Preventer for Main

Dear All,

Although my sailing season may not begin until next year...I can still dream!

I am wondering about how you all set up preventers.  I am inclined to attach a nylon line, one port and one starboard, to the boom end, run forward to a turning block as far forward as I have (not really sure where that is) and then back to the cockpit. 

In a race to Bermuda we had the bad experience of racing down a large wave on a broad reach, first rolling, then yawing and then the preventer, which was attached to a bale on the boom, broke.  This was aboard a Tartan 41, another S&S design.  The force of the gybe snapped the gooseneck - by the grace of God, no one was injured.  That was not the case for crew on other boats, unfortunately.

So, I would like to plan a better solution.

Fair Winds,

Chris 

Hello Chris,

You raise a good question, and one that we have considered for our sailing on Anthea (41/1979).  Our solution is to use a boom brake, rather than a preventer.  We use the Weichard boom brake and have been very happy with it, though there are other good boom brakes on the market, too.  We use the boom brake to facilitiate jibes in heavier air and seas.  And in the event of an uncontrolled jibe, the brake will slowly allow the boom to cover over to leeward in a (hopefully) controlled manner.  The problem with fixed preventers is how to release them with the main backwinded; often something breaks before they can be carefully/safely released.  We have found Nigel Calder's discussions of preventers and brakes quite informative.

Good luck!

Mark (s/v Anthea)

Dear Chris
If you have the spinnaker pole foreguys led to the cockpit a good arrangement is to take the foreguy on the appropriate side, and connect it to the boom preventer line outside the shrouds.
Then the preventer can be released from the cockpit.
It is advisable to keep the foreguy/preventer in a clutch that can be opened quickly under load, not in a jammer or cam cleat. If kept on a winch quick release must be considered.
For yachts with Navtec hydraulic vangs controlled from a cockpit panel with selector valve - please note that the selector valve must be in position Vang for the releaf (safety) valve to be active for the vang.
The releaf valve works only for the selected function.
Kind regards
Lars

Dear Mark,

Thank you.  I watched a couple of videos of the brake in action but they don't show, as one would expect due to difficulty of filming, any rough-sea conditions.  Are you confident that it would suffice in severe weather?  Of would you consider another methodology under those conditions?

Fair winds

Chris

Dear Lars,

Thank you.

I see the value in your set-up.  Where on the boom would you attache the preventer? 

The foreguy/sheets currently do not come to the cockpit but I think it wise to move the winches used for the spinnaker to a position behind the primary winches.  To do this, some sort of support will need to be fabricated so that  they sit above the cockpit coaming.  Turning blocks may also need to added.

Currently, I do not have Navtec hydraulic vang/back stay adjuster, but am familiar with it from a previous boat i owned.  This is one more decision to make at some point bust since I am most inclined to cruise and not race, I don't know that I will spend the money on this equipment.  I will say, however, that these devices were quite useful. 

With warm regards,

Chris

Dear Chris
The preventer should be attached near the outboard end - then there is less risk that the boom breaks if it hits the water.
Kind regards
Lars

Dear Chris,

Good question about the boom brake in severe weather.  I guess the answer depends on how severe the weather is and how reefed down the main is.  The brake has worked fine for us when jibing in 35 knots with a double-reefed main.  The Weichard brake tension can be adjusted depending on how one runs the line through the device.  So long as we reef when necessary, we think the brake should work fine in heavier winds.  Hope that helps.

Regards,

Mark

Hi

I go along with Mark (ANTHEA) on the boom brake system.

We have had a Boom Walder for maybe 30 years now and have always been in control of accidental jibes (is that possible?)   We have each end of the line that passes through the brake on a winch, one either side of the cockpit.  We have this line pretty tight as it keeps the boom down.   Sometimes when the sail is back-winded the boom will not go over to the leeward side because the line is tight, but by easing either end of the line from its winch the boom will go over in a controlled manner.  (By having the line not so tight the boom will go over as soon as the jibe occurs.)   Be sure to have the attachment points for the blocks on deck STRONG – there is a lot of load there, especially the shock load.

We are not in favour of having unnecessary lines crossing the foredeck and anyway, coming back from the stem they chafe on or get caught on dorades etc.

Its just our choice.

