Preventer Rigging -- Lessons from the Platino Disaster

[Dockhead]

Originally Posted by thinwater

. . . But I'm not sure that the math does not change at some boat size. The accident we are discussing illustrates that increasing size and power may require better tools to control the power, more back-up systems, and better training in both seamanship and engineering in general. Maybe a brake is more useful with a boom that weighs that much.

Possibly the accident we are discussing illustrates rather that a 2/3 tonne boom is a dumbass idea ab initio. The highly experienced professional crew had no clue what they were dealing with in that bloated mass. I think there is a designer behind this who just didn't fully appreciate that "the math DOES change at some boat size." He just scaled it up on his drawing board and called it good. This is bad design. And poor discrimination on the part of the client who bought it. A rig of that size can't be handled with just scaled up same stuff that we have on normal sized boats. And putting on a monster in-boom furler on a rig that size seems just silly to me.

[thinwater]

Originally Posted by Dockhead

Possibly the accident we are discussing illustrates rather that a 2/3 tonne boom is a dumbass idea ab initio. The highly experienced professional crew had no clue what they were dealing with in that bloated mass. I think there is a designer behind this who just didn't fully appreciate that "the mast DOES change at some boat size." He just scaled it up on his drawing board and called it good. This is bad design. And poor discrimination on the part of the client who bought it. A rig of that size can't be handled with just scaled up same stuff that we have on normal sized boats. And putting on a monster in-boom furler on a rig that size seems just silly to me.

Yeah, that's another way to put it. At some point you transition from being able to use the "Armstrong" method to needing better systems.


One of the problems is trying to make a large boat easy for a very small crew to sail. That works great, right up to the moment where something goes wrong.

[a64pilot]

A boom brake is anything but complex.
An autopilot is complex, a wind vane is complex, a watermaker is complex, so is a Diesel, etc. etc. but not a boom brake, it’s about as simple as a screwdriver.
No, I think a lot of you guys see them as a crutch, training wheels, no real sailor would have one, they don’t need it,they are better than that, until one day they aren’t.
Having a boom brake displays your novice status. That’s fine with me, I’ll never be a pro sailor no matter how long I Sail, I concede that.
I had ours sitting below for five years, didn’t think I needed it either as I had never had an accidental Gybe, and then one day the autopilot didn’t keep up and I did.
It’s a lot like a car wreck, once it begins it’s going to its conclusion, your along for the ride.
I have never had an air bag inflate on any car I’ve ever driven either, but I don’t remove them,and I wear my seat belt every time, even though I’ve not needed one for 40 yrs.
I see the brake like an air bag, it’s always there, it’s not something I need to rig because I know I’ll need it.
Those extra lines that get in your way, well I find them to be excellent hand holds.

But then I wasn’t born in a sailboat crossing the roaring 40’s either, I’ll take a little help whenever it’s available.

[a64pilot]

Dockhead you keep getting back to the mass of the boom, however I feel certain that any system that couldn’t handle the mass, couldn’t handle a back winded sail either.
That preventer was inadequate, period.

On edit, the cause of the death was an accidental Gybe, secondary to that of course was an inadequate strength preventer, then the mass of the boom came into play, although depending on velocity, even a lightweight boom of only a few hundred lbs will kill. Remember it’s not just the boom, but the mass of the sail also.

My reasoning is the mass isn’t what broke the preventer, without movement mass isn’t much of a force, it’s mass and velocity, and it didn’t have any velocity until after the preventer broke.
However I believe it would have been prudent to have some kind of backup system in place seeing as how much mass the boom had, and the almost certainty that once it got loose, there was no safe way to corral the thing.

If you go to have a big boat built, with the kind of money we are talking about, I’d say to set some aside and have an Engineer conduct a systems safety analysis, it’s been an FAA required thing forever, we even did it on single engine Crop Dusters, it’s why in my opinion that several Boeing Execs should go to prison, because there is no conceivable way that they weren’t informed about the failure modes of their 737 max system.
https://www.faa.gov/regulations_poli...chap3_1200.pdf

Anyway if one had been done on that boat, then the owner would have been made aware that with mass of that boom, and the inadequate preventer, that a disaster was possible.

