9 Times Wind Force!!
We used to have a chapter about boom brakes in our Sail Handling and Rigging Online Book, but I recently deleted it. My recommendation is to not use boom brakes and rig a proper preventer instead.
Here’s why I made this change.
Why We Don’t Recommend Boom Brakes
23 CommentsReading Time: 7 minutes
More Articles From Online Book: Sail Handling and Rigging Made Easy:
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Hi John,
Thank you for extending the application of Kurt’s spreadsheet to the case of boom brakes. The loads are very convincing in orders of magnitude, with all the consequences on structural reinforcements should anyone wish to “properly” install a boom brake, and potential damage otherwise.
I would suggest a couple of additional drawbacks: having a piece of metal hanging under the boom waiting to hit someone is one, especially when the device isn’t active. Another is that you loose the option to dump the vang, and for those that have a main traveller, to lower it in a gust. These are two independent quick responses that I like to keep available off-wind. Not to mention that sail trimming is likely to require adjusting the control line tension, which I understand requires some tuning too.
We’ll continue to focus on the preventer which keeps improving with every article you write on the topic.
The efforts you put in to drive critical safety points are much appreciated, thanks again.
JL
Hi Jean-Louis,
Thanks for the kind words, and good points on those further disadvantages.
The pic of my boom brake is a few years old – and a bunch of other things have changed around it since – but the basic idea remains the same. It was built by the original owner who spent 14yrs sailing the boat 40,000m plus around the world. Him and his wife have a literal collection of PhD’s between them and I learned a lot talking with him.
The triangle idea may not be unique, but I’ve never seen another one locally. It’s trivial to set up and not all that sensitive to line pre-tension because it’s working just like a rappelling device that really only cares about the working load on it. In practice I just set it to be ‘not loose’ and that seems good enough.
The basic idea is that the action of the brake does not start happening until after the boom has travelled past midships. The angles of the points of attachment were carefully thought through, and I can confirm this is what happens in practice.
The handful of unexpected gybes I’ve encountered, the boom moved very quickly across midships until the brake tightened up and then with a bit of squealing it comes to rest without a bang.
The essential claim being made here is this boom brake design is only loaded when the wind loads on the sail are at a minimum and most of the forces it’s handling are just the momentum of the boom itself.
Oh and just for clarity – we use a preventer most of the time downwind, although obviously I’ve been caught out a few times. I see the two as handling different aspects of the gybe – the preventer to stop the unintended event and the brake to smooth the action of the intended one.
Hi Philip,
An an interesting implementation, for sure. That said, I’m thinking that if the boom starts off the jibe that fast and then slows to a stop the forces must still be high, particularly given the geometry, so I personally would not be at all comfortable with the rather light looking attachments and the rings.
Hi Philip,
After thinking more on this, I would suggest running the set up through the calculations in chapter above and then applying the answer to the fittings, particularly that ring and the bail on the boom. My thinking is that, as I write above, even if something has lasted a long while, if it’s not strong enough to take the calculated load including a realistic safety factor it should be fixed or removed. To me this is a case of the classic low probability, but high consequence, risk that can result in a nasty accident just when we least expect it because it’s been fine for years.
Yes that original bail never struck me as strong enough. The mailsail the boat came with had a closed foot, but since replacing it with an open foot I’ve changed the connection to a decent dyneema loop wrapped around the whole boom. Same with the mainsheet connection as well.
The original deck attachments have been completely changed along with all the rest of the deck fittings as well – the engineer in me could not resist.
And on reflection I’ll get my local shop to crack test the rest of the setup, or even just remake it a bit beefier. It’s been so simple and forgiving I’m loath to give it away.
Hi John,
I have no additional info about boom brakes since I have little experience with them. For a while I looked into different types, but concluded that I didn’t feel comfortable with the core idea, which seems to be that it can prevent the crash at the end of a failed gybe, which is only part of the problem with a failed gybe. The main problem is that it failed, duh, and thus caused risks.
You say false safety is worse than no safety. I could not agree more! This topic has been at the front of my mind for some years, in many contexts.
If we think a boom brake will help us save a failed gybe, that piece of equipment will make us feel safer, which will increase the probability of a failed gybe. We can deny it as much as we want. Feeling safe still changes our behaviour.