David  43/12

Hi all,
as I am often sailing with inexperienced crew, I consider the preventer one of my best friends.
When we bought our boat, we kept the system her former owner had installed. Both preventers (one for each side) are permanently rigged. The starboard leads from the boom to a block (roller) on the starboard toerail just aft of the lower shroud, and from there along the toerail to a second block back to about where the steering wheel is - and up to a winch on the cockpit coaming.
The portside preventer is attached to the boom with the same shackle, goes to a first block on the port toerail, back to a block on the boom next to the attaching shackle, and from there parallel to the starboard preventer. They end on the same winch on the starboard side of the cockpit.
The rigging may not be ideal in some regards -- as Lars pointed out, the attachment is too far forward if the boom should dip in a wave, and we have additional lines to step over when we go to the foredeck. However, it has some advantages as well: first, the preventer can double as a downhaul for the boom. Second, and foremost, it is permanently rigged, so it takes me about ten seconds to have a preventer set -- or taken off, which means that the preventers come to use far more often.
I sometimes saile a wooden classic yawl, and here the preventers have to be tied to the boom ends and led forward as far as possible. Quite often, when the going gets rough, once we realize that a preventer would be useful, the going is already rough enough that simply attaching the lines to the booms becomes a risky adventure, particularly on the mizzen ... and the lines are always in the way in maneuvres or require someone to be sent foreward to loosen the lines in the right moment. And compared to that, our permament double preventer is pure comfort.
I will try to get some pictures of the lines.

Best, Martin
Age of Swan, 48/039

Dear all,
here are the pictures I promised. I took the pics with the sail down, so both preventers are tight (and the boom does not make any noise when the boat rolls at anchor).
Martin

Preventers, forward view

Preventers, winch on cockpit coaming

Dear Lars,

Sorry for the delay in my reply; I have been traveling.

Is there a preferred method of attachment?  I assume that something that goes around the boom and not, for example, an eye strap, is better.

With warm regards,

Chris

Dear Mark,

Yes, it does help and thank you.

I am concerned about conditions that I have experienced or about which I have read; e.g., 35 knots sustained over a long period of time, possibly days, so that the seas have built to substantial levels.  Under these conditions, racing done the face of the wave, especially in our narrow-stern boats, promotes yawing and rolling, the combination of which can produce unexpected jibes.

However, you make an excellent point about the size of the main.  I found with my Tartan 41, unless racing, that the boat sailed better with a reefed main on all points when the wind got over 18 knots.  At 35 knots, I would typically sail well with a triple reef.

With warm regards,

Chris

Dear David,

Thank you.

I appreciate your taking the time to describe the set-up and I can only agree about your comment to take care that the line runs to a very secure deck fitting or winch.  The load, under an accidental jibe, is exceptional.

I plan to do some more research about this and your comments will help.    As an additional note, one of my concerns about this issue arose after thinking about the weight of the boom.  I have the original and it is really heavy! 

With warm regards,

Chris

Dear Martin,

Thank you for your thoughtful reply.

I agree, having made the error many times, reefing too late, no preventer; etc.; that a permanent set-up makes the use of a preventer much more likely.  In the past I have sailed single-handed a lot, although I hope that my sons will take up some of the slack now, and would like to be prepared for bad circumstances, not reactive. 

Like you and others, I am torn between keeping the deck clear and clean and having a solution that works all the time.

With warm regards,

Chris  Mabels's Casse Tete  43/003 

Dear Chris
Preventer attachment
With the original boom you have the rotating bail at the aft end, or you could add a bail some distance forward, this needs to be thru bolted. The latter assumes you do not use the original roller reefing arrangement.
If you use a strap around the boom it needs to be secured so it can not slide fore and aft
Kind regards
Lars

Dear Lars,
Thank you. I am not using the original roller furling method on my boat and so could use the rotating bale as you describe.

I saw a picture of a S&S design in a book that had the sail furled around the boom as originally intended. I assume this method of sail-shortening was good in theory but not in application. Having never used it, I wonder why designers did not continue to include it.


With warm regards,
Chris

Dear Chris
With the old roller reefing booms the mainsail became far too full after a few turns of the boom, but the opposite is required when reefing.
As roller furling booms are in use today the sailmakers have found a way around this, and it would be interesting to get the Forum Sailmaker comments on this subject if possible.
Kind regards
Lars

Chris:

Aboard Hiro Maru we have a preventer permanently attached to the boom approximately i/4 distance in from boom end.

The preventer line reaches approximately to the mast where we attach it to separate port starboard control lines led forward to port/starboard blocks at the bow. This control line leads back to the mid-ship spinnaker guy winches. Although this arrangement means a person has to be stationed mid-ships we already have a person tending the guy at this position so it works for me. The preventer is a requirement for the Bermuda Race and it has worked well for us in actual use.

I have attached some photos for reference.

Regards,

Hiro

Preventer line attached at boom

Preventer line attached at boom

Preventer line stowed on boom.

Dear Hiro,

Thank you for your reply and for the very clear pictures; I understand exactly how you have your preventer set up and I like it. I have wondered about moving the spinnaker winches to a place behind the primaries in the cockpit. The same method could be used with the lines running to the secondaries now in the cockpit. I need to give this some more thought but surely, I will need to set up a preventer when I get out on the water!

With warm regards,

Chris