interesting failure- dyneema rig terminal

[Benz]

Originally Posted by double u

...why use in-millions-of-cases-tried-&-true-stainless-standing, when you can go to these length to have rigging your angry/drunk/idiot marina neighbour can cut with a knife...

Why hijack a thread that has become very interesting to vent an uneducated opinion that nobody cares to hear?

Start your own thread on synthetic vs metal if you like, but let us follow Mark's progress in peace.

[seandepagnier]

Originally Posted by double u

...why use in-millions-of-cases-tried-&-true-stainless-standing, when you can go to these length to have rigging your angry/drunk/idiot marina neighbour can cut with a knife...

This is an example of what not to do with synthetics and tangs and how to correct it. It is very useful to see these types of failures to understand the limits and avoid making the same mistakes.

There is no way to correct stainless since it is not the right material and fails unpredictably weakening from stress cycles and is also very simple to cut using bolt cutters.

[Franziska]

Originally Posted by double u

...why use in-millions-of-cases-tried-&-true-stainless-standing, when you can go to these length to have rigging your angry/drunk/idiot marina neighbour can cut with a knife...

Well, this is extremely rare to happen, isn't it?

Here are a couple of plus points:

Dyneema rigging is saving you a ton of weight aloft which improves sailing performance.

You can actually do it yourself with a bit of study upfront.

The material price is often lower.

If you oversize the Dyneema a bit UV is equally not a real issue for many years.

Not a lot of things not to like actually...

[markxengineerin]

Yes, nothing "tried and true" about stainless rigging. On my boat alone, in the last year, there have been 4-5 cases of death by crevice corrosion. I'm talking about bolts that snapped while snugging them up by hand, a chainplate that disintegrated instead of bending (after I removed it), and misc brackets on deck. Stainless rigs work well when replaced at certain intervals (very expensive and wasteful IMO) or when they sit around un-used and un-tested 99% of the time (most sailboats).

Downsides of Dyneema from what I have seen so far, in 1 month of use
-Chafe is a big concern. My radar reflector ball wore partway through one of the shrouds while I slept, which was entirely my fault, but is a non-concern with metal rigs
-while it is lighter, I have un-done some of that advantage with the massive compression posts. They are not light. This could be corrected in a future iteration of the mounting system, now that I have a better understanding of the loads and baseline mast than when I started.
-Nobody knows or has published the relationship between rig tension and ambient temperature. I will be working on this once it's all back together, but it will take a while, and there will be a lot more variation vs. a steel rig.
-Nobody has justified the "stiffness" of dyneema. Colligo has posted a chart, but it conflicts with other sources, and I think it's likely to depend on temperature. I should have studied this while I was set up to do it, but too late now, will have to wait for another year.
-Very limited durability/lifetime vs. UV etc data available. Again, only from Colligo and it would be nice to have more info
-Cost was not all that different, depending on where you are in the country. Dyneema prices keep going up, I want to say the dyneema itself cost about $2000, and this was over a year ago. Prices have gone up since. Equivalent new stainless parts would be $3000 or so- estimated by a rigger in Virginia. Other locations you could pay double or more, so I'm not sure how reliable that estimate is. Either way, if I didn't make the fittings myself, I would not have saved any money. If I was doing this again, I would not go synthetic again, but I am glad I went through this process, learned a ton.

[markxengineerin]

Backing plates are in- a dab of GFlex epoxy on each corner to hold them in place while I assemble the rest, and lots of TefGel on the temporary bolt threads to hopefully prevent them from getting glued in place overnight.



Looking around the yard, the bigger and higher end boats have this style of mast connection for the shrouds, providing a little more support for the "compression tube":

Compression tube being the wrong name- the bolts are just acting as pins, no pre-load needed or even beneficial, as long as the nuts are prevented from loosening off by other means. This style looks more difficult to convert over to "hangers" by the standard methods I've seen.

[clockwork orange]

I haven't read every post so i don't know if this has been mentioned but, since you did mention earlier that you used 5/8"-11 threaded rod for the pin i would suggest having a machine shop thread a piece of rod instead so that the only thread is outside of the mast, just enough thread on each end for the nut. 5/8" threaded rod is really closer to the strength of a 1/2" solid rod.

