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rgleason · 17-10-2019, 04:40

As an additional safety, I think the preventer line should be secured to allow the elastic to work, but to provide a backup should the elastic fail.

Cpt Pat · 21-10-2019, 21:23

Quote:

Originally Posted by sailorboy1

I'm thinking the same thing and wonder why a boom broke can't be rigged pretty much the same as a preventer.

Here are some pics of how my Dutchman boom brake is arranged.

Tension the line a few inches and it's on. Release the clutch cleat and it's off. The braking action is continuous through the full arc of the boom. More tension = more braking action. It's also effective at keeping the boom from driving you nuts when wallowing around in light airs. Just give the line a little tug and you'll halt the flopping boom when it's in any position.

The boom is never completely "prevented" from swinging - so you won't find yourself with a fully inflated main that's taken aback, violently spinning your boat while pushing it astern. (Backing down hard on your rudder is bad for its health.) The boom will swing across -- just slowly and under control.

Plus, it's always available from the cockpit. No underway rigging needed.

rgleason · 24-10-2019, 03:36

Capt Pat that looks like a decent rig. Do the preventer lines ever touch the cabin? If so, do they abrade? That was my hangup/problem with most brakes, also the added line across the deck. But I think I would get used to it if it dod not damage the cabin.

I like your integrate solar and the vertical stay deployment!

Cpt Pat · 24-10-2019, 09:02

Quote:

Originally Posted by rgleason

Capt Pat that looks like a decent rig. Do the preventer lines ever touch the cabin? If so, do they abrade? That was my hangup/problem with most brakes, also the added line across the deck. But I think I would get used to it if it dod not damage the cabin.

I like your integrate solar and the vertical stay deployment!

The line does touch the cabin top and handrails, port and starboard, but just barely. The only lateral movement of the line is an inch or two when tension is adjusted. All of the lateral movement when the boom swings is at the brake itself. The line crossing the sidedeck is a trip hazard, but I got used to stepping over it.

The panels on the stays work really well. The panels were intended to be mounted on a rigid surface so I added aluminum reinforcing bar stock to prevent twisting. The panels are hung with shock cord and the weight is supported by a line passing through a block vertically at the spreader level on the forward mast - the line can be let out to align the panels closer to a horizontal orientation. They've been up there for 7 years, have been through gales, and they are still harvesting rated power. They do create some windage, but since they are at the CLR there is no yawing tendency.

jtsailjt · 31-10-2019, 04:56

Quote:

Originally Posted by transmitterdan

A boom that doesn't move has zero kinetic energy.

What you wrote above is true but tells only part (most) of the story because the sail itself, as it is being backwinded in strong winds, suddenly transfers its kinetic energy to the boom and then to the preventer. If the sail were a rigid, flat, plate that would not be the case, but with a fabric sail that’s not absolutely flat, when 50 knots of wind instantly shifts from one side to the other it can suddenly transfer quite a lot of energy to the boom and on to the preventer so some kinetic energy is still in play.

I have preventers permanently rigged from the end of my boom (will switch to dyneema this winter for lower stretch) but I very rarely use them, especially in strong winds. That’s because when I’m going downwind and the relative wind is over about 20 knots, just the jib or jib and staysail provide all the horsepower I need so the main is not used. If I’m having trouble with rolling and/or keeping the sail full, I change course slightly to tack downwind or rig a whisker pole on the jib to help stabilize things. It’s a more comfortable ride and eliminates any risk of a dangerous jibe. I’ve got a carbon fiber adjustable length whisker pole so it’s quite light, but I recognize even that has potential for danger if it gets out of control so in strong winds, unless it’s absolutely necessary to go directly downwind, I find that for me it makes more sense to just use headsail(s), put the wind about 45 off the stern, and zig-zag back and forth across my course to my destination. Lots of talk on this thread about the huge forces during a jibe in high winds and how to deal with all that, but why even put yourself in that position? You’re much better off letting just your headsails pull you along than trying to control your main going downwind in more than about 20 or 25 knots.

Also, in strong winds with a preventer rigged, which is usually accompanied with waves big enough to cause some rolling, I wouldn’t even think of trusting my autopilot to steer. It seems to me that’s just asking for trouble. Maybe a wind vane type would be ok but I don’t have one so don’t know. But I’ve never seen an electronic autopilot that will steer in those conditions even close to as well as a reasonably competent helmsman can, and given the potential for danger involved in a high wind jibe, I just don’t go there.

