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Old 13-09-2019, 14:11   #1
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Stack Pack and sail performance

Because of a couple recent posts I've just learned about stack packs. I have been thinking about replacing my worn boom cover and adding lazy jacks. The stack pack looks like it would provide both. However, I'm concerned about how the pack affects the sail out on the water. Not just going to wind but I have a loose footed sail so I can slacken the outhaul and get a nice full sail in light air. Will the stack pack significantly affect that ability? Would those of you who have a stack pack on your boat please pass on your experience. Thanks.
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Old 13-09-2019, 14:23   #2
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Re: Stack Pack and sail performance

It depends on the design and quality I'd say. If you look back at the thread I started a couple of days back there were a couple of pictures of little boats with stack packs that looked more like a baggy trysail. They can certainly be untidy and if they're a significant size relative to your main then they'd have to have some effect. The design also determines whether they would interfere with the foot of the sail. My preference of having the pack below the boom is partly for that reason.
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Old 13-09-2019, 15:05   #3
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Re: Stack Pack and sail performance

Many racers with packs have a method to slack the jacks and roll up canvas of the packs so they are lashed alongside the boom and don't block the foot of the sail.
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Old 13-09-2019, 15:12   #4
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Re: Stack Pack and sail performance

I am not a racer (although I love to sail fast).

What Calif. Ted described is exactly how Dragonfly does it.
Here's mine in very light air, approx 3 knots.
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Old 13-09-2019, 15:19   #5
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Re: Stack Pack and sail performance

senor,
who makes the stack pack for your boat?
I've done a little research and it appears that Doyle's system is attached to the sail and runs on the boom track so that would interfere with my loose footed main. However UK-Halsey's lazy cradle is advertised as able to be rolled up next to the boom when you loosen the lazy jacks as mentioned by Calif. Ted.
Anybody have either of these systems and would you comment on how they work when sailing? Thanks.
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Old 13-09-2019, 17:14   #6
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Re: Stack Pack and sail performance

Quote:
Originally Posted by billdre View Post
senor,
who makes the stack pack for your boat?
I've done a little research and it appears that Doyle's system is attached to the sail and runs on the boom track so that would interfere with my loose footed main. However UK-Halsey's lazy cradle is advertised as able to be rolled up next to the boom when you loosen the lazy jacks as mentioned by Calif. Ted.
Anybody have either of these systems and would you comment on how they work when sailing? Thanks.

I have the Doyle stack pack. The instructions for putting it on said to put the lazy jack blocks on the mast. I think that is a mistake as the lazy jacks are too close and interfere with the sail shape. I think it would be better if the blocks were on the spreaders and set a little wider. I don't race much, but I drop the lazy jacks and roll up the stack pack on the sides of the boom when I do. There are a couple of battens in the top of the stack pack that make rolling it up fairly easy. I have a loose footed main and the stack pack does not cause me any issues. It would seem to be more of a problem if it wasn't loose footed.
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Old 13-09-2019, 20:34   #7
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Re: Stack Pack and sail performance

We made it ourselves after doing a big improvement in the original design which was on the boat. Imagine having a 15 foot long boom with a full battened mainsail with no topping lift. The only thing holding up the boom when the mainsail was being dropped was the lazyjacks which were held up with one clamcleat !!!
We quickly decided that was completely unacceptable, so we added a Boomkicker.
It made the boat simple to singlehand as well.
The lazyjacks now only need to control the lateral actions of the main sail when it's dropped and not the weight of the boom and the sail. BIG improvement !



One cam cleat on the starboard side of the boom lifts both sides of the sail covers.
The line goes up to a block which is connected to the three lines holding the starboard sail cover to a line which goes to a spreader, and then back to a deadhead connection on the boom. The previously named block is connected to a line around the front of the mast and and to a spreader on the other side of the mast, then back down to a block which holds up the port lines to the sail cover. The port side is similarly rigged, but the deadhead line goes up to the block and back down to the three support lines to the sail cover. When the starboard line is released, it allows the starboard block to rise up several feet which lets the port side block drop down. When starboard line is tightened, both sides rise up. The reason the port side line is deadheaded to the boom is to give equal forces to both sides of the sail cover.



Somewhere on CF YEARS AGO, I posted a drawing of this.
Bottom line, I raise the main, dump the line which holds up both sides of the cover, we roll them up , hook six bungie loops and we're sailing. Reverse the process, and we dump the main and zip it shut.
If it isn't raining tomorrow, I'll do my best to take some better pics.


