I was out sailing on a beautiful day in Baltimore when all of a sudden, the clew on sail starts flopping in the wind. I thought perhaps that my dyneema lashing had come off the cleat, but in fact it was that the stainless steel shackle that connects the end of the boom to the clew that blew up!
Bob,
Unusual, so how did you recover?
Brian
Dropped the sail. Not a huge problem really. I should have just put in the first reef and kept sailing.
I’ve seen these things go on very rare occasions a few times over 41 years.
If there’s someone who knows metallurgy, they could probably tell you the cause if you have a picture that shows more of the cross-section surface of the break.
Sometimes it just pays to replace old rigging just on the principle that it can’t hurt.
– Bob
Hi Bob
Glad you were safe!
Had the topping lift shackle do the same thing this past summer in very heavy conditions while heading to Boston from Kittery, ME. Noticed the block/lines flopping around near the aft end of the boom.
When we got into the outer Boston Harbor we slowly lowered the sail into the stackpack while making sure we were directly into the wind allowing the sail to lay on the dodger and bimini. A piece of the shackle was still attached, looking the same as your shackle photo. Put a new shackle in place and was able to properly lift the aft end of the boom to prevent damage to the bimini during the hour long trek to Constitution Marina.
Peter Grabow
I agree with Bob N, I’m new to “old” boats, but after two seasons with Soave I’m getting the hang of preventive maintenance.
Seems like “immortal” materials ( or I thought to be immortal as a dinghy racer ) like stainless steel, aluminum, and fiberglass all eventually fail after 30-10,000 years or so.
What will fail when ?
Preventative maintenance helps me rest easier, and redundancy for critical items is worth the extra weight and expense.
The pin from one of my wishbone hanger shackles broke with minimal effort when dropping Soave’s wishbone this fall. Minor inconvenience ( having to saw it off ) but a gentle reminder that nothing is immortal.
I’m accumulating a bunch of “2nd life” parts in my junk box that I use in less mission critical settings than sailing…
Not having seen the fracture surface of the break, I suspect it fractured because the stainless steel was brittle. It is a clean break with no deformation , which indicates a brittle fracture.
There is a very small chance it failed by fatigue. If so, the fracture surface would be relatively smooth and have clamshell like markings
As well, in the photo of the boom, it looks like the shackle might have had a side load on it instead of a straight pull. A side load can reduce a shackle strength in the range of 40%
Stainless steel can become brittle during the forging and subsequent cooling process, if the cooling rates are wrong. In service, the steel could then fail under a shock load. A scratch or gouge on the surface, increases the likelihood of a brittle fracture.
The shackles at marine stores are very likely properly forged and the card they are attached to, will give give a load rating. Usually this is the working rating, which has at least a 4:1 safety factor before failure would occur. At a local hardware store I have seen about 5 shackles on a ring for a few dollars, and of course no load rating. The stainless steel may also below grade and incorrectly forged.. I would not use these for any critical application.
John Barbour
Nature 26U
Toronto.
On my final sail of the year. I lost the same shackle. It fell on to the deck without the split ring that holds it in place but the shackle itself was badly bent. I suspect that the split ring failed. I have had split rings fail before, once catastrophically racing on a J105 when the mast stay flew off cracking the deck. I am replacing with a heavier duty Garhauer block and shackle but am concerned that the shackle may be too big for the pad eye. Boat is on the hard and I’m not going to clamber around inside the cover to check but I do think that the shackle which was like yours is too small. I wish I had thought to reef and continue sailing. Still, might not have been a good idea. Reefing the day before in heavy winds I got an override on the winch.
Gemini suggests… " The image provided appears to show a brittle fracture of a metal component, likely a rod or bar."
When asked for explanation of observation, Gemini added " Chevron marks or radial lines that point back to the fracture origin are often visible. The image you provided shows these radiating lines, indicative of brittle cleavage."
The bottom line, it broke.
I asked Gemini if inspection may have identified the potential for failure.
Answer : " For the type of failure shown in the image, which appears to be a surface-initiated crack that led to a brittle fracture, the most suitable Non-Destructive Testing (NDT) methods for detection prior to failure are Liquid Penetrant Testing (PT) , Magnetic Particle Inspection (MT) , and Eddy Current Testing (ET) .
My thoughts based on experience with Soave … Replacing critical parts of unknown origin and parts showing wear is probably the safest and most cost effective approach. For expensive stuff “like masts” I’ll start using penetrant testing more frequently.
Thanks for the thought provoking photo. I think I’ll buy some shares of AI stocks tomorrow.
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Have a sailing buddy who got a deal on some pretty shiny stainless shackles. Look great until the head shackle on the spinnaker blew apart rather spectacularly dropping the sail under the boat and ripping it. Turned out that these were cast parts not forged.
You get what you pay for when it comes to fittings.
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I was in the local sailboat store - where you can get very good quality parts - and I bought a Wichard shackle. The guy at the counter asked why I needed such an expensive shackle for just a 33’ boat. I asked him how it is that the safety or lives of myself or my crew are less important than of someone who owns a larger and more expensive boat. The customer near me agreed and the clerk (a very young guy) learned a lesson. Or seemed to, anyway.
Shackles are not expensive parts, compared to many others on the boat. And they tend to be very important. I had a no-name shackle deform to the point where it was scary. I replaced it with a Wichard. Wichard or Schaefer are the only ones I’d trust and it seems that whenever I’m looking for hardware around here I end up finding a Wichard that fits. Your mileage may vary.
Read carefully. Some companies list working load and you should not exceed that, because it leaves plenty of safety margin. Some companies list breaking load and you should definitely follow the 4:1 rule that John states. Also, forging is expensive and the manufacturer will definitely brag it up if it is forged. If it doesn’t say “forged” it probably isn’t - even in a marine store.
I use carabiners to clip my fenders to the lifelines and even those are properly forged marine quality hardware. Why? Because there’s a chance they might be used for some other purpose in an emergency and I don’t want to worry about them. (Plus, they come with a no-snag gate.)