One of the most common ways that people get killed or maimed on a sailboat is by being hit by the boom. So, what can we do about that? Pretty obvious answer: Rig a preventer.
Such a nice simple solution, right? Well, unfortunately, no, it’s not. Rigging a proper preventer can be a pain in the neck. But there are things we can do to make rigging a proper preventer easy and quick.
But before we get into that, have you noticed that I seem to be overusing the word “proper”? That’s no accident. You see, a lot of the gear I see out there being used to restrict the swing of the boom does not constitute a proper preventer.
These set-ups might be boom brakes, like the one that Colin writes about here. Or boom tackles, where a line is taken to the boom, then down to a block near the rail, and then to a winch or tackle. A lot of people call these preventers, but they are not.
A valuable post and I look forward to seeing the follow up. I definitely agree it’s critical to have the line lead back aft, especially on a cruising boat.
I’d just like to add some thoughts to your statement that one should “always have a proper preventer rigged whenever the boom is let out far enough to make it work”.
I routinely use a boom tackle when sailing anywhere between close-hauled and a reach, when the angle of a preventer rigged forward would be wrong.
While the boom can travel less far in these cases a sudden change of course, or wave-induced roll in light winds, can still send it across the cockpit with dangerous force.
(It also saves me having to go forward to the mast to fiddle with the kicking strap as I can use the combination of mainsheet and boom tackle from the relative safety of the cockpit).
Cheers,
Pete
Hi Peter,
I totaly agree on the importance of controlling the boom properly at all times, including when the boom is too far in for an end boom preventer to work.
Having re-read Colin’s excellent post on boom brakes (see link in post) several times while writing this post, I’m coming round to the idea that a boom brake and proper preventer may be the ultimate answer. See my answer to Dick’s comment below.
The nastiest stars I’ve seen from a close encounter with a boom were actually close-hauled, in very modest breeze, close inshore; – I was using binos to pick up my leads, head near the boom, because I was steadying my back against the falls of the mainsheet.
Although the sea was far from sloppy, a bunch of things conspired to cause the boat to give a little wriggle, dropping the turn of her bilge to leeward, easing the mainsheet and setting my head a little closer to the boom – and then a sudden lurch combined with the foot of the sail pulling tight (from the counter-roll of the boat, rather than anything to do with the wind) — and suddenly the boom rotated like the cracker of a whip, about its horizontal long axis — not far, and it was not a heavy boom, but if anything, that lack of mass compounded the capacity for cat-like acceleration.
At the same time, the mainsheet snapped tight, propelling my shoulders up and forwards and possibly initiating another inertial counter-rotation whiplash impulse to the inverted pendulum of my head, throwing it back closer to the boom.
However it happened, the oval shape of the boom meant its arc intersected forcefully with my skull. I received no lasting injury, because it was smooth aluminium, although it hurt like hell … but if it there been a cheek block or cleat in the wrong place, I’m not certain I’d have been so sanguine … more like sanguinating, if not leaking cerebral fluid …
and, if I was capable of coherent thought, wishing I had thought to bring a crew.
And the most sobering thought is that I actually had a boom tackle rigged, pulling against the mainsheet, to stabilise the boom. In the light airs I had not set it up fully hard, as I was continually fine trimming as the puffs came through. It was nevertheless snug enough that I’d had no qualms doing what I did.
Hi Andrew,
I have to say that the thing that jumps out at me from your story is the importance of staying away from the end of the boom and the mainsheet in the same way that one should never step into the bight of a heavily loaded line. I know this will sound harsh and unfeeling, but I need to say it: Someone leaning against the mainsheet on “Morgan’s Cloud” would get some very strong words from the skipper, none of which would be “Merry Christmas”.
The point being that no amount of gear can compensate for being in the wrong place at the wrong time and not being mindful of the dangers around you.
Now don’t get me wrong, I’m not saying I have never made the same type of error. That would be hypocritical coming from a guy who broke his leg stupidly simply because he was not mindful about an obviously slippery log. But we all must keep in mind as we discuss gear that the most important safety gear we have at our disposal is located between our ears.
John, As frequently happens, your analysis cuts right to the quick of things. Keeping aware (and away) of those possibilities where a bit of bad luck could maim you is an important reminder, especially as no systems are in any way foolproof.