[a64pilot]

Look up Normalization of deviation.
It’s what got NASA on the Space Shuttle accidents, it’s why someone may have an accidental Gybe when they have a preventer but it’s not rigged.

One of the basic tenets of a safety system is it has to be in place always, no body see’s all accidents in time to prevent them, or o f course there would only be intentionals and not accidents.

[Dockhead]

Originally Posted by a64pilot

Dockhead you keep getting back to the mass of the boom, however I feel certain that any system that couldn’t handle the mass, couldn’t handle a back winded sail either.
My reasoning is the mass isn’t what broke the preventer, without movement mass isn’t much of a force, it’s mass and velocity, and it didn’t have any velocity until after the preventer broke.

The logic here seems kind of broken -- or maybe I'm just not understanding what you're saying.



In any case, that boom needed to be under control, and it wasn't. That pathetic preventer had no chance. Neither the designer nor the crew appreciated the challenge.

Originally Posted by a64pilot

However I believe it would have been prudent to have some kind of backup system in place seeing as how much mass the boom had, and the almost certainty that once it got loose, there was no safe way to corral the thing.

If you go to have a big boat built, with the kind of money we are talking about, I’d say to set some aside and have an Engineer conduct a systems safety analysis, it’s been an FAA required thing forever, we even did it on single engine Crop Dusters, it’s why in my opinion that several Boeing Execs should go to prison, because there is no conceivable way that they weren’t informed about the failure modes of their 737 max system.
https://www.faa.gov/regulations_poli...chap3_1200.pdf

Anyway if one had been done on that boat, then the owner would have been made aware that with mass of that boom, and the inadequate preventer, that a disaster was possible.

I think that's right, and surely "systems safety analysis" should be part of the design process even if it's not totally formalized.


A 2/3 tonne boom is just not safe at all if it is controlled only by an improvised preventer, which may be drastically mis-improvised as this one was. If you really must have a boom like that, then I guess you need some kind of hydraulic brake on it.



For me this is where the ketch rig comes in. I just wouldn't want any part of a boom like that, hydraulic brake or not.

[Dockhead]

Originally Posted by thinwater

. . . One of the problems is trying to make a large boat easy for a very small crew to sail. That works great, right up to the moment where something goes wrong.

Beowulf has a lower rig than my Moody 54, with no doubt lighter booms and easier to handle sails. I don't think it's necessary to have 2/3 tonne booms, to make a large boat easy to sail for a very small crew. I don't think a large boat made for a small crew needs to be unsafe at all. This is just arrogance and carelessness in the design process. No doubt whatsoever the designers spent some time getting the blue flood lights on the spreaders which illuminate the tall mast in harbor to shine just right. They weren't thinking about the right things.

[thinwater]

Originally Posted by Dockhead

... They weren't thinking about the right things.

Yes. That.


And I tend to agree with you on divided rigs and such. At some point, a man is only so strong, and this is a proven, robust solution. Back in the day, it was almost a badge of honor, that a boat was large enough to justify a divided rig.

[a64pilot]

Originally Posted by Dockhead

The logic here seems kind of broken -- or maybe I'm just not understanding what you're saying.



In any case, that boom needed to be under control, and it wasn't. That pathetic preventer had no chance. Neither the designer nor the crew appreciated the challenge.








I think that's right, and surely "systems safety analysis" should be part of the design process even if it's not totally formalized.


A 2/3 tonne boom is just not safe at all if it is controlled only by an improvised preventer, which may be drastically mis-improvised as this one was. If you really must have a boom like that, then I guess you need some kind of hydraulic brake on it.



For me this is where the ketch rig comes in. I just wouldn't want any part of a boom like that, hydraulic brake or not.

What I’m trying to say is that the accident cause wasn’t the boom’s weight. A parked car has no kinetic energy, a stationary boom has no kinetic energy either.
I guess your saying there was no sail up and the booms weight broke the preventer? If so, then that preventer was so weak that I don’t see how it could withstand the weight of a full sail back winded.

