Posted by Eric S on April 19, 2005 at 20:36:23:
In Reply to: Fins snaggingand Kelp posted by Chuck Tribolet on April 19, 2005 at 09:03:55:
I have a little knowledge in metalurgy, mostly from my welding school days, so I think am somewhat qualified to comment on this issue.
I am not 100% sold on spring straps and I'll tell you why.
All metal is subject to fatigue when bent contsantly over and over again. The wire in a spring technically gets bent every time the fin is pulled on and off. Even though the metal is hardened so the grain will retain memory it still gets compromised from movement.
Additionally, the stainless steel used for spring material would have to be 400 series stainless instead of 304, 310, 316,etc., meaning that it contains not only heightened amounts of chromium and nickel, but it would have to contain a measure of carbon as well to become hardenable. Anytime you have carbon we all know what happens, you get rust and/or corrosion, especially in the presence of salt water.
The problem I see with spring straps in there would be no warning prior to a failure. I don't think there would be any way to accurately inspect them to avoid breakage. Not only that, stainless, weather it be 300 or 400 series, can suffer from an internal corrosion similar to a tooth cavity where the corrosion starts as what appears to be a small hole and the metal is eaten from inside out. The the oxide is a smelly black sludge. In something the size of spring wire there's not much material there to sacrifice!
Spring straps seem like a good idea on the face, but upon further study of metals it is evident that they indeed may not last a lifetime.
I think regular rubber straps work just fine and can be inspected regularly for any signs of wear prior to each dive. They are also much more economical.
Now if the springs they use are made of monel then thats another story. I have very limited knowledge of the properties of monel or if it can even be used for spring material in any form.
But as far as I understand stainless spring material is 400 series.
Another option I have considered would be to take some of those heavy rubber bungee straps, not the regular colored bungees, but the thick flat rubber ones with the metal hooks on each end and make something out of those.
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