What are the factors that lead to a dismasting?

[m]

higgs

Yep, "it depends" ... on the environment ... on the size if the wire and the displacement of the boat ... on the usage of the wire ...Fresh water is kind to wire, wire in the PNW lasts longer than wire in the tropics.Industrial fallout is unkind to wire. If the boat lives in acid rain country the wire won't last as long.If the forestay and backstay are the same diameter as the upper shrouds and the uppers are sized with a 2.5 or 3.0:1 safety margin, the backstay sees the lowest load on the boat and will last longer than the other wires.On a 20 year old wire I wouldn't state that it is sound in writing, but I wouldn't refuse to put it back on the boat either. I'd look very carefully for cracks in the swages, any signs of distortion on bearing points inside eyes and forks and I'd probably want to do a chemical dye check for cracks on any swaged fittings and on the threads of the rigging stud and threaded toggle if I had the turnbuckle to inspect. Mechanical terminals would be taken apart and checked before it went back on the boat.In SF 5-7 years is not outrageous, in Vancouver 10-15 years is a number that I can live with. 40,000 miles at 6 knots is 6,666 hours ... 666 hours a year for 10 years ... 13 hours a week sailing ...... it depends

 

[henkmeuzelaar]

Numerous factors but simple to prevent

Unless you get rolled, of course. Even then, though, some very strong rigs have survived. On another board, one poster even reported being dismasted by a flying roof, (and used that as an argument against redundancy because that would not have helped much in that case....)The simple and most effective preventive approach is to use redundant (back-up) stays or shrouds rather than to just make everything stronger, as advised by some posters! The relevant failure statistics are pretty straightforward. In short, if you are dealing with a low probability failure event (such as rigging failure) redundancy wins hands down, whereas for high probability failure events upgrading/reinforcing may make more sense. Here is why: Imagine you have a standard shroud or stay with a .01 (1 in 100) failure probability under a particular shortlasting set of circumstances. By installing gold-plated wire/rod/fittings etc. you would be very lucky indeed to bring that failure probability down by 10-fold (i.e. to .001), simply because even the most carefully manufactured metal component has a finite threshold probability of possessing hidden flaws.... Incidentally, similar threshold phenomena will plague the efficacy of your installation and/or maintenance procedures as well. In other words, it will never become perfect.On the other hand, by backing that stay or shroud up with an independently attached stay or shroud of equal strength the probability of near-simultaneous failure will basically be reduced by a factor 100 (i.e. to .0001).Nonetheless, for high failure event probabilities, let's say .5 (1 in 2) , redundancy will only buy you .25 (1 in 4). Thus, careful upgrading (plus similarly careful installing and maintaining) could then be the preferred approach. In its most common configuration, redundant rigging only requires a suitable inner stay plus running backstays. About 80% of the mid-sized cruising sloops here in the S Pacific appears to have an inner stay of some kind and perhaps 60% do have running backs. Nearly all 50+ft vessels have both. Have funFlying Dutchman"Rivendel II"(currently on the hard in Port Vila)

 

[higgs]

moody:

Your reply sounds reasonable to me - thanks.

 

[higgs]

Lots of things can happen

One dismasting occured when a friend was stepping his mast and it might be worth mentioning. The friend was not the original owner. Someone must have replaced the turnbuckle for the back stay. The new turnbuckle came with a toggle to accept the T fitting at the end of the back stay. The problem was that the new new turnbuckle's toggle was larger than the original. My friend had not noticed this and in this particular situation, as the mast was stepped, the T slipped out of the toggle causing the mast to come down. The mast survived, but the bow pulpit did not.

 

[Moody Buccaneer]

built in redundancy ...

