrode away like stainless would. _________________ Spennie the Wind Junkie
www.WindJunkie.net |
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rigitrite
Joined: 19 Sep 2007 Posts: 520 Location: Kansas City
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Posted: Tue Jul 23, 2013 10:53 am Post subject: |
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The nut is probably brass, which doesn’t suffer the same problems that stainless steels do. Most people also don’t realize that some brass alloys have yield strengths about the same as mild steel: they’re remarkably strong. The biggest danger the nut faces, is damaging the threads: brass is fairly soft, SS is pretty hard. Also, the nut doesn’t experience the bending forces that the bolt does. The fin material around the nut will probably fail before the nut does. _________________ Kansas City |
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inf2003
Joined: 15 Jan 2009 Posts: 148
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Posted: Tue Jul 23, 2013 10:53 am Post subject: |
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so Is stainless steel a non ferrous metal containing little or no iron ore? |
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superkraut
Joined: 18 Mar 2001 Posts: 346
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Posted: Tue Jul 23, 2013 11:52 am Post subject: |
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ouch - Stainless Steel such as the ubiquitous 316, is about 70% iron |
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andydavis
Joined: 11 Apr 1999 Posts: 319 Location: Point Isabel
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Posted: Tue Jul 23, 2013 12:47 pm Post subject: |
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rigitrite wrote: | The nut is probably brass, which doesn’t suffer the same problems that stainless steels do. ... Also, the nut doesn’t experience the bending forces that the bolt does. The fin material around the nut will probably fail before the nut does. |
yeah, brass actually has worse problems. Maybe you've never witnessed it, called dezincification...the zinc essentially just leaches away, leaving a rotten, spongy matrix.
I don't know what you're talking about. The bending moment on a bolt in a Tuttle or Power box is zero. With the a tightly fitting fin/box connection, any bending moment on the bolt itself, even if the fin impacts something, is probably about zero. Zero bending force on the bolt. |
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rigitrite
Joined: 19 Sep 2007 Posts: 520 Location: Kansas City
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Posted: Tue Jul 23, 2013 1:14 pm Post subject: |
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Yes, heard of de-zincification, but I don’t think that’d be a problem in non-chlorinated water. It happens to plumbing componants that are bathed in municipal water for a long time is what I know about it.
My point about the bending forces on the bolt are from the picture at the start of the thread; there is a very small amount of bending force on the bolt to force that crack to progress. You are correct that most of the force on the bolt is tension, this also helps to progress the crack. If the forces where purely tensile, then the beach marks would make concentric circles around the final brittle failure (like a bullseye). When there’s bending, they march across from a specific initiation point to the rupture line (exactly like the picture).
Don’t ever get me started on composites or non-metallic materials; the geek-out on this thread already goes to 11. _________________ Kansas City |
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windoggi
Joined: 22 Feb 2002 Posts: 2743
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Posted: Tue Jul 23, 2013 1:15 pm Post subject: |
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isobars wrote: | I put on a pair of rubber gloves before clicking on this thread. | I was wondering when you'd show up. _________________ /w\ |
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