HR shackle explodes

[fxykty]

Five years ago we had an HR block and a matching block on our running backstays explode during heavy conditions. Last week we had another HR shackle explode. This time during upwind sailing in short seas - this one was on one of our mainsheet blocks. A very loud bang and the mainsail goes slack. First look was up at the rig and the sail, then with relief saw it was just the block failure.

The take aways are that HR steel is brittle and does not deal gracefully with shock loads above working loads.

[pcmm]

Who is "HR"? Sounds like an "unknown" brand to me

[ozolli]

Originally Posted by pcmm

Who is "HR"? Sounds like an "unknown" brand to me

HR stands for High Resistance (stainless steel). It's in fact 17-4Ph stainless steel or 1.4542.
HR has been in use by Wichard for their shackles.

[GordMay]

Originally Posted by pcmm

Who is "HR"? Sounds like an "unknown" brand to me

High-Resistance (“HR”) shackles are forged in either, marine grade High Resistance ‘17-4PH’ stainless steel, or (sometimes) ‘TA6V’ Titanium.

Both Harken, and Wichard, at least, offer “HR” shackles.
Wichard claims that their HR shackle can be up to 60% more resistant than a shackle in 316L stainless steel.

AISI 316 Stainless Steel vs. S17400 (‘HR’, 17-4PH) Stainless Steel
➥ https://www.makeitfrom.com/compare/A...tainless-Steel


I see ozolli beat me to it.

[pcmm]

So I guess the question remains, who's shackle here failed? The OP used "HR" like it was a brand not a specification... and what size shackle was it on what size boat under what load?

[thinwater]

The threads are not stripped or have the matching part attached. There is no evidence of mousing wire (SS wire could have failed, particularly if over-twisted during installation). Mousing requires regular inspection.



Are you sure this did not just come unthreaded? This is not actually a gear failure. I've tested these to failure, and this is not what a strength or fatigue failure looks like IMO. I've also seen unthreaded failures, and they look like this.

[Mal Reynolds]

I've had an HR shackle blow up when going upwind in 10 knots. Upon inspection it was obviously crevice corrosion. Maybe it's related to oxygen deprivation where metal meets metal.

Yours does look different though. Maybe you just had a defective part.

I replaced mine with another HR shackle for simplicity, but learned to keep an eye on it.

[Tin Tin]

How old was the shackle?