Lazy jacks

I like to use bare dyneema because it is slippery and will not chafe the sail/sewn seams (which dacron will). Bare dyneema is also dead easy to splice loops in, to cascade the lazy jacks, and you don't need to use thimbles (which also makes the whole system easier on the sail)

For a 28' boat you could easily use 3mm.
 
parsifal said:
What would be the best diameter and type of rope to use for the lazy jacks on a 28' sloop?
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I'd second the 4mm dyneema suggestion, but would recommend splicing thimbles in the ends. The silky sweet system this will create is a real joy, once you have experimented to find the appropriate length of line for each section.
 
Just one more thing - no idea if it's true but I got a ticking off from the rigger for running the jackstays to the spreader instead of the mast. He seemed pretty convinced about it.
 
dom said:
Just one more thing - no idea if it's true but I got a ticking off from the rigger for running the jackstays to the spreader instead of the mast. He seemed pretty convinced about it.
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That's interesting, because I was thinking of doing that. I wonder what the rigger had against it.
 
parsifal said:
That's interesting, because I was thinking of doing that. I wonder what the rigger had against it.
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I think his point was that the spreaders are there primarily to take compression forces angled directly towards the mast. Apparently a strut under compression will magnify perpendicular forces created by the lazy jacks, which can occassionally lead to spreader damage/failure. I have therefore moved my lazy jacks to the mast a couple of feet above the spreaders, but am happy to clarify the reasoning if you like.
 
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If you're designing from scratch, try to get the line nearest the mast close enough to the mast that the shortest batten can't hook under it and far enough out so the batten can't get between the first line and the next on at the top.

I used SS rings rather than thimbles - nor possibilities of sharp edges.
 
dom said:
I think his point was that the spreaders are there primarily to take compression forces angled directly towards the mast. Apparently a strut under compression will magnify perpendicular forces created by the lazy jacks, which can occassionally lead to spreader damage/failure. I have therefore moved my lazy jacks to the mast a couple of feet above the spreaders, but am happy to clarify the reasoning if you like.
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Better not let your rigger see this

http://ecx.images-amazon.com/images/I/51d-FBKErpL._SY300_.jpg

:nonchalance:

(ps A good read, by the way. Also available on DVD)
 
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Take a line between the two fixed points of the cap shrouds (top and bottom) and the the spreaders should bisect the angle of this line, which in turn normally requires the spreaders to angle up slightly.
Horizontal spreaders are a no no > they should be 90 deg from the shroud and not 90 deg from the mast.

So having set them up correctly its daft to start pulling them down with the weight of the mainsail.
Any downward force on the spreader can effect this angle especially if the cap shroud are not locked or seized in place.

The elastic in my system pulls out the slack when the main is hoisted and obviously expands when its dropped and allows a lot easier adjustment whilst in the process of flaking.
It also takes up when the topping lift is raised or when you load up lots of kicker and mainsheet whilst sailing.
It essentially means once they're up I no longer have to adjust them as it happens automatically.
 
Thanks for explaining your thinking.

On my boat I have a u-bolt type cable clamp secured to the cap shrouds below the outer end of the spreader to maintain the isosceles triangle having the spreader as its base and its equal sides being those portions of the cap shroud and mast above it. The spreaders are 1-1/4" o/d thick-walled aluminium tube upon which I have stood when working up the mast. So I don't really see how a lazy jack, secured a few inches out from the mast, and which has no function except to keep a loosely flaked sail on top of the boom, is ever going to exert sufficient downward pull to bend a spreader.
 
Lazy Jacks

I used 6 mm braid on my 27 footer, and they work a treat. It is useful to have adjustable lines: ease when hoisting the main and tighten when lowering. Also very useful for taking in the extra sail when reefed. They are connected to a block either side of the mast, above the mast spreaders. The two lines are then bridled to a single line, which passes through two pulleys and thence to a clutch on the coachroof. I can let you know the arrangement of the lazy jacks themselves, if you wish.
 
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