Was it really meant as a preventer? Or maybe just a way to keep the boom from swinging around when the sail was down? I used to pull my traveler to one side and use a ratchet strap from the boom to the other side to form a triangle to hold the boom in place when motoring in weather with the sail down. I do not think that a ratchet strap could possibly be strong enough to preventer though, just a way to keep the boom from constantly swinging back and forth a foot or so. Of course the brake holds it in place now.




What I am trying to say is that surely something that could handle a full sail being backwinded suddenly in a squall is way more than strong enough to merely hold a boom stationary, even a stupid heavy one.

Maybe they never expected it to function as a preventer?

I’m finding it hard to believe that if it was that weak that any experienced sailor would think it could hold the forces a preventer is required to hold?

[a64pilot]

This thread that just got started is why I’ll always have that brake rigged now, because I don’t have the experience to know when it’s necessary, and when it’s not.
Very Sad Reminder
http://www.cruisersforum.com/forums/...d.php?t=225216

[jmh2002]

On the complexity subject and the modern (and seemingly endless) spiralling of this I have to say that after a lifetime on so many boats, both power and sail, many of which were leading edge designs, often overly complex, but both immensely challenging, as well as immensely satisfying when it all came together as originally envisioned, I guess I have come somewhat full circle and now look to return to simplicity as and where possible.

For me that doesn't mean no systems or no comfort onboard, but in relation to this thread it does mean that I intend my next boat to be light weight, have a split rig, be easily driven so require smaller sails, and the mainsails will be of a boomless design.

I realise that this involves some compromises and may not work for everyone nor on all types and sizes of boat. And I accept that.

But it's food for thought nonetheless.

[Dockhead]

Originally Posted by a64pilot

This thread that just got started is why I’ll always have that brake rigged now, because I don’t have the experience to know when it’s necessary, and when it’s not.
Very Sad Reminder
Very Sad Reminder - Cruisers & Sailing Forums

It's important to understand what things kill sailors so you know what to concentrate on in your safety thinking. The top ones are Overboard, CO, Propane, Boom. I guess just those four things probably account for 90% or maybe even 99% of the accidental deaths on sailboats. OK, maybe Falls from the Rigging would a fifth thing.



I would suggest for basic boom safety:


1. Keep your body, and those of your crew, out of the boom's potential path at all times. If you have a boat with a boom low enough to hit the head of someone standing in the cockpit, sell it. Or at least then, never stand up in the cockpit. I wouldn't, personally, have a boat like this, even a small one.



2. If you don't have a gas strut vang, get one. Or if you can't afford it, then be very diligent not to let the boom get low enough to whack someone.



3. Preventer or brake on whenever the boom is out beyond the rail, or much beyond the end of the traveler. Without exception.



4. Always stabilize the boom when it's out far enough to swing around, by setting the preventer and mainsheet hard against each other. Snatch loads from any play there can break stuff, including any preventer. Even if you have a brake, you need a preventer for this.


5. Don't trust the pilot too much, when sailing very deep. Use wind mode where possible when sailing very deep, if that is reliable, but stay behind the helm and alert.


6. Get rid of the mainsail when sailing very deep, when the conditions create a material risk of dipping the boom, or if the wind is stronger than your preventer or brake can deal with a backwinded main.


7. Be sure your preventer is correctly rigged and that every element of it is strong enough for the purpose. Not like the pathetic preventer on Platino.

[Dockhead]

Originally Posted by jmh2002

On the complexity subject and the modern (and seemingly endless) spiralling of this I have to say that after a lifetime on so many boats, both power and sail, many of which were leading edge designs, often overly complex, but both immensely challenging, as well as immensely satisfying when it all came together as originally envisioned, I guess I have come somewhat full circle and now look to return to simplicity as and where possible.

For me that doesn't mean no systems or no comfort onboard, but in relation to this thread it does mean that I intend my next boat to be light weight, have a split rig, be easily driven so require smaller sails, and the mainsails will be of a boomless design.

I realise that this involves some compromises and may not work for everyone nor on all types and sizes of boat. And I accept that.

But it's food for thought nonetheless.