Nice theory Henk, and your logic is good, but I've never heard that reason for adding inner forestays and running backs to most boats. Rigs seldom go over the transom (unless you hit a bridge). They sometimes go over the bow when sailing downwind. They most often go over the side due to a shroud failure. Shrouds always show fatigue before head stays and backstays do. Most boats don't pitch quickly enough to shock load the fore and aft stays.When sailing upwind, the mainsheet and leech of the main sail provide built in redundancy for the back stay. I can see a case for twin backstays because the main cannot provide backup when the sheet is eased. The luff of the jib and jib halyard provide redundancy for the forestay. Some furling systems that do not use the halyard (CDI and Spintec?) do not provide this back-up.The most common reason for having an inner forestay is to set a small headsail. The running backs are there to provide tension for the inner stay and to keep the inner stay from pulling the mast out of column between the top spreaders and masthead. They also provide redundancy, but that is not their primary function. This is a very common addtion to rigs that are heading offshore, particularly those with roler furling on the headstay and no place to hoist a proper heavy air or sorm jib.One of the nice rigs (Lyle Hess Cutter I think) uses a permanent aft lead intermediate to the inner forestay hounds. These provide both tension for the inner forestay and redundancy for the backstay and upper shrouds. They also reduce or eliminate any need for twin backstays. The drawback to the rig is that the permanent intermediates restrict the boom when off the wind. Adding a highfield lever would allow them to be left tensioned when sailing upwind and allow the leeward shroud to be eased when reaching or running. Conventional running backs require extra winches or expensive (high load) tackles that are just enough trouble to use that they get ignored. They also tend to require adjustment from tack to tack and when close reaching.Another good practice to have one of the reef points put the headboard at the level of the inner forestay. The mainsheet loads through the leech of the sail then share the halyard and inner stay loads with the running backs.On single spreader rigs, I prefer double lowers so the loss of one lower does not make the rig come down. On double spreader rigs, I like to see the intermediates run down to the deck to act as backup for the upper. Many modern rigs terminate the intermediates and uppers at the lower spreader and one rod or wire carries the load of both wires from the spreader to the deck. The intermediates are usually lightly loaded so it is not a real big deal, but it puts extra terminations into the system.

 

[Randall B361]

Keel vs. deck stepped mast

What's better to have, a keel stepped mast that snaps off above the deck, or worse, tears a hole in the deck in the process of a dismasting - or a deck stepped mast that flops over the side?

 

[Franklin]

Henk

In Moody's defense, I think we should categorize racers as a unique bunch because they are always pushing to boat to and many times beyond it's capabilities. That's why 10 million dollar plus boats loose their mast.

 

[Franklin]

Randall

I do believe that most mast do break at the spreaders, not at the deck. given that though, maybe, just maybe, a keel stepped carbon fiber shroudless mast may be best. Definately less parts to fail.

 

[henkmeuzelaar]

Franklin, are you saying.....

that when racers break their forestay the stick crashes aft but when cruisers break their forestay the stick crashes sideways or forward? Or are you implying that cruisers never break their forestays? If so, where does that leave Paul Cossman (for whom I have great respect as he may well be the only Hunter owner who ever made the treacherous Tonga/New Zealand passage forth and back)?At any rate, I think Moody Buccaneer is quite able to defend himself, as I will no doubt soon find out Have funFlying Dutchman

 

[Moody Buccaneer]

