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Old 25-07-2016, 03:33   #1
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Forestay failure on mast crane

Greetings everyone, this is my first time to ask something of you and I have to say you all seem like old friends having read your queries and instructive answers to the many issues raised over the years.

So here goes - I have been working on a 36' Moody Halbedier circa 1969 for the past three years and finally the day dawned when I declared (Tuesday the 19th of July 2016, just last week) that I would be heading out for sea trials.

All was well until, while sheeting the headsail in hard there was a loud crack and down came the forestay. The net result is that the forestay broke out of the mast crane attachment point. This has resulted in damage to the foils and all has been salvaged as far as possible.

The point of this post to to ask your advice on how to go about fixing the mast crane as clearly there was a weakness in the aluminium attachment point where the forestay attaches to the very top of the mast.

The mast crane is not a separate section but integral to the mast which has a taper on the uppermost section, so this cannot be removed and the mast will have to be unstepped in order to repair/reinforce/ remake the crane attachment.

This may well be a most unusual happening but if anyone has any idea as to how to proceed please be kind enough to advise.
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Old 25-07-2016, 04:17   #2
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Re: Forestay failure on mast crane

Well, it looks like the good news is that you didn't lose the rig. Though breaking rigging while sailing isn't exactly on the top 10 fun things to do list

I haven't had any coffee yet this morning, so I'm not sharp as yet. But I'm not clear as to where things failed when I look at the pics. To some degree you make it sound as if there was a failure in the mast component of the headstay. Correct? Or did the headstay fail just below where it attached to the mast? Also, how old is the standing rigging & the headstay? Do you have a furler? And if you have a furler, is there a retaining piece which alters the angle of the halyard which holds up your jib?

It would help to see pictures of all of the other broken pieces, plus the top parts of the furler if possible. And both ends of your stays are properly toggled, I hope. Though if the headstay itself broke, then it could be time to swap out everything. But that's a call that's tough to make via the internet.


If you have a furler, I'm guessing that things failed just at or right below where the wire entered the swage/terminal. That happens with headstays in furlers as it's the only place that there's room for the stay to flex in a seaway. And things fail there due to the rest of the stay being much more rigid, as it's stiffened by the furler's foil section. Plus there's also a lot of weight on the headstay that's constantly moving, between the furler's weight & that of the sail. So the fatigue cycle is magnified at that location.

The above happened to another CF member, with more serious results. And later on, a rigger told them that he has people swap out their headstays after 4 years, vs. 10 for the other standing rigging. For the reasons of accelerated fatigue on them, caused by furlers, as mentioned.
Such a headstay failure happened to Ellen MacArthur in one of her solo round the world record attempts. Even though her headstay was a size or two larger than was evenn suggested by the riggers. Though fortunately it didn't cost her her rig, or the record.

One other thing which sometimes happens to headstays, is a halyard wrap. Sometimes it even wraps around the stay more than once. And that puts a lot of stress on the stay, which can lead to premature failure. This can happen if the halyard retainer breaks, if it's lead angle is poor, or if there's a long length of halyard below it where it's affixed to the mast. So getting the dimensions right with its mounting, & the height of the hoist(ed sail), etc., can be critical.
It also sometimes happens to boats which don't have furlers, with the same nasty results. But it's less common on such boats.

Also, another possible failure point is a broken/bad swage or rigging terminal. Or, that the wire got unknowingly damaged when the end fitting was put onto it. So seeing that fitting now might be helpful, as would knowing what type of wire ends you're using.

And there's slim chance that a toggle or pin failed. Due to age, fatigue, or a flaw in the metal itself. That, or rarely, a ring/split pin breaks & slips out, & you can figure how a gravity storm happens not too long afterwards.


