Forestay breaks for second time in three years
- Thread starter Spadman007
- Start date
Yes. I am also on a mooring ball so I have the mast up all the time. The stay broke just above the top compression fitting. Just saw that Blue Water Yachts suggest a thicker stay (5/32 instead of the normal 1/8) if the mast is left up.
Can you post a photo of the break, and is there a toggle at both ends of the forestay?
I can't post a photo as the boats still on the mooring ball with the mast laying in its crutch. The break is right above the first (top) swage on the looped end and there is a toggle only on the upper end and a threaded stud at the furler end. Weather is suppose to be very windy the next couple days so I won't have a chance to pull the boat out till later this week (i'm about an hour away from the lake)
Also check your rig tension once repaired. sounds to me like your stays may be a bit loose allowing the mast to pump or move a bit in higher winds. This puts wear on the fittings and could be your ultimate cause of the problem.
I think your boat is a fractional rig, tighten your backstay just until you see the mast start to bend, then slack until it barely straightens out. If you have backstay tensioners, make sure they are fully extended or opened for least working tension.
-Will (Dragonfly)
On the M25 and lower... the back stay is slack unless running down wind. I don't really know why they were designed that way but I've owned three and sailed on more than that and they were all that way. It is also true that the shrouds were a little slack and instead of turn buckles they used the really cheap tension brackets like these
The recommendation in post #9 about pumping as the culprit may be the correct answer. Macs were made to trailer and not to sit on a mooring ball. So the O.P. may need to work on the standing rig to tighten it up a bit if he keeps it on a ball.
The recommendation in post #9 about pumping as the culprit may be the correct answer. Macs were made to trailer and not to sit on a mooring ball. So the O.P. may need to work on the standing rig to tighten it up a bit if he keeps it on a ball.
FYI, that boat has a rotating mast and no backstay.
You need to have a good toggle on the forestay both at the top and bottom especially with a furler so that you dont get point loading on the cable. Add in rotating mast.. and you REALLY need a good toggle at the top of the forestay. I think 26M folks have figured out what toggle method works with the rotating mast... but I dont know what it is.
You need to have a good toggle on the forestay both at the top and bottom especially with a furler so that you dont get point loading on the cable. Add in rotating mast.. and you REALLY need a good toggle at the top of the forestay. I think 26M folks have figured out what toggle method works with the rotating mast... but I dont know what it is.
The forestay is most likely breaking due to work hardening. The wire flexes, the metal gets brittle, a few wires break. Repeat until the last wire breaks and the forestay parts. That’s what’s happening to break two forestay sin a couple of years.
It's not breaking because i'ts too weak. The loads generated when it's just sitting at the mooring without any sails or heeling are comparatively light, Getting a bigger diameter forestay won't stop the work hardening. You've got to reduce severity of the bending of the wire rope.
You say the forestay broke both times at the gap between the thimble and the first nicopress compression sleeve, right? That's where the bending is occurring. You need to allow it to bend else where rather than between the thimble and the nico -ress compression sleeve. So you have to change something the geometry of the rigging.
Your boat has a rotating mast, with the "jesus shackle" at the mast hound, righ?
Here's a picture from the Mac 26M owner's manual. Is this how your forestay is rigged?
When there is a lateral (non-axial) load on the forestay, the wire is flexing between the thimble and the sleeve, leading to work hardening. If you can rig it so that the lateral pressure is transferred to the top of the forestay, the cable won't flex repeatedly to the point of breaking individual wires.
I would recommend a couple of approaches to reduce wire bending
1. Figure out a way to limit the rotation of the mast when it's on the mooring. You could bolt a lever onto the mast near the foot, and attach lines to limit the rotation. Google "mast rotation control arm".
2. *** Very Important: add an extension plate (or a rigging toggle) to the top of the forestay, similar to the two upper shrouds. This will permit one more axis of rotation that will greatly reduce the degree to which the wire rope is being bent. (you will need to shorten the forestay to compensate for the added hardware).
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Yes, rotating masts are great candidates for dyneema forestays because their forestays flex more. Rotating masts cause more flexing of the wire and require frequent inspection.
but.....
first of all, the repeated forestay breaking is, in my opinion, caused by concentrated flexing at a point, so the most direct solution is to reduce flexing at that point by changing the attachment hardware.
Dyneema used for a forestay should be sized for minimal creep, (not for minimal breaking strength, such as you do for wire). Therefore it has to be a special type of dyneema that is be prestretched and heat set. It You can’t use other kinds of dyneema. For example, Amsteel Blue isn’t the right kind of dyneema.
hank on sails for use with dyneema forestays must be fitted with Soft shackles, rather than brass hanks.
Dyneema forestays are not compatible with reefing furlers with rigid extrusions that require internal turnbuckles.
Colligo makes a EF furler for dyneema forestays, expressly designed for rotating masts, but it’s very expensive. It doesn’t reef, but it allowquick headsail changes using soft shackles.
for rotating masts which are common on multihull, a lot of owners use dyneema forestays, but with soft-hank-on sails.
im not an expert on dyneema standing rigging, but I’ve worked with it a little and have some on two of my boats since 2014. But I still have wire forestays with rigid reefing furlers. I don’t personally own a boat with a rotating mast, but I have made sails for Mac 26Xs and some multihulls.
Judy B
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