Stack Pack (and lazy jacks) for main - anyone have tips for making?

Jud - s/v Sputnik

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Rex - Brilliant !  Thanks for all the details.

My wife sews very well, but isn’t in the sailing world/marine industry (sewing just a serious hobby, not work) so sometimes doesn’t always catch certain design/construction features that someone who is would intuitively know.  But I can see how between your detailed description/drawing and instructions elsewhere, we could figure it out.

Can definitely see how having a lazy bag you wouldn’t want to go back to a sail cover, especially if using the boat very frequently - i.e., live aboard cruising for extended periods.

I see you have the “control” end of your lazy jacks at the mast, whereas Cisco (above) does his differently, at the boom - to avoid mast slapping of the control line/halyard. Per one of iStream’s posts above, he said uses 3mm Dyneema (at mast lazy jacks halyard/control line), which is light enough not to slap in the wind, he says.  (He has a lazy bag/sail pack, whereas Cisco doesn’t - perhaps that’s the key difference for where the control line would/could go? Or maybe doesn’t matter, if you use a light line, like iStream.)

 
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t.rex

Member
The reason for the cleats at the mast and not on the boom is to limit the chafe damage to the acrilan. The lazy jack halyard on the boom is external to and presses against the sail cover/lazy bag, whereas at the mast, the halyard can be led 'underneath'.

There is also the fact that the lazy jack halyard being much longer is also more forgiving:

- Do you pull up on the topping lift and lazy jacks to give yourself more headroom at the dock ?

- Do you remember to ease the lazy jacks before sheeting in the mainsail ? 

- 2 mm unobtainium would rip a spreader off the mast. 3 mm dyneema will slowly rip the stitching at the outboard attachment. 4 mm three strand nylon will last forever and with the money saved, you could buy me a beer.

 
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IStream

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FWIW, I haven't had any issues with my 3mm dyneema.

At the mast, the jack halyards go through small cheek blocks so the fasteners are in shear. Prior to changing to dyneema, the jack halyards went through small blocks on the underside of the spreaders so the only thing keeping them in place was a few fine threads in aluminum.

At the bag, the jacks wrap around the fiberglass battens running along the top of the bag so the forces are well distributed and don't tear out any stitching. 

The reason I went to dyneema was to isolate the compliance in the system to the bag itself. Though the dyneema has essentially no stretch, the bag has plenty of give and holds a better shape as it fills with the sail when I drop it. 

 

cianclarke

Member
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Boston, MA
I had Doyle build me a stack pack, which I was very happy with even if it's one of the more expensive ones out there. I asked them to omit the lazy jacks they normally include, and they shaved off some $. 

Instead, I also used 1/8" (or 3mm) Dyneema, with low friction rings at the joins - because everybody knows Dyneema is faster than Sta set.
I sketched two possible designs in Google Sketchup to help visualise, and pull measurements from.

image.png  

I ended up going with the design on the left. I calculated from SketchUp the lengths of the various pieces, and at the joins spliced Tylaska FR3 low friction rings. This video gave me some ideas & helped refresh my memory on the brummel splice, one-side-fixed.

Then, I put two pad-eyes on the spreader (instead of cheek block on the mast) about 1/3rd of the way out, and attached a block to that. Idea was to help with sail raising, to make life a bit easier. 

Total cost was about $180 all in, parts from Defender. 

 

t.rex

Member
Sorry, didn't mean to get on IStream's case for his choice of materials. Dyneema is great stuff. The manager of the sail loft won't let me near it. For lazy jacks we usually use 4 mm braided polyester in the same color as the lazy bag.

Regarding non-stretchy lines, this reminds me of the time when I retrieved one of my lazy bags that the client claimed had failed at the outboard attachment point. I call it the Electric Winch Syndrome:

So we go aboard this 50 footer, heavy, junk on the trunk, with the boom skyed way up to allow headroom in the cockpit. The mainsheet is still on the electric self-tailing winch and when I ease, it groans like a maxi going round the weather mark. All this at the dock!