Dick Stevenson, s/v Alchemy
Dear John,
I too consider the boom to be one of the most. if not the most, potentially lethal pieces of kit on a boat. Even if close hauled or close reaching where the boom draws straight to the traveller, a momentary burp in the wind can cause the boom end to jump a few inches with impressive force and velocity. On Alchemy we try to have the boom triangulated at all times fixing the boom in place.
I have used what you call a boom tackle and I call a boom vang/preventer for well over 40,000 miles and am quite content with its performance, both as a vang and as a preventer. We also have an end-of-boom set-up for ugly and/or unpredictable conditions. A few comments;
I know some do it, but I have never seen a toe rail up to the task of a vang/preventer. The side deck attachment should be the equivalent of a running back stay attachment. One should not condemn a side deck preventer because some use the toe rail. (Boom breakage is also possible, but you can spread the load and know your equipment.)
In the vast majority of cases, mainsails becoming back-winded (gybing) generate quite mild pressures, especially if the boom is fixed and has no opportunity to run out and generate momentum. These occasional gybes are not uncommon and usually result from my pushing the limits a bit too much (waiting too long to volitionally do the work of gybing the main and jib when the wind is backing or veering) and is easily brought to back into line by a course change getting the wind to fill the correct side of the main.
It is largely downwind that this is an issue, much less so when on a broad reach, but maybe there as well. When there is enough wind (and seas) to be anxious in this area, there is likely enough wind so the mainsail can be put to bed. The boat likes it better to have its power pull from the front. This is easier on the autopilot/vane as gusts will not twist the boat around as much. My experience is I go almost as fast, with more comfort and much less stress by dousing the main early and not worrying about a preventer, side decks or end of boom.
On cruising boats, I consider the scenario you describe of being wildly out of control as generally unlikely. For sure,you have to know your boat and its behaviour in various conditions. Alchemy tracks well and I try to keep her sailing at less than 75-80% of her capacity. It is that last 20% percent or so where people get hurt and damage to the boat occurs. I feel I can make a judgment when to go to our end of boom preventer. In the meantime, my side decks vang/preventer, controlled from the cockpit, is always keeping the boom in check, wild sailing or the much more common everyday sailing.
I worry that your condemnation a side decks preventer will leave an opportunity for injury to take place. I believe that the boom should be controlled by triangulation at all times especially the vast majority of sailing that is regular everyday sailing where guard is down. Side decks prevention is basically a no brainer/no hassle method whereas every end of boom system has more, often much more, hassle (at least that I know of as yet). I can see some boats experiencing an end of boom preventer as just too much hassle for crews to use all the time and not avail themselves of a side deck preventer because of your critique leaving them unprotected from the everyday boom dangers.
My best and looking forward to the next segment,
Dick Stevenson, s/v Alchemy
Hi Dick,
Thanks for a well reasoned and interesting comment. A couple of thoughts.
First, for clarification, when I said to the toe rail, what I really meant was that area, not necessarily the toe rail itself. Like you, we have a massive through bolted pad eye that we use with our boom tackle.
Second, I’m absolutely certain that you and Ginger manage boom risk as well or better than anyone and that you will make the right decision of when to rig an end boom preventer. But you two have decades and tens of thousands of miles of experience, others do not and so I still feel more comfortable recommending an end boom preventer be rigged at any time that the boom is far enough out to make it work. After all, if it’s rigged then there is no chance of disaster, so no decision must be made.
Third, I also agree that controlling the boom when it is trimmed too far in to make an end boom preventer work is important too. We do that with a tackle as shown, Colin with a boom brake, you two with a line lead from each side. Having given a lot of thought lately, I’m beginning to think that the ultimate boom safety is a boom brake and end boom preventer. The brake having the advantage that it will bleed load if something does go wrong.
Having said that, we won’t be rigging a boom brake because we don’t want to obstruct our jacklines—the classic dilemma of weighing one risk against another.
There is one area where I do have to disagree, and that is the level of risk presented by the three scenarios I postulated. I feel that it is substantially higher than you do and I stick by that. My position is that all three can happen with bad consequences in as little as 15 knots of wind. No, none of them will happen often, but it only takes once for someone to be very badly hurt or to die.
I also don’t like the practice of striking the mainsail in heavy weather, common though it is. The reason being that if the weather deteriorates to the point where you need to heave-to you are then faced with rounding up to re-hoist, which, when offshore, can be very unpleasant, and even dangerous in any wind over about 20 knots. Ditto if you are forced to change course, say to turn into a channel. I much prefer to keep things under control by reefing and balance the area of the main against that of the jib top, which makes for a nice stable rig, helps steering, and reduces the roll.
