By PhilipH2 - 2 Aug 2019
I saw this on Cruisers' Forum and thought it was worth sharing here but suspect vast majority of OCC Members know how to rig a preventer correctly, still if anyone is not sure here it is:
https://www.maritimenz.govt.nz/commercial/safety/accidents-reporting/accident-reports/documents/Platino-mnz-accident-report-2016.pdf
and the relevant diagram:
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By PhilipH2 - 2 Aug 2019
+x
I should say that we rig the preventer from the end of the boom and not in the middle.
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By Dick - 3 Aug 2019
+x+x I should say that we rig the preventer from the end of the boom and not in the middle.
Hi Philip and all,
Thanks for highlighting some design elements of this important, and often neglected, collection of gear. This gear is rarely called into play, but when it does get called upon, could prevent your rig from catastrophic failure or, worse, prevent a head injury or a crew being swept off the boat.
I looked at the url and found a very long paper. The design alone, however, has features that I believe problematic, possibly dangerous.
First and foremost is the green hash-marked line going forward from a point on the boom about 1/3 back from the aft end. This is a recipe for a broken boom. If, when running hard in seas, you dip your pole end in the water, there will be tremendous pressure on that forward preventer line which will be directly transferred to the boom. The boom is likely to break or bend at the point where the preventer line attaches. Much better to bring the attachment to the boom end where loads will be compressing the boom and not bending it.
The rest of my comments are a bit fuzzy as interpreting the diagram was a bit of a challenge. It looks like preventer lines/pennants are being brought to the toe rail and to snatch blocks. In general, snatch blocks are not up the shock loads that a preventer can generate and toe rails certainly are not. Any connections of this sort on the side deck have to be very robust and installed with significant backing plates.
In general, an offshore preventer, to my mind, should go from boom end to the bow and back to the cockpit where it can be controlled, likely by a cleat rather than a brake. If it is called into use, the forces on the boom are primarily compression, a direction the boom should handle well. When the preventer line is more mid boom, the forces try to bend and fold the boom and the forces are much too likely to succeed.
Come back with questions/comments/thoughts.
My best, Dick Stevenson, s/v Alchemy
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By Dick - 3 Aug 2019
+x+x+x I should say that we rig the preventer from the end of the boom and not in the middle. Hi Philip and all, Thanks for highlighting some design elements of this important, and often neglected, collection of gear. This gear is rarely called into play, but when it does get called upon, could prevent your rig from catastrophic failure or, worse, prevent a head injury or a crew being swept off the boat. I looked at the url and found a very long paper. The design alone, however, has features that I believe problematic, possibly dangerous. First and foremost is the green hash-marked line going forward from a point on the boom about 1/3 back from the aft end. This is a recipe for a broken boom. If, when running hard in seas, you dip your pole end in the water, there will be tremendous pressure on that forward preventer line which will be directly transferred to the boom. The boom is likely to break or bend at the point where the preventer line attaches. Much better to bring the attachment to the boom end where loads will be compressing the boom and not bending it. The rest of my comments are a bit fuzzy as interpreting the diagram was a bit of a challenge. It looks like preventer lines/pennants are being brought to the toe rail and to snatch blocks. In general, snatch blocks are not up the shock loads that a preventer can generate and toe rails certainly are not. Any connections of this sort on the side deck have to be very robust and installed with significant backing plates. In general, an offshore preventer, to my mind, should go from boom end to the bow and back to the cockpit where it can be controlled, likely by a cleat rather than a brake. If it is called into use, the forces on the boom are primarily compression, a direction the boom should handle well. When the preventer line is more mid boom, the forces try to bend and fold the boom and the forces are much too likely to succeed. Come back with questions/comments/thoughts. My best, Dick Stevenson, s/v Alchemy
Hi Philip,
Agree, preventer to boom end. See previous comment. Dick
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By bbalme - 4 Aug 2019
On Toodle-oo! we rig the preventer whenever we're more than about 110 degrees off the wind. Penants on the boom are connected to a line that goes through a low friction eye attached to the toe rail at the bow and come back to a clutch in the cockpit. We can adjust as that as we trim the mainsheet.
Dick's concerns about the strength of the toerail sound a little alarmist - too much Morgan's Cloud perhaps? - since the tensioning line to the boom lies at such a low angle to the toe rail (not 90 degrees to it) it is certainly well strong enough for the job at hand.
Having a simple to deploy (and therefore always gets deployed) preventer system has been a significant contributor to our safe and enjoyable sailing experience.
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By PhilipH2 - 4 Aug 2019
+xOn Toodle-oo! we rig the preventer whenever we're more than about 110 degrees off the wind. Penants on the boom are connected to a line that goes through a low friction eye attached to the toe rail at the bow and come back to a clutch in the cockpit. We can adjust as that as we trim the mainsheet. Dick's concerns about the strength of the toerail sound a little alarmist - too much Morgan's Cloud perhaps? - since the tensioning line to the boom lies at such a low angle to the toe rail (not 90 degrees to it) it is certainly well strong enough for the job at hand. Having a simple to deploy (and therefore always gets deployed) preventer system has been a significant contributor to our safe and enjoyable sailing experience.
My goodness, having an aluminium boat you take lots of things for granted as pretty much what can be welded is welded. So we have part of the preventer (well two actually, port and starboard) that starts at the end of the boom, runs the length of the boom and has a spliced eye with a Wichard snap shackle that is tied off to a cleat on the boom when not in use. The rest of the preventer is similar with another Wichard snap shackle stowed midships on the guardwires and a long line that goes right forward round a stanchion base and back to the cockpit to a cleat. So stanchion base is welded to the deck and cannot be ripped out. Cleat at stern is welded and cannot be ripped out. Is there a weak point? Yes the two snap shackles are connected together and could fail but they were seriously expensive and we pray that you get what you pay for - and we have the same set up on both sides of the boat. Has kept us safe so far, and occasionally we do sail by the lee.