In the tragic situation that began this discussion, the way the preventer was rigged was just awful and as others have suggested it makes me think it wasn’t even intended as a preventer, but rather just to apply a downward force to help control the upward and downward motion of the boom as the boat rolled. Or maybe they just completely lacked any understanding of using vectors to analyze forces. Whatever the root cause of this tragic event, I think he discussion it prompted on this site may contribute to saving lives in the future so something positive will have come from it.

Student_Driver · 23-02-2021, 12:14

I have been thinking about safety and have been going through old threads looking for information. This thread has been very informative and humbling. There is so much I don’t know. Boom safety has always been a concern and I’ve been a fan of boomless motorsailors like SY Jess Sea (Maclear Harris) or SY Aria (Palmer Johnson). Am not in the market for boats that size but do love the safety advantages.

I may replace my boat or make heavy modifications to my current boat. If I decide to refit my current boat, i can build a dedicated preventer system such as the one in question if it materially improves safety.

I’m interested in feedback regarding a gybe control system called “gybe draulic” which is used in SY Gefion. I’ve never seen the arrangement and can’t find anything on the web.

There’s a huge vang like structure that connects the boom to a 4-5” wide steel shaft. That shaft drives a bilge mounted 3’ gear which in turn drive two opposing racks, shafts and hydraulic pistons.

Listing for SY Gefion

https://www.yachtworld.com/boats/199...efion-3555894/

I’ve never seen the arrangement and can’t find anything on the web. Has anyone seen anything like this or have an opinion on the practicality, and efficacy of such a system

This thread has had a big impact. Previously I had wanted an in boom furler but the Platino and Volare incidents have me seriously reconsidering. Am also now thinking about the lower effort to furl and unfurl an in mast mainsail as well as the safety considerations balanced against weight aloft and sail shape.

My main is about 700sq/ft and I displace 50K lbs. I’m probably at the edge of size for a brake? I’d prefer to slow and dampen the gybe rather than preventing and risking a back-winded situation with control issues and adverse heel angles.

wingssail · 23-02-2021, 13:28

I've weighed in earlier but I think I can add to my earlier views.

1. A large boat adds huge forces that have to be dealt with. This week I sailed on a 63' Frers design from the late 70's. Fantastic boat! But the forces at play are almost unimaginable. It took two large men on a coffee grinder to bring in a jib. One alone (me) could barely manage the kite sheet. And when we were close reaching with an assymetrical (in 22kts true wind) and the helmsman was having trouble controlling the boat, I imagined a round up. Oh My God! That huge mainsail and that huge kite both flogging and the boat on it's side! Everyone was lounging on the deck with a beer and the next minute it would have been chaos.

That was not even an accidental jibe situation.

So big boats must command some respect, massive respect.

It is too easy for a person with simply too much money in his hand and little appreciation of the forces involved to take on the most dangerous thing, a very large sailboat.

In my mind, when you go over 40 ft it becomes dangerous, over 50 it becomes deadly, and over 60', the forces are unimaginable.

2. For controlling the mainsail against accidental gybes I vote for simplicity. A line of substantial strength from the end of the boom to a block on a stong point on the rail forward of the shrouds and back to a winch in the cockpit is simple but effective. Tensioned against the mainsheet it will hold the boom stationary. An accidental gybe may put the sail againt the preventer but it is unlikly to break the preventer if strong line is used. There is no momentum happening. I need don't see the need for an elastic link but it is not harmful. Boom brakes and devices suggested may be OK but they are not required for safety. In my opinion a boom brake clutters the area under the boom and gets in the way without adding safety. Other devices are simply added equipment which is unnecessary, complex and heavy.

Is a simple preventer enough? I say YES. For example we (I) did a stupid thing on the helm and gybed in 26 knots true off the cost of Costa Rica one night. The preventer, a simple length of 3/8 poly double braid, not only held the boom from gybing, but it held the boat down on it's side, horizontal, until I could release the preventer. I have a big mainsail (obviously, it held our boat on its side for several minutes).