Hi Dick,
One more point. One of the reasons that I wrote this post was because of my concern that the CCA article that you link to does not mention an end boom preventer at all, and therefore I feel that said article is badly flawed.
The bottom line is that the author has completely ignored the basic mechanics of lever arms and the huge and extremely dangerous loads imposed by the system he proposes.
To propose such a system without highlighting those loads and without mentioning the need for an end boom preventer when broad reaching and running is simple wrong and dangerous into the bargain. The fact that it’s is published on the CCA site just makes it worse.
There *is* a way, I’ve discovered, to safeguard the boom from the potentially boom-breaking loads which vanging the boom to the side-deck can generate.
I’ve become a big fan in recent years for a ‘progressive fuse’, connecting the side-deck block to the pad-eye or deck tang. By progressive, I mean a connection which fails in stages, except for the last stage, which matches the strength of the vang line. The first failure acts like a “warning shot”, and each successive failure (if the load is sustained) bleeds off some more energy, and allows the boom a little closer to the point where it comes in over the gunwhale, and starts smacking heads.
The final stage (if it ever makes it that far) pulls the boom up short, at the point where a person on the lee sidedeck is close to being at risk, but the boom is no longer square to the wind . Importantly, the boat will have been provided with a bit of time to both roll and yaw with the ‘punch’ of the wind, (not necessarily, on a voyaging sailboat, assisted by the helm) through angles whose aggregate effect has proved in practice (at least up to boats in the mid-40′ range) sufficient to further reduce the loads.
Caveat: I have not tried this setup, because I am not convinced it would be entirely suitable, on heavy, narrow, traditional vessels which do not quickly recoil from being caught catastrophically aback, (and, incidentally, where the narrow beam at the mast station means the attachment point is a long way forrard on the boom, which is typically long and often slender)
In fact, it is not suited to any boats where the slenderness of the boom relative to potential loads is already a limiting consideration.
The failure element in the form I initially tested was very simple, consisting of a bundled collection of separate lashings, freestanding at the time of their creation, perhaps starting with two turns (or ‘laps’ of the endless circuit) for stage one, three for stage 2, four for stage three, and so on: all the same length, contained in an offcut of tubular webbing, and collected at each end by the pin of a suitable shackle.
The final stage should be maybe 30% stronger than the penultimate stage, being calculated to have sufficient turns to match the breaking strain of the vang line. The latter is preferably a material and layup which provides a SMALL amount of additional shock absorption, to cope with pulling up against the non-failing final stage.
This has proven to be a good system, very accurate and easy to calibrate, and the quality control and verifiability is unmatched. However (even when there are many stages) it is unavoidably somewhat jerky in operation, giving the boom and fittings a somewhat harder time than optimal … so once I had established that this was a valuable concept, I progressed to a more sophisticated energy absorption element, with a closer approximation to an analogue resistance curve, rather than the rigorously digital response of the multiple lashing setup. The system as described should, however, be kept aboard in case the ‘smarter’ element does what it is ultimately designed to do. And for long trips, plenty of cord of the same exact specification would also be a desirable and reserved item.
The improved element comprises a sandwich of webbing, sewed together in such a way that it rips open in a zig-zag sequence, making an interesting noise, and progressively putting up more of a fight.
In recognition of John Harries “sleepy dummy” challenge, and because sewing the sandwich is laborious, it MAY pay to rig a lighter, slightly shorter lashing which bridges the space occupied by this webbing element. The twofold purposes are to protect the latter from ‘seeing’ any initial load, and to fail noisily, if the mainsheet is naughtily ground in.
Provided the mainsheet and/or vang lines are not nylon, the strain energy in the mainsheet is fully released by a short swing. Hence this ‘warning’ failure does not need to apply a nasty load to the actual sandwich, which remains unaffected.
My experience would suggest this to be a necessary enhancement only when the mainsheet is taken to a winch. Even some quite large modern boats will accordingly not need this extra safety fuse.
I’ve since done some research, and found that this webbing stack is a recognised technology (eg, Google “Yates Screamer”). It seems to be used mainly to arrest falling humans, either linemen and the like, as when working in elevated personnel buckets, or on the leisure side most commonly it is issued to inexperienced climbers using “via ferrata” > metal cable ‘fixed lines’, set up in places (in parts of the European Alps) where challenging tramping routes feature easy but not trivial climbing pitches.