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By Dick - 6 Aug 2019
+xOn Toodle-oo! we rig the preventer whenever we're more than about 110 degrees off the wind. Penants on the boom are connected to a line that goes through a low friction eye attached to the toe rail at the bow and come back to a clutch in the cockpit. We can adjust as that as we trim the mainsheet. Dick's concerns about the strength of the toerail sound a little alarmist - too much Morgan's Cloud perhaps? - since the tensioning line to the boom lies at such a low angle to the toe rail (not 90 degrees to it) it is certainly well strong enough for the job at hand. Having a simple to deploy (and therefore always gets deployed) preventer system has been a significant contributor to our safe and enjoyable sailing experience.
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By Dick - 6 Aug 2019
+xOn Toodle-oo! we rig the preventer whenever we're more than about 110 degrees off the wind. Penants on the boom are connected to a line that goes through a low friction eye attached to the toe rail at the bow and come back to a clutch in the cockpit. We can adjust as that as we trim the mainsheet. Dick's concerns about the strength of the toerail sound a little alarmist - too much Morgan's Cloud perhaps? - since the tensioning line to the boom lies at such a low angle to the toe rail (not 90 degrees to it) it is certainly well strong enough for the job at hand. Having a simple to deploy (and therefore always gets deployed) preventer system has been a significant contributor to our safe and enjoyable sailing experience.
Hi Bill,
I wrote my comment, as it was my take that someone following the diagram to put together a preventer might go wrong, perhaps seriously wrong, if following the diagram.
You are right, in my understanding, to take your preventer line to the bow as, among other attributes, it gives by far the most forgiving angle to absorb loads which may be asked of it. The diagram has lines to the bow and to amidships. It sounds like we all agree that the preventer should go to the bow. It also sounds like there is general agreement to take the preventer to the end of the boom. This is in contrast to the diagram where the attachment point is well away from boom end. In my comment I was referring to the diagram and only the diagram, at least as I interpreted it and only to those aspects I considered problematic.
Your defense of using the toe rail may be completely warranted when the toe rail in use is at the bow and the forces are significantly softened by the advantageous angle, as you accurately noted. There is the added benefit of the load being largely in shear to the fasteners, hopefully bolts, that are securing the toe rail.
I, however, was only referring to the use of the toe rail as depicted in the diagram. In the diagram the pennant goes from the attachment on the boom to a snatch block on the toe rail near amidships. (This loads the fasteners at their weakest: eg not in shear.) This amidships position escalates the forces dramatically. The angle of this pennant to the amidships toe rail is quite dis-advantageous compared to the one you refer to when taking the line to the bow: the forces would be similarly quite different. For the vast majority of the time, these forces are pretty minimal and easily handled. However, when the forces are generated by the onset of an uncontrolled gybe that you wish to prevent, (or dipping boom end in the water) the shock load forces will be momentarily huge. Many toe rails are aluminum extrusions and are not designed to take those kinds of loads in that direction. There are few toe rails that can tolerate that shock load and I write, in part, to discourage readers from thinking that they can use their amidships toe rail to stop an uncontrolled gybe.
Similarly, I would discourage any boat from having their preventer go to any location but the end of the boom: I believe a mid-boom attachment of a preventer is a recipe for a broken boom.
Those are the major caveats I have to following the diagram.
And Bill, I very much support your comments that for an offshore boat; that having an easily deployable preventer line is an important safety item and, in my casual observations, is too little used.
Let me also say a couple of words about your aside that I am (possibly) alarmist and overly influenced by the John Harries’ Attainable Adventures Cruising web site. When I write about procedures and gear and design for cruising safely, I am writing for offshore voyaging boats. As such, my focus is on what is in the reasonable realm of possibility in a boat at sea for a couple of weeks or two or longer. I do not want a boat fully prepared at all times for the worst possible scenario, a hurricane for instance, but I do try to write for those possibilities that do occur with some degree of regularity on a passage making boat. For a preventer system, that would include an unplanned gybe in winds of 20-30kn caused either by a passing nighttime squall and wind shift or by helmsman inattentiveness. It is for that degree of safety that I write for, that gear should be designed for and for which I believe every offshore boat should be prepared to deal with at all times
My take is that John, and generally the AAC contributors, write their articles and comments with a similar degree of carefulness in mind. And although I have disagreed with John and AAC at times, I do not find the site alarmist and that when it comes to engineering and assessing systems, such as the loads being discussed above, they are quite accurate.
That said, lets move away from talking about people and judging their motivations, alarmist and otherwise, and look to the specifics of what makes for a solid preventer system.
