Boom Preventor/Brake on a catamaran

[sosumi]

Greetings,

As many new posters before me have mentioned, I appreciate the wisdom and counsel I have gleaned over the past months I have been around. I also appreciate the suggestions by some that Google is, indeed, my friend as well as local searches on the forum site. I haven't come up with any really good articles, videos, diagrams, etc. that answer my question as to how to fit a boom brake or preventor (b/t) on this boat.

I've seen, what seem like, some very well engineered (b/t's) but most mount under the boom leaving no room for the lines or sheets to get across the bimini amidships....and if the lines go forward, it's not much of a fair lead around the cockpit----make sense?

My cat, is a Privilege 37. The bimini is no more than nine inches below the boom stretching out to the traveler. How does one mount a (b/t) with this setup? Controlled jibes are fine but it's the "accidental" ones that concern me with the ensuing torque/shock against the mast. With such a wide traveler, I'm trying to avoid the long swing "accidentals".

The boat is "new to me" since Sept of last year. My sailing, thus far, has been Florida ICW and coastal but I'm jumping across to the Bahamas in a month or so and would appreciate any advice or recommendations.

Thanks,
Bob
(Sosumi)

[44'cruisingcat]

Well the wide traveller helps you avoid the "long swing" accidental gybes. Having the traveller right at the end of that long track means you don't need a lot of loose mainsheet out when going downwind. A backwinded main won't go far, it certainly can't get all the way across to the other shroud.


We also rig a preventer though, which on our boat is a line through a stand-up block on the side deck a metre or so aft of the shrouds. Primarily I use this to pull the boom down, which helps keep the sail from chafing on the shrouds, but it does help avoid accidental gybes.

[sosumi]

Thanks for the reply.

I do have blocks on the side decks also. How do you attach the lines to the boom?

[44'cruisingcat]

I just tie it on to the mainsheet block shackle. I keep it on there all the time, use it when anchored to keep the boom still, and then as a preventer when sailing.

[travellerw]

Originally Posted by 44'cruisingcat

I just tie it on to the mainsheet block shackle. I keep it on there all the time, use it when anchored to keep the boom still, and then as a preventer when sailing.

I do this as well!

[UNCIVILIZED]

A few thoughts, & tips. Plus some links:

Given that you have a wide traveler, you can use that to your advantage in terms of mitigating the shocks involved with a gybe. Several of the top boats in the Cal 40 fleet, owned & skippered by Pro’s, have begun using (dynamic) climbing ropes for their traveler control lines. And evidently, it allows them to simply slam gybe the boat, due to the energy absorbing nature of said lines. So it may be worth a try.
And IIRC, it was Estarzinger who posted this information.

Also, on a cat, if you have a preventer on, & accidentally gybe, wont the main being held over on the wrong side, likely cause you to capsize?
I can’t say that I’ve ever tried it, to test the theory out, but… I’m thinking that perhaps a brake is a better way to go.

As to finding information on here. Go to the horizontal blue bar, near the top of the screen, & click on the Search icon. A menu should drop down, & on it, select Advanced. This will cause a new window to pop up. In it, on the LHS of the screen will be a box that you type your key search word or phrase into.
In this case, type in Preventer, & then right below it, select the option to search Thread Titles only. Not the Entire Posts option.
You’ll get dozens of hits, including some on Brakes as well, & comparisons of them vs. Preventers.

Here’s what I got when I did it http://www.cruisersforum.com/forums/...rchid=11374201
And here’s a recent, long, & detailed thread on Preventers, which said search yielded http://www.cruisersforum.com/forums/...ng-160777.html

PS: It’s also possible to rig lines as “fuses”. Singly, or in progression. So that they break at a set (ballpark) loading. In order to dissipate energy, or to serve as a warning that you’re getting close to overloading something.

They’re based on the concept that line type X, of size Y, breaks at strength Z, when tied into knot type; A, B, or C. Or is spliced into a configuration to the same effect.
And they’re commonly used on large racing boats, so that the skipper/crew know when they’re pushing a piece of gear, or sail, near it’s limits. So that they can then, throttle back a bit, & save their gear, sans damage.

For example: When I had a Searunner, I spliced one into the line which held my centerboard down. So that if it struck something, the “fuse” would blow, & allow much of the impact loading to be gently dissipated. And the board would be partially kicked up.
Then, depending upon the situation, I could either go & let the board up, in order to splice in another fuse right then. Or, if I needed the board down, in order to maintain control of the boat, I could simply haul it back down, using the original primary control line, sans fuse.

So, perhaps it’s possible to incorporate such into a preventer system on a large multi. So that the fuses blowing, gives you the time you need in order to quickly ease the boom over, via the preventer, while preventing you from flipping.

But, such is only a theory. And you could simply rig a true preventer. Using anything from dynamic climbing ropes, to Spectra.

