Boom Brake Question.

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goeasy123

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I'm told that attaching a preventer to the middle(ish) of the boom, rather than the end, puts a higher load on the boom which might break it. So why are boom brakes attached at the middle(ish) and won't have the same damaging effect. It's not because the boom brake offers a softer swing because the instruction for my boom brake say you can lock the boom in position by pulling the line in hard.
 
lw395, I'm not talking about controlling an intentional gybe. I'll still do that in the usual manner with the main. I'm using the boom brake to control unintentional gybes and to stop the rig rattling in light/variable down wind conditions/
 
The boom brake I use is actually a climbing descender: it’s used as a shock absorber to take the punch out an unintended gybe. There’s no way I could put enough tension on it to lock the boom in place without using a winch, which isn’t going to happen. So it’s fine mounted on the centre of the boom, actually using one of the main sheet fittings. Come to think of it, all the stresses of the boom as on the mid point, because that’s where the main sheet is, not at the end of the boom. So I don’t have any concern about where’s it mounted.
If we’re doing a long down wind sail, I’ll dispense with the brake and rig a preventer, but it’s a hassle removing and replacing it when we’re intentionally gybing fairly frequently, hence the brake.
 
I think if you are sailing in big seas, maybe I should say 'in big swells' and accelerating down the swells, lose steerage as a result of the speed, there can be every chance of accidental gybes. You need a team of good helmsmen (you tire quickly). Not everyone sails with a team of gorillas.

Big seas and 'good weather' might not occur at the same time in the UK - but in the tropics it is very common to have huge seas at the back end of a cyclone/typhoon, blue skies and lighter winds - accidental gybes are not uncommon.

Lots of yachts have boom brakes - they tend to be short crewed and sail oceans (obviously, in the grand scheme of things, not many sail oceans short handed).

But because boom brakes are not common on racing yachts (who tend to have large crews) and would not be used in inshore waters then the exposure to the devices is limited and there maybe some confused thoughts.

It appears to be an excellent topic to air in this forum.

Andy - I can vouch for my scenario - been there done that.

Jonathan
 
Neeves that all makes total sense as you always do. But: why not make a preventer, for that scenario?
My limited experience of boom brakes is, the geometry can't be got right, and the preventer line pulls the boom down not firwards.
 
Mine's a helical groove type boom brake and the main sheet is connected at the end of the boom. It's grippy enough to lock the boom and it says in the manual that this is a thing to do. Here's what I think (hope) happens. When you tighten the line the boom is held in position by the friction between the line and the helical groove. There are 2 force in play at this point because the line runs either side of the boom.

On the otherhand if it was just a preventer attached mid boom then you would have two opposing couples bending the boom.... i.e. the main at the end and the preventer in the middle. This is why there have been reports of boom failure with this set up and why a preventer at the end of the boom is recommended. Incidently, for the same reason if the main is fixed mid boom then the preventer should be fixed mid boom??

Am I right in assuming that my brake set up applies the minimum or at least acceptable out of balance load?
 
Andy Todd said:
I'm told that attaching a preventer to the middle(ish) of the boom, rather than the end, puts a higher load on the boom which might break it. So why are boom brakes attached at the middle(ish) and won't have the same damaging effect. It's not because the boom brake offers a softer swing because the instruction for my boom brake say you can lock the boom in position by pulling the line in hard.
Click to expand...

We saw (IIRC a ketch) in Figuerra da Foz a few years ago with a broken boom, said to have been caused by unintentional gybe when using brake.
 
Andy Todd said:
I'm told that attaching a preventer to the middle(ish) of the boom, rather than the end, puts a higher load on the boom which might break it. So why are boom brakes attached at the middle(ish) and won't have the same damaging effect. It's not because the boom brake offers a softer swing because the instruction for my boom brake say you can lock the boom in position by pulling the line in hard.
Click to expand...

My boom brake doesn't lock anything even when winched tightly. It slows down movement of the boom across the boat.
 
If you had climbing rope in your boom brake you would add some more elasticity.