My best, Dick Stevenson, s/v Alchemy
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By Dick - 7 Aug 2019
+x+xOn Toodle-oo! we rig the preventer whenever we're more than about 110 degrees off the wind. Penants on the boom are connected to a line that goes through a low friction eye attached to the toe rail at the bow and come back to a clutch in the cockpit. We can adjust as that as we trim the mainsheet. Dick's concerns about the strength of the toerail sound a little alarmist - too much Morgan's Cloud perhaps? - since the tensioning line to the boom lies at such a low angle to the toe rail (not 90 degrees to it) it is certainly well strong enough for the job at hand. Having a simple to deploy (and therefore always gets deployed) preventer system has been a significant contributor to our safe and enjoyable sailing experience. Hi Bill, I wrote my comment, as it was my take that someone following the diagram to put together a preventer might go wrong, perhaps seriously wrong, if following the diagram. You are right, in my understanding, to take your preventer line to the bow as, among other attributes, it gives by far the most forgiving angle to absorb loads which may be asked of it. The diagram has lines to the bow and to amidships. It sounds like we all agree that the preventer should go to the bow. It also sounds like there is general agreement to take the preventer to the end of the boom. This is in contrast to the diagram where the attachment point is well away from boom end. In my comment I was referring to the diagram and only the diagram, at least as I interpreted it and only to those aspects I considered problematic. Your defense of using the toe rail may be completely warranted when the toe rail in use is at the bow and the forces are significantly softened by the advantageous angle, as you accurately noted. There is the added benefit of the load being largely in shear to the fasteners, hopefully bolts, that are securing the toe rail. I, however, was only referring to the use of the toe rail as depicted in the diagram. In the diagram the pennant goes from the attachment on the boom to a snatch block on the toe rail near amidships. (This loads the fasteners at their weakest: eg not in shear.) This amidships position escalates the forces dramatically. The angle of this pennant to the amidships toe rail is quite dis-advantageous compared to the one you refer to when taking the line to the bow: the forces would be similarly quite different. For the vast majority of the time, these forces are pretty minimal and easily handled. However, when the forces are generated by the onset of an uncontrolled gybe that you wish to prevent, (or dipping boom end in the water) the shock load forces will be momentarily huge. Many toe rails are aluminum extrusions and are not designed to take those kinds of loads in that direction. There are few toe rails that can tolerate that shock load and I write, in part, to discourage readers from thinking that they can use their amidships toe rail to stop an uncontrolled gybe. Similarly, I would discourage any boat from having their preventer go to any location but the end of the boom: I believe a mid-boom attachment of a preventer is a recipe for a broken boom. Those are the major caveats I have to following the diagram. And Bill, I very much support your comments that for an offshore boat; that having an easily deployable preventer line is an important safety item and, in my casual observations, is too little used. Let me also say a couple of words about your aside that I am (possibly) alarmist and overly influenced by the John Harries’ Attainable Adventures Cruising web site. When I write about procedures and gear and design for cruising safely, I am writing for offshore voyaging boats. As such, my focus is on what is in the reasonable realm of possibility in a boat at sea for a couple of weeks or two or longer. I do not want a boat fully prepared at all times for the worst possible scenario, a hurricane for instance, but I do try to write for those possibilities that do occur with some degree of regularity on a passage making boat. For a preventer system, that would include an unplanned gybe in winds of 20-30kn caused either by a passing nighttime squall and wind shift or by helmsman inattentiveness. It is for that degree of safety that I write for, that gear should be designed for and for which I believe every offshore boat should be prepared to deal with at all times My take is that John, and generally the AAC contributors, write their articles and comments with a similar degree of carefulness in mind. And although I have disagreed with John and AAC at times, I do not find the site alarmist and that when it comes to engineering and assessing systems, such as the loads being discussed above, they are quite accurate. That said, lets move away from talking about people and judging their motivations, alarmist and otherwise, and look to the specifics of what makes for a solid preventer system. My best, Dick Stevenson, s/v Alchemy .
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By neilm - 5 Sep 2019
What kind and size of line for the preventer ?????
I am puzzled as to how springy a preventer should be. Nylon ? Dyneema/Spectra or something in between.
We have gybed with Dacron and with nylon, and both avoided a big bang, although the nylon let the boom go a long way across.
What are members thoughts?
What size line? We have an 8mm Spectra pennant at the moment and joined to a 14 mm three-strand nylon line, so we are intermediate in elasticity.
47 foot boat with 550 sq ft main.
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By bbalme - 5 Sep 2019
My take is that you want a little give in the preventer to avoid any impact loads, so we use some very stout 5/8" double braid penants on the boom and then the main preventer lines are attached by bowline to the penant and are made of 1/2" sta-set double braid. Ours is a 44ft boat with 650 sq ft main.
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By Dick - 5 Sep 2019
+xMy take is that you want a little give in the preventer to avoid any impact loads, so we use some very stout 5/8" double braid penants on the boom and then the main preventer lines are attached by bowline to the penant and are made of 1/2" sta-set double braid. Ours is a 44ft boat with 650 sq ft main.
Hi Neil,
I agree w/ Bill. Nylon, in reasonable sizes, might allow the boom to go full swing if the tip is dipped in a wave as it stretches a great deal. HM lines are like wire and would make transmit shock loads directly into the preventer system un-modified by any cushioning. Double braid Dacron/polyester in ½ inch is my choice (significantly smaller main), but size should be chosen commensurate with load estimates. Mine is regular untreated Dacron by a good manufacturer. Sta-Set is likely also fine: it has been worked to decrease stretch, but does not approach HM line, I believe. My experience w/ Sta-Set X is that it is stiff and hard to handle, less so w/ Sta-Set: fine for halyards, but less user friendly for lines needing handling like sheets etc.
It would be interesting to have a rigger weigh-in. If anyone is near one (I am not), one might ask and give a report. Make sure they are experienced with offshore boats and not just coastal cruisers.
My best, Dick Stevenson, s/v Alchemy
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By alshaheen - 11 Sep 2019
When I recently overcame barriers to access the Forum, with Bill's assistance, he invited me to start making "controversial posts". So, I'll start here!
I am in fundamental disagreement that the best preventer arrangement is a line from boom end to the bow. I know it is a very popular system but I suggest below what I believe is a far superior system.
Looking at fundamentals, the primary purpose of a preventer is, when running downwind, to prevent an uncontrolled gybe. I would suggest that an equally important use is to restrain a heavy boom from slopping about in a seaway when winds are light. In fact, aboard Al Shaheen, we used our preventer more often for this than running downwind. A sub-set of the first function is to use a preventer system to actually control a gybe.
Any preventer system needs to be effective, and easy and safe to set up in rough weather, preferably without having to go to the bow, and can be controlled from both sides of the boat without having to re-rig after a gybe.
The disadvantage of the "boom end to the bow" arrangement is easily seen from the geometry; the angle between the line and the boom is necessarily acute so the line is not very effective in restraining movement of the boom. Consequently, it is not an effective system for restraining movement of a boom in a seaway.
I suggest a more effective arrangement is as follows if I can explain it adequately without a diagram.
A two-part purchase, on both sides of the boat, positioned just aft of the aft lower shrouds with a line running from a pad-eye on deck through a block with swivel and Wichard hook then back to another block attached to a pad-eye on deck then aft to a rope clutch accessible from the cockpit and positioned so that it can be led to a winch.The block with a Wichard hook is then attached to a boom fitting just aft of the vang. When running downwind with the boom say 70 degrees from the boat's centreline, the attachment point on the boom is nearly vertically above the deck attachment so the boom is restrained very effectively. This system can be set up hard, especially if led to a winch and it may be attached to the boom (both sides) and left in place even when not sailing downwind, or attached in anticipation of a downwind leg.
