Preventer Rigging -- Lessons from the Platino Disaster

[Montanan]

Originally Posted by a64pilot

I believe some just don’t like brakes.
They didn’t grow up with them, don’t see the need, and may not trust them.
That and apparently BIG brakes aren’t made. My opinion on that is that there isn’t enough of a market to make money is all, not that physics has a practicable limit on how big a brake can be.

However having limited experience, I cannot comment with certainty.


I would have expected factory installed, Engineered systems on high end boats though. I wonder why there isn’t?

Agreed I did not find boom brakes for truly large sailboats.
As you say, there would be very little demand for such, so a custom build would be expected, certainly a cost item well within the budget of a large vessel, or perhaps for a ketch or schooner with their smaller sail sizings could be equipped with the commercially available boom brakes.

As the size of the sail area needing to be braked increases one would seem to approach a limit of dissipation of the heat across specific materials that are under friction contact, e.g. the rubbing of rope on a metal surface which would lead to melting of the rope and an inability to have a brake that works through many cycles of heating / braking. That is when a somewhat more complex braking scheme would seem to be required such as to be more like brakes used on vehicles, motorcycles, utility vehicles, cars, trucks, or even perhaps magnetic eddy brakes. Systems where the friction is not based on rubbing of the rope but instead between two high heat capacity surfaces, e.g., brake shoe versus metal disc or drum.

Braking a boom is just simply dissipating energy over a period of time and distance of travel so as to lesson the velocity of travel and the peak loading. One could model the amount of joules involved and design accordingly. The amount of energy of boom braking being far less than say the energy involved in slowing the vessel.

No rocket science involved, just a conversion of force energy to thermal properties and management of the thermal energy. If the boom [or mast] is made of aluminum / aluminium then one has a ready heat sink to dissipate the point based heat of the brake into. Alternatively one could just have a liquid jacket on the brake to absorb the heat of mechanical braking during the incident of use.

[Dockhead]

Originally Posted by Montanan

Agreed I did not find boom brakes for truly large sailboats.
As you say, there would be very little demand for such, so a custom build would be expected, certainly a cost item well within the budget of a large vessel, or perhaps for a ketch or schooner with their smaller sail sizings could be equipped with the commercially available boom brakes.

As the size of the sail area needing to be braked increases one would seem to approach a limit of dissipation of the heat across specific materials that are under friction contact, e.g. the rubbing of rope on a metal surface which would lead to melting of the rope and an inability to have a brake that works through many cycles of heating / braking. That is when a somewhat more complex braking scheme would seem to be required such as to be more like brakes used on vehicles, motorcycles, utility vehicles, cars, trucks, or even perhaps magnetic eddy brakes. Systems where the friction is not based on rubbing of the rope but instead between two high heat capacity surfaces, e.g., brake shoe versus metal disc or drum.

Braking a boom is just simply dissipating energy over a period of time and distance of travel so as to lesson the velocity of travel and the peak loading. One could model the amount of joules involved and design accordingly. The amount of energy of boom braking being far less than say the energy involved in slowing the vessel.

No rocket science involved, just a conversion of force energy to thermal properties and management of the thermal energy. If the boom [or mast] is made of aluminum / aluminium then one has a ready heat sink to dissipate the point based heat of the brake into. Alternatively one could just have a liquid jacket on the brake to absorb the heat of mechanical braking during the incident of use.

I always thought boom brakes were a good idea and I looked into this once. As you say the engineering is challenging for a large vessel because of the amount of heat involved.



Would be pretty hard to retrofit, but for a new built one might consider an elevator brake with a windlass on it, and some kind of cable or dyneema connection to the boom.


I think elevator brakes would fit the purpose nicely, being designed to dissipate similar amounts of energy. E.g. https://kebblog.com/residential-elevator-brakes/


Would be complicated and expensive, but maybe worth it. You could switch it on and off electrically. I would think that it would be fine with attachments at mid boom since it would not be attempting to hold the boom rigidly.


You could switch it electrical from the helm and release it when you're trimming the mainsail.




But the other takeaway for me from this interesting discussion is that it is a big mistake to design a boat with a gigantic boom and then make it gigantically heavy like in this case, and then not deal with these forces. I think that's a fundamental design defect, compounded by serious carelessness of the crew in not appreciating the total inadequacy of the preventer. This made me think that I really wouldn't want a boat with a mainsail bigger than what I have now, and that if I go to a larger boat as I am planning, this is a strong reason for making it a ketch. With carbon booms, if not the entire rig.

