Rigging a Spinnaker on a Catamaran

[Epicurean]

I have some questions about setting up a spinnaker on my 47' catamaran. After watching a bunch of Youtube videos it looks to me like I should get a trigger release shackle for the sheet. How do I determine what size should I get?
2. I assume the sheet should be long enough to go from the clew fully extended through whatever blocks, etc. to the winch. What size? I would think Dyneema to keep it light so the weight doesn't pull the clew down in light airs.
2. Where does the tack attach? I've seen a) Windward bow - Catamaran Guru, b) end of bowsprit - a sailmaker I know, and c)two lines, one to each bow, joined at a shackle at the tack - Cat Impi. I kind of like the latter but I've never flown one on a catamaran.

[fxykty]

Originally Posted by Epicurean

I have some questions about setting up a spinnaker on my 47' catamaran. After watching a bunch of Youtube videos it looks to me like I should get a trigger release shackle for the sheet. How do I determine what size should I get?

2. I assume the sheet should be long enough to go from the clew fully extended through whatever blocks, etc. to the winch. What size? I would think Dyneema to keep it light so the weight doesn't pull the clew down in light airs.

2. Where does the tack attach? I've seen a) Windward bow - Catamaran Guru, b) end of bowsprit - a sailmaker I know, and c)two lines, one to each bow, joined at a shackle at the tack - Cat Impi. I kind of like the latter but I've never flown one on a catamaran.

Well, a few things to consider.

First off, is the spinnaker symmetric or asymmetric? That fundamentally changes how it’s set and handled.

Second, based partly on answer 1, what is your deployment/dousing system: sock, furler, or nothing? That determines some of the finer points of the rigging.

For a symmetric spinnaker with or without a sock, the traditional set up (as per Cat Guru):

• 4 control lines: two sheets and two guys (alternatively called braces)
• Lines, if covered dyneema, should be minimum 8mm diameter for decent hand grip. Guys should be one size larger if you go for minimums
• Length of each sheet is two times your boat length plus beam plus the distance to your sheet winch on one side
• Length of each guy is one and a half boat lengths plus beam plus distance to your guy winch on one side
• On each side, connect the outboard end of a sheet and a guy to a snap shackle that has a nice big ring. A sailmaker or rigger can advise on the size of the shackle, based on sail size and expected wind range
• On each side, each guy leads from the tack and through a block on the bow, then back to its winch. When the sail is set, the guy attached to the leeward tack (the clew now!) is the lazy guy and is loose
• On each side, each sheet is lead outside everything to a block on the outside of each stern, then back to its winch. When the sail is set, the sheet attached to the windward tack is the lazy sheet and is loose
• When the spinnaker is set, keep the tack and the clew at the same height, and keep the windward luff vertical. Ease the sheet until the luff just curls
• To reach, ease the tack, but not further than the centreline
• Gybing is simple, just pull on the lazy sheet until you’ve taken the pressure off the (now old) guy, then let the old guy go. Take up pressure on the new windward guy until the tack is in position, then let off the (old) sheet

For an asymmetric spinnaker on a top down furler or a sock or nothing, the standard set up:

• Two sheets for the clew, each two and a half times the length of your boat plus beam plus distance to sheet winch on one side
• If furled, then no guy needed - the bottom furler will connect to the end of the bow pole or to a tack line
• If not furled, then one or two guys, depending on whether you want to fly the tack from a bow pole or from the windward bow. For two guys, each guy one boat length plus beam plus distance to winch. For one guy, pole length plus boat length plus distance to winch.
• Sizes same as for the symmetric
• Each sheet can be tied to the sail, no need for shackles, but each guy is shackled independently to the tack
• If two guys, each guy leads from the tack and through a block on its bow, then back to its winch. When the sail is set, the guy attached through the windward bow takes the load and the guy attached through the leeward bow is the lazy guy and is loose. I think this is the Cat Impi setup you referred to
• If one guy, set through the end of the pole. Lead it back to a winch so you can adjust the height of the tack
• Similar to genoa sheets, each sheet is lead outside everything to a block on the outside of each stern, then back to its winch. The lazy sheet is lead around the front of the forestay and depending on gybing method, inside the tack (if furling) or outside the tack (if Gybing inside out). In the latter case have something on the end of the bow pole that will keep the lazy sheet from falling under the pole
• Gybing can either be done by furling the sail, then unfurling on the other side (only if it has a furler of course). Otherwise, with or without a furler, you can let the sheet go completely so the clew goes way forward, then haul in the new sheet like crazy until the sail is trimmed on the new side - effectively turning the sail inside out

Hope this helps.