Previous posts have commented on shock loads and the strength toe-rails and deck fittings. In this arrangement, when set up properly and properly used, shock loads do not occur. That's not to say that the system should not be designed for shock loads; it should. In my case I had alloy decks of 6mm plate with 10mm inserts welded in high load areas.
I take no credit for this design; it came from the late Mike Pocock, past OCC Commodore formidable designer of ocean cruising boats and was developed from his own experience of a lifetime of ocean cruising.and featured in all his recent ocean cruising boat designs.
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By bbalme - 11 Sep 2019
I knew I should never have helped you onto the forum!!!
You're going to have to draw me a picture, photograph it and email it to me so that I an upload it and add it to your post. Why? Because, I can't quite picture what you're describing and my preventer system follows what I thought you explained to me back in the Azores in 2013! I followed your advice and now I'm finding out I apparently screwed up!!
From your description, it sounds like a potential boom breaker - so I'd really like to see a picture.
Cheers!
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By simoncurrin - 12 Sep 2019
We have been using a Dutchman for the last 13 years which does all of these things, is permanently rigged, very simple to use and adjustable.
It would, however, be nice to have some downwind sailing to use it more!
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By Dick - 12 Sep 2019
+xWhen I recently overcame barriers to access the Forum, with Bill's assistance, he invited me to start making "controversial posts". So, I'll start here! I am in fundamental disagreement that the best preventer arrangement is a line from boom end to the bow. I know it is a very popular system but I suggest below what I believe is a far superior system. Looking at fundamentals, the primary purpose of a preventer is, when running downwind, to prevent an uncontrolled gybe. I would suggest that an equally important use is to restrain a heavy boom from slopping about in a seaway when winds are light. In fact, aboard Al Shaheen, we used our preventer more often for this than running downwind. A sub-set of the first function is to use a preventer system to actually control a gybe. Any preventer system needs to be effective, and easy and safe to set up in rough weather, preferably without having to go to the bow, and can be controlled from both sides of the boat without having to re-rig after a gybe. The disadvantage of the "boom end to the bow" arrangement is easily seen from the geometry; the angle between the line and the boom is necessarily acute so the line is not very effective in restraining movement of the boom. Consequently, it is not an effective system for restraining movement of a boom in a seaway. I suggest a more effective arrangement is as follows if I can explain it adequately without a diagram. A two-part purchase, on both sides of the boat, positioned just aft of the aft lower shrouds with a line running from a pad-eye on deck through a block with swivel and Wichard hook then back to another block attached to a pad-eye on deck then aft to a rope clutch accessible from the cockpit and positioned so that it can be led to a winch.The block with a Wichard hook is then attached to a boom fitting just aft of the vang. When running downwind with the boom say 70 degrees from the boat's centreline, the attachment point on the boom is nearly vertically above the deck attachment so the boom is restrained very effectively. This system can be set up hard, especially if led to a winch and it may be attached to the boom (both sides) and left in place even when not sailing downwind, or attached in anticipation of a downwind leg. Previous posts have commented on shock loads and the strength toe-rails and deck fittings. In this arrangement, when set up properly and properly used, shock loads do not occur. That's not to say that the system should not be designed for shock loads; it should. In my case I had alloy decks of 6mm plate with 10mm inserts welded in high load areas. I take no credit for this design; it came from the late Mike Pocock, past OCC Commodore formidable designer of ocean cruising boats and was developed from his own experience of a lifetime of ocean cruising.and featured in all his recent ocean cruising boat designs.
Hi John,
If I understand you correctly, your preventer is attached to the boom just aft of the vang (perhaps a third of the way aft of the gooseneck) and goes to the side deck just aft of the shrouds and then back to the cockpit for adjustment with a b&t arrangement between boom and side deck to a winch for increased purchase. It sounds like there is only one attachment point to the boom.
Your use of this arrangement is to control the heavy boom from slopping around in light air and leftover swell. I believe this is a good idea, works well, and we do the same on Alchemy. But that use, to my mind, is more accurately described as a side deck boom vang than as a preventer. Although it can function as both, its main purpose is to keep the boom down and immovable. It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom.
And, yes, a preventer is to prevent uncontrolled gybes, but it is also in place to prevent damage to the boat/boom if the boom tip gets dipped into the sea: perhaps when the roll of the boat coincides with a wave top. This is an admittedly rare, but with enough ocean time, also a predictable event.
This is a potent way shock loads might occur. The boom end would immediately be dragged aft and, in the arrangement you describe, the load would go directly to the point-loaded part of the boom just aft of the vang attachment. This, as you mentioned, is set up hard and is almost vertical for very little give. I suspect, the boom would likely just fold up like cardboard (or the attachment to the boom would give way). It is this scenario that a preventer to the boom end is designed to prevent in addition to an uncontrolled gybe.
I believe this why preventers are almost always recommended to boom end. Yes, it causes some extra work when gybing the boat, but in ocean passages, this will not often occur and going to the bow when in downwind conditions is not so fearsome.
My best, Dick Stevenson, s/v Alchemy
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By Dick - 12 Sep 2019
+xWe have been using a Dutchman for the last 13 years which does all of these things, is permanently rigged, very simple to use and adjustable.It would, however, be nice to have some downwind sailing to use it more!
Hi Simon,
Would the Dutchman release enough and quickly enough to prevent boom damage were you to dip the boom end into the sea at speed?