[markxengineerin]

Yes, the new bolts ($20 each from McMaster Carr) are not threaded where they would be in bending, are not allowed to be in bending at all anymore by design such that the joint takes the bending instead, and also 5x higher yield strength by switching to grade 8 steel instead of the 316 stainless. I have little doubt that the repair is stronger than the original factory wire setup. The factory used a 5/8-11 bolt for the uppers, and a size down from that for the lowers, with a threaded portion loaded in shear. I believe there was a lot of fretting going on with that setup, as when I hammered bolts the bolts out, large piles of white powder came too. This is to be expected where a stainless bolt moves against an aluminum bushing of sorts under high load in a salty environment. It worked until now because it was big enough, but I would be willing to bet that joint or the tang itself the failure point in a de-masting situation, with all new parts. Just look at the usual size differences between tangs and chainplates. Standard practice makes sense given the locations, weights, and materials used, but with titanium chainplates, those aren't going to corrode anymore, so I might as well attempt to make the top connection similar in strength to the bottom one. Now capable to 8000+ pounds.

[Celestialsailor]

You're using a steel bolt for this?

[markxengineerin]

Yes- the bolts are all steel, not stainless. They'll be coated in west system resin and then some type of other white paint on top (any recommendations?)

I doubt corrosion will be a problem, as I hope to keep the mast out of the water. Steel bridges over salt water, steel suspension components in a cars that drive on salted roads (even un-painted), and plenty of rigging on older boats used non-stainless in what I judge to be similar applications.

A grade 8 fastener can also afford to lose about half of its strength due to corrosion and still be as strong as a brand new 316 stainless equivalent. IMO stainless is way over-specified on sailboats due to good marketing->popularity->low cost which is a virtuous circle type situation and makes it tough for any alternatives to gain traction. I'm (obviously) not arguing steel bolts are better than stainless for all applications on a boat, this is a side observation.

[neilpride]

Originally Posted by markxengineerin

Yes- the bolts are all steel, not stainless. They'll be coated in west system resin and then some type of other white paint on top (any recommendations?)

I doubt corrosion will be a problem, as I hope to keep the mast out of the water. Steel bridges over salt water, steel suspension components in a cars that drive on salted roads (even un-painted), and plenty of rigging on older boats used non-stainless in what I judge to be similar applications.

A grade 8 fastener can also afford to lose about half of its strength due to corrosion and still be as strong as a brand new 316 stainless equivalent. IMO stainless is way over-specified on sailboats due to good marketing->popularity->low cost which is a virtuous circle type situation and makes it tough for any alternatives to gain traction. I'm (obviously) not arguing steel bolts are better than stainless for all applications on a boat, this is a side observation.

As a side note: Salt deposits can get all the way to the top of the mast, if you're ever anchored for a few days in an open bay with off-shore winds or somewhere with low ground level and off-shore winds for a few days, you can see how the salt deposits and moisture stick to everything.

With steel,the one that will fall first is aluminum.

[markxengineerin]

With steel,the one that will fall first is aluminum.

Do you mean the steel will cause the aluminum to corrode worse than stainless would? Either way, I am curious about that if anyone knows!

[neilpride]

Originally Posted by markxengineerin

Do you mean the steel will cause the aluminum to corrode worse than stainless would? Either way, I am curious about that if anyone knows!

Exactly, the mess when the steel start to corrode in contact with bare aluminium its fenomenal.

[neilpride]

316 ss leave no residues when start to rust like steel, most corrosions isues in a aluminium mast between 316 ss and alu are due to bad preventive measures and errors in the installation.

[Knotical]

Originally Posted by Patrick of M

Excellent thread, lots of different perspectives etc.
Basically what the internet is good at, and nobody called anyone names or even got all shirty.... yahoo

Completely agree with this, even when people were critical of your ideas and methods you listened to them, admitted your mistakes, and responded with respect - keeping the thread civil and on topic. As a result, people who criticized you still remain interested in the thread and want to see what solution you come up with.

Good luck with your project.

[Celestialsailor]

Originally Posted by markxengineerin

Do you mean the steel will cause the aluminum to corrode worse than stainless would? Either way, I am curious about that if anyone knows!

I really don't know why you continue to reinvent the wheel. I had mentioned before that you previously used all-thread which is a no-no but you argued that also. All-thread sets up failure points at every thread. A simple Stainless bolt with it's threads terminating at or just outside the mast is what has been done for the last 70+ years. A simple layer of mill tape around the bolt will help insulate it from the aluminum. Again...you are over thinking these things.