The reason I don't like preventers is, or are, that if it goes wrong (and its a yacht - so going wrong is inevitable) then you have a real mess. A main cleated at the mainsheet, the preventer cleated, a spinnaker pole on the wrong side and the spinnaker in the sea - real mess in a lightweight yacht.

Today we jibe downwind, as cats are like dogs dead before the wind. Our jibe angle is large and I can do it single handed - though its a bit laborious. Because we are not running before the wind, we are trying to ensure the head sail stays filled and the traveller being wide (or long) means we are not actually using much mainsheet. Also because we are not sailing dead down wind its difficult to accidentally jibe the yacht. The other advantage of a cat is that if you have the sails trimmed correctly - your are moving relatively fast, the apparent wind is low and the yacht stays flat, or flattish (never let it be said multis sail flat!)

Our experience of accidental jibes was when we raced our X99 in HK (and some of our actual and predicted jibes became accidental when someone got something wrong - it happens).

I'd prefer a preventer that had some of the attributes of a boom brake - something as anoccasionalyachtsman suggests might have a bit of give.

Jonathan
 
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Jeaneau 30 I am currently fixing has a Whichard brake. As above, it slows things down, not locks the boom. The sheet is attached to the boom end and the kicking tackle likely puts more load on the boom.
 
I have a Walder on my 50 foot IP.

In answer to the first point, sailing the boat correctly is all very well, but if you set a boat up for crusing, and expect to have less experienced people on the helm at 2 am in the morning, wow it makes a lot fo sense. Accidents happen!

I can and have gybed in 30+ knots (just havent got around to trying more) without any drama, and with complete control. I can lock up the boom completely as others have described.

Its a great piece of kit.

Getting the correct rope, and the correct tension is absolutely key, but thats it.

Could it break the boom. I dont know. I guess it gets pretty loaded up if you have the tension wrong and the boom crashes over. I avoid doing that which isnt difficult if you have the control line marked up. The IP boom is pretty substantial as well and I have a special strong point attached so I reckon its ok. The boom should move slowly through its arc with no crach or bang when it comes to a stop in a very controlled way. If it deosnt there isnt enought tension on the rope.

One point. I have seen people fit boom brakes so that the brake doesnt scribe and equal radius throughout the travel of the boom. I appreciate that sometimes the spray hood may get in the way with a CC but usually this can be achieved perhaps with some cord to keep the brake tilted forward when there is no tension on it.

Great peice of kit and wouldnt be without.
 
I also use a climbing descender, a big figure of 8 one. Probably only suitable for boats under 30 foot but works great and only costs a few pounds.. For me it is most useful when inexperienced people are helming - a insurance policy against a mistake.
 
that if it goes wrong (and its a yacht - so going wrong is inevitable) then you have a real mess. A main cleated at the mainsheet, the preventer cleated, a spinnaker pole on the wrong side and the spinnaker in the sea - real mess in a lightweight yacht.

This scenario is why I don't use a spinny. All the same, things can get quite exciting if the wind gets behind a prevented main, which is why my preventer is permanently rigged though a block forward and back to a cleat in the cockpit, ready for immediate release. The same line allows me to pick up my mooring from the cockpit if it's too windy to get it from the bow. Clip it on to the mooring pennant and let go. The boat's then attached and I can pull the line in at leisure - it once took half an hour, because I could only grab a bit in the lulls; I tried to wind it in on the mast winch, but didn't like the way the mast was bending...

As for where to attach a preventer, there are advantages to having it half way down the boom - it's less likely to garrote the crew, for one thing, but forces are much higher. Many an AWB has the main sheet attached mid-boom, so I presume the booms are suitably reinforced. In that case, I'd expect it to be fine, but my main sheet is at the end of the boom, so that's where the preventer goes
 
The force on a preventer can be much more than the mainsheet load.
Consider the boom and mainsail clew hitting a wave when you're doing 9 knots.
It'sa different world from the preventer we rig in light airs to stop the boom shaking the rig on ever bit of motorboat wash.
 
dgadee said:
My boom brake doesn't lock anything even when winched tightly. It slows down movement of the boom across the boat.
Click to expand...



As did my home made one using a Petzl figure of eight and the two midships cleats - the line was rove through the centre of the cleats using those as direction changers without too much friction and then led back to the cockpit where they were made off/tensioned.