I don't mind a certain amount of complexity. It's nice to have comfort and functionality if you are spending months every year on board as I do, and some complexity is worth it. The biggest issue which comes with complexity is not necessarily proneness to failure, but maintenance. I am hoping that I will be able to afford a pro crewman on my next boat, as I had the first few years on this one. In order to finally escape the "boat repair in exotic places" syndrome, but that affects rather simple boats as well as complex ones.


I like your "light weight, have a split rig, be easily driven so require smaller sails, and the mainsails will be of a boomless design", which sounds a lot like Dashew's formulas. More and more I love the idea of the boat being larger but lighter, a bit narrow, easily driven, with a modest rig, especially, a modest split rig with really modest sized sails. This formula is a real winner in my opinion. You get speed from waterline length and light D/L so you don't need huge amounts of power required by monstrosities like Platino.



I've experienced that to a minor degree with my own boat, which is a lot lighter (188 vs 300 D/L) and a lot longer (47' vs 32' LWL) than my last boat, and so which is so easily moved compared to my old boat, which tremendously magnifies sailing pleasure. Being easily driven opens up a whole range of sailing configuration -- put all the sail up to go fast if you want to (but even then it's not a massive amount of power); or sail with one sail or another or mainsail and staysail to cruise effortlessly along and still faster than the old boat at full chat. I'd like to take that up yet another notch with a bit bigger boat with a bit more Dashew-like configuration, with the split rig as the crowning glory of it, even if it costs some ultimate upwind ability.



Just not the boomless mains, however, but YMMV. Booms can be manageable and can be safe, when designed with thought and care and as part of a rig which was designed with modesty and taste, not like Platino. I'm thinking -- full batten mains and carbon booms, shorter than what I have now (6 meters) and much lighter. Although in-mast furling is not yet off the table either.

[jmh2002]

You are not wrong of course Dockhead, and we agree on all points.

And my default recommendation is serious full batten mainsails, mast track system, and a nice slab reefing setup. No in mast or in boom. The external slab reefing is just so bullet proof and easily fixable or able to be jury rigged while cruising with normal blocks and lines that are carried onboard.

Electric winches and a nice setup solve most of the physical ease of use aspects and can do double duty for other purposes too.

My food for thought suggestion is for those that want to take a further step back and away from all of that. Be that for cost, or just for the simplicity aspect.

And it does involve compromises of course. Still no free lunch here, sorry.

But on the plus side, measured in either cost, weight, or complexity:

- no mast track system
- no huge battens
- much less weight aloft
- no boom dangers
- not the same preventer requirement
- etc
- etc

As part of an overall simpler concept this I will accept the compromises involved, and accept the benefits too. It makes a lot of problems or questions simply 'go away'.

[Dockhead]

Originally Posted by a64pilot

. . . What I am trying to say is that surely something that could handle a full sail being backwinded suddenly in a squall is way more than strong enough to merely hold a boom stationary, even a stupid heavy one.

Maybe they never expected it to function as a preventer?

I’m finding it hard to believe that if it was that weak that any experienced sailor would think it could hold the forces a preventer is required to hold?

Well, but think about that one -- the boom weight 660kg or whatever, and most of it is hanging out beyond the attachment point. Then, the preventer is rigged to magnify the force even further. Can it even stand the static force when the boat is heeled or rolls? Just barely I'm guess. Then with all that inertia plus the lever arm, just imagine what happens if there is any slack in the system, even just stretch of the apparently cheap and old polyester cordage, much less what happens if someone slacked the mainsheet a hair and forgot to harden up the preventer. Just an inch of stretch at the attachment point might be three inches at the end of that massive boom -- imagine the snatch load. Imagine what happens when the boat wallows in a quartering sea.



The mass of the boom is a HUGE factor. A 660kg boom is just not fit for purpose without massively engineered provision for controlling those loads. I guaranty you that ZERO analysis of those loads was done by the designer -- the preventer system -- the life and death function of keeping that massive beast under control -- was left by the designer for the crew to improvise out of old leftover cordage. That is just total malpractice as far as I'm concerned.