Henk

Henk, no offense but ... I'm a professional rigger ... we design and build masts. We probably have seen more rig failures than most sailors ... they come to us with the broken parts. Broken forestays are pretty rare compared to broken shrouds. They have become more common with the proliferation of roller furling. Think about how a mast can fall aft after a headstay failure with the jib up. If the sail is tacked to the stem fitting the luff of the sail and the halyard have to also fail. If there is a furler installed the only way for the stick to fall aft is because the stem fitting, clevis pin, or toggle fails. Of course when I say shroud failure I include the entire system from chainplate to tang fitting. In a properly designed rig, the wire should be the weak link. If some other part of the system fails it is poor design, poor maintenance or damage.Cruisers tend to sail with loose rigs on the mistaken theory that a tight rig stresses the the rig and boat more. The reality is that loose rigs have a higher failure rate than slack rigs. It's a fact, ask any mast builder.After damage and corrosion, fatigue is the cause of failure in metal rigging. That is a fact, it is the nature of metal. It is also a fact that lateral rigging sees higher shock loads during normal operation than fore and aft rigging does. That is the nature of sailboats. I did not mean to upset you, but I have NEVER read any mast or rigging text that suggests that the primary functions of an inner forestay and running backstays is redundant mast support. A secondary function sure, but that's not the primary reason for them. If anyone knows of a design text that suggests inner forestays and running backstays are primarily for redundant mast support, I would like to add it to my library. That fact that internet forums of sailors think it, carry's very little weight. Internet forum sailors don't tend to be engineers or designers of masts and rigs. I don't have to read 10 years of posts here to know that there are very many sailors that don't have a very good grasp of the physics of materials or sailing. I talk to several of them every day at work.I really didn't want to start a rant, but the fact that your boat hasn't broken anything is not remarkable. It just indicates to me that you pay closer attention to your boat than many and are not unlucky. If you chose to think that it is because you have an inner forestay and running backstays, fine. Unless you have a design brief from a NA that says so, don't go telling people that that was the intent when the rig was designed. No well maintained boat of decent design should ever have a rig failure. That one other boat lost his mast after a forestay broke is not remarkable either. Do you know what the exact cause of the failure was? What exactly were the conditions? The return from Hawaii usually includes some upwind work, was the jib up? Did the halyard fail also? Did the tack fitting pull out of the deck? If he was sailing downwind how did the forestay break?When you say there are 4 or 5 link points in the forestay of a B&R rig. That is probably news to B&R. Are you counting 2 clevis pins and a toggle at the top of the stay as three, the lower swage as one and the lower toggle and clevis pin as two more? That's the same as any rig.As far a Maximus goes, IIRC that is not the first rig that boat and crew have lost. I've expressed my opinion on the safety margins and design of that rig to another designer earlier this evening. I'm pretty sure the head sails on that boat are tacked on deck, it is a design error to have the same fitting carry both the headstay and the tack loads. A single point failure should not bring a well designed rig down.From my point of view, there are many sailors that don't spend enough time to know their rig. Many don't do annual inspections and wouldn't know what to look for if they did. Some cruisers are almost proud of the fact that they know little or no rig or sail theory, how many times have you heard, "That doesn't matter to me, I'm a cruiser not a racer"? I have people question the need to replace all the standing rigging on their boat after I've spotted 3 cracked swages from the dock and haven't even gone up the mast yet. What does it take to figure out that all the wire is the same age, 3 out of 8 wires have visible cracked swages from 10 feet away and a close inspection will probably reveal flaws in some of the other wires? Why risk a rig to save a few dollars?If you have a local sailor's exchange who do you find pawing through someones used rigging looking for something that might fit their boat? I've never had a racer bring in a handful of used wire and ask us to make it fit their boat, cruisers do it several times a year.So once again, I'm sorry I ruffled your feathers. I'm better off not questioning the collective opinions and shared folklore of the sailors here and biting my tongue when I read things I know to be wrong.I'll crawl back into my hole now. I'm sorry I ever questioned you.Happy New Year all.

 

[dave]

factor # 1 - human factor

check your rigging. Besides, it's the only factor you can control so do it.

 

[G. Bean, s/v Freya]

Inner Forestay Comment

Moody, I remember from a video by Mark Schrader on heavy weather tactics that the inner forestay was used to support the mast when the mainsail is reefed as the original forestay is too high up to counter the forces on the main adequately. He said the mismatched rig would lead to pumping and failure over time or something to that effect. The inner stay also brought the center of effort of the storm jib down and closer to shortened main’s. Granted, he was talking about sailing in snot for days (weeks?) on end which is much different than the occasional day’s reefing that most of us do.Oddly enough, I have experienced a head stay failure and I can verify that the genoa will definitely keep the rig up. Our failure was due to wire being way, way past it’s prime for our San Francisco conditions and the “break” (It went like the frayed rope in the “Perils of Pauline” movies) happened at a spot where we damaged the stay a few years prior.

