Preventer Rig on a Vagabond 47
 

In Vava'u Tonga prepping the Vagabond 47 to sail to Samoa, Cooks, French Polynesia, Hawaii.

I have a rigging question:

The the captain wants to create a point for a preventer on both sides by
taking out the 5/8" pin that connects with bottom of the turnbuckle to
the chainplate and put in a SS 1/2" shackle with that pin where the
5/8" was. The eye of the shackle extends out with another smaller
shackle on it and a block attached to that that will go to another
block on the main boom. There are a total of 6 shrouds on each side
. . . The captain says the shackles were expensive and believes they
are US made. I will take some photos and send. I hate to mess
with rigging points like this and would much rather put a large U-Bolt
thru the bases of both turnbuckles that share one of the 3 chainplates
. . . . or . . .I don't know . . . .

Please let me know your thoughts . . .

Thanks,

B r u c e

Putting a shackle on the chain plate over, as it were, the turnbuckle fork is not an uncommon way to make an auxiallary attachment. Because 1/2 does not equal 5/8, there are potential problems.

If the pin and hole are not reasonably matched, you get unfair wear on both and an unfair bending strain on the pin. This, combined with the fact that the smaller pin is weaker, may put the rig below acceptable specifications. In practice, much in cruising yacht rigging is significantly over-engineered and a modest decay in strength might be tolorated but I'd certainly wonder.

I'd especially wonder since it's just a preventer and there are so many excellent ways to make an attachment without erroding the integrity of the rig as it is. For example, you might (quite neatly I might add) selvagee a shackle right around the chainplate below the turnbuckle fork. Along that line, leave out the shackle always on the selvagee, just attaching the shackle or 'biner on the preventer directly to one turn of the selvagee. That way there's nothing clattery when that side's to weather.

Thanks Ian
 

Thanks Ian,

I expressed my concern to the skipper . . . . and we posed the question to some other friends at dinner last night and the consensus was to keep the integrity of the rig, just as you said, and to go back to the U-Bolt or carabiner around the base of the turnbuckle where it meets the chainplate.

Cheers,

B r u c e s/v "PARADISE BOUND"

Sometimes you see a U-bolt or 'biner hooked through the turnbuckle lower fork, fitting between the fork and the chainplate, but this does not seem to me much of a good idea. A selvagee is just a sort of strap loop - I make them from inner or outer bits of left-over double braid from other projects. I think one of Brion's books show how to use one on a pole, like for a safety line when aloft on a mast. But what I had in mind here was simply a loop around the chainplate itself, below the turnbuckle fork and held down by that fork.

Two ways of attaching occur to me.

You could make a nice loop, like a soft quoit. Put the loop on the preventer shackle or 'biner or whatever you have there and then hold the loop out on a finger simply pass it around the chainplate twice and bring the bight back to attach to the preventer shackle. You'd only need to unhook one side of the loop for tacking and wrapping it around the chainplate and reattaching would be dirt simple.

Alternativly you could make the selvagee a loop that's wrapped permanently around the chainplate like three loose winds of a service and just pull one wind out enough to get the preventer's shackle or 'biner attached.

Either is a nice soft attachment.

G'luck

Options
 

Hello,
First, I'm glad you let go of that shackle idea; undersize pin, unfair loading, and threat to overall rig integrity would have been unfortunate. If you do put your preventer in this area, Ian's selvagee method will be the cleanest, strongest, quietest way to do it. But I would much prefer to take preventers forward to the bow, and leading from the boom end. That way you have much more leverage, to the point that you won't need a purchase, just a single line. You also won't risk snapping your boom in a swell. We use a setup where there's a boom-length piece that lives on the boom to which you attach a long deck piece when you deploy. That way you can set or strike on any point of sail.
Fair leads,
Brion Toss

I'd not had the wit, when I've lead preventers to the bow, to have the boom length bit just there. Sure solves a lot of problems.

This assumes that you have a vang or very heavy boom to keep the sail from folding around the spreaders, of course. I'd gotten into the habit of combining the functions in part because on long legs I much prefer to tack downwind as it's mostly faster and even when not it's more restful and safer than worrying about a gybe.

Good to be reminded of the basics and the alternatives.

Thank you Brion.

Many biggish yachts use a preventer, in the form of a line with carbide clip that runs through a block on the boom end from the bow or fwd,and then along the boom and into the cockpit, just like the main sheet.
Rob