Preventer Rigging -- Lessons from the Platino Disaster

[Don C L]

Yeah I think you are right Suijin, what I left out of the cascade was the damage to the helm taking out the hydraulic controls for the furling system, so they couldn't douse the sails to get control and get around to go for the MOB. There's a lot to unpack in there.
Still, as bad as conditions were, a boat should be able to be rounded up in a hurry when needed.

[jmh2002]

Originally Posted by Kenomac

Some of you should go back and review post #3. Our preventer broke in an instant, the forces in play on a 53ft boat are intense compared to 30-40ft boats. On our 63ft 36 ton boat, the forces in play are mind-boggling and impressive to say the least. The mast is 90ft tall and the sail area larger than most houses. In 50 knots of wind, us humans on a boat like the one abandoned... are like a flea on an elephants behind. You absolutely can’t imagine what will happen when you encounter those forces...unless you’ve been there. A boom brake on a 36 ton boat won’t work, that’s why you don’t see them in use or being sold.

Yes, but with all due respect, as the boat gets bigger, the gear gets bigger too, as you are well aware of.

Your preventer 'breaking in an instant' is not so much about the size of boat but the relative size of equipment used.

These days there are a lot of big boats around, and plenty of sufficient equipment to handle the loads. If things break in an instant probably they were not designed for such a load in the first place...

[Kenomac]

I think its time to roll up my pant legs, exit and let the CF experts take over the discussion, after all... what could someone who’s actually experienced this sort of event possibly have to offer?

Have a nice time.

[a64pilot]

Originally Posted by Don C L

Yeah I think you are right Suijin, what I left out of the cascade was the damage to the helm taking out the hydraulic controls for the furling system, so they couldn't douse the sails to get control and get around to go for the MOB. There's a lot to unpack in there.
Still, as bad as conditions were, a boat should be able to be rounded up in a hurry when needed.

But apparently rounding up would be insane

[jmh2002]

Originally Posted by Kenomac

I think its time to roll up my pant legs and let the CF experts take over the discussion, after all... what could someone who’s actually experienced this sort of event possibly have to offer?

Have a nice time.

And why are my comments without validity? Other members here have some sailing experience too...

I might have also experienced this situation, on smaller, bigger, and the same size yachts as you have.

The forces on your 63ft 36 ton boat might be, as you said, mind boggling, and therefore I trust that you can also appreciate how they might be on a 130ft 200+ ton yacht.

Gear 'breaking in an instant' is never good, and it normally means something is not specified correctly to handle such a load, or (as is also often the case) is not being used as expected/designed.

[accomplice]

Originally Posted by Don C L

Still, as bad as conditions were, a boat should be able to be rounded up in a hurry when needed.

The report suggests some reasons why they were unable to roundup. Kenomac and I suggest reasons they may not want to.

The report points to an AP failure due to leaking hydraulic fluid. The hydraulic rams would still try to control the rudder, but one of them would have a difficult time extending with sufficient force. This could create a situation where the AP could not control a gybe from occurring, but could prevent handsteering.

The reports also points out damage to the wheel and pedestal that may have made control difficult. While later, with the debris cleared, the wheel could be turned, that may not have been the case after the initial gybe.

The report also discusses damage to the ram attachments on the quadrant -- and that the ram mounts were only fiberglass and secured with small bolts.

To put the boat into the wind with an unrestrained boom and sloppy seas in a gale would not put the boom in a position to be easily captured. Furthermore, to put oneself in the path of that boom would require a level of courage and, perhaps stupidity, that is rare.

Regardless, the survivors reported that the boat was out of control, by which I understood to mean that putting her into the wind was not an option.

[Cadence]

About all that can be agreed on, it was a sad situation. it sounds like one of those situations that you had to be there.

[Breaking Waves]

a few comments:

#1 The notion that a preventer MUST fail on a boat this size is silly. This is just a matter of engineering. I have accidentally backed a lot of main's, including the main on a 112'er, and none of the preventers broke.

#2 Dockhead - this engineering is ALL about dynamic loads. The static wind loading calculation will tell you NOTHING at all. Even with a very tight and high modulus preventer, there is a significant dynamic shock load when the leach snaps thru. If there is any boom movement then it will be worse. This preventer was obviously very poorly engineered - the angles were bad; but also according to the report it broke at a knot (where the extension joined the pennant). It should have no knots in it ever at all. And it was a piece of **** line to start with (to paraphrase the report )

#3 I personally would consider it bad seamanship on a boat like this to be sailing quite deep in gusts to 48kts, with the wind backing and forecast to continue backing, with the mainsail up. The main will create steering issues and is just asking for an accident. They would easily have been doing hull speed with just headsails, with much better steering control and much higher safety margin.