The boom brake safety contribution is questionable, as discussed here, which for me is a big red flag. How can it possibly result in a positive result when all factors are counted? It can’t.
I feel that we (myself included) may often overlook the level of sound seaworthiness of a vessel and our equipment may become a sedative to not be suitably aware of issues. I’m not saying that we shouldn’t try to make our boats safer and that we shouldn’t buy gear that makes us feel safer. I just say that we should look at the total effect. Gear plus mind. How do we operate the whole thing? A boat full of safety equipment may put its crew in more danger than a boat with less equipment and more awareness.
When thinking of risks there are two sides to the prevention of consequences, stopping the event from happening, and minimizing the consequences if the event happens. It doest matter why the accidental gybe happens, but when it does you may be grateful that the forces were reduced at the end of the gybe. The idea of a damper is not that unusual in retarding loads for soft landings e.g. inertial reals, variable chokes on hydraulic lift cylinders. I think a device that decelerated the boom would be useful if properly designed.
Hi Alastair,
I agree, if such a device could be designed that was less dependant on constant adjustment and had decent geometry so it was not overloaded, I would be all over it. That said I would want it to keep the boom from accelerating in the first place, not just damp down the stop, so that it would prevent anyone getting hurt as the boom and mainsheet cross the cockpit. Otherwise I far prefer a proper preventer that prevents the boom moving in the first place.
In fairness to Pip, that you tube is nine years old and maybe not relevant to her current sailing. Perhaps it should be removed from you tube as a lot of people, you and I included admire Pip as both a sailor and a person. That clip is pretty out of date
Hi Peter,
Good point. The problem is, and the reason I highlighted it, is that said video is at the top of search results on boom brakes and it would be all too easy for someone to conclude that because Pip did the video and was positive that boom brakes and attaching them to a turnbuckle toggle is a good idea. So tough on Pip, and maybe unfair, but we also have to own the things we have said. This is one of the reasons I like having most everything I have written here at AAC where I can change or delete it when I learn that I have made an error.
It’s not unfair. As insights develop and lessons learned, then it is right to point out outmoded or wrong ideas, it happens frequently in science and usually no one is bothered. What would be unfair is not identifying the issue because of someone’s status. This sort of insight is why I continue to subscribe to AAC.
Hi Alastair,
Good point, and thanks for the support on that, and the kind words.
Yep completely agree with both of you on this
Hello John,
Love your site. Always a lot of good information here, and I realize it’s focussed more on offshore than coastal.
That being said, we just finished our fifth year of sailing as coastal sailors and use a Walder Boom Brake. It’s been nothing less than a godsend for a guy – this guy 🙂 – that fears the accidental gybe like an 80’s kid did quicksand. It has given me increased confidence going downwind since hooking it up three seasons ago. (To be clear, not OVER confidence, as I’m a pretty cautious sailor.) Would your recommendation about eliminating it extend to coastal, or are you speaking primarily about offshore use?
Thanks again for the informative read. Take care.
Hi Brian,
First off let me say that I totally get where you are coming from. It’s really hard to have a piece of kit that has worked well for you called into question. I should know since that has happened to me many times. The most notable when it was proved to me that the side deck jacklines I had clipped to for over 30 years are worse than useless.
That said, no, offshore or inshore makes no difference to the fundamental that a very smart professional engineer has shown conclusively that the fundamental geometry (just like sidedeck jacklines) is flawed. And another pro engineer has verified that (Matt’s comment).
Given that, when we hit one of these things we need to take a deep breath and turn our thinking around from: “I have used this for years and so it’s fine”, to “I have used this for years therefore I’m trusting it to keep me safe, but what if it’s not strong enough to do that in a bad situation?”
Here’s a metaphor. If you owned a great car that had made you feel safe, but then an engineer proved that the seat belt anchors where not strong enough to withstand a head on at over 50 miles an hour, and here’s how to check if your car’s anchors are strong enough. What would you do?
So then the process becomes “OK I need to check this”, and this chapter gives you the tools to do that for your boom brake. Better yet, I give you a check list (blue box).
But here’s a caution, it’s really easy in this situation to start bending all the variables to get the answer we want, so we must guard against that.
One more thought. If you fear an accidental jibe (very wise) how much do you fear an accidental jibe where the boom breaks at the brake mounting or the brake parts off. This is the classic low probability, but high consequence accident that hurts people and the very fact you trust the brake makes you more vulnerable, not less.