[timbenner]

I have been using a "Gybe Easy" on my 38' Lagoon for roughly 5 years now. Works great and it's not too expensive!! A must have, IMO.

Mine is mounted just forward of the bimini top and/or dodger. Which puts it in the middle of the boom. The Gybe Easy works by friction, so in light wind, you leave some slack in the control line generating less friction. In heavy winds, increase the tension in the control line, generating more friction.

My setup starts with the control line tied off to a "U" bolt, on the starboard side of the salon top, just forward of the dodger. Then up to the Gybe Easy hanging from the boom. Then down to a turning block on the port side of the salon top, back to a rope clutch at the helm.

Don't buy the rope they sell with the Gybe Easy, it has too much friction.

This is a very important safety feature. A must have in my opinion.

[sosumi]

by Tim Benner
My setup starts with the control line tied off to a "U" bolt, on the starboard side of the salon top, just forward of the dodger. Then up to the Gybe Easy hanging from the boom. Then down to a turning block on the port side of the salon top, back to a rope clutch at the helm.

I've looked at the Gybe Easy but thought it too long vertically under the boom but in your setup it would hang nearly horizontal to the boom....correct?

Did you use backing plates under the roof for the U-bolt and turning block?

Thanks,
Bob
(Sosumi)

[Mark Thurlow]

Try the Walden Boom Brake. Not cheap but very effective.

Search will give you vids etc

[timbenner]

Originally Posted by sosumi

by Tim Benner
My setup starts with the control line tied off to a "U" bolt, on the starboard side of the salon top, just forward of the dodger. Then up to the Gybe Easy hanging from the boom. Then down to a turning block on the port side of the salon top, back to a rope clutch at the helm.

I've looked at the Gybe Easy but thought it too long vertically under the boom but in your setup it would hang nearly horizontal to the boom....correct?

Did you use backing plates under the roof for the U-bolt and turning block?

Thanks,
Bob
(Sosumi)

The "U" bolts I mentioned are through bolted on the aft end of the aluminum jib car tracks, with SS backing plates. That's through the outer salon top, through the inner salon liner. Inside the salon, there's a wood trim piece that gives access to the jib car track bolts.

The top of the Gybe Easy has a shackle to hang it vertically from the boom. So it hangs vertically. There are pictures on the Yahoo Lagoon group Owners web site in the "I Dream of Jeanne" photo album.

[maxingout]

Our Privilege 39 catamaran never had a problem with jibing the mainsail. The reason is simple.

We had two lines going to the end of the boom at all times, so the boom was absolute immobile. No moving or swinging.

The mainsheet fixed the boom to the traveller on one side of the boom. A heavy duty line with a triple purchase fixed the boom to a deck fitting on the other side of the traveller.

It did not matter what our point of sail, we always had lines to port and starboard attached to the end of the boom keeping it absolutely stable and quiet. It works good at anchor so you don't have to listen to the boom swing.

When it comes time to jib the mainsail, we slack one line and tighten the other to keep the boom from swinging in an uncontrolled manner.

If you look at the picture, you will see the red mainsheet to starboard going to the traveller, and the white vang lines to port and attached to a deck fitting.

[Scaramanga F25]

A WALDER boom brake, made in France, or a rubber snubber ( big thick rubber band with bronze eyes on each end ) wrapped around the boom and attached to deck or rail have worked for me on longish booms.

[UNCIVILIZED]

Thoughts regarding a Preventer (as in fixes the boom in place) contributing to a capsize?

[Oliver L.]

We use a preventer for anything aft of 90 degrees AWA. However, I run it around the bow cleat and then back to the aft cleat, where I fix it. That way, in a gust, the boom can move upwards and deflect some of the power.

I have heard that it is physically impossible for a cruising cat to capsize from wind forces alone, but I have obviously not put this theory to the test. A heavy boom like on our boat swinging 90 degrees freely before the mainsheet would try to stop it would in my opinion rip out the traveller. Then it would continue on to do as much damage as possible to your leeward shroud. I prefer much more a backed mainsail.

Oliver

[maxingout]

In a circumnavigation, I never lifted a hull out of the water. Not even close.

I don't like to break things as it is expensive, and people can get hurt when things fly around.

I sail conservatively and reef before problems happen. I give up some speed, but I get where I am going. I don't like sailing above ten knots speed because I have to stand at the wheel and next to the sheet ready for problems that might occur.

When I am sailing at seven knots, the autopilot is extremely happy, and I don't have to tend the sheets or pay attention to the wheel.

In our circumnavigation, I hand steered the yacht no more than 100 hours. The autopilot did the rest. If I had pushed the boat to the max, I would have spent thousands of hours at the wheel.

Our end of the boom preventer was no problem. Might not work for you go fast sailors.