#4 IDK about controlling the boom after it broke free, with hardware flailing around. I think you would have to have been there. I suspect there was a way to do it. Typically when using preventers, I will set up both port and starboard ones, to make a gybe easier - if that had been done here it would have given them an immediate way to restrain the boom (using the opposite side one) unless it also broke ofc.

#5 regarding boom brakes . . . they are pretty hard to engineer for boats this size. In addition to raw loads, there is a significant heat problem with line friction as it lets the jybe thru (the line cover will melt, as it does when you smoke a spin sheet on a winch on a boat this size). It is certainly possible to engineer something which would work - but it would take some significant effort and the market size is too small, and to my knowledge no-one has done a serious job of it.

#6 there were a lot of mistakes and a lot of red flags beforehand. Unfortunately, the crew did not seem to take this voyage very seriously and did not seem to have been schooled in proper technique. Any seaman with a furling boom on a boat this size would have realized how heavy it was, what a danger it would be if flailing around, and multiple plans to deal with it. I do have to say I am impressed the rig stayed up as long as it did.

[Montanan]

Sad story:

1). The preventer leading from the bow should be kept taught so as to not allow the boom to shift aftward to any significant degree once the mainsheet has been trimmed for the proscribed course of navigation. Without the possibility to move athwartship the boom will not build inertial forces which can be massive with a huge boom and the force of a significant wind on a large mainsail.
2) The preventer should utilize as open of an angle on the boom as can be rigged so as to reduce the force loading potential on its attachment points, as close to perpendicular as can be achieved, albeit an open angle is much easier to attain on a wide beam catamaran than a narrow beamed monohull.
3). ALL of the preventer rigging components should be sized adequate for sustaining the PEAK loading arising from an abrupt gybe.
4). A substantial boom brake should be set to absorb the energy of a gybe and convert the energy into friction and strain / stretch, in addition to the use of a robust preventer. A boom brake would have dramatically slowed the motion of the boom and can act like a second mainsheet / traveller configuration.

I haven't read the entire incident report, but it seems that they could have started the motor and sailed up wind so as to contain the boom from having further violent impacts into the shrouds when it was caused to swing about by a wind shift from the aft. Presumably they would have desired to head up wind to return towards where their man overboard person would be.
Sure a boom without a mainsheet attached to the deck, or without a functioning boom brake will tend to slew about when it over compensates while attempting to self align into the wind when headed upwind, and the broken off traveller car will be a bashing, hazardous object, but the boom will not move upwind and push into the shrouds holding the mast if the bow is facing the wind.

So I get that their boom was truly uncontrolled, yet I am wondering if one could still manage to hove to by backing the foresail and turning the rudder to offset the force of the foresail and thus stabilize the trajectory of the vessel relative to the wind so as to minimize the loose KABOOM from wandering about violently.

I haven't tried to hove-to with my mainsail just completely left eased off and thus am not sure how my boat and its boom would handle under that arrangement of sail configuration. I have been on boats where we were able to comfortably hove-to with just a foresail deployed and the main completely lowered.

Have any of you attempted to hove-to with essentially an uncontrolled boom with the mainsail fully reefed? If so please provide us with a description of how the boat handled and whether the boom would become a wild carening object under the influence of the backwinding from the foresail.

[JPA Cate]

Folks are always writing that forces go up A LOT with bigger boats. Our boat is a light 46 footer by comparison. The boom's 17 ft. long. When we broke it, it was from a puff that came around a mountain and forcefully backed the main, when we had been broad reaching. After the fact, we discovered that there was a pre-existing crack there. It was in flat water, unlike what happened to Platino, and the two of us were able to handle it once we had motored to a wind shadow spot.

I think it's hard to visualize just how dangerous things are when they get loose, unless it has happened to you. We have double preventers, continually mounted, just a little aft of the hard preventer, which we do not use much. They are polyester double braid, 3 part tackles, led aft to cockpit winches, and attached just aft of the capshrouds forward. They pull down on the boom. We know this is not the arrangement suggested for bigger boats. They were very handy when a main sheet shackle broke and the boom got loose. We were able quickly to get it where we wanted it.

For those of us who speak in feet, 3 m. seas are 10 ft. Even without the 2 m.(~6'4") cross swell that is enough sea to roll the boat all around, plus poor Platino had that dreadfully massy boom and sail flailing around. A64 mentioned the destabilizing effect of seeing your friends die; but also there had to be a self preservation thing trying to happen. [Had a furler come loose once, contact with a body with it flailing would have caused breakage or death, if the drum hit you, it did bend a stanchion.] They all would have been in shock, shaking from adrenalin overload, and I know they did the best they could.

I do not have big boat experience, not really qualified to comment there, but I can surely imagine that our problems would have been harder to solve with massier gear.