Thanks, Dick
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By alshaheen - 12 Sep 2019
+x+xWhen I recently overcame barriers to access the Forum, with Bill's assistance, he invited me to start making "controversial posts". So, I'll start here! I am in fundamental disagreement that the best preventer arrangement is a line from boom end to the bow. I know it is a very popular system but I suggest below what I believe is a far superior system. Looking at fundamentals, the primary purpose of a preventer is, when running downwind, to prevent an uncontrolled gybe. I would suggest that an equally important use is to restrain a heavy boom from slopping about in a seaway when winds are light. In fact, aboard Al Shaheen, we used our preventer more often for this than running downwind. A sub-set of the first function is to use a preventer system to actually control a gybe. Any preventer system needs to be effective, and easy and safe to set up in rough weather, preferably without having to go to the bow, and can be controlled from both sides of the boat without having to re-rig after a gybe. The disadvantage of the "boom end to the bow" arrangement is easily seen from the geometry; the angle between the line and the boom is necessarily acute so the line is not very effective in restraining movement of the boom. Consequently, it is not an effective system for restraining movement of a boom in a seaway. I suggest a more effective arrangement is as follows if I can explain it adequately without a diagram. A two-part purchase, on both sides of the boat, positioned just aft of the aft lower shrouds with a line running from a pad-eye on deck through a block with swivel and Wichard hook then back to another block attached to a pad-eye on deck then aft to a rope clutch accessible from the cockpit and positioned so that it can be led to a winch.The block with a Wichard hook is then attached to a boom fitting just aft of the vang. When running downwind with the boom say 70 degrees from the boat's centreline, the attachment point on the boom is nearly vertically above the deck attachment so the boom is restrained very effectively. This system can be set up hard, especially if led to a winch and it may be attached to the boom (both sides) and left in place even when not sailing downwind, or attached in anticipation of a downwind leg. Previous posts have commented on shock loads and the strength toe-rails and deck fittings. In this arrangement, when set up properly and properly used, shock loads do not occur. That's not to say that the system should not be designed for shock loads; it should. In my case I had alloy decks of 6mm plate with 10mm inserts welded in high load areas. I take no credit for this design; it came from the late Mike Pocock, past OCC Commodore formidable designer of ocean cruising boats and was developed from his own experience of a lifetime of ocean cruising.and featured in all his recent ocean cruising boat designs. Hi John, If I understand you correctly, your preventer is attached to the boom just aft of the vang (perhaps a third of the way aft of the gooseneck) and goes to the side deck just aft of the shrouds and then back to the cockpit for adjustment with a b&t arrangement between boom and side deck to a winch for increased purchase. It sounds like there is only one attachment point to the boom. Your use of this arrangement is to control the heavy boom from slopping around in light air and leftover swell. I believe this is a good idea, works well, and we do the same on Alchemy. But that use, to my mind, is more accurately described as a side deck boom vang than as a preventer. Although it can function as both, its main purpose is to keep the boom down and immovable. It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom. And, yes, a preventer is to prevent uncontrolled gybes, but it is also in place to prevent damage to the boat/boom if the boom tip gets dipped into the sea: perhaps when the roll of the boat coincides with a wave top. This is an admittedly rare, but with enough ocean time, also a predictable event. This is a potent way shock loads might occur. The boom end would immediately be dragged aft and, in the arrangement you describe, the load would go directly to the point-loaded part of the boom just aft of the vang attachment. This, as you mentioned, is set up hard and is almost vertical for very little give. I suspect, the boom would likely just fold up like cardboard (or the attachment to the boom would give way). It is this scenario that a preventer to the boom end is designed to prevent in addition to an uncontrolled gybe. I believe this why preventers are almost always recommended to boom end. Yes, it causes some extra work when gybing the boat, but in ocean passages, this will not often occur and going to the bow when in downwind conditions is not so fearsome. My best, Dick Stevenson, s/v Alchemy
Dick
You have correctly interpreted my description of the "Pocock" design of preventer system as fitted to many of his ocean cruising boat designs notably Blackjack (the late Mike Pocock), Troubadour (the late Stuart Ingram) , Sadco (the late Noel Marshall), as well as Al Shaheen. In the case of Taonui (Tony Gooch) now renamed Moli (Randall Reeves) Mike Pocock redesigned the rig after Tony's dismasting in the south Atlantic. All these OCC members have put in collectively hundreds of thousands of ocean miles in rugged ocean passages without, to my knowledge experiencing problems arising from "boom in the water". I am a conservative ocean sailor and in circumstances where boom-in-the-water was likely I would reduce sail, itself quite easy downwind with the Pocock reefing system.
You commented " It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom". Not can, it does stop unintentional gybes! With the boom held almost immobile there is very little energy in the gybe so boom damage is very unlikely.
In my 60 year sailing career I have experienced many boats with "boom end to bow " preventer systems and can confidently say that I am a complete convert to the system I described which I believe to be infinitely superior. Were I to be commissioning a new boat I would undoubtedly specify it again.
