Boom twists while reefing... - SailNet Community
 
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post #1 of 6 Old 01-08-2012 Thread Starter
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Boom twists while reefing...

A question that has plagued me for some time. Why does my boom twist up to 90deg when I reef?

My reefing setup a "jiffy reefing" setup I believe (tack is hooked separately to the boom near the gooseneck) and is as follows: I have a winch on the starboard side of the boom and a cleat to affix the working reef line. The reef line goes inside the boom and exits at a sheave at the AFT END of the hollow boom.

The reefing line then exits the aft end of the boom, goes through the leech reefing cringle and back down to the the port side of the boom where it is fixed to an eye with a bowline. The eye it is fixed to is part way up the boom, about the same fraction forward as the reef cringle is forward.

When I crank down on the reefing line the boom lifts and the line snugs the cringle up to the boom as it should, but the whole boom rotates/twists at the gooseneck. The starboard, or winch side, of the boom ends up facing the sky.

The boom is a Spartec spar and they were supposedly a really good spar maker/designer, but I wonder about the reefing lines exiting at the aft end of the boom. Other boats have the reefing line exit part way aft at a block on the starboard side instead of the aft end.

Anyone able to give hints at what's wrong (if anything at all)? If so you get extra points for doing it without the help of pictures or a diagram.

MedSailor

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post #2 of 6 Old 01-08-2012
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Any chance your boom was originally a 'roller reefing' (around the boom) setup? Plenty of boats in the 60s and 70s seemed to have been set up that way. If so there will be a 'hex' type of gear drive built into the boom at the gooseneck.. if it's been converted to slab reefing the original crank handle may well have long disappeared.

In any event there's no need for the boom to have that much rotational freedom of movement and I'd be looking at the gooseneck arrangement to see if you can 'pin' the boom to prevent that rotation. 90 degrees, esp, seems an awful lot of 'free play'...

Ron

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post #3 of 6 Old 01-08-2012
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That's a very common system. It sounds to me like maybe you're just cranking it too tight. Your mainsheet should keep the bottom of the boom down.
After you set your reef and snugged up the halyard, try easing the reef line slightly.

You might also simply tie the reef line off at the cringle instead of bringing it back down to the boom. You will lose the purchase, but with a reefing winch, that shouldn't be a problem. Then there won't be any forces trying to twist the boom.
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post #4 of 6 Old 01-08-2012
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I've seen plenty of booms where the reefing line exit at the aft end of the boom. Often there are two or three sheaves side-by-side for the outhauls. The center is the normal outhaul and the outside sheaves are for reef 1 and reef 2.

Does the reef line exit on the starboard side of the aft end? Normally what you do is have the reef line exit on one side of the centerline (stbd), go through the leech cringle, entering on the same side (stbd) and exiting on the other (port). Then it goes down to the boom on that side (port), wraps under the boom and up the other side (stbd), and is tied to itself. E.g., tie a bowline in the end of the line around the line as it comes down to the boom on the port side. This works with a loose footed main or a one with holes for the line to pass though in the foot shelf.

There are a number of advantages to wrapping the line under the boom instead of going to an eye.

You don't have an eye that the reefing line is trying to twist off the boom. You don't even need the eye.

It's much stronger as the entire boom is taking the force of the reefing line vs just the attachment point of the eye.

The loop will slide for and aft on the boom to be positioned directly under the leech cringle, where it belongs. The eye can not move to match the sail.

How does the reefing tack attach exactly? I wonder if that's the thing that is twisting your boom and not the leech.
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post #5 of 6 Old 01-08-2012
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I had the same problem with my 33 Morgan O.I. and the problem turned out to be a loose bolt in the end of the boom near the connection to the mast. I added a star type lock washer, torqued it down and it hasn't happened since.

Hope this is helpful,

Gary
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post #6 of 6 Old 01-08-2012
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Your leech reef cringles are probably adding a LOT of friction to the reef and forcing the unreefed portion of the sail to be 'principally' attached to the side of the boom or nearer to the reef line terminal attachment than the centerline.

Several things can lessen this ... SLIPPERY reef line and/or Goļot 'reefing blocks' / blocks that fit inside the ID of the reef cringles .... OR mount a 'secondary' cheekblock on the 'other' side of the boom opposite the terminal connection ... boom aft sheeve --> cheekblock --> reef cringle --> reef line terminal connection.

Goļot reefing cringle blocks: http://www.goiot.com/pdf/p48a.pdf
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