[a64pilot]

Mass of the boom is significant, and even if a boom had no mass at all, the mass of the sail is significant.
However I believe the greatest force is the sail itself, in my opinion anything that can handle the forces of a back winded sail in high winds, can handle the forces from the mass of the boom and sail.

With anything, you can build to contain a force, however when forces become large enough that usually gets difficult, requiring greater and greater strengths to do so, at some point if possible it’s way more conservative to design to absorb a load in a controlled release.

Things don’t scale linearly, and what is easily accomplished in small boats isn’t so easily accomplished in larger boats. You basically run into the square cube law
https://en.m.wikipedia.org/wiki/Square–cube_law

I would assume the best brake would be built into the mast / boom and not rely on any kind of limes, and may be Hydraulic?
But maybe that would be too heavy and one based on lines is better.
For what I think you want to do, I think if money is available, you’ll end up in a twin engined ice rated steel hull boat, and likely a ketch.
One that gasp is in all honestly primarily Diesel driven, cause when push comes to shove Diesel is more reliable than sail, cause you can’t control the wind.

[Dockhead]

Originally Posted by a64pilot

Mass of the boom is significant, and even if a boom had no mass at all, the mass of the sail is significant.
However I believe the greatest force is the sail itself, in my opinion anything that can handle the forces of a back winded sail in high winds, can handle the forces from the mass of the boom and sail.

I don't think you're appreciating the significance of the inertia of a heavy boom and the snatch loads that a swinging heavy boom can impart to destroy travelers and human bodies.

Originally Posted by a64pilot

. . . For what I think you want to do, I think if money is available, you’ll end up in a twin engined ice rated steel hull boat, and likely a ketch.


One that gasp is in all honestly primarily Diesel driven, cause when push comes to shove Diesel is more reliable than sail, cause you can’t control the wind.

Well, even those of us who are the most fanatical sailors, use the diesel a great deal of the time, I think few of us motor less than half the miles we make.


In the Arctic in the summer, there are sometimes weeks of dead calm, interspersed between violent storms. The calms are often your weather windows, so a lot of your miles are going to be diesel-powered. Of the miles I did last year in the Arctic Ocean I guess 80% of them were pure motoring, not motor-sailing, but motoring.


I JUST MISSED buying a 65' gorgeously refit alu pilothouse ketch, with twin 140hp diesels and under 1000 hours each. Last week. In Holland. So you are very close to the mark.

[a64pilot]

What little bit of flying I did North Arctic circle in Summer, was either dead calm, or nothing flew, but honestly a LOT of dead calm, and temps much higher than I expected to.
On approach to Tuktoyoktuk you could see the ice pack in the distance, but air temp was pushing high 70’s.

On the mass of the boom, I’m not underestimating it, but think it isn’t any greater than say the whole sails aerodynamic load in 35 kts of wind. I know that a swinging heavy boom has a tremendous amount of kinetic energy, but neither a preventer or a brake has to deal with that kinetic energy, they don’t catch something after it has built up inertia, they stop it from developing inertia, at least the boom, the sail of course has some slack.
I wouldn’t be surprised if either a brake or a preventer would be broken from the inertia of a swinging boom, I think stopping one suddenly would likely mean something is going to break, maybe the boom, but something is going to let go, especially if subjected to repeated cycles.
Not trying to cute, but they are called preventers, not catchers, catching one is I believe a whole nuther ball game.

[Breaking Waves]

Originally Posted by Dockhead

I think few of us motor less than half the miles we make.

This is something which has changed enormously the past couple of decades.

When we started it was rare for bluewater sailors to motor more than a few hours per week - mostly for battery charging - you simply sat when you were becalmed. I remember us sitting for 10 days once. We sailed in 5kts of breeze pretty much the whole way from st Helena to the equator - can't remember how far that was but lets say round number 1500miles. When we quit there was a lot more motoring but 50% was still rare - was still considered 'bad form' and only for the type A's who were rushing to the next destination. And yea, now it is common.

And yea, this was true even in the highish latitudes - we sailed under (cruising) spinnaker most of the way from Scotland to Iceland, lots of sailing in 5-8kts of breeze, pretty much only ran the motor to get in and off the commercial docks. From horn to Fremantle (in the southern ocean) we did not even carry enough fuel to motor much (59 days at sea) so we used our wind vane (rather than autopilot) to save power and reduce battery charging.

I personally think it is a change for the worse for the cruising community, but there is no stopping it and no point in ranting about it.

[Dockhead]

Originally Posted by Breaking Waves

This is something which has changed enormously the past couple of decades.

