My turnbuckle has failed........

[FasterHorses]

FH has been hauled out for winter storage......
The task has been completed, however not without a hitch. The marina calls me at work to tell me that the turnbuckle connecting the backstay has failed during the haulout, and that they recommend that I have our rig inspected and the backstay replaced. The marina continued on with the haulout and replaced the turnbuckle with one they had on hand. When I got down to the boat and looked at the condition of the turnbuckle, I noted that it is the same thing that happened a few years back, was this a sign? Concerned as to the cause of this, I asked the mechanic who replaced the turnbuckle but he could not pinpoint the cause, but did raise a point about lubricating all my turnbuckles. So here is my question(s)..... Has this happened to anyone else and did you find a cause? What type of lubricant would be adequate to use and frequency?

 

[dlochner]

How old is your standing rigging? It could be at are near its end of life.

Yes, lubricate the turnbuckle. Each spring I give the studs a quick shot of McLube, makes tuning the rig much easier and less likely to strip the threads. I've also used Lanocote, however, that stuff remains a bit sticky and seems to pick up dirt and grit. A dry lubricant is probably best and try not to spray on to the deck.

 

[smokey73]

What the heck? I've never seen the whole threaded fitting "pull out" the threaded portion in one continuous strip! I"ve seen many a threaded fastener strip or the receiving portion of the fastener strip but that failure mode is really strange. Wonder what Mark's Handbook (Mechanical Engineer's bible) says about this?

Those look like some sort of "threaded insert." What brand are these turnbuckles? Where they repaired at some point in the past with a helicoil or some other brand of threaded insert?

Inquiring minds want to know. This is a failure mode we all should want to know more about.

 

[markwbird]

Pulled the threads right out. At both ends no less. Too tight? Vibration causing metal fatigue? Substandard turnbuckles? All of the above?

 

[jssailem]

Those look like some sort of "threaded insert." What brand are these turnbuckles? Where they repaired at some point in the past with a helicoil or some other brand of threaded insert?

My first thoughts. A helicoil, but I have never heard of that application a turnbuckle. Besides it would be an expensive repair when compared to an average turnbuckle.

That is unusual and a pair. Looks like it could have been a manufacturing issue. When they cut the threads they damaged the threads. I can conjecture that the motion of the mast would have strained the threads. Causing metal fatigue on the threads. Perhaps they became galled. Then when removed the threads just broke out of the turnbuckle. I suggest you were very lucky this season.

It is a good example of the need to select well made (some might say EXPENSIVE) turnbuckles when assembling your rig. Those you might find in Harbor Freight or some discount store, might not be the best choice to hold a critical item (the Mast) in place.

I would agree, a careful inspection of all of your rigging would be advised.

While we all would like to buy parts that will last forever it just does not happen.

 

[thinwater]

From Lewmar:

What do you recommend for lubricating the turnbuckle threads?
For turnbuckles with dissimilar metals, for example a bronze screw (chrome plated or exposed bronze) in a stainless steel body, any good waterproof grease is adequate. Lanicote is also used frequently. Oil, especially some of the oils with Teflon can also be used. For turnbuckles with stainless steel screws in stainless bodies, a grease containing Molybdenum Disulfide should be used. A dry lubricant containing Molybdenum Disulfide can be used. At this time, we know of no lubricant which comes close to the effectiveness of Molybdenum Disulfide in preventing galling. Note that Molybdenum Disulfide is black and makes sails and hands black very effectively!

 

[Tedd]

Besides it would be an expensive repair when compared to an average turnbuckle.

Not if you already have the inserts and tools. I can put one in for you in a few minutes, for peanuts. I wouldn't, but I could...

 

[justsomeguy]

From Lewmar:

I wonder why they felt the need to capitalize "molybdenum disulfide"? ¯\_(ツ)_/¯

 

[Calif. Ted]

I think I've only seen threads pull out in stainless when they have been cross threaded or thread pitch mismatched.

