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socalrider

Broken mainsheet shackle First 405

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Bit of a fright coming back today from a weekender with the wife; about a mile from our slip I noticed that my main sheet block is hanging on by half a shackle! I suspect it may have snapped earlier in the voyage when the boom shock loaded it a couple times on a broad reach when the wind turned light and shifty in the midst of a choppy sea state. Certainly could have been much worse!

 

Back in the slip, it sure looks under-spec'ed; haven't broken out the calipers yet as the rain was starting, but I'd guess it's a ~1/4" twisted D shackle; the twist also appears to have been distorted. The sheet is mounted close to the boom end (traveller at forward end of cockpit). 6-1 sheet, and about 350sqft of mainsail area.

 

Anyone seen something like this before? Advise? I can just swap a new one in & inspect regularly, but I'd like to put in something better - this boat is mostly daysailed in San Diego, so it's not getting exposed to anywhere near what the design loads should be.

post-121273-0-38236300-1488770124_thumb.jpg

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Bit of a fright coming back today from a weekender with the wife; about a mile from our slip I noticed that my main sheet block is hanging on by half a shackle! I suspect it may have snapped earlier in the voyage when the boom shock loaded it a couple times on a broad reach when the wind turned light and shifty in the midst of a choppy sea state. Certainly could have been much worse!

 

Back in the slip, it sure looks under-spec'ed; haven't broken out the calipers yet as the rain was starting, but I'd guess it's a ~1/4" twisted D shackle; the twist also appears to have been distorted. The sheet is mounted close to the boom end (traveller at forward end of cockpit). 6-1 sheet, and about 350sqft of mainsail area.

 

Anyone seen something like this before? Advise? I can just swap a new one in & inspect regularly, but I'd like to put in something better - this boat is mostly daysailed in San Diego, so it's not getting exposed to anywhere near what the design loads should be.

It looks like everything on that traveler is beaten to shit - do you ever look at/fix/replace things? I fear your entire boat is dangerous if this is any indication of the maintenance level

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Why are the cam cleats looking so haggard? What are they hitting that is causing all those deep scrapes? The shackle looks to be 3/16" which should be OK load wise but it's also rusty and rusty stainless can beget stress.

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When the boom is out, the block lays down on its side and comes in contact with the cleats - that's what is beating up the cleats and bottom of the block.

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Twisted shackles can't hold shit. This is because the load isn't along the shaft, it is always at an angle to it, always working side to side. Also the shackle is constantly microscopically grabbing as the load moves along it's edge. We used to snap massive twisted shackles on my 60' cat till we woke up to the problem.

 

You are better to use 2 D shackles with a spring holding them in line and your block upright or, as mentioned, get a proper pedestal block mount.

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Change to standup toggle it is stronger and will hold the block up so it won't lay on the windward traveler. I have one and it works good

http://www.harken.com/productdetail.aspx?sku=1896 they also make it in high load model

 

76$ for a small machined piece of steel plus a pin and some plastic, wonder what the high load version costs... you'd think they were making motorcycle parts..

 

 

I don't use a twisted shackle on mine, but had a similar problem of the block falling over when changing tacks...

 

ended up with two springs under the block, the only thing is you want to use a threaded pin on the shackle as getting a cotter pin etc on , between two springs is quite an accomplishment..

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I would say that the shackle is over 20 years old.

Just replace it every 10 years, and review the rest of the car, since you are at it, new cleats (alu, not plastic or carbon). ANything else would involve more changes.

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+1 on the stand up shackle - better than springs IMHO, have used both, especially on larger boats. I also agree you should change out the cleats with new Harken 150's after you install the standup shackle.

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Change to standup toggle it is stronger and will hold the block up so it won't lay on the windward traveler. I have one and it works good

http://www.harken.com/productdetail.aspx?sku=1896 they also make it in high load model

 

76$ for a small machined piece of steel plus a pin and some plastic, wonder what the high load version costs... you'd think they were making motorcycle parts..

 

 

I don't use a twisted shackle on mine, but had a similar problem of the block falling over when changing tacks...