When we started it was rare for bluewater sailors to motor more than a few hours per week - mostly for battery charging - you simply sat when you were becalmed. I remember us sitting for 10 days once. We sailed in 5kts of breeze pretty much the whole way from st Helena to the equator - can't remember how far that was but lets say round number 1500miles. When we quit there was a lot more motoring but 50% was still rare - was still considered 'bad form' and only for the type A's who were rushing to the next destination. And yea, now it is common.

And yea, this was true even in the highish latitudes - we sailed under (cruising) spinnaker most of the way from Scotland to Iceland, lots of sailing in 5-8kts of breeze, pretty much only ran the motor to get in and off the commercial docks. From horn to Fremantle (in the southern ocean) we did not even carry enough fuel to motor much (59 days at sea) so we used our wind vane (rather than autopilot) to save power and reduce battery charging.

I personally think it is a change for the worse for the cruising community, but there is no stopping it and no point in ranting about it.

I'm not sure much has changed except that some boats have better mechanical propulsion and more tankage.


You should be careful to distinguish between what kind of passages. Really long passages, like intercontinental passages, I think nearly everyone sails nearly all the time, don't they?


It's the shorter ones where you might have a choice to use the motor or not where you might motor rather than wait for wind. The higher the latitude, the more that makes sense, because bobbing around waiting for wind you are exposing yourself to getting clobbered by the next weather system which comes through.


Last year we sailed from the Solent out the East end of the Channel, then up the East Coast of the UK to the Orkneys, then from there to the Faroes and from there to Eastern Iceland. From there to Scorseby Sund in NE Greenland. Back the same way. We motored quite a bit along the UK coast going up, in calms, but once we cleared the top of Scotland we sailed 90% of the time until we got into the Arctic Ocean, whereupon it was 90% motoring.


Way back was the same, although it was upwind from Iceland to Faroes, then a spectacular sail from Faroes all the way past the Orkneys and Scotland and almost the whole East Coast of England in just 4 days, including one day of 218 miles, a personal best in this boat, and no motoring except leaving Torshavn Harbour and entering Wells-Next-The-Sea in East Anglia.


And to put it into perspective, we only used two tanks of fuel for this whole trip, including a whole summer of generator and heater usage, notwithstanding the days of motoring between Iceland and Greenland. We bunkered once in the Faroes on the way up, bought a few jerry cans in Greenland, bunkered again in Iceland, and arrived in Cowes with fuel in the tanks.





So YMMV. I think people motor because they can. People avoid bobbing around becalmed for a variety of sound reasons, if they only have the capability of doing so. In any case, any boat good for use in the Arctic needs to be a very good motor boat, whatever its sailing qualities are.

[Breaking Waves]

Please don't take my comment as a criticism - it's simply an observation.

Originally Posted by Dockhead

I'm not sure much has changed except that some boats have better mechanical propulsion and more tankage.

yea, lol . . . . an absolute ton has changed in the cruising community the past several decades. It is an entirely different thing these days. GPS was a simply enormous change. Even the ashore side has changed dramatically - when we started there were not international ATMs (eg if we were foreign we had to wire money in, could not get it out of a local machine) and many places the international phone lines were so bad that faxing home (that we had arrived) was the usual solution.

And yea, boats have gotten bigger with bigger tanks and better engines, and yea, this has meant a lot more motoring, because as you say people can. Again that is not a criticism. People are using the capability they have.
But I do think it has not been positive on the spirit of the community.

Really long passages, like intercontinental passages, I think nearly everyone sails nearly all the time, don't they?

No. Transatlantic - 50% motoring is now not at all uncommon. and near 100% motor sailing in the arc is not so uncommon.

So YMMV. I think people motor because they can. People avoid bobbing around becalmed for a variety of sound reasons, if they only have the capability of doing so.

sure


In any case, any boat good for use in the Arctic needs to be a very good motor boat, whatever its sailing qualities are.

if you say so. But several of our extremely experienced (vastly more experienced that you are) high latitude friends from past decades would disagree.

I personally would suggest 'needs' is probably not accurate, but would be ambivalent about say 'is desirable'. We had significant motor problems when we were in the Falklands and S Georgia, and I can tell you first hand it is perfectly possible to do that cruising (mostly) engineless.

A problem is that motor boats are much more convenient and comfortable, but typically the better the motor boat, the worse the sailing - twin engines with twin props is an example - twin props really hurts sailing performance (unless they are retractable which creates complication issues) and I am surprised you were considering it. Steve Dashew's last boat is in my mind the logical outcome of developments - just leave the rig off, and it was a damn good vessel ( I cruised in company, and a bit on board with him).

