Boom Preventer

[flaming]

I disagree. If there's no room for movement, there's no shock loads.

Which part of the rig do people think will be damaged by use of a tight and strong preventer?

That would be the case if the mainsail is a board. However as the sail will need to go from full on one side to full on the other it will move and then refill with a bang. Nothing like as big a shock as if you allow the boom to move, but still there will be a shock.

I don't think that Dynema would be an issue for the preventer, but I also don't think it's an application where the extra cost is worth it.

 

[Refueler]

That would be the case if the mainsail is a board. However as the sail will need to go from full on one side to full on the other it will move and then refill with a bang. Nothing like as big a shock as if you allow the boom to move, but still there will be a shock.

I don't think that Dynema would be an issue for the preventer, but I also don't think it's an application where the extra cost is worth it.

This is an important factor ... that sail is not as yo0u say a flat board ... it has s 'full body' that can exert quite a shock when it fills regardless of boom moving or not.

 

[bikedaft]

there was a thread on here a while ago about static and dynamic loads which was (i think) about boom preventors? iirc a boat had allowed a dynamic load to go on the boom preventor, and it broke. i cannot remember if injury resulted. comparison was made with climbing static and dynamic loads.

(i think) you want to avoid dynamic loads if at all possible.

i don't see the point in having anything other than a v tight preventor, which would prevent a gybe. booms kill by head injuries and MOB's, stating the bleedin' obvious?

although we have never used one until we had kids.

 

[Poignard]

A block P & Std at bow attached to most forward pulpit supports.
Shackled SS carabiner on end of boom.Line with bowline knot either end around everything via blocks forward to stern cleats P& Std.
Easy peasey to engage/disengage by simply clipping line onto carabiner and trimming and cleating off on windward side,right next to where im sitting,if block failure forward you still have second pulpit supports to offer a secondary barrier before anything too disastrous occurs.has multiple uses when not in use.To gybe,bring main into central position, unclip and repeat on new tack

That's pretty much what I have except that I have a line [strop] a few feet long clipped to the after end of the boom, the free end of which can be clipped to either the Port or Starboard preventer as required.

When not in use it is held taut under the boom with a bit of shockcord.

My 28' Twister is narrow enough that I can stand in the companionway and reach either rail where the preventers are clipped ready to use, and attach/detach the boom strop to whichever is to be used.

 

[Gsailor]

Too long a thread for me to read all posts.

I did note in the OP that a “preventer” was mentioned as opposed to a “brake” which simply slows a gybe (if I am correct), accidental or not.

I hated sailing by the lee, but once forced to by a yacht master examiner, I rigged a preventer. I still sailed very carefully in a narrow channel to avoid an accidental gybe. I would have preferred to hand the main and sail under foresail.

 

[jaminb]

"...............However another though occurred, could I use the spinnaker pole down haul attached to the permanently installed lines? Would it be sufficiently strong (AWB bolted through the deck but behind a head lining)....... jamimb


I do a similar thing. Rigged a second long downhaul as well so the lines go from near the end of the boom forward to the foredeck and back to winches/jammers by the companionway. They can be clipped on easily, as my boom is pretty short, and I can sail with both ready to use. Most of the time, when not in use I just pull the snap shackles to the blocks on the foredeck.

I am sure some might feel they are a bit feeble but I am happy with them for the sailing I do.

.

Thanks all for your responses.

Doug having read about snapping 10mm dynema I doubt my pole downhaul attachment is strong enough! think I will stick to using my long mooring lines through the bow cleats and clipped / tied to permanently rigged lines from the end of the boom to the gooseneck.

 

[dolabriform]

We have a semi permanent rigged preventer in 8mm braid on braid. It's attached to the end of the Selden boom which has preventer printed on to it in the loop at the end.

We've only crash gybed it once in a F6, the line stretched a few inches!

As mentioned above, dealing with the backed main was easier once we had rolled the polled genoa away.

 

[pandos]

Common factors in six ocean racing deaths and two escapes

This article is worth reading.