We remove the lazy bag from the boom and the owner-installed lazy jacks. They must have been at least 9 mm diameter.

Obviously my fault.

 

IStream

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No worries, t.rex, I agree that the dyneema is massive overkill from a strength perspective and the 4mm braided poly is plenty strong enough. I went with the dyneema mainly for its (lack of) stretch characteristics. 

 

Black Jack

Super Anarchist
Just plain lazy jacks with a regular sail cover: Mine came from the local hardware store.

I thought of it just as a mock up but it has become the finish product. Ingredients: 1/4" 3 strand, 2 tiny cheek blocks, 1/4" thimbles, 2 cleats, 6 eye straps. 

Deployed: 

View attachment 436703

Stowed: 

View attachment 436704

The one mistake was to mount the turning blocks at the spreaders. They needed to be raised about 5' above, but I don't think you can mount that block too high with a long footed main (too low is usually recommended.)

Other realizations: In use, the legs are not tightened when deployed, I leave a little slack. This forms a better 'basket' that cradles the flakes and tends to guide the flakes on top of each other. Then add 4-5 loose sail ties, just to hold the flakes, uncleat jacks, gather and stow at the mast, finally, tighten the sail ties. All compact, easy cover. 

This main is tough to tame but we've come to terms. 

View attachment 436705
mine was two very small harken cheek blocks midway up on mast and a series of eye loops in small stuff cordage. all in 36 dollars. Like yours - simple, inexpensive and elegant is best.

 
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toddster

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A timely topic - has me doodling spider webs onto my sail plan when I should be writing reports...

I've had the parts for this project in the "project bin" for a couple of years.  Such a simple thing but... confusing.  

Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears, so I'd say yes. Can't dock the boat like that and there isn't always a convenient place to drift and flake the sail.    And the old sail cover is on its last legs and never really fit the new sail anyway.

Re: leading the halyard to the spreaders.  I installed a couple of blocks for this purpose last time the mast was down.  Seemed better to through-bolt than to secure with threads.  Dunno if there are issues with loads on the spreaders.  Maybe the resulting angle is too low? PO added a topping lift but it's rigged kind of stupidly.

Come to think of it, how does the sail bag /stackpak affect reefing? I guess one has to cut it to stop short of the gooseneck and horns? I guess the clew lines would have to run on the inside of all this - need to leave gaps for that in the bag. Or make it sort of "loose footed" 

t.rex provides a nice formula to follow - when scaled to fit.  Not sure a 12-foot boom needs four falls... 

Comparing spreader-height halyard block vs. 2/3-sail-height I see the big difference is in the angles at the aft end. (obv) Well shoot - should have done this before drilling holes in the spreaders.  Are the loads great enough for this to make a big difference?  Does that extra line up high aid in catching the sail, or is all the action down near the boom anyway?  Another example of the old "design-build" vs "build-design" conundrum.  

image.png

 

SailingTips.Ca

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Just plain lazy jacks with a regular sail cover: Mine came from the local hardware store.
Totally agree - I used cheap nylon single braid from the local hardware store to "prototype" my lazy jacks about 12 years ago and they are still going strong!

I have cheap plastic cleats just below the gooseneck that are used to stow them 99% of the time, except when lowering and flaking the sail.  

 

El Borracho

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A timely topic - has me doodling spider webs onto my sail plan when I should be writing reports...

I've had the parts for this project in the "project bin" for a couple of years.  Such a simple thing but... confusing.  

Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears, so I'd say yes. Can't dock the boat like that and there isn't always a convenient place to drift and flake the sail.    And the old sail cover is on its last legs and never really fit the new sail anyway.

Re: leading the halyard to the spreaders.  I installed a couple of blocks for this purpose last time the mast was down.  Seemed better to through-bolt than to secure with threads.  Dunno if there are issues with loads on the spreaders.  Maybe the resulting angle is too low? PO added a topping lift but it's rigged kind of stupidly.