Sorry for the long post.
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Old 13-09-2019, 20:49   #8
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Re: Stack Pack and sail performance

I found the old thread.
My posts are 4, 5 and 8.
#5 has the drawing of the lines and blocks.



On-Boom Sail Cover Idea
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Old 14-09-2019, 08:04   #9
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Re: Stack Pack and sail performance

I have a stack pack and always slack off the main lines (cheek block on the boom a couple feet from the gooseneck and a small plastic cleat just forward of it) so the cover fabric is below the sail, down at or below boom level but high enough so it does not drag on the bimini and tie off the forward end at the gooseneck.

I noticed a significant difference in slower windward performance, especially in light airs, if I did not lower the stack pack fabric to below the bottom of my loose footed sail on my catamaran.
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Old 14-09-2019, 08:05   #10
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Re: Stack Pack and sail performance

I love the stack pack on my Nonsuch 30.
It hangs from the wishboom, which keeps it spread when open.
Unzip and hoist....Drop and zip.
Easy.
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Old 14-09-2019, 08:28   #11
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Re: Stack Pack and sail performance

Quote:
Originally Posted by Calif.Ted View Post
Many racers with packs have a method to slack the jacks and roll up canvas of the packs so they are lashed alongside the boom and don't block the foot of the sail.
On boats I crewed for racing, we were dismantling the packs entirely before races (but rolling it as described here for training).
BUT - if you do not race seriously, the benefits of a stackpack will be much more than the small price in ability to trim sails or the additional windage.
IMHO - if not racing, go for it without second thought.
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Old 14-09-2019, 08:36   #12
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Re: Stack Pack and sail performance

Using 'rigid' upper tubes on either side of the stack pack, and a pulley system of lazy jacks from the mast allows the enclosure to be lowered to reduce interference with the foot of the sail, and less wind resistance. There is an increase in weight aloft, but the 'rigid' tubes (mine are 2" diameter fiberglass tubes) enables one side of the enclosure to be lowered enough to provide some additional downwind sail area. Note, you need to be careful to avoid chaffing with mid-boom sheeting when running.



I'd photograph mine but the system is off the boat during the hurricane season.
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Old 14-09-2019, 09:18   #13
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Re: Stack Pack and sail performance

A client of mine has one of those chic and expensive gentleman's daysailers and it has a Stack Pack for handling the boat's fully-batten'd and square top mains'l. This client single-hands often and I'm sure he could not do this so easily without the system -- which combines Lazy Jacks and a very trim and tidy zipper'd cover. The pack is loose footed. I cannot really imagine a loss of performance because of the pack itself because it is all very low in the sail plan. I suppose, however, someone could imagine all kinds of windage loss for the lazy jacks' lines but these can be moved to the mast and out of the air-flow, if need be. The client does not move them as he does not want to leave the cockpit -- with safety in mind. This pack is a Doyle but I have also used and liked Mack Sail's system and liked it for having an "endless" zipper that can be moved from front or back.
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Old 14-09-2019, 10:33   #14
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Re: Stack Pack and sail performance

I have a Doyle unit. The system does use a bolt rope in the boom, but requires a loose-footed main. Doyle re-cut my footed main to make it loose-footed as part of the purchase. The sail does not attach to the stack pack.

As Bill said above, installing the lazy jacks to the mast (and not the spreaders) is probably not the best approach. I installed Harken micro-blocks to the under-side of my spreaders, about halfway out from the mast on each side. It probably helps that I have a single-spreader rig, and the spreader height is near the height Doyle recommended for the lazy jacks. The wider slot from the spreaders helps in hoisting the main, with less opportunity to catch a batton on the lazy jacks.

I configured my lazy jacks to easily adjust tension on the front of the mast. The upper lazy jack lines (port and starboard) are actually a single line run from the lower jacks over the boom, through the spreader blocks, down the front of the mast where they come together to a SS ring with a line to a horn cleat.

I can loosen the jacks enough to tie-off the stack pack to the boom and pull the jack lines forward to the mast - effectively moving the stack pack and jacks from interfering with the sail. As a cruiser, however, I don't really do this. I don't see the difference in boat speed to be worth the effort. That would be different if I was racing.
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Old 14-09-2019, 11:46   #15
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Re: Stack Pack and sail performance

I love myMack Pack. The lazy jacks can be loosened and brought fwd if desired and the pack can be rolled/secured but I have never tried it.
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