I read the full report on one of the boats where they lost control of the boom, after a preventer broke and the mainsheet broke loose. (It's a pretty sobering report)

The take aways seem to be, rig a continuous preventer from the end of the boom to well forward so it has a good angle and use splices/shackles rather than knots.

 

[B27]

Bear in mind that some people rig a 'preventer' in relatively light winds to 'prevent' the mass of the boom upsetting the sail when there's more sea than wind.
In my view the best way to actually prevent uncontrolled gybes is to sail a bit higher, or if the sea is out of line with the wind, gybe and sail on the tack which works better.
On the one hand I sail a cruiser and wish to 'arrive alive' without excess stress, on Sundays I race a Laser and the odd swim is to be expected.
If you're not racing, and the main is getting threatening, reef it.
Maybe it's sometimes wrong to rely on a good preventer to allow you to set 'too much' main?

My background involves a lot of dinghy racing, sometimes sailing downwind is quite dynamic and the urge to go lower than you're comfortable with should be resisted. If you're pushing the boat into the 'difficult zone' with a less than expert person on the helm, or worse still, a cheap pile of electronics, maybe consider heading up into a more forgiving corner of the polar?

Being blown along dead down wind is all very easy, until it isn't!

 

[doug748]

Yes, we tend to always look for definitive answers on the Forum, this is right and that is wrong. Most of the time there are no universal rights and wrongs. I have light preventers because I sail that way in light conditions and don't go offshore. Most of the time they are steadying the boom in waves and light air. The rest of the time they prevent the gybe but I would not rely on them in hard conditions, I would head up, reef and sail modestly.

The geometry of my boat would mean that strong preventers might endanger the rig through failure of the shrouds. Shock loading against wires in tension, the gybe loads would be huge.

.

 

[bikedaft]

I often sail downwind with foresail only, have been hit too many times over the years by the boom. We have a relatively small main, however, makes about a knot's difference

 

[Kelpie]

Bear in mind that some people rig a 'preventer' in relatively light winds to 'prevent' the mass of the boom upsetting the sail when there's more sea than wind.
In my view the best way to actually prevent uncontrolled gybes is to sail a bit higher, or if the sea is out of line with the wind, gybe and sail on the tack which works better.
On the one hand I sail a cruiser and wish to 'arrive alive' without excess stress, on Sundays I race a Laser and the odd swim is to be expected.
If you're not racing, and the main is getting threatening, reef it.
Maybe it's sometimes wrong to rely on a good preventer to allow you to set 'too much' main?

My background involves a lot of dinghy racing, sometimes sailing downwind is quite dynamic and the urge to go lower than you're comfortable with should be resisted. If you're pushing the boat into the 'difficult zone' with a less than expert person on the helm, or worse still, a cheap pile of electronics, maybe consider heading up into a more forgiving corner of the polar?

Being blown along dead down wind is all very easy, until it isn't!

We're coming to this from different perspectives. I see almost no downside to rigging a preventer. I've yet to hear a single example of a correctly rigged (tight, boom end) preventer causing rig damage. The main downside that I can think of is that if you need to suddenly alter course (e.g. collision avoidance, or MOB), a preventer introduces another step which could cost critical time.
On a long passage, sailing ~20⁰ off your intended course simply to keep the main filled isn't really a long term strategy, and will necessitate extra gybes, which is more work and risk for the crew.
You mention the possibility of a mistake or failure of the (auto) helm- yet another reason to rig a preventer. Several times our windvane has been unable to respond quickly enough to a wind shift or particularly big wave knocking us off course, and the preventer did its job and changed what would have been an alarming and possibly dangerous crash gybe into a fairly gentle stall.

I totally agree with you about dinghy sailing though. In strong conditions a fast dinghy can become a real handful dead downwind. I usually prefer to avoid it, and zig zag in a series of broad reaches instead.