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By Dick - 12 Sep 2019
+x+x+xWhen I recently overcame barriers to access the Forum, with Bill's assistance, he invited me to start making "controversial posts". So, I'll start here! I am in fundamental disagreement that the best preventer arrangement is a line from boom end to the bow. I know it is a very popular system but I suggest below what I believe is a far superior system. Looking at fundamentals, the primary purpose of a preventer is, when running downwind, to prevent an uncontrolled gybe. I would suggest that an equally important use is to restrain a heavy boom from slopping about in a seaway when winds are light. In fact, aboard Al Shaheen, we used our preventer more often for this than running downwind. A sub-set of the first function is to use a preventer system to actually control a gybe. Any preventer system needs to be effective, and easy and safe to set up in rough weather, preferably without having to go to the bow, and can be controlled from both sides of the boat without having to re-rig after a gybe. The disadvantage of the "boom end to the bow" arrangement is easily seen from the geometry; the angle between the line and the boom is necessarily acute so the line is not very effective in restraining movement of the boom. Consequently, it is not an effective system for restraining movement of a boom in a seaway. I suggest a more effective arrangement is as follows if I can explain it adequately without a diagram. A two-part purchase, on both sides of the boat, positioned just aft of the aft lower shrouds with a line running from a pad-eye on deck through a block with swivel and Wichard hook then back to another block attached to a pad-eye on deck then aft to a rope clutch accessible from the cockpit and positioned so that it can be led to a winch.The block with a Wichard hook is then attached to a boom fitting just aft of the vang. When running downwind with the boom say 70 degrees from the boat's centreline, the attachment point on the boom is nearly vertically above the deck attachment so the boom is restrained very effectively. This system can be set up hard, especially if led to a winch and it may be attached to the boom (both sides) and left in place even when not sailing downwind, or attached in anticipation of a downwind leg. Previous posts have commented on shock loads and the strength toe-rails and deck fittings. In this arrangement, when set up properly and properly used, shock loads do not occur. That's not to say that the system should not be designed for shock loads; it should. In my case I had alloy decks of 6mm plate with 10mm inserts welded in high load areas. I take no credit for this design; it came from the late Mike Pocock, past OCC Commodore formidable designer of ocean cruising boats and was developed from his own experience of a lifetime of ocean cruising.and featured in all his recent ocean cruising boat designs. Hi John, If I understand you correctly, your preventer is attached to the boom just aft of the vang (perhaps a third of the way aft of the gooseneck) and goes to the side deck just aft of the shrouds and then back to the cockpit for adjustment with a b&t arrangement between boom and side deck to a winch for increased purchase. It sounds like there is only one attachment point to the boom. Your use of this arrangement is to control the heavy boom from slopping around in light air and leftover swell. I believe this is a good idea, works well, and we do the same on Alchemy. But that use, to my mind, is more accurately described as a side deck boom vang than as a preventer. Although it can function as both, its main purpose is to keep the boom down and immovable. It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom. And, yes, a preventer is to prevent uncontrolled gybes, but it is also in place to prevent damage to the boat/boom if the boom tip gets dipped into the sea: perhaps when the roll of the boat coincides with a wave top. This is an admittedly rare, but with enough ocean time, also a predictable event. This is a potent way shock loads might occur. The boom end would immediately be dragged aft and, in the arrangement you describe, the load would go directly to the point-loaded part of the boom just aft of the vang attachment. This, as you mentioned, is set up hard and is almost vertical for very little give. I suspect, the boom would likely just fold up like cardboard (or the attachment to the boom would give way). It is this scenario that a preventer to the boom end is designed to prevent in addition to an uncontrolled gybe. I believe this why preventers are almost always recommended to boom end. Yes, it causes some extra work when gybing the boat, but in ocean passages, this will not often occur and going to the bow when in downwind conditions is not so fearsome. My best, Dick Stevenson, s/v Alchemy Dick You have correctly interpreted my description of the "Pocock" design of preventer system as fitted to many of his ocean cruising boat designs notably Blackjack (the late Mike Pocock), Troubadour (the late Stuart Ingram) , Sadco (the late Noel Marshall), as well as Al Shaheen. In the case of Taonui (Tony Gooch) now renamed Moli (Randall Reeves) Mike Pocock redesigned the rig after Tony's dismasting in the south Atlantic. All these OCC members have put in collectively hundreds of thousands of ocean miles in rugged ocean passages without, to my knowledge experiencing problems arising from "boom in the water". I am a conservative ocean sailor and in circumstances where boom-in-the-water was likely I would reduce sail, itself quite easy downwind with the Pocock reefing system. You commented " It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom". Not can, it does stop unintentional gybes! With the boom held almost immobile there is very little energy in the gybe so boom damage is very unlikely. In my 60 year sailing career I have experienced many boats with "boom end to bow " preventer systems and can confidently say that I am a complete convert to the system I described which I believe to be infinitely superior. Were I to be commissioning a new boat I would undoubtedly specify it again.
Hi John,
Perhaps we might have to agree to disagree on this on.
It may be boat size: mine is smaller, I believe, than most you refer to and this makes me closer to the water. I also know that when I have my sails built, I have it done so that reefs lift the boom, which also makes it less likely to dip end in water when in heavier weather.
I like what you describe as it always has the boom triangulated and under control as I consider the boom as one of the more dangerous objects on a boat and keeping its movement predictable is an important safety feature. It is what we do on Alchemy at all times as well.
And I agree that a side decks preventer can prevent gybes as there is little energy with the boom not moving to a bit of back-winding if course is regained relatively quickly. It also happens on Alchemy occasionally. That said, there could be a lot of energy in a serious backwinding if an autopilot fails or a big wave slews the stern around.
All in all, I very much advocate an end of boom preventer line when running hard in high seas.
My best, Dick Stevenson, s/v Alchemy
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By simoncurrin - 12 Sep 2019
Dick
Absolutely yes it would. It is infinitely adjustable SI can be a boom brake or a boom lock. We use ours as a brake and only lock it to secure the boom when the sail is not up. Bill McLaren managed to break his boom by forgetting to release a conventional preventer before gybing (planned). That wouldn’t have happened with a Dutchman.
Simon
+x+xWe have been using a Dutchman for the last 13 years which does all of these things, is permanently rigged, very simple to use and adjustable.It would, however, be nice to have some downwind sailing to use it more! Hi Simon, Would the Dutchman release enough and quickly enough to prevent boom damage were you to dip the boom end into the sea at speed? Thanks, Dick
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By David.Tyler - 13 Sep 2019
I watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct.
In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway.
Of course, we do have our own problems to find answers to:
The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter].
When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to cause it.
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By Dick - 13 Sep 2019
+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to cause it.
Hi David,
It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas.
my best, Dick
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By Dick - 13 Sep 2019
+xDick Absolutely yes it would. It is infinitely adjustable SI can be a boom brake or a boom lock. We use ours as a brake and only lock it to secure the boom when the sail is not up. Bill McLaren managed to break his boom by forgetting to release a conventional preventer before gybing (planned). That wouldn’t have happened with a Dutchman. Simon +x+xWe have been using a Dutchman for the last 13 years which does all of these things, is permanently rigged, very simple to use and adjustable.It would, however, be nice to have some downwind sailing to use it more! Hi Simon, Would the Dutchman release enough and quickly enough to prevent boom damage were you to dip the boom end into the sea at speed? Thanks, Dick Hi Simon,
Interesting. Thanks for the input: it sounds like a worthwhile piece of kit.
