Boom Preventer using Jib Blocks

[c130king]

Leon, Paul, Doug,

Thanks for the info. I will use my jib cars on the forward tracks as my boom preventer for now...keeps me from having to buy blocks for attaching to the stanchion. I will probably attach one end of the line to the end of the boom and the other to horn cleats I have in the cockpit. I can preset these lines before I leave the dock and not have to worry about going forward to hook anything up.

The EZ Cleats will be for Genoa control when on the beam to running. If I close haul I won't need the boom preventer (nor the EZ Cleats) and will use the cars on the cockpit coaming tracks with the winch to get the Genoa hauled in tight.

I will leave my vang as is.

Thanks,
Jim

T minus 18 days and counting

[c130king]

All,

Re-hasing this thread from last December as I continue to investigate boom preventer techniques and the discussion on down-wind sailing in another current thread.

Over Christmas I tried the preventer technique in the post above this one...couldn't make it work. So now I have a new plan.

Connecting to the end of the boom was not working. If some of you are disconnecting the base of your vang from the bottom of the mast and connecting it to other locations on the side of the boat (stanchion or car/padeye on the jib tracks) then I should be able to connect my preventer to the boom at the vang attachment bail and have sufficient leverage to keep the boom from accidentatly gybing.

I will not move my vang...seems to be too much hassle to me...even with quick disconnect. I will attach a block to the base of the stanchion where the baby stays are attached for mast raising. The preventer line will run from the boom (at the vang attachment bail) to the block on the stanchion and then back to the cockpit. I can rig a seperate one on both sides. Normally these will stay slack. Once I have the sails set for downwind I think I can pull the appropriate preventer line tight and secure in the cockpit...on a winch probably. When I need to gybe I slack the line, gybe, then pull the other side tight.

Pros:
Don't have to leave the cockpit

Cons:
Two more lines running back to the cockpit

But will it work?? That is the big question. I will be back in Florida on 30 Aug and I will give it a try (after I do all my installs/mods I have planned).

Thoughts?

Cheers,
Jim

[bscott]

Jim, I have found that I can use my triangle traveller as a preventer. It is a 4:1 vang that attaches from a separate boom bail to a spin track slide on the genny track. It will not let the boom go beyond mid ships on a gybe. It also acts as a boom vang on a reach as it has alot of downward power on the boom. I can fine tune my reaches with the main sheet and the genny track vang sheet. Down side is I have to disconnect the genny vang and switch it to the new leeward genny track after each tack.

bscott

[c130king]

BScott,

I got to be honest and say I don't quite understand your set-up. Are you saying a seperate vang attached to the boom and to the coaming track where we would normally put our Genny blocks? I can't picture how that would work as a preventer. Any chance you have pictures?

Thanks,
Jim

[bastonjock]

Jim the easiest way to make a preventer is to run a line from the cockpit through the cleats at the bow and back to the cockpit,you attach one end to the boom and pull the line in tight and make off somewhere conveinient,i.e stanchion.I was thinking of fitting a block to the spare hole where the furler attaches itself the deck.The one that was on the boat when i did my DS course was a simple but very effective line run from the cockpit to the cleats and back.

[Rick Westlake]

Jim, I have found that I can use my triangle traveller as a preventer. It is a 4:1 vang that attaches from a separate boom bail to a spin track slide on the genny track. It will not let the boom go beyond mid ships on a gybe. It also acts as a boom vang on a reach as it has alot of downward power on the boom. I can fine tune my reaches with the main sheet and the genny track vang sheet. Down side is I have to disconnect the genny vang and switch it to the new leeward genny track after each tack.

bscott

Sounds like my "Double main sheet" mod (posted 24 June 09), if anyone would like a photo of this "trick":

http://www.macgregorsailors.com/modt/in ... ?view=1186

(Edited to add a direct link to the mod that I'd posted. Hope this helps.)

[bscott]

Jim, it's the same as Rick's double main sheet set up but I use a separate boom bail approx 6" forward of the main sheet bail with a 4:1 vang that is snap shackled to a separate genoa car on the track on the gunnel. The main function of the triangle is to control the boom on a reach but it will prevent the boom from gybing past midship. It applies a lot of leverage on the boom and really helps to flatten the main as Rick will attest. I have a Garhauer 4:1 with 50' of line which lets me run the boom all the way to a true run with the car in the absolute forward position.

I wish I had pics, maybe Rick can post his

bscott

[c130king]

Rick, BScott,

Thanks for the pics. I still don't see how it would work as a preventer. I routinely have the boom out beyond the coaming tracks...seems to me as if the line would have to be forward of the boom to prevent it from swinging aft during a gybe.

Matt,

I tried the technique you stated. The angle was too shallow to work for me. The line would not hold back the boom. Seems as if I need a steeper angle.

I will try to connect it from the boom bail at the vang to the base of the stancion next to the mast. Hopefully that will provide a better angle and sufficienct leverage to hold back the full main if it gets backwinded.