 

[Refueler]

Bear in mind that some people rig a 'preventer' in relatively light winds to 'prevent' the mass of the boom upsetting the sail when there's more sea than wind.
In my view the best way to actually prevent uncontrolled gybes is to sail a bit higher, or if the sea is out of line with the wind, gybe and sail on the tack which works better.
On the one hand I sail a cruiser and wish to 'arrive alive' without excess stress, on Sundays I race a Laser and the odd swim is to be expected.
If you're not racing, and the main is getting threatening, reef it.
Maybe it's sometimes wrong to rely on a good preventer to allow you to set 'too much' main?

My background involves a lot of dinghy racing, sometimes sailing downwind is quite dynamic and the urge to go lower than you're comfortable with should be resisted. If you're pushing the boat into the 'difficult zone' with a less than expert person on the helm, or worse still, a cheap pile of electronics, maybe consider heading up into a more forgiving corner of the polar?

Being blown along dead down wind is all very easy, until it isn't!

We have our odd differences ... but this post sits high with me.

If I find that a strong preventer is called for - then I ask myself what else can I do ... as B27 suggests here - alter the course slightly ? Its not unknown to actually increase speed by altering just a few degrees - getting the main to behave better without need for mooring rope style preventers ...

 

[B27]

We're coming to this from different perspectives. I see almost no downside to rigging a preventer. I've yet to hear a single example of a correctly rigged (tight, boom end) preventer causing rig damage. The main downside that I can think of is that if you need to suddenly alter course (e.g. collision avoidance, or MOB), a preventer introduces another step which could cost critical time.
On a long passage, sailing ~20⁰ off your intended course simply to keep the main filled isn't really a long term strategy, and will necessitate extra gybes, which is more work and risk for the crew.
You mention the possibility of a mistake or failure of the (auto) helm- yet another reason to rig a preventer. Several times our windvane has been unable to respond quickly enough to a wind shift or particularly big wave knocking us off course, and the preventer did its job and changed what would have been an alarming and possibly dangerous crash gybe into a fairly gentle stall.

I totally agree with you about dinghy sailing though. In strong conditions a fast dinghy can become a real handful dead downwind. I usually prefer to avoid it, and zig zag in a series of broad reaches instead.

Sailing 20 degrees off course sounds like a lot, but the cosine of 20 degrees is 0.94.
So if your speed remains the same, then it takes you 6% longer.
Sailing around the West Country, I often find my bilge keel boat rolls in the waves if I try to sail too low.

On a longer passage, the trick is to plan a series of gybes which will make the best of the changing current and shifting winds.
I don't always get that right, with the wind not obeying the forecasts.

 

[Kelpie]

Sailing 20 degrees off course sounds like a lot, but the cosine of 20 degrees is 0.94.
So if your speed remains the same, then it takes you 6% longer.
Sailing around the West Country, I often find my bilge keel boat rolls in the waves if I try to sail too low.

On a longer passage, the trick is to plan a series of gybes which will make the best of the changing current and shifting winds.
I don't always get that right, with the wind not obeying the forecasts.

At least on our boat, you have to choose either a dead run at 180⁰, or a broad reach at about 150⁰. In between the two is the dead zone where flying both sails on the same side will just result in a blanketed genoa.
It's amazing how often that turns out to be the course you need to be on

 

[john_morris_uk]

At least on our boat, you have to choose either a dead run at 180⁰, or a broad reach at about 150⁰. In between the two is the dead zone where flying both sails on the same side will just result in a blanketed genoa.
It's amazing how often that turns out to be the course you need to be on

Oh how true!

 

[john_morris_uk]

My two penny worth. All IMHO…

A preventer really ought be to the end of the boom or close to the end as possible.
A preventer that breaks isn’t doing its job.
A preventer should be led back to the cockpit and rigged in such a way from as far f’wd as possible that it doesn’t put load on guardrails and rigging in the event of the mainsail backing.

I’ve known of booms breaking from preventers rigged mid boom to rail etc. (Horrible unseamanlike practice.)

If we’re on a run for any extended period we drop the main and rig twin headsails poled out either side.