Really improved things in rolly downwind sailing. And, in the best PBO tradition, cost was minimal.
 
DownWest said:
Jeaneau 30 I am currently fixing has a Whichard brake. As above, it slows things down, not locks the boom. The sheet is attached to the boom end and the kicking tackle likely puts more load on the boom.
Click to expand...

Just clarification. The kicker pulls down, the force is limited by the tackle design, and the boom was specified with these factors in mind. The Wichard brake pulls to the side and the force is not limited by a tackle. The boom is probably several times stronger in one direction than the other.

There have been several reports of people breaking booms as a result of locking the boom in place with a boom brake. This has also happened with preventers rigged mid-boom.

I'm thinking "locked down" should be a matter of degree. In other words, you might tension the line more than you would for normal jibing, to add stability, but not so much that it was actually locked. It would probably also help to mount the brake as far aft as possible, although this is limited by beam (the arc problem).

A thought, outside the box. The magic "arc" normally speced for brakes assumes you want to be able to ease the boom nearly 90 degrees. However, a multihull or B&R rig boat seldom eases the boom past 45 degrees. In this case, a simple geometry exercise will demonstrate that the control line anchor points, and thus the boom attachment, can be considerably farther aft. In fact, I know some boat that are rigged this way, and it is smooth. The trick is to still maintain a sensible arc.
 
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I am not personally an expert but here is what I work on. It says so in the Selden guide so I take that advice. I would welcome verification from anyone else who actually makes booms; there is an awful lot of speculation on this subject. I considered setting up a boom brake on our 44 footer and decided against.

The boom is not typically designed for horizontal stresses at the kicker take-off point. Yes, a boom brake can feel great and calm things down gybing (accidentally or deliberately) in moderate and even in strong winds, but you have no way to know at what point it becomes a breaking rather than braking load.

A preventer should be attached at the same point as the mainsheet. The challenge we have (with aft-swept spreaders) is getting a wide-enough angle to the boom; we overcome this by running the preventer to the bow fairlead (with chafe protection if more than a few hours), and by using low-stretch line, and by pre-tensioning such that the boom is held pretty rigidly in place.

If smashing the boom end into a wave and breaking it with the preventer is a serious concern, I would raise the boom and sheet it in, and/or reef so there's less sail to thrust in the water, and/or head up 15 Deg and lose the preventer entirely.

Shoot me if you think I am wrong. Or, more appropriately, check in with the fella that actually made your boom.
 
thinwater said:
Just clarification. The kicker pulls down, the force is limitied by the tackle design, and the boom was specified with these factors in mind. The Wichard brake pulls to the side and the force is not limitied by a tackle. The boom is probably several times stronger in one direction than the other.
Click to expand...
RJJ said:
I am not personally an expert but here is what I work on. It says so in the Selden guide so I take that advice. I would welcome verification from anyone else who actually makes booms; there is an awful lot of speculation on this subject. I considered setting up a boom brake on our 44 footer and decided against.

The boom is not typically designed for horizontal stresses at the kicker take-off point. Yes, a boom brake can feel great and calm things down gybing (accidentally or deliberately) in moderate and even in strong winds, but you have no way to know at what point it becomes a breaking rather than braking load.

A preventer should be attached at the same point as the mainsheet. The challenge we have (with aft-swept spreaders) is getting a wide-enough angle to the boom; we overcome this by running the preventer to the bow fairlead (with chafe protection if more than a few hours), and by using low-stretch line, and by pre-tensioning such that the boom is held pretty rigidly in place.

If smashing the boom end into a wave and breaking it with the preventer is a serious concern, I would raise the boom and sheet it in, and/or reef so there's less sail to thrust in the water, and/or head up 15 Deg and lose the preventer entirely.

Shoot me if you think I am wrong. Or, more appropriately, check in with the fella that actually made your boom.
Click to expand...
I think you are dead on. You are one of the few to recognize that swept back spreaders on a mono add an additional challenge. Multihulls have more beam and thus avoid this problem.

Except for racers, it seems obvious that most of us would be reefed when we are rolling the boom into waves!
 
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