 

[henkmeuzelaar]

I may have to wait for ground hog day.....

to continue the discussion with Moody. At the end of his last post he said he was crawling back into his hole and I do respect anyone's explicit wish to be left alone.Meanwhile, though, I would like to say to Dave that his post definitely wins the prize for brevity (yes, I do have reason to be jealous of that .However, I have two beefs with his (somewhat defaitist) statement that checking the rigging is the only factor we can control, namely: (1) redundance and/or upgrading are active steps that are at least as important, especially since(2) even the best of inspections is still likely to miss any "hidden flaws" (I guess that's why they are called "hidden").Allow me to get back on my *box one more time:Redundancy is a universally accepted approach to serious risks that have a low probability of occurring. How often does a parachute fail? Yet, would you want to jump out of a plane without a spare one, even if you inspected your primary chute extra carefully?? Nuff said, I hope.Have funFlying Dutchman

 

[G. Bean, s/v Freya]

Redundancy

Henk, at the risk of “poking the bear” I don’t think your parachute analogy is the appropriate one. Redundancy, as in the parachute analogy would mean a second set of shrouds and stays sistered in next to the primary rigging, ready to take up the slack if the primary rigging fails. Is this really what you have? To push the point further, do you have double hulls as a hedge against hitting a shipping container? My experience with inner forestays and runners is to put bend in the mast for better sail shape, not to make the rig more rigid. If rigidity was all important, our rigging would be made with chain. Besides, weight aloft is the enemy, not our friend. You hinted at the one active thing we all can do to preserve our rigs and that is to know when (and how) to lift up on the throttle. You never having a rigging part fail or a sail rip is a testament to that thought. If the rig was properly designed in the first place, there is no reason to “upgrade or beef it up”, unless you are looking at increasing performance by eliminating weight aloft.

 

[henkmeuzelaar]

Nah, Bean, that is EXACTLY what I meant !

Rivendel had neither an inner stay nor running backstays when we bought her new in 1991, so we had to install them before we made our first larger offshore trip (Santa Barbara <-> Hawaii in 94). The running backs only serve the function of keeping the stick inboard, particularly when the staysail is pulling pretty hard. In practice, however, we ALWAYS set at least one running back, even though it makes tacking and gybing a bit more work.The inner stay serves indeed several different purposes. However, I fail to see why the fact that it also can carry the staysail, a series of festive flags or a forehatch awning, while helping me steady myself on the open foredeck, should in any way detract from its 24/7 role as a back-up forestay!To rely on a headsail's luff cord, tack shackle or even halyard, as gratis forestay backups, as argued by Moody, sounds to me like hoping to use a Scottish kilt as a redundant parachute.... Rivendel's inner stay has a breaking strength of approx. 14,000 lbs, I believe, whereas our genoa components only have a fraction of that strength. That doesn't mean, of course, that these genoa components can never save the day. You gave a fine example of how it worked for you. In WWII some pilots even jumped out of their planes and survived w/o any parachute at all. None of them tried it twice, I presume....Have funFlying Dutchman

 

[Dave the Kid]

What 's the first - Running out of beer?

BTW Mr. F. Dutchman- a pessimist maybe, but never a defeatist. 'Checking' implied checking their age as well as what they look like. You can admire my posting brevity but I am in awe of your mastery of redundancy!

 

[Big Joe]

Moody

Can you give me your thoughts on a "Solent Rig"? I would appreciate any inout from you or others on that configuration.Thanks,Big Joe

 

[Big Joe]

Moody

Sorry , fat fingers here, I meant "input" ... damn.