It'll be easier to form a hypothesis with more pics, & a more concise description of what failed. Along with the requested rigging description info. Though I hope that the above helps.
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Old 25-07-2016, 05:38   #3
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Re: Forestay failure on mast crane

Thank you so much for responding - let me try to answer all your questions so that you can focus on the issue without the ambiguity, sorry

1. Correct, the rig was not lost fortunately.
2. Yes the failure was in the mast component of the headstay actually whrere the Staylok toggle terminal attached. The fitting in the photo was replaced with a new Staylok toggled swage and the photo shows where it was attached and the aluminium buttress flanges integral to the masthead crane. If you can imagine that same photo and you exerting sufficient force on the toggle fitting in order to wrench it out of the mast component, you will have the picture. These photos were taken prior to the re-fit.
Incidentally the forestay is completely undamaged - the stay is 10mm wire Staylok and toggled top and bottom with a rigging screw below the furler, and even the upper Staylok terminal, complete with clevis pin and split pins, is intact indicating the it was forceably wrenched from the mast component.
3. The rig is new all round (April 2016) and the furler is a return halyard type with twin foil grooves so no halyard wrap is possible. Six individual foils are damaged and need to be replaced.

No other photos available on the individual components yet as I am not on board currently.

I hope this helps and apologies for not being more concise in the first place.
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Old 25-07-2016, 05:48   #4
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Re: Forestay failure on mast crane

This may all just be me stupidly misinterpreting those photos, but...

Are those pins in your masthead hollow?

Is your masthead 3 parallel plates? If so, rather than the toggle you have in the pic, you'll want a 'double jaw' toggle. Its got a jaw on each end, rather than an eye on one end and a jaw on the other.

You'll insert it such that it hugs the middle plate, grabbing hold in each of the two spaces formed by your 3 masthead playes.

Schaefer 1/2" Pin Double Jaw Toggle

This way you are spreading the load a little better across the pin and the plates. You need a toggle with enough throat to it to not bottom out on the plates. You have to pay attention to the geometry to make sure you get one that fits, for a given pin size different manufacturers have very different jaw depths, leg width, etc.

Pics of the failure would certainly help.
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Old 25-07-2016, 07:13   #5
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Re: Forestay failure on mast crane

The pins are hollow but only two parallel plates, not three but I certainly appreciate your reasoning.

I had better get out there soon to photograph the Staylok toggle terminal, which is still strongly intact.

Is it possible to keep this post/thread open until I can return with the photos? if so, I will post the result as soon as I can - thank you for your input thus far.
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Old 25-07-2016, 09:08   #6
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Re: Forestay failure on mast crane

Quote:
Originally Posted by Frontiersman View Post
The pins are hollow but only two parallel plates, not three but I certainly appreciate your reasoning.

I had better get out there soon to photograph the Staylok toggle terminal, which is still strongly intact.

Is it possible to keep this post/thread open until I can return with the photos? if so, I will post the result as soon as I can - thank you for your input thus far.
I think the thread should remain active indefinitely, at least for a few months so that shouldn't be a problem. If you do have a problem reposting contact one of the moderators (there's a menu bar at the very bottom of the page with an option "contact us").

If I understand the problem, where the stay attaches to the assembly of welded plates at the top of the mast some part of the aluminum plate that holds the pin for the forestay has broken. If that is the case then the proper fix is to pull the mast and have a very good welder cut off the old and weld in new.

You could get by possibly by sistering some new bits in but that really wouldn't be the right way to do it.

Please note that I said a very good welder as aluminum (or aluminium as you call it over there) is tricky to weld and if not done correctly can weaken the metal. Here is not my area of expertise but it might require some kind of tempering or some process to maintain or restore the strength.
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Old 25-07-2016, 09:25   #7
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Re: Forestay failure on mast crane

Quote:
Originally Posted by Frontiersman View Post
The pins are hollow but only two parallel plates, not three but I certainly appreciate your reasoning.

I had better get out there soon to photograph the Staylok toggle terminal, which is still strongly intact.

Is it possible to keep this post/thread open until I can return with the photos? if so, I will post the result as soon as I can - thank you for your input thus far.
I wonder if the failure was that the hollow pin started to buckle. Then the load on the plates would be increasing less parallel to them, the cotter pins meant really to just hold things in place would start having to take rig tension, the plates would bend inward, etc. etc.

The pin diameter itself looks huge and not particularly weak, so my theory is probably garbage.

I'm curious to see the hardware you actually had up there and what exactly broke. Glad you managed to save your rig.
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Old 25-07-2016, 09:40   #8
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Re: Forestay failure on mast crane

My understanding is that a mast crane has the purpose of attaching a spinnaker above and forward of the fore-stay to avoid halyard wrap. Is your boat a cutter rig? fore-stay failure cause by failure of the mast attachment seems strange as it is easy to engineer bigger safety margins with direct attachments to the mast. Using a crane sounds like an owner's post construction modification to me. You might want to try to determine what the original rig looked like.
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Old 25-07-2016, 10:07   #9
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Re: Forestay failure on mast crane

Thank you for that response - yes you have it correct in that the mast plate attachment point has simply sheared away by brute force presumeably leaving two open/mangled holes in the plates because the holding pin on the top end of the stay is completely intact.