3. It is essential to prevent a boom strike on the head of a crew member. On a boat the size of mine it is certainly a concussion and maybe a death. No one standing in the cockpit will get hit by a the boom on our boat, but standing on the side deck, it is possible. For that reason we always set a preventer, unless racing, then we must be extremely vigilent. I will say that in 35 years of racing it has not happend yet. (Judy is the guardian, she lets nobody out there without a constant and vigilent, warning). I will say this, when judy yells "JIBING!", everybody on deck bends at the waist.

So, for a cruising boat:

Respect the forces at work on a big boat.
Keep a preventer on and keep it simple
Be alert to the danger of gybes.

Photo1, on a calm day Judy acts as a preventer. She is ready to yell "Jibing!"
Photo2, Crossoing the Indian Ocean, we keep the preventer on

**Don C L** · 23-02-2021, 15:45

Agreed Fred! I think when folks are starting out boat lengths are just a bunch of numbers that’ll sound pretty close.
I bet your boat felt a bit smaller after spending some time on the Frers!
Btw I wonder which Frers that was? Got a photo?

wingssail · 23-02-2021, 17:03

Quote:

Originally Posted by Don C L

Agreed Fred! I think when folks are starting out boat lengths are just a bunch of numbers that’ll sound pretty close.
I bet your boat felt a bit smaller after spending some time on the Frers!
Btw I wonder which Frers that was? Got a photo?

Yes, I got back on my boat and I stood on the deck looking down at her and I thought, "What a nice little boat!"

The Frers 63 was Swiftsure. Famous for many years in California owned by Sy Kleinman, now owned by Matt Schempp and docked in La Cruz, Mexico. (Further research indicates Swiftsure is a Frers 58, not a Frers 63)

I didn't take any photos when we were out, although there were many photo ops, I was busy. But here is one taken a few days earlier.

BTW. Last weds Swiftsure tacked to starboard while we were coming in on port tack. They came out of the tack with rights on us but I thought I could clear. Then that monster started to accellerate, (a fact which I determined only after I passed the point of no return). I held on, I had no choice at that point, and we passed about 10' in front of him. I'm not doing that again.

Photo (dave eberhard): Swiftsure, Frers 58, crosses Olas Lindas at the start.

jmh2002 · 23-02-2021, 18:46

Quote:

Originally Posted by wingssail

1. A large boat adds huge forces that have to be dealt with. This week I sailed on a 63' Frers design from the late 70's. Fantastic boat! But the forces at play are almost unimaginable.

In my mind, when you go over 40 ft it becomes dangerous, over 50 it becomes deadly, and over 60', the forces are unimaginable.

I used to sail on a 40m / 132ft masthead sloop. Now THAT really had some huge forces to be dealt with...

This was a performance cruiser for her day, a Farr design, with a fin keel and a spade rudder.

And no in mast furling either - instead just a big fully battened main on a track and car system.

Putting a slab reef in the main when the breeze was up was, ah... interesting to say the least!

(or bloody scary, depending on how you look at it and where you were standing)

**Don C L** · 24-02-2021, 16:52

Quote:

Originally Posted by jmh2002

I used to sail on a 40m / 132ft masthead sloop. Now THAT really had some huge forces to be dealt with...

This was a performance cruiser for her day, a Farr design, with a fin keel and a spade rudder.

And no in mast furling either - instead just a big fully battened main on a track and car system.

Putting a slab reef in the main when the breeze was up was, ah... interesting to say the least!

(or bloody scary, depending on how you look at it and where you were standing)

Yeah and how about changing those headsails on the foredeck? Sure ain't like handling sails on a Sabot!

Hoodsail · 22-01-2023, 11:34

Catching up here...just read the report on the Platino incident, link on thinwater's site. A small part of this wreck was close to home as i had an undersized, my mistake, Dutchman's boom brake rigged on my boat. We crashed gybed running down to Bermuda and the brake was overwhelmed by the force of the main (during daylight and main not reefed), in about 30-40k of wind. My main sheet is rigged to the binnacle and ripped the binnacle mounted compass right off during the gybe. Afterward, we secured a line from mid-boom to a cleat about mid-ships (starboard side), just needed to keep in mind as much whenever we decided to tack. That was some serious force. Can't imagine having a 1300+ pound boom w/ traveler in tow flying back and forth across the cockpit. That boat is just tooooo big...

ErnestV · 22-01-2023, 13:11

Just found a nice little trick, probably not for everyone, but might get you going safely dead downwind without danger - although it looks just not really racer-like ;

https://youtu.be/GJG2QI5h2e8?t=529