They are used because they are reliable, self tending, durable, consistent in their failure loads, and provide a very smooth, soft arresting force with lots of energy absorption. In the boat situation, they only fail as far as they need to, protecting both the crew (crucially) and the boom (importantly). At the same time, this setup permits the simplified user interface of side-deck vangs, which keeps the crew in the cockpit, AND aft of the “death alley” zone of the mainsheet throughout gybes.
The midspan of the windward vang tackle can pass through a ring or S-hook, enabling it be lifted towards another ring seized to the aft lower, above the heads of (perhaps crouching) crew travelling forrard on the windward jackline. On the lee side it is necessary to do the twin-tether shuffle to safely cross the vang tackle when beating or close reaching, but when running there is not a problem.
As a practical example: On a 40′ cruiser-racer with a tall three spreader rig and a heavy Leisurefurl boom, this allowed a 2:1 vang on either side to be safely used to triangulate against the topping lift and mainsheet on all points of sail, offering effectively a full-width “boom gallows” for all purposes on demand, even in conditions where the boom might dip or catch a high sea when surfing at speed (although with modern, beamy hulls, moderate length booms, and swept spreaders, this is admittedly seldom seen).
It worked well for controlling gybes without the need to shorten the mainsheet, right up to the hairy edge as might be chanced when offshore racing with a strong crew in a gale, the vang tail being taken to a spare secondary winch on either cockpit coaming. The characteristics conferred by the geometry would be particularly valuable when an inline rig with running backstays requires the boom to be ‘middled’ for some time while the runner guys do their baton-pass routine. I say this because the achilles heel of the “proper” traditional preventer is that, once the boom is near amiships, the geometry approaches that of a toggle, where the axial compression loads in the boom, fed through the gooseneck into the mast, escalate very steeply indeed because the angle of the preventer has become so acutely close to the boom. If an unrehearsed stuffup means the boom, having crossed the midline, must be returned to the original gybe, in big seas, perhaps coinciding with a squall from a new quarter, the ‘user interface’ of the side-deck tackles is much less challenging, offering much speedier, safely controlled reorientation of the boom in either direction at any instant.
In very light winds, the mainsheet can be left slack, and the triangulation of the two vangs and the topping lift be used to position the boom. This requires minimal tensions, because the force vectors form a balanced star. The topping lift directly sets the leech curve, and does not need changing unless the wind builds. During a tack, the boom will stay close to where it needs to end up, so there is little change needed. Compare this with having to haul the main traveller right across the cockpit to the new windward extreme, and keep juggling the traveller and mainsheet to re-establish the leech tension whenever the angle of attack changes.
If you like the sound of this, I strongly recommend engaging an offshore sailing type with broad knowledge of boat rigs, and preferably some background as an engineer, ideally in such fields as industrial heavy lift practices (a broader field like this seems desirable to me, if this project represents a departure from their established norms in the sailing arena), to design and specify the oddly angled tangs which should be fabricated for the sides of the boom, along with their positions (they should generally go aft as far as the lifelines permit when the boom is squared outboard, and quite high up the sides of the boom) and the necessary backing plates and, conceivably, doublers to locally strengthen the boom and spread the loads into the surrounding metal.
In the Leisurefurl case mentioned above, it has proven unnecessary to go to the extreme of doublers. Backing plates of 1/4″ SS, somewhat larger than the generously sized baseplates of the tangs, were tapped for multiple machine screws, and bedded on /insulated by heavy mylar smeared with non-setting compound/corrosion inhibitor. These fittings have served with no signs of the extrusion cracking, or indeed of undue stress concentrations at any location, for ten years in challenging waters. Obviously corner radii need to be as large as practicable.
Initially we fitted the strongest ratchet blocks available to the tangs on the boom (Lewmar 100mm Ocean) but the very first inadvertant crash gybe on a loose vang in a rising gale by an inexperienced and disoriented helmsman at 0300 on the first leg of the maiden circumnavigation liberally strewed the decks with acetal bearing balls. The strongest plain blocks in the same size from Lewmar have coped perfectly well ever since, and in practice there has always been a spare winch, so the putative advantages of ratchet blocks were illusory. They do however work well on smaller installations, allowing a 2:1 to easily be handled without recourse to a winch on, say a tall masthead-rigged 25 footer.