Having arrived at that understanding then, your logic is to effect a repair by welding - that is good news if it can be repaired that way but I take your cautionary advice on the bit about the tempering.

The question then is how does one find a 'very good welder' and maybe the only way of knowing is if it never fails again . . . ?
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Old 25-07-2016, 10:16   #10
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Re: Forestay failure on mast crane

If in fact the aluminum webbing failed, then a very good welder is the answer. I'd start by querying all of the local riggers. If a particular name comes up 2 or more times from competing riggers, go with it.....don't balk at cost, a really good welder won't come cheap.


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Old 25-07-2016, 10:18   #11
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Re: Forestay failure on mast crane

Quote:
Originally Posted by Frontiersman View Post
Thank you for that response - yes you have it correct in that the mast plate attachment point has simply sheared away by brute force presumeably leaving two open/mangled holes in the plates because the holding pin on the top end of the stay is completely intact.

Having arrived at that understanding then, your logic is to effect a repair by welding - that is good news if it can be repaired that way but I take your cautionary advice on the bit about the tempering.

The question then is how does one find a 'very good welder' and maybe the only way of knowing is if it never fails again . . . ?
First let me emphasize, welding is not my area of expertise. I know just enough to be dangerous. So, other than fixing it right and find a good welder, please take all comments with a grain of salt. In fact maybe use the whole shaker.

I do know that welding aluminum is trickier that plain iron or steel but it isn't rocket science. To find a good welder I would just start asking around my area, talk to other boaters, the local boat yard, get some opinions and references. If they are still around and you can find a number maybe ring the company that originally made the mast and ask for a recommendation.
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Old 25-07-2016, 10:30   #12
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Re: Forestay failure on mast crane

Thank you chris95040 and dave22q . . . the mast has no owner modifications other than an extended VHF bracket and a heightened mount for the tri-colour nav light, otherwise all original. There is also a very strong spinnaker attachment point.

These items may not be obvious as the photos show the condition before the refit.

The yacht is not cutter rigged.

The pin is large and shows no sign of buckling.

I will post photos of the hardware that was up there and then you could possibly determine the best way forward, meanwhile thank you all for your inputs
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Old 25-07-2016, 11:06   #13
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Re: Forestay failure on mast crane

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Originally Posted by Frontiersman View Post
Thank you chris95040 and dave22q . . . the mast has no owner modifications other than an extended VHF bracket and a heightened mount for the tri-colour nav light, otherwise all original. There is also a very strong spinnaker attachment point.

These items may not be obvious as the photos show the condition before the refit.

The yacht is not cutter rigged.

The pin is large and shows no sign of buckling.

I will post photos of the hardware that was up there and then you could possibly determine the best way forward, meanwhile thank you all for your inputs
Wow. I've gotta see that masthead - Are you sure the retaining pins were installed? Without them, the headstay pin could start sliding out, possibly getting jammed up in between the plates, until finally popping loose with a "bang"...

It seems unlikely the pin sheared right through the plate, the holes are well situated deep inside those plates.

So maybe a weld failed? In all the examples I've seen of this style masthead, the masthead plates are solid plates that run from the back of the masthead to the front. The backstay and the headstay are actually pinned to different ends of the same plates. Seems awfully strong.

But in your case, I think I see the headstay attached to an "ear" that is welded to those main plates? If that's the case, then failure of that weld could be the root cause?
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Old 25-07-2016, 11:24   #14
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Re: Forestay failure on mast crane

Have a rigger look at it. Welding aluminum is not that expensive. However, it does raise questions about your mast's integrity.
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Old 25-07-2016, 12:24   #15
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Re: Forestay failure on mast crane

Look up the specs of the extrusion then look up Selden's catalog. Maybe on of their drop-in mast top boxes will fit? They are cast alu made.

Chopping off the top then setting a new drop in box is an option. Ours is custom welded SS job.

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