A very fair question. That raises a couple of separate issues.
1) Salt crystals cause damage on board boats in a couple of different ways, and it is important to know how those salt crystals do damage to appreciate how to deal with it.
For steel salt's damage is caused by its hygroscopic nature. The salt actually pulls water out of the air, right up against steel, and it is this water that then causes it to rust directly underneath the crystal. The only way to remove it is to clean off the crystal itself.
On stainless you have the same problem as above, plus the fact that stainless steel when underwater is actually less noble than when it is dry. So you have a very small area of lowered electrical
potential touching an area of higher potential, with an electrolyte in contact with them.... This is a battery
, and causes both rusting of the steel, and micro pitting. This is the cause of crevice corrosion
, which is what makes old stainless even if it looks ok hard to trust.
In dyneema you eliminate the above, but add the abrasive nature of a crystal impregnated in a line. This can be highly abrasive to stranded lines and is a real concern, but dyneema has a few advantages over most lines that really help here.
1) it has a cooeficient of friction about half that of Teflon. Which means that It is actually more slippery than Teflon. This helps keep the crystals from being able to cut into the fibers themselves since they just slip between the fibers.
2) dyneema is incredibly hard to cut. Because of its chemical structure dyneema is one of the most cut resistant materials on the planet (actually dyneema is more abrasion resistant than steel if the threads are the same size). Salt crystals just don't have the abrasion power to cut the line under the forces experienced in a stearing cable. At least not on a scale that is dangerous to the structure of the line itself.
As for line stiffining - unlike most lines that absorb water, dyneema is hydrophobic. Which means that water is not absorbed by the fibers itself. So you don't get the same types of deposits in the line as you do on say Sta-set after a few years. My 3 year old halyards are just as soft and supple as they were the day they went into service
In day to day use aboard cruising boats it depends on the application, but there are a few things to keep in mind. First it doesn't require regular greasing like steel steering cables do (everyone does grease the cables as per manufacturers recommendations right?
). So you eliminate one point of grease on the boat and it's contamination, since dyneema is self lubricating (that coefficient of friction again). Secondly it does fine in dirty environments, none of the chemicals found on a boat will effect it chemically, though keeping it clean is always a plus.
As for stuff rubbing on it... I wish I could post the pictures of where my life lines have rubbed a hole in the piling near my boat. The line looks fine, but there is a 3 inch wear spot in the wood.
In tug boats dyneema lasts about twice as long as steel cable when used a tow hawsers. This is one of the dirtiest jobs on the planet. The same is true for pulling trees through Oregon
forests as lashing lines (if you have ever watched that show axe men
, some companies have replaced all their steel with dyneema and getting much longer life's out of it than steel). I could go on, but you get the idea I hope.
Finally on cruising boats there is now a recommended replacement interval of 8 years of Dynex Dux (heat treated dyneema that is stiffer and stronger) standing rigging
. This is compared to the 8-10 year replacement interval of stainless standing rigging depending on type of fittings used.
Finally dyneema is incredibly easy to splice. It takes no tools, no particular skill, and just a quick explanation will have most people performing professional quality splices in just a few minutes. This means that the 200' 1/4" piece I carry in my sail bag can be made to do duty for pretty much anything on board in minutes. And is amazingly cheap
(about 1/2 the price
of sta-set for the same MBL, so it doesn't have to be wished over or considered 'racing gear
to expensive for cruisers' .
It was pointed out in a PM to me that commercial
advertising is only allowed in certain parts
of the forum, and that I seemed to be running afoul of this. So let me be clear, I am no longer a professional sailor, though I did work my way through college and law school
as a rigger/paid crew on race
boats. But I have no financial interest in dyneema or anything else people use on their boats. Unless you sue a manufacturer and happen to ask me to represent you.