I should just leave this topic here - probably of no value to either you or I in debating it

[thinwater]

Originally Posted by a64pilot

... I would assume the best brake... be Hydraulic?...

I just read 25 pages of posts, many good, some not thought out in terms of engineering, to come to the obvious.


For example, attach a pair of Dyneema cables to the boom near the vang point, lead them to turning blocks near the shrouds that go under the deck, and lead to a pair of adjustable shock absorbers. This could scale to any size, be build from existing components, and the heat dissipation problem goes away. I have intentionally left off a few details to avoid getting hung up in them. This is done on huge floating structures. Is there a reason the concept cannot fit? The greatest problem I see is the range of adjustment, but I think that can be solved with clever use of valves.



Not a preventer. That is a different thing and serves a different (but related) purpose--a preventer is more about stability and has a different leverage angle. The problem with preventers is not strength, it is controlled release. The two tasks require different leverage points (forward vs. beam).

[Dockhead]

Originally Posted by Breaking Waves

Please don't take my comment as a criticism - it's simply an observation.


I should just leave this topic here - probably of no value to either you or I in debating it

Not at all ; it doesn't bother me at all.

Motoring 50% over a transat! I never heard of such a thing. I'm sure you're right and my knowledge is just outdated. Thanks for clearing it up.

[a64pilot]

We motor because we can, it’s pretty much that simple.
Besides to motor sail costs maybe a half gallon an hour, charges the batteries or keeps them full, enables full use of the inverter to make water, make ice, and often cuts passage time way down, sometimes it the difference between getting there in the afternoon or the middle of the night, and depending on where there is, you may need daylight to stay safe.
It’s obvious that you can in fact sail anywhere on Earth, because people have, but may have spent months more doing so, and may even have been iced in in high latitudes where if they could have motored they could have escaped that etc.

Now we are primarily a sail boat, and she is more comfortable and faster, and certainly more relaxed under sail, but if I can’t sail, I’ll motor as opposed to be becalmed.
But then we don’t cross Oceans either, but if and when we do, I plan on carrying extra fuel so that I can motor if needed, it’s just another tool in the box is all, and having that capability is I believe additional safety.


But I’m sure your right, sailing / cruising is vastly different now, with water makers, GPS, satellite comms, EPIRB’s and I don’t know what all else.
There even used to be a time when scaling Everest put you into a very small exclusive club that only a fraction of a percentage of people were capable of. Now it seems if your in good physical condition and have enough money you can scale Everest.
Not belittling it, I could not, I’d die trying I’m sure, or more likely of course just quit, but it’s not what it once was.

[wingssail]

Originally Posted by a64pilot

I believe some just don’t like brakes.
They didn’t grow up with them, don’t see the need, and may not trust them....

For some of us there is another reason: Avoiding complexity of a device for which there is little need.

The boom brake is a big friction device hanging from the boom, in the way of movement over the cabin top, with lines to the side deck which obstruct the passage forward and back and adjuster lines or levers, and weight, and vision obstruction...OMG how much crap do we need to have so that gently easing the boom over in a gybe is automatic?

I can lead my preventer line, which is normally tied to the end of the boom and coiled out of the way, forward to a turning point by the shroud, or forward of that if needed, and back to a winch, where it is cleated. It is only in the way when it is deployed, and then it is very little complexity or obstruction.

My preventer line "prevents" excessive movement of the boom and accidental gybing of the mainsail and boom, and when a gybe happens the boom can be eased over by controlled release at the winch.

The preventer is so simple and easy, and normally out of the way. On the other hand the boom brake is a nuisance 365 days a year. In my case it would have been handy in about two times in 30 years when I had failed to set a preventer and needed it.

Of course no one mentions this argument. In fact it is overlooked to the point that I have to conclude that reducing complexity, clutter, and needless automation is not even a valuable objective to most people.

That is how boats become over loaded and cluttered with things which have utility only rarely and where simpler alternatives exist.

For you who love to sail, who have the joy of sailing, make your boat simpler.

For you others, you'll spend your days carefully evaluating every automation or labor saving device. Ask everyone which one is "best', and debate that subject endlessly, go to every boat show and buy something at every one of them, install them all, and spend your days making your boat more "perfect" instead of sailing it. Then wonder why it isn't much fun, and you spend so much time motoring.

[wingssail]

Originally Posted by a64pilot

We motor because we can, it’s pretty much that simple.
Now we are primarily a sail boat, and she is more comfortable and faster, and certainly more relaxed under sail, but if I can’t sail, I’ll motor as opposed to be becalmed.