[MikeFergie]

I do the same on my cat as Sailing Impi does. I made a bridle to attach to the bows. On the bridle I use the Tylaska shackle to attach to the tack. I use normal bowlines on the sheet lines. I pull the tack to release the sail and pull down the sock

[Davy J]

I use a single line with a loop knot and snap shackle in the center, blocks attached at each bow. This arrangement allows me to position the tack for the wind direction.

The snap shackle allows me to "blow the tack", however, usually, I just head further down wind, allow the main to blanket the spinnaker and then bring down the sock.

[belizesailor]

Epicurean,

What kind of boat and what spinnaker related deck hardware do you have?

Examples: do you have blocks at the bows? Turning blocks near the stern (for spin sheets)? Rope clutches for spin haldyard at the mast, deck house?

[Epicurean]

Sorry, I obviously should have said it's an asymmetric with a sock. I don't think a pole is called for since the beam is 24'. Therefore no guys. Also, I should have said this is a cruising boat so I don't anticipate many jibes. Hence I think one sheet is best to keep fewer ropes on deck. And the one sheet can be shorter.
I notice before dousing there's an option of dumping the wind by easing the sheet in light winds or releasing the tack on heavier winds.
Someone said they recommend opening the headsail (genos) a third to prevent "wineglassing" but most don't seem to do that. Why? On my old monohull I had a wineglass once; a real pain.
But I still don't know what size trigger release shackle I need.

[Epicurean]

Originally Posted by belizesailor

Epicurean,

What kind of boat and what spinnaker related deck hardware do you have?

Examples: do you have blocks at the bows? Turning blocks near the stern (for spin sheets)? Rope clutches for spin haldyard at the mast, deck house?

Right now I only have eyes on the bows and stern for blocks and winches to be repurposed for the spinnaker sheet. I need sheets, blocks, and shackles.
It's a lightweight catamaran (47') with narrow hulls and daggerboards.

[Cpt Mark]

wrt dyneema. I had planned on splicing dyneema into a double braided rope to reduce weight. Last weekend a buddy wit the same Cat as I, fouled one of his sheets into the prop.

Having had to cut lines/sheets off the props of boats when i was in that business it's not fun and with Dyneema??? I'm rethinking that one now. Anyone have thoughts on this?

Wrt to which shackle, maybe this will help.
https://www.fisheriessupply.com/tyla...les-small-bail

You might consider one size larger? Another approach would be to ask a sailmaker what kind of loads could you expect on the tack with your spinnaker.

[Scubaseas]

Originally Posted by Epicurean

Sorry, I obviously should have said it's an asymmetric with a sock. I don't think a pole is called for since the beam is 24'. Therefore no guys. Also, I should have said this is a cruising boat so I don't anticipate many jibes. Hence I think one sheet is best to keep fewer ropes on deck. And the one sheet can be shorter.
I notice before dousing there's an option of dumping the wind by easing the sheet in light winds or releasing the tack on heavier winds.
Someone said they recommend opening the headsail (genos) a third to prevent "wineglassing" but most don't seem to do that. Why? On my old monohull I had a wineglass once; a real pain.
But I still don't know what size trigger release shackle I need.

Asym, sock, cruising, single sheet? Why do you need a trigger release at all? Just buy a single dedicated sheet and leave it tied on. Use light weight but strong sheet like NER VPC or covered dyneema . Put a long tack rope on it. To douse ease the sheet (like almost let it go ease) and if necessary let out 5 to 6' on the tack line.

[belizesailor]

Originally Posted by Scubaseas

Asym, sock, cruising, single sheet? Why do you need a trigger release at all? Just buy a single dedicated sheet and leave it tied on. Use light weight but strong sheet like NER VPC or covered dyneema . Put a long tack rope on it. To douse ease the sheet (like almost let it go ease) and if necessary let out 5 to 6' on the tack line.

Agree, asym w a sock...no need for complicated rigging or a trigger release. Thats the advantage of this rig...its simple.

Asym is normally tacked down near center line. You can use a belt over the existing head sail (furled) and a single tack line from belt hardware to a fitting near base of forestay. No need for guy lines. The most complicated part of this set up is the sock and its control lines...also the most likely part to get all fouled up!

It is handy to have block & tackle from the bows to the tack so you can move the tack, but its not necessary. Just get familiar with your set up first then decide if you want to add that.

Typically you would still install turning blocks well aft of the primary winches. Sheets go thru these blocks then back to the winches. But depending on the size of the chute and how the line leads work out, this may not be necessary.

Its good practice to not cleat the end of the spinnaker sheet (so it can be cast off quickly) but on a cruising boat with no dedicated crew to constanstly trim/monitor the spinnaker, it usually gets cleated, just be sure it can be released quickly and run free (no stopper in the end).