 

ended up with two springs under the block, the only thing is you want to use a threaded pin on the shackle as getting a cotter pin etc on , between two springs is quite an accomplishment..

zip tie the springs together, insert a split ring, cut the wire ties free, easy.

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I recall doing a traveller shackle fix like this mid-race many years ago with some Dynema and a piece of plastic tube to stand the block up...Last time I heard they were still going around with it like that.

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Change to standup toggle it is stronger and will hold the block up so it won't lay on the windward traveler. I have one and it works good

http://www.harken.com/productdetail.aspx?sku=1896 they also make it in high load model

76$ for a small machined piece of steel plus a pin and some plastic, wonder what the high load version costs... you'd think they were making motorcycle parts..

 

 

I don't use a twisted shackle on mine, but had a similar problem of the block falling over when changing tacks...

 

ended up with two springs under the block, the only thing is you want to use a threaded pin on the shackle as getting a cotter pin etc on , between two springs is quite an accomplishment..

zip tie the springs together, insert a split ring, cut the wire ties free, easy.

 

 

 

sweet, thanks.. the last time I took it apart , it took me about 5 minutes to get everything back together.. I was quite amazed..

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Nylon traveler line is well-proven as a shock absorber. I am also certain that a stronger connection is NOT the answer--that will just make something far more expensive break. If you are breaking shackles--even a twisted hackle--you need to reduce the shock load.

 

Also, what is the mainsheet? Is it polyester DB (good), or something high modulus (bad)? Something has to give. There is simply no need for forces that high.

 

http://sail-delmarva.blogspot.com/2016/09/line-selection-is-low-stretch-more-myth.html

 

5800+lot,+chafe+guards,+EVAPCO+007.jpg

My traveler is 8mm climbing rope. Has been for 5 years. I switched to nylon after trying Dyneema (it was given to me) and seeing what a mistake that was. Similar size mainsail--it is only 3:1 because it is winched.

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go soft shackle...

This. Or continuous loop that passed through and shackled to the bottom of the block. Will give you enough space for the block to lean over downwind and not hit your car.

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Nylon traveler line is well-proven as a shock absorber. I am also certain that a stronger connection is NOT the answer--that will just make something far more expensive break. If you are breaking shackles--even a twisted hackle--you need to reduce the shock load.

 

Also, what is the mainsheet? Is it polyester DB (good), or something high modulus (bad)? Something has to give. There is simply no need for forces that high.

 

http://sail-delmarva.blogspot.com/2016/09/line-selection-is-low-stretch-more-myth.html

 

5800+lot,+chafe+guards,+EVAPCO+007.jpg

My traveler is 8mm climbing rope. Has been for 5 years. I switched to nylon after trying Dyneema (it was given to me) and seeing what a mistake that was. Similar size mainsail--it is only 3:1 because it is winched.

Not to discount anything you said here in general but I think the OP's issue was progressive, long-term degradation of the strength of the shackle. If it'd been new when this happened your analysis would apply.

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go soft shackle...

Explain. That block is not made for that.

 

I like soft shackles and have many, but that hole in the 3x block is not the answer.

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+1 on the stand up shackle - better than springs IMHO, have used both, especially on larger boats. I also agree you should change out the cleats with new Harken 150's after you install the standup shackle.

 

That is a windward sheeting car, it requires its a modified version of rhe 150 cam. Other than the rash, which is common on the windward units if you don't use a spring or stand up shackle, you can build these assuming the teth are not worn.

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The cams actually work just fine; the rash is just cosmetic. I think the correct answer is a pedestal; nothing else will get the block to clear the cams. In the meantime I did a temp fix with two D-shackles. Worked great on our sail this afternoon. I think the original setup was a 3:1 (the vessel came with an old spare 3:1 main system); the narrower block doesn't interfere with the cams. No good way to winch it though. Strange.

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go soft shackle...

 

Explain. That block is not made for that.

 

I like soft shackles and have many, but that hole in the 3x block is not the answer.

How do you figure that. Just push the rope thru the hole. Assuming it's the same size line as the pin is it will be stronger than the stainless it replaces.

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