Come to think of it, how does the sail bag /stackpak affect reefing? I guess one has to cut it to stop short of the gooseneck and horns? I guess the clew lines would have to run on the inside of all this - need to leave gaps for that in the bag. Or make it sort of "loose footed" 

t.rex provides a nice formula to follow - when scaled to fit.  Not sure a 12-foot boom needs four falls... 

Comparing spreader-height halyard block vs. 2/3-sail-height I see the big difference is in the angles at the aft end. (obv) Well shoot - should have done this before drilling holes in the spreaders.  Are the loads great enough for this to make a big difference?  Does that extra line up high aid in catching the sail, or is all the action down near the boom anyway?  Another example of the old "design-build" vs "build-design" conundrum.  

View attachment 436938


Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears
Probably not. Get a longer boat.

A well proven method of design is to very carefully copy every feature of a successful existing design. Especially so with canvas projects.

 

IStream

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A timely topic - has me doodling spider webs onto my sail plan when I should be writing reports...

I've had the parts for this project in the "project bin" for a couple of years.  Such a simple thing but... confusing.  

Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears, so I'd say yes. Can't dock the boat like that and there isn't always a convenient place to drift and flake the sail.    And the old sail cover is on its last legs and never really fit the new sail anyway.

Re: leading the halyard to the spreaders.  I installed a couple of blocks for this purpose last time the mast was down.  Seemed better to through-bolt than to secure with threads.  Dunno if there are issues with loads on the spreaders.  Maybe the resulting angle is too low? PO added a topping lift but it's rigged kind of stupidly.

Come to think of it, how does the sail bag /stackpak affect reefing? I guess one has to cut it to stop short of the gooseneck and horns? I guess the clew lines would have to run on the inside of all this - need to leave gaps for that in the bag. Or make it sort of "loose footed" 

t.rex provides a nice formula to follow - when scaled to fit.  Not sure a 12-foot boom needs four falls... 

Comparing spreader-height halyard block vs. 2/3-sail-height I see the big difference is in the angles at the aft end. (obv) Well shoot - should have done this before drilling holes in the spreaders.  Are the loads great enough for this to make a big difference?  Does that extra line up high aid in catching the sail, or is all the action down near the boom anyway?  Another example of the old "design-build" vs "build-design" conundrum.  

View attachment 436938
FWIW, my jacks look more like your blue ones, with the turning blocks just below the first spreader. It works fine, but I've got a full-batten main and I think that makes it more forgiving of jack geometry. 

As for reefing, mine is done from the cockpit so the issue of the back at the gooseneck is moot. 

 

IStream

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I can only speak to my arrangement but the reefing line to my tack just lives inside the cover. When the cover is open and the sail raised, it doesn't have to go through a hole in the bag or anything. On my boat, the reefing line to the clew fastens to the boom and goes up to the reefing clew before going to a sheave at the boom end and then to the reefing works inside the boom. That requires one penetration of the bag near the anchor point on the boom. 

This seems like the kind of thing that t.rex, having made so many of these, can speak to better than I can. 

 
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SailingTips.Ca

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Victoria, BC
One would still need to make provision for the lines to pass through the cover, no?  
If you stow the lines against the mast and boom once the sail is folded they will fit inside a standard cover with no modifications. 

You only need to modify the cover if you want to leave the lazy jacks deployed with the cover on.

 
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t.rex

Member
A timely topic - has me doodling spider webs onto my sail plan when I should be writing reports...

I've had the parts for this project in the "project bin" for a couple of years.  Such a simple thing but... confusing.  

Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears, so I'd say yes. Can't dock the boat like that and there isn't always a convenient place to drift and flake the sail.    And the old sail cover is on its last legs and never really fit the new sail anyway.

Re: leading the halyard to the spreaders.  I installed a couple of blocks for this purpose last time the mast was down.  Seemed better to through-bolt than to secure with threads.  Dunno if there are issues with loads on the spreaders.  Maybe the resulting angle is too low? PO added a topping lift but it's rigged kind of stupidly.