[fxykty]

Originally Posted by Epicurean

Sorry, I obviously should have said it's an asymmetric with a sock. I don't think a pole is called for since the beam is 24'. Therefore no guys. Also, I should have said this is a cruising boat so I don't anticipate many jibes. Hence I think one sheet is best to keep fewer ropes on deck. And the one sheet can be shorter.

I notice before dousing there's an option of dumping the wind by easing the sheet in light winds or releasing the tack on heavier winds.

Someone said they recommend opening the headsail (genos) a third to prevent "wineglassing" but most don't seem to do that. Why? On my old monohull I had a wineglass once; a real pain.

But I still don't know what size trigger release shackle I need.

Pole is the bow pole. Do you have one?

With an asymmetric the guy can be called the tack line. With the Cat Impi setup you will have two, one to each bow (so that the tack can be moved to windward). It’s nice to lead these lines to the cockpit rather than handle them on the tramp, especially if the wind picks up a bit and you want to move the tack.

Don’t plan on never gybing - how else do you expect to go somewhere dead downwind if your sailing angle is 150*? Have two sheets, it’s really not a big deal. The sheets will need to be long to allow for gybing. Not allowing for this is penny-wise and pound-foolish.

I’m not in favour of ever separating the tack line from the tack on a cruising boat - not worth losing control of that corner. The alternative is to have longer tack line(s) that can be eased a long way out for drops.

Unfurling the genoa/jib partially is a good idea when hoisting in light and rolling conditions to help prevent a forestay wrap. It’s also a good way to depower the sail prior to dropping, especially if you haven’t hoisted the main.

You don’t need a fancy trigger release shackle - regular snap shackles are just fine. For size, what is the safe working load of the furler? The shackle should be the same or higher.

[fxykty]

Originally Posted by Epicurean

Right now I only have eyes on the bows and stern for blocks and winches to be repurposed for the spinnaker sheet. I need sheets, blocks, and shackles.

It's a lightweight catamaran (47') with narrow hulls and daggerboards.

I would suggest snatch blocks with snap shackles, or with soft shackles for lighter weight and more strength. Snatch blocks are useful for a lot of things around the boat so three or four are not too many. With tack lines to both bows you will need four, or three if you want to move the sheet block from one side to the other along with the sheet.

If you only fly it from a bow pole, then you only need a single block on the end of the pole (or LFR).

[Epicurean]

Originally Posted by Cpt Mark

wrt dyneema. I had planned on splicing dyneema into a double braided rope to reduce weight. Last weekend a buddy wit the same Cat as I, fouled one of his sheets into the prop.

Having had to cut lines/sheets off the props of boats when i was in that business it's not fun and with Dyneema??? I'm rethinking that one now. Anyone have thoughts on this?

Wrt to which shackle, maybe this will help.
https://www.fisheriessupply.com/tyla...les-small-bail

You might consider one size larger? Another approach would be to ask a sailmaker what kind of loads could you expect on the tack with your spinnaker.

I don't have a sailplan. I think I first need to know/guess the size of the spinnaker then I can ask the Tylaska rep which shackle size.

Good point about lines around props. I have folding props. BE CAREFUL.

[Epicurean]

Originally Posted by Scubaseas

Asym, sock, cruising, single sheet? Why do you need a trigger release at all? Just buy a single dedicated sheet and leave it tied on. Use light weight but strong sheet like NER VPC or covered dyneema . Put a long tack rope on it. To douse ease the sheet (like almost let it go ease) and if necessary let out 5 to 6' on the tack line.

Makes sense to just let the sheet out. You have a mono, as did I. I think on a cat speed of release of the pressure is more important. At this point I don't have the experience. Although triggering a shackle might seem quicker than letting go the sheet, it requires going up in the bow (dangerous? and time consuming). I think I'd like to get the Tylaska shackle and then get the experience to decide which way to go.

[Epicurean]

Originally Posted by belizesailor

Agree, asym w a sock...no need for complicated rigging or a trigger release. Thats the advantage of this rig...its simple.

Asym is normally tacked down near center line. You can use a belt over the existing head sail (furled) and a single tack line from belt hardware to a fitting near base of forestay. No need for guy lines. The most complicated part of this set up is the sock and its control lines...also the most likely part to get all fouled up!

It is handy to have block & tackle from the bows to the tack so you can move the tack, but its not necessary. Just get familiar with your set up first then decide if you want to add that.

Typically you would still install turning blocks well aft of the primary winches. Sheets go thru these blocks then back to the winches. But depending on the size of the chute and how the line leads work out, this may not be necessary.

Its good practice to not cleat the end of the spinnaker sheet (so it can be cast off quickly) but on a cruising boat with no dedicated crew to constanstly trim/monitor the spinnaker, it usually gets cleated, just be sure it can be released quickly and run free (no stopper in the end).

What you say about no stopper makes sense. However, if it runs out, then one has to be vigilant that it doesn't foul the prop.