 

[smokey73]

I think I've only seen threads pull out in stainless when they have been cross threaded or thread pitch mismatched.

Interesting failure mode. Looks like what we saw in the OP picture so not threaded insert but certainly disconcerting. Really not "stripped" threads as we normally see but rather shear of the threads away from the base material.

 

[capta]

Not if you already have the inserts and tools. I can put one in for you in a few minutes, for peanuts. I wouldn't, but I could...

Are there stainless or bronze ones? I've only seen steel.

 

[Ralph Johnstone]

Has this happened to anyone else and did you find a cause?

Can you supply a picture of the two end fittings to show the condition of their threads ?

 

[Tom J]

FH has been hauled out for winter storage......
The task has been completed, however not without a hitch. The marina calls me at work to tell me that the turnbuckle connecting the backstay has failed during the haulout, and that they recommend that I have our rig inspected and the backstay replaced. The marina continued on with the haulout and replaced the turnbuckle with one they had on hand. When I got down to the boat and looked at the condition of the turnbuckle, I noted that it is the same thing that happened a few years back, was this a sign? Concerned as to the cause of this, I asked the mechanic who replaced the turnbuckle but he could not pinpoint the cause, but did raise a point about lubricating all my turnbuckles. So here is my question(s)..... Has this happened to anyone else and did you find a cause? What type of lubricant would be adequate to use and frequency?

View attachment 187236View attachment 187237

On the positive side of this almost catastrophic failure, it's good that it happened during haul out, and not "out there". On the negative side, that is a complete failure of a critical component. I would have thought a swagged fitting would fail before the turnbuckle itself.
As far as cause, a lot of strain was put on the part that failed. How was the boat hauled? If it was by Travel Lift, care must be taken that the fore stay or back stay do not impact the cross member at the top of the Travel Lift. At the marina I worked at, we often had to remove a stay and hooked up a temporary stay with a halyard, etc. Some boats fit into the straps without hitting the cross member, and some didn't.

 

[Dave Groshong]

If you send in your old rig, our prices are unbeatable! If you want to measure each piece and send pictures of the ends, I can give you a quote prior to mailing the old rig in.

 

[thinwater]

Not if you already have the inserts and tools. I can put one in for you in a few minutes, for peanuts. I wouldn't, but I could...

But it is a terrible repair. Stainless vs. stainless is never used in rigging turnbuckles for a reason.

 

[thinwater]

I think I've only seen threads pull out in stainless when they have been cross threaded or thread pitch mismatched.
View attachment 187242

That's not a mismatch, that is classic galling damamge. If it were the iether of the former the threads at the end of the bolt would show severe damamge. The nut was tightened too quickly under high load with no lubricant. And probably overloaded too.

The OPs damamge was not from over stress. The treads are far too long for that. Something else would have brokken first. This is galling damamge, the result of no lube. A little unusual bronze, but not if you ask riggers. Reasonably common if not lubed. The damamge was probably started when the rig was tightened, but became obvious when relieved.

The question is... who rigged the boat last year (I assume the stick is taken off every year)? I'm guessing it was not the owner, so the rigger that last touched it has some explaining to do. The grease should have lasted "a few years" without difficulty. Not 10 years, but a few.

 

[dLj]

That's not a mismatch, that is classic galling damage.

With all due respect, this is not galling. Galling presents itself with material transfer between the two components that are interfacing each other. those images did not present that specific cause. If it were galling, the material would be strongly "stuck" to the other side...

@FasterHorses given the photos that you have uploaded it's a bit difficult to give an exact cause of failure. To do so would require detailed images both of the male threaded component, more detailed images of the parts shown, and the internal surfaces of the female threaded component. At first glance, it appeared as if you had heli-coils inserted in the female side of that turnbuckle. But since I've had a bit more time to look closely at the images you did upload, it may simply be that the threads from the female side have broken. That may have occurred through a number of mechanisms, the more likely is fatigue. You ask about using lubrication, but the real question is how old are those turnbuckles. You also state this is the second time one has broken. Given the small amount of information available at this point, I'd have to say that you may do well to replace all turnbuckles. Also a review of how you are using these may be in order. Lubrication could be part of that review.