Same with me with side deck jacklines. I trusted them and so was less carful assuming they would save me than I would have been with no jacklines at all.
Hope that this helps you decide what to do.
Thanks John, appreciate the detailed reply.
Caveat, I’m speaking entirely from theory & math, not from experience (I have never used one of these devices).
I would say John’s assessment is, overall, correct.
If the idea is to use a boom brake instead of a preventer, you run into the loads-and-angles problem. It won’t prevent the accidental gybe; at best, it’ll slow the gybe, but with momentary peak forces on the brake & its line that are similar to those of a fixed preventer in the same highly non-optimal spot.
If the idea is to use a boom brake to control the speed of a gybe, then what are you doing with the mainsheet? If the sheet’s handled properly, then the brake isn’t doing much if anything; if you let the brake do all the work, then the slack sheet becomes a serious hazard in itself. And you still have the loads-and-angles problem.
If the idea is that the brake should slow the gybe so as to prevent a hard crash of the boom into the aft lower shrouds, OK, good idea in principle. But you STILL have the loads-and-angles problem, and the slack mainsheet problem, and no brake is going to slow a crash gybe by enough to save the skull of an unfortunate deckhand who happens to be in the boom arc.
And yeah, you need to be SUPER careful about what you tie this stuff off to. Naval architects design chainplates for a standing-rigging pull aligned perfectly with the chainplate, and nothing else. Likewise for all other rigging components; they’re designed for one specific load path, and if you load them off-axis you have no idea what’s going to happen. “Oh, I’ll put a padeye in the deck then” well what is the padeye transferring its load to? 1/16 inch of fibreglass on the inside of an inch of balsa? These things take planning.
I was crew on a delivery a couple of years back and got a real world taste of one of theses things. I was on night shift running in about 25-30 knots. A wave pushed the stern to port and the double reefed main gybed with great violence. The preventer was on, and IF it slowed the boom at all, it was no more than 5%. The captain came up and proceeded to accidentally gybe another 2 times. (The seas were really confused) All that extra gear didn’t seem to do a damn thing. The forces were just too great. I’d rather focus my energies on a good preventer. Thanks for the great article.
P.S.: We should have had 3 reefs, but the single line reefing had jammed up in the boom, so don’t get me started on that topic, that’s a debate for another day 😉
Hi David,
A scary story. Good to hear that no one was hurt. I also think it illustrates something I have long believed: generally simpler systems are better. So in this case a properly rigged bow preventer and single line reefing with the tack on a hook would have avoided both issues.
The Walder Boom Brake has been around for 50 years. If it was so inherently dangerous why haven’t more gear failures and serious accidents been reported? Why are they still in business? As an engineer myself, I’m all for running the numbers, but where the rubber meets the road is in real world testing of properly rigged equipment. Have you invited Walder to comment on your calculations and assumptions?
Hi Jesse,
Sure I can see that way of thinking about it. After all we had a chapter on boom brakes for years.
But there’s a lot of stuff around boats that actually does not work well, or is dangerous. For example the wire halyard reel winch was around for decades before people finally realized that things were dangerous and there was a better way. But I don’t think asking reel winch manufactures the question would have yielded anything useful.
And what about side deck jacklines? Fundamentally useless and yet the majority of offshore boats still use them and world sailing sanctions them.
And let’s not forget that the same geometry has already killed.
The other thing is there is no reliable accident reporting in sailing, so there may have been many more accidents.
And then there’s the really nutty stuff like attaching the boom brake to a chain plate, or the fact that some (all?) boom brakes must be constantly be adjusted to even work.
Add it all up, and I want no part of them, but each of us must make our own decision and the above article gives us the tools to do that.
Heck, I even make suggestions to make boom brakes safer for those who want to keep them. What’s not to like.
And of course any boom brake manufacturer can put their view forward in the comments.
Hi Again Jesse,
I had another look at the Walder and found this page that scared the heck out of me: https://boom-brake-walder.com/leading-to-the-cockpit/?lang=en
Seriously? These photos represent an implied recommendation from Walder to do things that are, at least in my view, very dangerous. The worst ones being the attachment to turnbuckles and their toggles with rings. That clinches it for me. I would not listen to anything that company has to say.