In answer to Dockhead's question of why they couldn't secure the boom, I think it was too unsafe to be somewhere it might have been possible. Also, supposition here, too, but a brand new megayacht, perhaps the assumption was that nothing would break nor fail, and perhaps they did not carry a spare tackle that would have been able to secure the boom, and nor was there a perforated toe rail where you could secure something. I rather doubt someone could have heroically got on it, riding it like a horse, the main was in the way, they couldn't furl it. The guy who tried to lasso it, might have had a chance (it's hard to keep the loop open in any event, and you've the motion of boat, as well as target to consider), if only there had been somewhere with a lot of purchase all ready to go, once the line got around the aft end of the boom. Otherwise, there was no safe place for it to be secured or safe way to get there.

Rest in peace, sailors.

Ann

[a64pilot]

Only thing I’d add to Ann’s thoughts is that quite possibly that 2/3 of the experience crew may have been taken out of the equation instantly.

[a64pilot]

Originally Posted by Breaking Waves

a few comments:

#1 The notion that a preventer MUST fail on a boat this size is silly. This is just a matter of engineering. I have accidentally backed a lot of main's, including the main on a 112'er, and none of the preventers broke.

#2 Dockhead - this engineering is ALL about dynamic loads. The static wind loading calculation will tell you NOTHING at all. Even with a very tight and high modulus preventer, there is a significant dynamic shock load when the leach snaps thru. If there is any boom movement then it will be worse. This preventer was obviously very poorly engineered - the angles were bad; but also according to the report it broke at a knot (where the extension joined the pennant). It should have no knots in it ever at all. And it was a piece of **** line to start with (to paraphrase the report )

#3 I personally would consider it bad seamanship on a boat like this to be sailing quite deep in gusts to 48kts, with the wind backing and forecast to continue backing, with the mainsail up. The main will create steering issues and is just asking for an accident. They would easily have been doing hull speed with just headsails, with much better steering control and much higher safety margin.

#4 IDK about controlling the boom after it broke free, with hardware flailing around. I think you would have to have been there. I suspect there was a way to do it. Typically when using preventers, I will set up both port and starboard ones, to make a gybe easier - if that had been done here it would have given them an immediate way to restrain the boom (using the opposite side one) unless it also broke ofc.

#5 regarding boom brakes . . . they are pretty hard to engineer for boats this size. In addition to raw loads, there is a significant heat problem with line friction as it lets the jybe thru (the line cover will melt, as it does when you smoke a spin sheet on a winch on a boat this size). It is certainly possible to engineer something which would work - but it would take some significant effort and the market size is too small, and to my knowledge no-one has done a serious job of it.

#6 there were a lot of mistakes and a lot of red flags beforehand. Unfortunately, the crew did not seem to take this voyage very seriously and did not seem to have been schooled in proper technique. Any seaman with a furling boom on a boat this size would have realized how heavy it was, what a danger it would be if flailing around, and multiple plans to deal with it. I do have to say I am impressed the rig stayed up as long as it did.

I think this seems to offer the most logical dissertation yet, in particular a brake works by converting kinetic energy into heat, that energy has to go somewhere, so there may well be a point to where do to heating one just can’t be made to work that dumps the heat into the line.
However I’m sure one could be engineered so that what amounts to a disk brake and shoes would be where the energy was dumped into, so you put $250,000 into Engineering, development and manufacturing and couldn’t sell enough to break even.

[charliehows]

Been a fair bit of discussion about boom preventers recently and it occurred to me; I learnt most of what I know about sailing as a kid, mostly from my Dad, who was a pretty experienced pacific ocean yacht sailor, navigator and cook. No-one ever taught me how to rig a boom preventer; no-one ever even mentioned the idea; In my many years of sailing, the idea of lashing my boom in the downwind position has never occurred to me as a good or even necessary idea; quite the reverse; I dont fancy finding myself in the position of having to try and release a backwinded mainsail after the boat has wandered that far off course.
The nearest I get to these sort of downwind solutions is a boom brake (very useful) and running double headsails (also very useful.)

[model 10]

I could build something with hydraulic system parts, no problem. It's not worth it for a small boat, but for a bigger boat it would be pretty straight fwd.

[charliehows]

Originally Posted by Montanan

Have any of you attempted to hove-to with essentially an uncontrolled boom with the mainsail fully reefed? If so please provide us with a description of how the boat handled and whether the boom would become a wild carening object under the influence of the backwinding from the foresail.

Well, yes indeed, I have tried HEAVING TO with an essentially uncontrolled boom - this is pretty much standard practice for short handed sailing; one HEAVES TO, once the jib is settled in the backwind position, one leisurely wanders forward and drops the now-pacified mainsail with the greatest of ease. As long as sail area is reasonably well matched to conditions, the procedure is pretty straight forward.