Come to think of it, how does the sail bag /stackpak affect reefing? I guess one has to cut it to stop short of the gooseneck and horns? I guess the clew lines would have to run on the inside of all this - need to leave gaps for that in the bag. Or make it sort of "loose footed" 

t.rex provides a nice formula to follow - when scaled to fit.  Not sure a 12-foot boom needs four falls... 

Comparing spreader-height halyard block vs. 2/3-sail-height I see the big difference is in the angles at the aft end. (obv) Well shoot - should have done this before drilling holes in the spreaders.  Are the loads great enough for this to make a big difference?  Does that extra line up high aid in catching the sail, or is all the action down near the boom anyway?  Another example of the old "design-build" vs "build-design" conundrum.  

View attachment 436938
Hi Toddster,

I'm envious of your graphics capabilities.

Maybe you can help me get across a point about how the lazy jacks guide the sail into the lazy bag. Let's add a new lineset in green.

- You nailed the position of the lazy jack halyard block (2/3 mast height)

- Shorten the distance from the halyard block to the first diramation to the equivalent of the cyan color. (100 cm?)

- Shorten the distance from the first diramation to the second fall to the equivalent of the cyan color. (150 cm?)

The point is; if the sternmost line in the lowest diramation is steep, the sail will tend to be ushered in the lazy bag if you are approximately head-to-wind.

The lower angled cyan color lazy jacks risk to hang the leech outside the lazy jacks if you are not perfectly head-to-wind.

Regarding your question about reefing, the zipper opens from luff to leech and actually beyond the lazy bag using some webbing. So the reefing lines that exit the boomcap don't wear on the zipper, pass through the reef clew grommet, then through the stern section of the lazy bag where parts of the bottom have been intentionally left open to pass the reef lines around the boom.

You're right, a 12 foot boom doesn't need 4 falls. You should see the looks I get when I try to convince owners that they only need 3.

 

toddster

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Hi Toddster,

I'm envious of your graphics capabilities.

Maybe you can help me get across a point about how the lazy jacks guide the sail into the lazy bag. Let's add a new lineset in green.

- You nailed the position of the lazy jack halyard block (2/3 mast height)

- Shorten the distance from the halyard block to the first diramation to the equivalent of the cyan color. (100 cm?)

- Shorten the distance from the first diramation to the second fall to the equivalent of the cyan color. (150 cm?)

The point is; if the sternmost line in the lowest diramation is steep, the sail will tend to be ushered in the lazy bag if you are approximately head-to-wind.

The lower angled cyan color lazy jacks risk to hang the leech outside the lazy jacks if you are not perfectly head-to-wind.

Regarding your question about reefing, the zipper opens from luff to leech and actually beyond the lazy bag using some webbing. So the reefing lines that exit the boomcap don't wear on the zipper, pass through the reef clew grommet, then through the stern section of the lazy bag where parts of the bottom have been intentionally left open to pass the reef lines around the boom.

You're right, a 12 foot boom doesn't need 4 falls. You should see the looks I get when I try to convince owners that they only need 3.
Like this?  Drawing is getting a little busy.  Shortening the upper segments makes the lines more vertical at the expense of more string aloft.  Looks like the most dramatic effect here is on the forward falls.

image.png

 

fufkin

Super Anarchist
My lazy jack set up has only 1 triangle line per side of the boom(as opposed to the 2 triangle patterns being shown) and the line leads back to the cockpit for tightening. Other than that I don't really touch them(other than pre drop tensioning), they stay up during sailing and when the mainsail cover is on. I have slits sewn where the lines run up from the boom. With careful steering and paying attention to the battens, it's pretty straight forward to get the battens clear of the lazy jacks when hoisting. The last couple of battens probably account for almost half the sail and because they're the longest they clear the lazy jacks, so its only at the beginning of the hoist that you have to pay attention. I used to loosen the lazy jacks a bit pre hoist but its not really necessary. Tightening pre drop helps with the fold.