Hi Andrew,
An interesting idea although I worry that someone is going to get hurt as the fuse starts to let go, the system also raises my anti-complication alarm bells.
To me at least, the end boom preventer is still a better system when reaching and running because it keeps the boom completely immobilized and the loads are, when caught aback, at least five times lower—lower load=safer every time.
When the boom is too far in for the end boom preventer to work, it would seem to me that a boom brake properly set is a better bet than the fuse system. At least with the boom brake you know the boom will move, albeit slowly, but with the fuse system one will assume the boom is not going to move, until one day the fuse lets go and it does.
An eye opener, for sure.
I’m one of those who thought they had it right by rigging a boom tackle. Certainly, it worked better than a vang for sail control as the wind goes aft. I was always able to control the boom in an offshore gybe with careful use of heading, the sheet, boom tackles (one permanent on each side) and sometimes the topping lift. (Not racing, rarely a cruising chute.)
I just never got caught in the examples you’ve given.
But you should have seen my expression while reading your post, probably a combination of horror and surprise as what you said sank in. I’m guessing you may have saved someone’s rig, or maybe someone’s life if others are equally affected by what you’ve written. It’s that strong a point.
Looking forward to your follow-up.
Thank you,
Stedem
Dear John,
A couple of re-joinders:
Rounding up to hoist the main in the conditions we are talking about would be a lousy thing to have to do. However, I agree with your previous recommendation that slippery mainsail track (ours is Antal) is a huge safety feature. Not only can we douse the main in a gale going downwind, but we can put a 3rd reef in without rounding up.
Generally, I much prefer to keep some main up for just the sail balance reasons you describe. That said, on my cutter (mast amidships or there-abouts), having any main up downwind in heavier, changeable, gusty conditions makes for a quite erratic course (we are usually on electric autopilot or vane, but hand steering would not do much better in the long run). (I would not strike the main except deep into downwind sailing.) Downwind, the boat corkscrews around the main/keel which, in gusts, loads up the turning momentum more than a headsail. With the sail area on the bow (or the staysail) we sashay around much less. I am also always surprised at how little sail area is needed to maintain good boat and steering speed downwind.
I absolutely concur that an end of boom preventer is the safest most seaman-like way to control the boom. In the interest of overall safety, everyday sailing as well as the much more rare wild conditions, I would want the readers to consider what their probable behaviour will actually be. A safety device used is superior to one put off or resisted. I suspect the CCA article is written in that spirit.
I believe you are correct that a hybrid system may be best. Your tentative (at this juncture) suggestion is a boom brake/end of boom preventer (with a side decks boom control at other points of sail). This solution has 3 pieces of kit and you are already resistant to the boom brake part of that solution. You are correct that my use of a side deck preventer is dependent on judgment as to when to move on to the end of boom preventer. Probably, like reefing and the myriad of other judgment calls we all make daily on the water, it is best done when first thought of.
My best,
Dick Stevenson, s/v Alchemy
Hi Dick,
Just to clarify, I’m not suggesting three pieces of kit. In my opinion, nothing, but nothing should compromise or change my recommendation of an end boom preventer.
What I meant was that I’m beginning to come round to the use of a boom brake, based on Colin’s excellent article about same. As I say in in this post, I have always felt that a boom brake was a far better option than any type of fixed mid-boom system that is left in place because it will slip and dissipate the huge loads caused by the basic geometry of any mid boom system.
Hi John,
Excellent post, especially because it clearly points out the risks of setting up an unsuitable preventer and may save somebody’s life.
In my naïve days I began rigging my preventer line directly through a hole in the toerail. The toerail is massive and through-bolted at about 8-inch intervals. Guess what? In my first gybe, the hefty line was cut like butter at the not-too-smooth inner edge of the toerail hole. That’s why people need to read your posts.
Anyway, I smartened up and now run my line 2/3 back on the boom and run it through the smooth midship cleat (yes, you guessed it, it’s ridiculously massive too). This gives me a tight angle on the line that runs back to dedicated winches, one for each side. I pretty much use it all the time, even sailing upwind – that way I never forget that it’s there. I keep the line snug to eliminate any momentum-induced forces. Works like a charm, super easy to set up and I treat it like my underwear – never leave home without it.
But this is on MY BOAT, probably not suitable to most modern sailboats.