When you report that Bill's boom busted because he forgot to release his conventional boom prior to a planned gybe: what was the design of the conventional preventer? Where was it attached to the boom?
Thanks, Dick
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By David.Tyler - 13 Sep 2019
+x+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to ca Hi David, It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas. my best, Dick
Dick, the Aero Rig is generally understood to be a commercial version of the Balestron rig, built by Carbospars in Hamble. The Balestron has been used on model yachts for many years, and the Aero Rig has been applied to yachts from a 22ft Hirondelle catamaran up to the 70ft 'Fly' and the 60ft 'Novara' - but I guess that you aren't referring to that rig, but to the soft wing sail that I and others sail under. Am I correct? If so, I'll start a new topic.
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By PhilipH2 - 13 Sep 2019
+x+x+xWhen I recently overcame barriers to access the Forum, with Bill's assistance, he invited me to start making "controversial posts". So, I'll start here! I am in fundamental disagreement that the best preventer arrangement is a line from boom end to the bow. I know it is a very popular system but I suggest below what I believe is a far superior system. Looking at fundamentals, the primary purpose of a preventer is, when running downwind, to prevent an uncontrolled gybe. I would suggest that an equally important use is to restrain a heavy boom from slopping about in a seaway when winds are light. In fact, aboard Al Shaheen, we used our preventer more often for this than running downwind. A sub-set of the first function is to use a preventer system to actually control a gybe. Any preventer system needs to be effective, and easy and safe to set up in rough weather, preferably without having to go to the bow, and can be controlled from both sides of the boat without having to re-rig after a gybe. The disadvantage of the "boom end to the bow" arrangement is easily seen from the geometry; the angle between the line and the boom is necessarily acute so the line is not very effective in restraining movement of the boom. Consequently, it is not an effective system for restraining movement of a boom in a seaway. I suggest a more effective arrangement is as follows if I can explain it adequately without a diagram. A two-part purchase, on both sides of the boat, positioned just aft of the aft lower shrouds with a line running from a pad-eye on deck through a block with swivel and Wichard hook then back to another block attached to a pad-eye on deck then aft to a rope clutch accessible from the cockpit and positioned so that it can be led to a winch.The block with a Wichard hook is then attached to a boom fitting just aft of the vang. When running downwind with the boom say 70 degrees from the boat's centreline, the attachment point on the boom is nearly vertically above the deck attachment so the boom is restrained very effectively. This system can be set up hard, especially if led to a winch and it may be attached to the boom (both sides) and left in place even when not sailing downwind, or attached in anticipation of a downwind leg. Previous posts have commented on shock loads and the strength toe-rails and deck fittings. In this arrangement, when set up properly and properly used, shock loads do not occur. That's not to say that the system should not be designed for shock loads; it should. In my case I had alloy decks of 6mm plate with 10mm inserts welded in high load areas. I take no credit for this design; it came from the late Mike Pocock, past OCC Commodore formidable designer of ocean cruising boats and was developed from his own experience of a lifetime of ocean cruising.and featured in all his recent ocean cruising boat designs. Hi John, If I understand you correctly, your preventer is attached to the boom just aft of the vang (perhaps a third of the way aft of the gooseneck) and goes to the side deck just aft of the shrouds and then back to the cockpit for adjustment with a b&t arrangement between boom and side deck to a winch for increased purchase. It sounds like there is only one attachment point to the boom. Your use of this arrangement is to control the heavy boom from slopping around in light air and leftover swell. I believe this is a good idea, works well, and we do the same on Alchemy. But that use, to my mind, is more accurately described as a side deck boom vang than as a preventer. Although it can function as both, its main purpose is to keep the boom down and immovable. It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom. And, yes, a preventer is to prevent uncontrolled gybes, but it is also in place to prevent damage to the boat/boom if the boom tip gets dipped into the sea: perhaps when the roll of the boat coincides with a wave top. This is an admittedly rare, but with enough ocean time, also a predictable event. This is a potent way shock loads might occur. The boom end would immediately be dragged aft and, in the arrangement you describe, the load would go directly to the point-loaded part of the boom just aft of the vang attachment. This, as you mentioned, is set up hard and is almost vertical for very little give. I suspect, the boom would likely just fold up like cardboard (or the attachment to the boom would give way). It is this scenario that a preventer to the boom end is designed to prevent in addition to an uncontrolled gybe. I believe this why preventers are almost always recommended to boom end. Yes, it causes some extra work when gybing the boat, but in ocean passages, this will not often occur and going to the bow when in downwind conditions is not so fearsome. My best, Dick Stevenson, s/v Alchemy Dick You have correctly interpreted my description of the "Pocock" design of preventer system as fitted to many of his ocean cruising boat designs notably Blackjack (the late Mike Pocock), Troubadour (the late Stuart Ingram) , Sadco (the late Noel Marshall), as well as Al Shaheen. In the case of Taonui (Tony Gooch) now renamed Moli (Randall Reeves) Mike Pocock redesigned the rig after Tony's dismasting in the south Atlantic. All these OCC members have put in collectively hundreds of thousands of ocean miles in rugged ocean passages without, to my knowledge experiencing problems arising from "boom in the water". I am a conservative ocean sailor and in circumstances where boom-in-the-water was likely I would reduce sail, itself quite easy downwind with the Pocock reefing system. You commented " It can stop unintentional gybes, but with the lever arm so close to the gooseneck, a violent un-controlled gybe might damage the boom". Not can, it does stop unintentional gybes! With the boom held almost immobile there is very little energy in the gybe so boom damage is very unlikely. In my 60 year sailing career I have experienced many boats with "boom end to bow " preventer systems and can confidently say that I am a complete convert to the system I described which I believe to be infinitely superior. Were I to be commissioning a new boat I would undoubtedly specify it again.