 

[Moody Buccaneer]

G. Bean

Thank you for pointing out that the Genoa will keep the mast up if the forestay breaks .. I think I mentioned that "Mark Schrader on heavy weather tactics that the inner forestay was used to support the mast when the mainsail is reefed as the original forestay is too high up to counter the forces on the main adequately. He said the mismatched rig would lead to pumping and failure over time or something to that effect. The inner stay also brought the center of effort of the storm jib down and closer to shortened main’s. Granted, he was talking about sailing in snot for days (weeks?) on end which is much different than the occasional day’s reefing that most of us do."There is a kernel of truth to this. But if that is exactly what he said, he got it wrong.A good cruising rig does not pump in a seaway, they are designed not to. They also do not invert from headboard loads at any reef point. The right combination of mast section and rig design prevents both. One reason that masts are larger fore and aft than side to side is that they need to take the loads of a reefed main when the headboard is not balanced by the headstay.The centre of effort of a storm jib is not effected by what stay it is flown from. If the centre of effort is 5 feet above the tack, it is 5 feet above the tack if the sail is on the jibstay, the headstay, the inner forestay, or your high school flagpole. The traditional school of thought is to set the storm jib on an inner forestay if the rig has one. Walt Shulz of Shannon Yachts makes a very good case for flying the storm jib from the headstay or jibstay. Weather helm in heavy air is a problem on many boats. Getting the centre of effort down reduces heel and can ease some of the weather helm, but what is really needed is to move the centre of effort forward also. Some boats will handle much better with the storm jib on the headstay than with the storm jib on an inner forestay.Here's link you might find interesting: Shannon Offshore http://www.shannonyachts.com/offshore4.htmlCheers,Randy

 

[Moody Buccaneer]

Big Joe

The Solent rig is the backwards version of Shulz's "Scutter" rig. There are advantages to both and disadvantages to both.For those that are not familiar with the rigs, I provided a link to the description of and reasoning behind the Scutter in my last post.Both rigs carry two roller furling headsails on two forward in line stays. Thus both rigs share some of the same design challenges. The first challenge is mechanical: It is difficult to provide proper tension for multiple forestays. The stay that carries the working jib needs to have greater tension than the stay that carries the Genoa. (The working jib is used in stronger breezes, so it needs a tighter stay). The second challenge is aerodynamic: The aft sail will always be in disturbed air from the furled sail forward.The Solent rig puts the Genoa forward and the working jib aft. The Scutter rig puts the working jib forward and the Genoa aft.The Solent Genoa gets clear air, but has to be tacked through the small space between the stays. The working jib always sees dirty air from the furled Genoa, but is easy to tack.The Scutter Genoa is easy to tack, but always sees dirty air from the furled working jib. The working jib see clear air, but has to tack through the slot.Neither rig is perfect. Both rigs place higher compression loads on the mast than a boat with a single stay. Neither rig is as efficient as a single headstay sloop with hanked on sails. Both rigs have more weight aloft than a single stay sloop.If I was to chose between the two, I would choose the Scutter. I think that the smaller sail forward makes more sense. The smaller furler working jib disturbs the Genoa less on a Scutter, than the larger furled Genoa disturbs the working jib. The Genoa is used more than the working jib so having it aft where it can tack across a clear foredeck makes sense to me. The high clewed working jib of the Scutter rig places the centre of effort a bit high, but it will tack through the slot easily. I'd be concerned about chafe on the Genoa if I had to tack it through the slot or furl it to tack. Another issue with the Genoa forward, is sheet length. The lazy sheet has to be much longer, it has to be nearly twice the length of the boat to be able to clear the inner stay, that's an extra 15 feet of line to handle every tack on a 30 foot boat.If I lived and cruised in an area where a lot of my sailing is done with the working jib and the Genoa was seldom used, I might chose the Solent rig. But even then I'd probably just fly a 130 instead of a 150 on the Scutter.Hope that all made sense :|Randy