Island Time 1,345 Posted January 6 Share Posted January 6 Well, this year id planned to replace the standing rigging on IT. Have to be sooner now, broke the forestay today, inside the furler drum, the threaded part of the swage failed as per pics below. Not my specialty, but seems to be an embrittlement failure which is not common. 14 years old. No visible corrosion. Quote Link to post Share on other sites
Island Time 1,345 Posted January 6 Author Share Posted January 6 Ok, we were sailing yesterday fully loaded. But it failed at anchor today with a decent bang as the preload released. Damn lucky not too lose the rig... Quote Link to post Share on other sites
LBD 212 Posted January 6 Share Posted January 6 See the line in the middle... that is where it has been bending back and forth and is the last point to fail. The crack clearly began in the root of the threads either side of that last failure line, and migrated to the center. Thread roots are stress risers.... This is less of an embrittlement failure and more of a flexing bending failure. The other clue is the broken piece sticking out appears bent to the right in the top photo. What is the toggle set up on the deck side of the turn buckle? Is the fracture line in line with the boats centre line or across? 1 Quote Link to post Share on other sites
aardvarkash10 1,160 Posted January 6 Share Posted January 6 we need a "holy sh*t" emoji 1 Quote Link to post Share on other sites
SloopJohnB 337 Posted January 6 Share Posted January 6 How many clevis are there attaching the forestay to the chainplate, you really need 2 to allow moment in all directions. 1 1 Quote Link to post Share on other sites
Frank 217 Posted January 7 Share Posted January 7 In my old life in aviation we would sometimes call that dull middle bit the fast fracture zone where the crack propagated at speed to final failure. The striations either side of that we regarded as fracture progress lines created as the crack propagated,probably over some years. Yes it certainly started at the thread root but it's hard to imagine where the cyclic loading is coming from, perhaps the furler ? There was an article in Boating NZ many years ago where some owner paid to have his rigging x-rayed, visually everything looked fine but the x-ray showed cracking inside several of the roll swages, (02 depletion area ?) basically they looked mint but were ticking time bombs. Inexpensive Dye penetrant could be used in situ for checking exposed threads, you dodged a bullet there, perhaps time for a lotto ticket ;-) 1 Quote Link to post Share on other sites
LBD 212 Posted January 7 Share Posted January 7 29 minutes ago, Frank said: In my old life in aviation we would sometimes call that dull middle bit the fast fracture zone where the crack propagated at speed to final failure. The striations either side of that we regarded as fracture progress lines created as the crack propagated,probably over some years. Yes it certainly started at the thread root but it's hard to imagine where the cyclic loading is coming from, perhaps the furler ? There was an article in Boating NZ many years ago where some owner paid to have his rigging x-rayed, visually everything looked fine but the x-ray showed cracking inside several of the roll swages, (02 depletion area ?) basically they looked mint but were ticking time bombs. Inexpensive Dye penetrant could be used in situ for checking exposed threads, you dodged a bullet there, perhaps time for a lotto ticket ;-) The cyclic loading comes from the forestay flexing side to side or possibly fore and aft... a look at the toggle setup will show all that is needed to know. I experienced exactly the same failure on a 1 1/4" thread on a turnbuckle on at 110 foot Crowther sailing Cat... lucky I spotted it before it broke. Only half of the correct toggle set up was fitted, the toggle would move fore and aft, but the thread was forced to flex side to side under sail pressure on different tacks or the furled sail swaying side to side in a sea way. 1 Quote Link to post Share on other sites
Frank 217 Posted January 7 Share Posted January 7 Wasn't Ceramco's rig brought down by a lack of toggles at the spreaders ? it was rod rigging as I recall and failed due to fatigue. Quote Link to post Share on other sites
K4309 450 Posted January 7 Share Posted January 7 13 hours ago, Frank said: but it's hard to imagine where the cyclic loading is coming from, perhaps the furler ? Wouldn't the cyclic loading come from waves? I'm not wanting to sounds like a smart arse, just very interested in this with respect to my own rig. Just common or garden variety sailing would set up cyclic loading wouldn't it? Wind energy on the sail, tacking (changing the force from one side to the other) and of course the boat moving through waves, with the resultant forces on the mast being counter-acted by the rigging. Quote Link to post Share on other sites
LBD 212 Posted January 7 Share Posted January 7 18 minutes ago, K4309 said: Wouldn't the cyclic loading come from waves? I'm not wanting to sounds like a smart arse, just very interested in this with respect to my own rig. Just common or garden variety sailing would set up cyclic loading wouldn't it? Wind energy on the sail, tacking (changing the force from one side to the other) and of course the boat moving through waves, with the resultant forces on the mast being counter-acted by the rigging. The main culprit is mass of a furled sail on the forestay when furled. this causes the forestay and turnbuckle to sway side to side with every boat roll or movement, small or large. the number of alternating bending cycles accumulate over the years until eventual failure 3 Quote Link to post Share on other sites
Jonquil 545 Posted January 7 Share Posted January 7 How is the furling drum attached to the stay? The stay, if properly toggled (and i'm sure it is) will naturally sway in an even arc. But if you introduce a hard spot, even for a few inches then you have a fatigue point. 1 Quote Link to post Share on other sites
Island Time 1,345 Posted January 8 Author Share Posted January 8 Dual toggle at base of forestay pin at base, T connector above it. No sign of bending, thread is dead straight. The break is spotlessly clean and shows no corrosion. Yes there is a small tear on one side, maybe 1-2mm of ripped thread. This fitting, for some stupid reason was 1/2 inch, but all the other stays are 5/8. New forestay on today, all 5/8, and 10mm wire (up from 8). Last time the rigging was replaced I just asked the rigger to duplicate it. I should have looked closer! 1 1 Quote Link to post Share on other sites
Island Time 1,345 Posted January 8 Author Share Posted January 8 53 minutes ago, Jonquil said: How is the furling drum attached to the stay? The stay, if properly toggled (and i'm sure it is) will naturally sway in an even arc. But if you introduce a hard spot, even for a few inches then you have a fatigue point. This, as it's an alado furler. Has a 50mm plastic clamp on the stay. But with the 2 toggles it "should" self align.... Had done about 30000 miles though. Quote Link to post Share on other sites
Jonquil 545 Posted January 8 Share Posted January 8 30000 miles at 5 knots is 6000 hours, if the stay wriggles each way once per second thats 21.6million cycles not counting time at anchor. time and pressure as andy dupres would say...... 1 Quote Link to post Share on other sites
aardvarkash10 1,160 Posted January 8 Share Posted January 8 2 hours ago, Jonquil said: 30000 miles at 5 knots is 6000 hours, if the stay wriggles each way once per second thats 21.6million cycles not counting time at anchor. time and pressure as andy dupres would say...... Cable (String) Fundamental Frequency Calculator Quote Link to post Share on other sites
Panache 5 Posted January 8 Share Posted January 8 Ever looked up at your rigging when motoring, you can get some nasty vibrations in the stays especially if the prop is a bit out of balance, or in some rev ranges the motor can be a bit rough causing the whole lot to shake even a small amount. All this can lead to fatigue over time. 1 Quote Link to post Share on other sites
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