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cammd said..
Just read part of the CYCA incident report on the 2024 s2h. I don't understand the section on preventers, in the report they are considered by many as relics from the IOR era that are not needed on modern racing yachts as crash gybes are less likely on boats with bow sprits running assymetrical spinnakers.

I am a little gobsmacked to read that given the fatal consequences in that race as a result of 2 crash gybes.

Clearly modern yachts are at risk of crash gybes with the consequences being no less catastrophic than they were to older designs. It doesn't make sense why preventers are so readily dismissed as a way to diminish the risks.

report's available at : cyca.com.au/cyca-publishes-report-reviewing-2024-rshyr-commits-to-implementing-safety-recommendations/

I agree section 4.2.2 seems to me to mostly rehearse opinion rather than analysis and evidence, and also is dismissive of boom brakes and preventers. Seems odd given two of the fatal incidents under review were the result of crash gybes.

Section 6.2.2 is bit more nuanced/even handed, as it is discusses them in relation to boats in the race, but again does not reference in-depth analysis or evidence of the effectiveness (or otherwise) of brakes and preventers.

Suggests no-one has ever done a scientific study of boom brakes/preventers. And perhaps finding or commissioning that sort of analysis was beyond the scope of the Review. I cant see whether or not there was a submission to the Review on the subject.

The finding (para 185) and the associated recommendation (para 212) are middle of the road, and given the limits of what comes before, does not seem to be based on reference to in-depth analysis or evidence.
"The Review Committee recommends that awareness and understanding of boom brakes and preventers should continue in training courses, but their use should be a personal choice that does not need to be regulated."

It will be interesting to see if coroner's reports (which I assume will be done) go into greater depth on preventers/boom brakes.

Q

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Quixotic said..

lydia said..
So on a 42 footer, 1600kg on the main sheet with end boom sheeting in a high wind gybe
About 3500 kg at the boom brake in recommended position.

If the preventer keeps boom movement to very little, the forces don't approach those levels.

Very interesting numbers and thanks for doing them.

As memories from IOR days reminds us, once the main is backed and held by a preventer the boat is almost always past the point of control and headed into a vicious round-down that will turn the boat, and the mainsail, at 90 degrees to the true wind. That means that anyone who tries to blow the preventer is going to be facing maybe 270-750kg of force, and that force will as you say, go through the roof as they ease the preventer. Handling such a load on a broached boat is more than scary, which is why we rarely used preventers.

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Trek said..
I must be a Philistine. We use ordinary stretchy Ocky straps. A selection kept below and put the chosen ones on for the conditions.

An ocky strap is going to do nothing to stop a big boom from coming across with 750kg or more of force behind it, unless you have about 1500 of them.

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Chris 249 said..

Quixotic said..

lydia said..
So on a 42 footer, 1600kg on the main sheet with end boom sheeting in a high wind gybe
About 3500 kg at the boom brake in recommended position.

If the preventer keeps boom movement to very little, the forces don't approach those levels.

Very interesting numbers and thanks for doing them.

As memories from IOR days reminds us, once the main is backed and held by a preventer the boat is almost always past the point of control and headed into a vicious round-down that will turn the boat, and the mainsail, at 90 degrees to the true wind. That means that anyone who tries to blow the preventer is going to be facing maybe 270-750kg of force, and that force will as you say, go through the roof as they ease the preventer. Handling such a load on a broached boat is more than scary, which is why we rarely used preventers.

If the preventer stops someone getting caught by an uncontrolled boom or mainsheet isnt that worth dealing with the above problem.
Wouldn't the loads be the same as a crash gybe with the exception of everyone on board is aware of it happening and can maintain more control of the gybe.

If the preventer is holding the boat down then there's a significant risk of people going overboard, and it's happened quite a bit. So it's a wicked problem - every 'solution' brings another problem. Given that there seems to be no real escape from the problem via hardware it seems we must get back to behaviour modification. It's not hard to drill into oneself the idea of keeping the head below boom level in hard running conditions at all times. There is very rarely any need to stand on the cabin top or side deck in the area swept by the boom in heavy air. From Optimists to maxi yachts, the best (and almost complete) cure to boom strikes is to keep your head down when necessary, so this is easy to get used to.

Personally the mainsheet sweeping across the cockpit seems to be the scariest issue since it's not easily cured by simply keeping your head down. I've got a standard Edson pedestal just behind the traveller with the stupid Edson "guard" pipe in front of the wheel. The sheet tries to catch over the guard, which is only secured to the boat by plastic fittings - and that was the standard setup for Edson!

So what about fitting proper angled guardrails fore and aft of the traveller to try to ensure that the bight of the mainsheet stays in a safer area if the boom comes over with the mainsheet off? I'm thinking that the aft one will angle up to the height of the binnacle to protect that properly, with a fair curve to ensure there is no spot where the sheet will catch. The forward guard would be a similar shape and the hope is that it will prevent people from being in the vulnerable area where the bight sweeps across, as well as directing the mainsheet into the area on the top of the traveller, between the two guards, when it comes across. There would be some space loss but these rails would form excellent handholds and harness points, and would be easy to remove for mild weather sailing.

This doesn't preclude a boom brake or preventer but it may actually be a more effective way of reducing the mainsheet hazard. And yes, in an ideal world the mainsheet would be tight when the boom gybed but particularly when shorthanded, the world is not ideal. A boom with a few feet of slack isn't the worst way to get through a gybe.

When cruising in a breeze we often just granny around and unlike a boom brake or preventer, the improved guard rails would work well in a granny situation.