Forestay broken above furling foil - what caused it?

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NickC

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The forestay on our Pandora has just broken between the top of the furling foil and the mast head.

This has only been unfurled once since the mast was lowered/stepped recently by a local boatyard. If there had been any damage noticed when the mast was down I assume they would have told me. So question is what caused this to break?

The furling is a foil over wire type whereby the uphaul goes around a pully at the top of the foil and back down to the drum, so other than the forestay there is nothing from the top of the furling gear connected to the mast head.
 
I suspect that the stay ended up being badly bent/kinked at some point when the mast was raised/lowered. As the wire showing at the top is the only flexible bit then it is important that the furler/foil is not jammed back towards the mast head or it could put a horrible bend at the top of the forestay which will weaken it considerably. Typical way I have seen this happen is when the mast gets raised and someone is not looking out for the end of the furler, which gets snagged on a deck fitting/stanchion/pulpit so pushes back against the mast along the stay.
 
vyv_cox said:
Almost certainly you have had a halyard wrap. See http://coxengineering.sharepoint.com/Pages/Halyardwraps.aspx. for a full explanation.
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Won't be in this case as he has an arrangement I used to have where the halyard goes round a small pulley at the foil head and down another groove in the foils to a cleat above the furling drum. All self contained so no jib halyard to the mast itself. Means you can't use the halyard to tension the luff.
 
neilf39 said:
Won't be in this case as he has an arrangement I used to have where the halyard goes round a small pulley at the foil head and down another groove in the foils to a cleat above the furling drum. All self contained so no jib halyard to the mast itself. Means you can't use the halyard to tension the luff.
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Right, I should have read the question more thoroughly. However, I doubt that a single bend in the wire would cause it to fail. Sounds like there was previous failure of a few strands.
 
vyv_cox said:
Right, I should have read the question more thoroughly. However, I doubt that a single bend in the wire would cause it to fail. Sounds like there was previous failure of a few strands.
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You could be right. I was also thinking with this type of arrangement it could be 'working' the forestay at this area, especially if it is not tight and not toggled. Could be fatigue failure, or a combo of both.
 
neilf39 said:
You could be right. I was also thinking with this type of arrangement it could be 'working' the forestay at this area, especially if it is not tight and not toggled. Could be fatigue failure, or a combo of both.
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Not sure what you mean by not toggled but was certainly quite tight. This arrangement seems to be a fixed forestay top and bottom with the furling foil swiveling around that fixed cable.
 
NickC said:
Not sure what you mean by not toggled but was certainly quite tight. This arrangement seems to be a fixed forestay top and bottom with the furling foil swiveling around that fixed cable.
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Toggles are simple shackle-shaped connectors that allow stays and shrouds to articulate in all directions. When they are not fitted the restraint in one direction leads to excessive stress, usually just where the wire emerges from a swaged joint, and fatigue follows. Look on my website for 'fatigue' under 'metallurgy' for several examples.

If you can post a photo of the failed stay, as close up as possible, I may be able to advise further.
 
Maybe a bit far-fetched but still a possibility. Was there a piece of electricians' tape or something similar wound tightly round the forestay, e.g., to mark a position? This could have been forgotten in place and, under the 'right' conditions, could have provoked crevice corrosion.
 
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