I agree with EVERYTHING you said, a64.

But in my case, we sail because we can, and because we love it, and that is why we have a sailboat.

I observe a lot of sailboaters who only sail if they can go straight to their destination, and then, only if they can do it without expending any physical effort of their own.

I work my butt off quite often to sail when it would be easier to motor, but it's worth it to me to do what I love to do, which is to feel a fine performing boat doing its thing, quietly, smoothly, swiftly.

I have no problem though, with others who don't share that need, most of them bought a different boat and can't anyway.

[Dockhead]

Originally Posted by wingssail

For some of us there is another reason: Avoiding complexity of a device for which there is little need.

The boom brake is a big friction device hanging from the boom, in the way of movement over the cabin top, with lines to the side deck which obstruct the passage forward and back and adjuster lines or levers, and weight, and vision obstruction...OMG how much crap do we need to have so that gently easing the boom over in a gybe is automatic?

I can lead my preventer line, which is normally tied to the end of the boom and coiled out of the way, forward to a turning point by the shroud, or forward of that if needed, and back to a winch, where it is cleated. It is only in the way when it is deployed, and then it is very little complexity or obstruction.

My preventer line "prevents" excessive movement of the boom and accidental gybing of the mainsail and boom, and when a gybe happens the boom can be eased over by controlled release at the winch.

The preventer is so simple and easy, and normally out of the way. On the other hand the boom brake is a nuisance 365 days a year. In my case it would have been handy in about two times in 30 years when I had failed to set a preventer and needed it.

Of course no one mentions this argument. In fact it is overlooked to the point that I have to conclude that reducing complexity, clutter, and needless automation is not even a valuable objective to most people.

That is how boats become over loaded and cluttered with things which have utility only rarely and where simpler alternatives exist.

For you who love to sail, who have the joy of sailing, make your boat simpler.

For you others, you'll spend your days carefully evaluating every automation or labor saving device. Ask everyone which one is "best', and debate that subject endlessly, go to every boat show and buy something at every one of them, install them all, and spend your days making your boat more "perfect" instead of sailing it. Then wonder why it isn't much fun, and you spend so much time motoring.

Eloquently argued!


It's really important not to forget this side of it; nevertheless, there is a balance to be found between complexity and function. I would not exclude a boom brake if there were an elegant solution for my particular boat which did not produce a vast amount of clutter and interfere with sailing.


And it's also right to keep in mind that preventers, rigged properly and handled properly, do work pretty well, and the cases where they can't deal with it are pretty rare. I have been sailing all my life, for decades, and I have never (knock on wood) broken anything in an uncontrolled gybe, and I've never broken a preventer. Knock on wood of course.

[thinwater]

Originally Posted by wingssail

For some of us there is another reason: Avoiding complexity of a device for which there is little need.

The boom brake is a big friction device hanging from the boom, in the way of movement over the cabin top, with lines to the side deck which obstruct the passage forward and back and adjuster lines or levers, and weight, and vision obstruction...OMG how much crap do we need to have so that gently easing the boom over in a gybe is automatic?

I can lead my preventer line, which is normally tied to the end of the boom and coiled out of the way, forward to a turning point by the shroud, or forward of that if needed, and back to a winch, where it is cleated. It is only in the way when it is deployed, and then it is very little complexity or obstruction.

My preventer line "prevents" excessive movement of the boom and accidental gybing of the mainsail and boom, and when a gybe happens the boom can be eased over by controlled release at the winch.

The preventer is so simple and easy, and normally out of the way. On the other hand the boom brake is a nuisance 365 days a year. In my case it would have been handy in about two times in 30 years when I had failed to set a preventer and needed it.

Of course no one mentions this argument. In fact it is overlooked to the point that I have to conclude that reducing complexity, clutter, and needless automation is not even a valuable objective to most people.

That is how boats become over loaded and cluttered with things which have utility only rarely and where simpler alternatives exist.

For you who love to sail, who have the joy of sailing, make your boat simpler.

For you others, you'll spend your days carefully evaluating every automation or labor saving device. Ask everyone which one is "best', and debate that subject endlessly, go to every boat show and buy something at every one of them, install them all, and spend your days making your boat more "perfect" instead of sailing it. Then wonder why it isn't much fun, and you spend so much time motoring.

And I agree with this.


I tested a bunch of brakes for an article, and at the end of the day, took then all off. They did function, but as you implied, I didn't need one.


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.