It seems that you are describing what Wichard have developed into the Gyb'easy which is attached to the underside of the boom just aft of the vang with lines taken to the side deck aft of the shrouds and then back to clutches at the cockpit (location depends on the boat). The device allows for three levels of friction and is supplied with climbing rope so that it will "slide" through the device. We have one and use it for sloppy seas and when gybing - how good is it for the latter? 6/7 out of 10. It is sold as enabling a controlled i.e. slow gybe from one downwind setting to the other but we do not operate like that, and always winch in the main so that the distance the boom travels is not too great. At the same time we have a standard boom end to bow preventer which we have used for thousands of miles - we trust the preventer and swapping from one side to the other is hassle free as the lines are in two parts and connect with Wichard clips.
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By simoncurrin - 13 Sep 2019
Dick
I am sorry I don’t know what sort of preventer the McClaren’s use. But his broken boom was at Ardfern for sometime.
Simon
+x+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to cause it. Hi David, It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas. my best, Dick
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By Dick - 17 Sep 2019
+x+x+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to ca Hi David, It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas. my best, Dick Dick, the Aero Rig is generally understood to be a commercial version of the Balestron rig, built by Carbospars in Hamble. The Balestron has been used on model yachts for many years, and the Aero Rig has been applied to yachts from a 22ft Hirondelle catamaran up to the 70ft 'Fly' and the 60ft ' Novara' - but I guess that you aren't referring to that rig, but to the soft wing sail that I and others sail under. Am I correct? If so, I'll start a new topic.
Hi David,
I was just interested in rigs in general and I have seen these aero rigs which, on casual observation, seem to check a lot of boxes. Dick
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By David.Tyler - 18 Sep 2019
+x+x+x+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to ca Hi David, It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas. my best, Dick Dick, the Aero Rig is generally understood to be a commercial version of the Balestron rig, built by Carbospars in Hamble. The Balestron has been used on model yachts for many years, and the Aero Rig has been applied to yachts from a 22ft Hirondelle catamaran up to the 70ft 'Fly' and the 60ft ' Novara' - but I guess that you aren't referring to that rig, but to the soft wing sail that I and others sail under. Am I correct? If so, I'll start a new topic. Hi David, I was just interested in rigs in general and I have seen these aero rigs which, on casual observation, seem to check a lot of boxes. Dick
I see. Well, since I've only sailed with one for an afternoon, and since I deplore the "armchair experts" who speak without benefit of first hand knowledge, I'm not really the right person to ask. All I can see is that there is nothing that the Balestron/Aerorig has in common with the rigs under which I sail. Within the OCC, you could contact Steve Brown, for some first hand info. And have a look at this, from Richard Woods, the catamaran designer.
But to keep to the topic under discussion here, I can certainly say that they clearly don't need a preventer!
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By Dick - 18 Sep 2019
+x+x+x+x+xI watch from the sidelines, a faint but sympathetic smile playing about my lips, as you guys bat these ideas back and forth concerning ways to prevent your preventers from causing your rigs to self destruct. In the junk rig world, we reckon the long, 180˚ gybe to be safest in heavy weather. Given sufficient searoom, we sail 90˚ by the lee so that sail is taken aback, then it comes across quickly, but harmlessly, and ends up empty of wind with a slack sheet, having nothing like shrouds to stop it short. Because we have to get so far by the lee to cause an intentional gybe, there is much less chance of an unintentional gybe. There is no boom to cause an elfin safety issue, as the "boom" is in fact just another batten. Applying a strong preventer to it would simply cause it to break. The only need I have felt to rig a preventer is in light going with a leftover sea, when the after sail of a ketch or schooner won't lie quietly, and then it's no more than a 6mm nylon line that will stretch if the sail is seriously backwinded, allowing the sail to come across. The fore sail of a ketch or schooner, or a single sail, is so far forward that it is not possible to rig a preventer - no matter, it wouldn't do any good anyway. Of course, we do have our own problems to find answers to: The sheet, as it comes across, must be prevented from snagging anything on the boat, or the crew, and the best way to do that is to rig a semicircular hoop over the cockpit. This comes in handy for rigging shade, as well, so is a good thing to add on a voyaging boat [note to self: must add one to Weaverbird this winter]. When gybing deeply reefed, we have to avoid a "fan-up", as the after ends of the yard and upper battens rise, and may get caught the wrong side of the topping lifts in high-peaked junk rigs. Again, there's an answer, which unsurprisingly is called a fan-up preventer. So yes, we do sometimes rig a preventer, but it's to prevent inconvenience, not to ca Hi David, It is always good to read about alternatives. At some point, if it interests you, I would be interested in your observations of the aero rig (I do not have the name right, I suspect) and how it relates to junk rigs. Casual observation indicates they share some similar design ideas. my best, Dick Dick, the Aero Rig is generally understood to be a commercial version of the Balestron rig, built by Carbospars in Hamble. The Balestron has been used on model yachts for many years, and the Aero Rig has been applied to yachts from a 22ft Hirondelle catamaran up to the 70ft 'Fly' and the 60ft ' Novara' - but I guess that you aren't referring to that rig, but to the soft wing sail that I and others sail under. Am I correct? If so, I'll start a new topic. Hi David, I was just interested in rigs in general and I have seen these aero rigs which, on casual observation, seem to check a lot of boxes. Dick I see. Well, since I've only sailed with one for an afternoon, and since I deplore the "armchair experts" who speak without benefit of first hand knowledge, I'm not really the right person to ask. All I can see is that there is nothing that the Balestron/Aerorig has in common with the rigs under which I sail. Within the OCC, you could contact Steve Brown, for some first hand info. And have a look at this, from Richard Woods, the catamaran designer. But to keep to the topic under discussion here, I can certainly say that they clearly don't need a preventer!
Hi David, Understood and agreed. Thx, Dick
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By johnenvanessa - 3 Feb 2021
Hello - thanks for starting the discussions on the preventers. Does anyone have experience with the Walder Boom Break (preventer) system? I would like to learn if it is any good or just expensive? Our boat is a Dufour GL 380. Thanks!
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