I will take pictures when I get back to my boat in on 30 August.

Cheers,
Jim

[Rick Westlake]

Rick, BScott,

Thanks for the pics. I still don't see how it would work as a preventer. I routinely have the boom out beyond the coaming tracks...seems to me as if the line would have to be forward of the boom to prevent it from swinging aft during a gybe.

Cheers,
Jim

I think it works adequately for me because I'm not sheeting the main so far out that the mainsheet bail is outboard of the genoa track. I'm using the setup more like a traveler that extends from rail to rail, and I don't let the main out so far that the bail is outboard of the genoa track car. If the wind is that far behind me, I'll run wing-and-wing and let the main spill some of its wind into the poled-out jib.

A proper preventer attaches to the end of the boom and leads outside the shrouds to the bow. You could cleat it there, or lead it through a block and then back to a cleat in the cockpit. You'd want the lines set up before you even think of needing them - perhaps along the top of the rub-rail, with the boom end outside the chainplates and the cockpit end inside; splicing a shackle on the boom end would let you attach it while the boom was centered over the cockpit, then you'd haul taut and cleat it off after you'd completed your gybe.

Beth Leonard, in The Voyager's Handbook (pg. 134), says "a good preventer is one the crew is willing to use virtually all the time." I can see that my "double-mainsheet trick" wouldn't be adequate for booming the main way out, but it works well enough for the way I'm managing my main. YMMV ....

[c130king]

That is the way I was seeing it. When I am wing-on-wing I have the main all the way out as far as I can get it without too much spreader rub.

I agree with your definition of a "proper" preventer but my experience is that 1) due to the narrow beam of the boat and 2) due to the aft swept spreaders preventing the boom from going out "too far"...a preventer from the end of the boom to the bow (or even the jib blocks on the cabin top track) of the boat just doesn't work right...the angle between the preventer line and he boom is so shallow that it doesn't prevent the boom from jibing uncontrolled. Others may have gotten this to work on a Mac but I couldn't get it to work.

So I am going to try the vang attachment point on the boom to the base of the stanchion...that is closer to a 90 degree angle and will hopefully prevent the boom from swinging.

May not work but it pretty much costs me nothing to try it.

Thanks for all the thoughts.

Cheers,
Jim

[bscott]

Jim, most boat mfgrs do not recommend attaching any running rigging to stanchions or pulpits as they are not intended to be shock loaded. Once the base is dislodged, you are screwed. The best point of sail on a Mac is on a beam/broad reach and the least is ddw.

bscott

[Newell]

Have used a single line preventer on my X for 5 or 6 years. Attaches to forward stanchion base support rod, no problem with strength issues after several jibes where I forgot to tighten the preventer. Uses a dedicated boom attachment hound that is located by putting the boom hard over and noting where a line from the stanchion to the boom can attach in a straight line. Attach the line by turning through a quick link then back to a cam cleat. I use the old furler cleat on the port side. The line attaches to the boom hound with a brass spring clip in my case. When taking down I use the preventer clip to hold all the lines and stays then place tension on the rigging so no bounce while traveling.

I got this idea from Murv, Commodore of the VYC in San Diego. It is very simple, works great, doesn't add much weight, easy to install and minimal cost. I wish I could install one on my D, but the stanchions are further forward than on the X.

Another example of how the KISS principle is relevant to sailors.

Newell
Fast Sunday 96X, Windancer 89D

[Kelly Hanson East]

Using a stanchion on a relatively small boat like the Mac is probably ok - especially if you take care to avoid shock loads - ie, tension your preventer once you get your main sheet set.

[beene]

The EZ Cleats will be for Genoa control when on the beam to running. If I close haul I won't need the boom preventer (nor the EZ Cleats) and will use the cars on the cockpit coaming tracks with the winch to get the Genoa hauled in tight.
Thanks,
Jim

Jim, I don't get it.

How do you use the jib tracks for your Genny? Do you furl it in till its a beach towel and re run the sheets inside the shrouds, through the jib cars to the winches?

I have never heard of anyone doing that. The most I have ever done with my Genny is resheet in between the upper and lower shrouds to improve pointing by a few degrees. But in the end, I decided it was just too much hassle to do that and I just leave the Genny sheeted outside the shrouds all the time now.

G

[c130king]

G,

Mis-communication on my part.

I use the EZ-Cleats on the cockpit coaming for the Genny. Love 'em...they work great...have not used the winches since I have had the EZ-Cleats.

I plan to use my old pulleys/cars/blocks (whatever they are called) on the Jib tracks on top of the cabin (next to the mast) for the boom preventer (in order to run the lines back to the cockpit)...or at least I will try this when I get back and see if it works.

I do not roll up the Genny and use it like a jib with the cabin top tracks/pulleys. Too much effort.

Cheers,
Jim

T-minus 28 days until I get back to the U.S.