Full battens drop into place pretty nicely. Its on harken cars, and if you just let go of the main halyard, the sail gets within %80 of folding itself. A couple of adjustments to the fold, then I'll put a couple of sail ties on, loosen the lazy jacks while putting the cover on, then once the cover is on, moderately tighten back up the lazy jacks back up. You can get the lazy jacks set fairly well without the slits in the cover, but the slits are maybe a tiny bit better aesthetically. It might not be a bad idea sew the cover(if you go this route) and put it on with the lazy jacks in place and then finalize the slit locations at that point... frankly I ran the lazy jacks out of the bottom of the cover(and up to the running blocks...or low friction rings if that's what your going to use) for years and there's no real major difference. The whole process of putting away the main takes maybe 5 minutes for one person, so no big deal really.

There is no external lazy jack halyard(not sure why you'd want or need one with this set up).  Just the two wires coming down from the mast and two small running blocks. The lazy jack line cleats on the boom, runs along the boom to the first running block, is lead up to the first aloft running block, back down to the boom, under the boom, back up to the second aloft running block, back to the boom, to the gooseneck area, and eventually back to the cockpit wear it is on a small stopper for loosening or tightening. 

I've noticed the two triangle set ups mainly on bigger mainsails than mine. I sail a masthead, 31 ft. So maybe that and the full battens allows me to use the 1 triangle set up. I'll not be the judge of exactly what length of boom/foot is the cutoff for the 1 triangle set up, but with full battens it seems like some of the boats in this general range and slightly above should be able to do it. The bottom two battens help with the remainder of the sail that lives aft of the lazy jacks(maybe one small sail tie as well) when dropping/folding so you don't really need to run the lazy jacks back as far as you might without full battens.

Anyway, it seems every deal is a little bit different with lazy jacks. The height that you attach at the mast though seems fairly constant. There's a harken video out there somewhere about a basic installation of lazy jacks and they show the basic height calculation, which seems to be about the same as what you guys are showing in the drawings.

 

Jud - s/v Sputnik

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Such a simple thing but... confusing.  

Does a 30-foot boat with single-spreader rig need lazy jacks? Well, when one drops the sail, it falls around the helmsman's ears, so I'd say yes.

View attachment 436938
Yes - notwithstanding suggestions to the contrary that they’re not necessary on a boat like yours.  My new boom —on a 33’ single-spreader boat— now extends out into the cockpit - dropping the main will absolutely result in the sail falling around the helmsman’s ears: exactly my new issue.  Or, if singlehanding, without lazy jacks, sail that’s fallen down will be an issue for me to deal with alone in the cockpit in heavy weather. 

I find that lazy jacks are “confusing” insofar as they seem to basically be all the same, yet there are several subtle variations on them.  Like cocktails.  There are lots of variations, but they’re simple at root, and they all work the same way to get you hammered if you drink enough of them.  If you try to install one of the lazy jack types, it’ll probably work fine, perhaps after a few tweaks.  Then sit back and have a drink or two.  

Now, sewing up a high-quality lazy bag/sail pack: that’s another fucking thing altogether!!

 
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t.rex

Member
Thanks Toddster,

You've done a nice study in the geometry and forces. I hope everyone is seeing that the higher up the lowest stern diramation is, the better the lazy jack is holding up the outboard end of the lazy bag AND is putting less strain on the attachment points AND is shepherding the leech into the lazy bag.

You're right in noticing it's a lot of line especially on the forward falls where the sail slides do most of the work.

The reality is often different when the rigger guy and I show up at the boat with a coil of dacron braid, scissors, a cigarette lighter, needle and thread.

Me: "How high is the halyard block from the boom ?"

Guy: "Nine meters."

Me: "Ok, let's cut the stern diramation 10 meters [folded in half makes 5], the bow diramation 8 m, and the upper diramation 9 m. With the splices and bowlines we should  have a nice short halyard."

Guy: "Nah, I'm gonna cut everything to 9 meters. It's easier."

Me: "No, but there's forces and angles to consider."

Guy: "Fuck you, I'm gonna cut everything to 9 meters. We always do it this way."

Me: "Sigh"

 

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