Just my 2 cents worth...

dj

 

[thinwater]

With all due respect, this is not galling. Galling presents itself with material transfer between the two components that are interfacing each other. those images did not present that specific cause. If it were galling, the material would be strongly "stuck" to the other side...

@FasterHorses given the photos that you have uploaded it's a bit difficult to give an exact cause of failure. To do so would require detailed images both of the male threaded component, more detailed images of the parts shown, and the internal surfaces of the female threaded component. At first glance, it appeared as if you had heli-coils inserted in the female side of that turnbuckle. But since I've had a bit more time to look closely at the images you did upload, it may simply be that the threads from the female side have broken. That may have occurred through a number of mechanisms, the more likely is fatigue. You ask about using lubrication, but the real question is how old are those turnbuckles. You also state this is the second time one has broken. Given the small amount of information available at this point, I'd have to say that you may do well to replace all turnbuckles. Also a review of how you are using these may be in order. Lubrication could be part of that review.

Just my 2 cents worth...

dj

On the bolt, I don't think I agree. Yes, the damamge starts with transfer, but often it is only visible at the 20x magnification level. I've seen the threads subsequently rip out in just that manner.

As for the turnbuckle, the threads are really too long for fatigue damamge. That's not an accident. And the mileage is way too low. Other stuff will break. I'm still voting for lack of lube.

 

[dLj]

On the bolt, I don't think I agree. Yes, the damamge starts with transfer, but often it is only visible at the 20x magnification level. I've seen the threads subsequently rip out in just that manner.

As for the turnbuckle, the threads are really too long for fatigue damamge. That's not an accident. And the mileage is way too low. Other stuff will break. I'm still voting for lack of lube.

There is no image of the bolt. If galling were the main problem then the nice shinny exterior on the threads seen in the two spirals would not exist. If galling were the issue, then the damaged threads would be embedded in the male side thread or embedded in the female side threads, Neither is the case in the original images.

I don't know what the mileage is you allude to, and fatigue can occur over any distance.

The main point of what I'm saying, is the images given are insufficient to know what caused these threads to break. But galling is not the main cause. The image below is a blow up of the one side that has a bit better focus, note the very shinny threaded surface that interfaces with the other threaded component. If galling were the cause, this would not look like this at all.

dj

 

[thinwater]

There is no image of the bolt. If galling were the main problem then the nice shinny exterior on the threads seen in the two spirals would not exist. If galling were the issue, then the damaged threads would be embedded in the male side thread or embedded in the female side threads, Neither is the case in the original images.

I don't know what the mileage is you allude to, and fatigue can occur over any distance.

The main point of what I'm saying, is the images given are insufficient to know what caused these threads to break. But galling is not the main cause. The image below is a blow up of the one side that has a bit better focus, note the very shinny threaded surface that interfaces with the other threaded component. If galling were the cause, this would not look like this at all.

dj
View attachment 187258

I did not say galling was a part of the bronze thread failure. I was responding to a failed SS bolt photo and sayingthat I did not thing it was mismatched threads. That is all I said.

Galling would be very unusual with bronze, which is the reason it is used for turnbuckles. Without a really close examination, this is a mystery. That fact that he said this had also happened a "a few years back" is interesting, suggesting a common factor. Fatigue seems unlikely. The boat is only sailed summers, probably not hard, and I assume the rig was professionally tuned (not slack). This makes fatigue seem unlikely. That the mechanic mentioned the lack lube is interesting. Also though t damamge is not galling, I'm wondering if the last mechanic spun the turnbuckle right up to tension, too fast (there is a LOT of heat generated if the threads are dry) and without lube, doing damamge at that time. Turnbuckles need to be tightened VERY slowly under load. Doing this fast is common, and often unnoticed error, because the damamge is hidden.