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Old 15-01-2015, 11:16   #1
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dumb asym spinnaker question

We got a total of ten sails with the boat, including an asymetrical spinnaker. We've laid it out on the patio, and figured out the sock etc. but have never tried using it on the boat. This coming weekend we have forecasts of 5 knot winds on both days, and I'm looking at this as a rare opportunity to put the spinnaker up and figure out how to rig and use it. We rarely get winds this light here. Very rarely. But it would be good to have some experience with the sail.

Previous owner told me to buy 70 ft. of light line for the spinnaker, that what he had was too heavy. And I did. But looking at photos of spinnakers set up, I wonder is that 70 ft. meant to make up two jib sheets for the spinnaker? I don't see that we would be gybing with a spinnaker, as moving the tack would be a pain. I assume one sets a spinnaker and pretty much leaves it all day, right? So, would you have one long jib sheet, like 70 ft. or would you still want two jib sheets of 35 ft. each? This is on a 40 ft. catamaran.
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Old 15-01-2015, 11:37   #2
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Re: dumb asym spinnaker question

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Originally Posted by Canibul View Post
We got a total of ten sails with the boat, including an asymetrical spinnaker. We've laid it out on the patio, and figured out the sock etc. but have never tried using it on the boat. This coming weekend we have forecasts of 5 knot winds on both days, and I'm looking at this as a rare opportunity to put the spinnaker up and figure out how to rig and use it. We rarely get winds this light here. Very rarely. But it would be good to have some experience with the sail.

Previous owner told me to buy 70 ft. of light line for the spinnaker, that what he had was too heavy. And I did. But looking at photos of spinnakers set up, I wonder is that 70 ft. meant to make up two jib sheets for the spinnaker? I don't see that we would be gybing with a spinnaker, as moving the tack would be a pain. I assume one sets a spinnaker and pretty much leaves it all day, right? So, would you have one long jib sheet, like 70 ft. or would you still want two jib sheets of 35 ft. each? This is on a 40 ft. catamaran.

This is roughly the setup on our boat, and the purpose "appears" to be to allow you to jibe the MPS/Asym by pulling the sheet around the front of the forestay. At least, that's how I understand it, and it is what has worked for us. Having said that, I am not at all certain and I find the super long sheet a pain in the backside (quite literally, as it ends up all over the cockpit seats). I am going to watch the responses here with interest as I have come close to shortening the darn thing a number of times.

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Old 15-01-2015, 11:37   #3
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Re: dumb asym spinnaker question

I'd be going with 2x70 foot of line

Assy's tack forward of the forestay/ meaning that the lazy sheet has to go from your rear winch, through the turning block around the forestay and tack of the sail, and back along the foot to the clew.

That's 10 feet (winch to block) + 40 feet (boat length) + 20 feet (foot of the sail)

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Old 15-01-2015, 11:37   #4
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Re: dumb asym spinnaker question

It will depend on how the asym is sheeted Canibul. On my 37-foot monohull our spinnaker sheets are at least 45, maybe 50 feet long. And yes, we rig both sheets and do tack and jybe at times. Mostly I'll just sock the asym first, but I've done it by letting the asym fly out around the forestay as well ... lots of fun that is .

It's only a guess, b/c I don't know your boat, but I'm pretty sure you'll need more than 35' for the sheet length. 70' might be a bit excessive, but it's better to be too long than too short.
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Old 15-01-2015, 11:38   #5
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Re: dumb asym spinnaker question

You would probably need 2 x 70' sheets, but I would measure (from winch, back to aft outside turning block, around the forestay, and back to about 1/2 way between the shrouds and transom). If you never jibe (silly) you only need one sheet. But that is silly. About 7/16" might be right. I use 3/8" on a 32' cat.

One factor is how flat is the chute. Some are for deep reaching and need to be tacked to the windward bow. Some are for beam apparent wind and are tacked to a centered bridle. Hoist the sail and try to determine which it is.

If the tack needs to go to the weather bow, take some spare dock lines and make a test bridle like this:
* put a loop around a bow cleat, to a block or carabiner, and back to the cleat.
* do the same for the other side.
* join these in the middle, about 2-3' above the front cross beam. This is where you clip the tack of the sail.

Now you have a simple bridle that has 2:1 purchase when moved side-to-side and allows for tack height adjustment. My permanent bridle is very similar. 3/8" line should be enough. Center the bridle before jibing, then haul to the new side after on the new tack. You will probably do an outside jibe above ~ 5 knots, and inside below that (inside/outside designates whether the sheet goes between the tack and forestay, or outside of the forestay).

Read-up first, and have fun. You should be able to fly that up to 10 knots true easy, 15 knots with practice... and you will be flying!

Do NOT bring it up on a beam reach, sheeted in, in anything but light air. There is a LOT of power in a breeze.
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Old 15-01-2015, 11:38   #6
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Re: dumb asym spinnaker question

I used to gybe mine on the outside of the forestay, so I needed two sheets, each a little over twice the length of the boat.

If you snuff it with the sock when you gybe, then you can get away with a single sheet. You'll have to walk it around to the lee side. I'd still make sure you had one long enough. 35' sounds a bit short.
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Old 15-01-2015, 12:52   #7
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Re: dumb asym spinnaker question

Never been on a boat with an asymmetrical spinnaker that didn't also have a bowsprit or retractable pole. Also never tacked one - downwind gybing only - so I will follow this thread with interest.

Don't understand the logic of one spinnaker sheet so looking forward to that discussion as well.
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Old 15-01-2015, 12:57   #8
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Re: dumb asym spinnaker question

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Never been on a boat with an asymmetrical spinnaker that didn't also have a bowsprit or retractable pole. Also never tacked one - downwind gybing only - so I will follow this thread with interest.
Multihulls can use their beam as a spinakar pole, tacking the chute to the weather hull, and then switching when jibing. Very effective and efficient for deep chutes. If they use flatter chutes, bowsprits work well. I've used both, for different chutes. However, a chute fixed to a centered sprit will never be efficient or stable when the wind is well aft of the beam.
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Old 15-01-2015, 13:49   #9
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Re: dumb asym spinnaker question

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. However, a chute fixed to a centered sprit will never be efficient or stable when the wind is well aft of the beam.
Yes, I can confirm that from painful experience. Anything less than about 20 degrees forward of directly astern and our MPS is a pain, even poled out. Someone here on CF suggested I start doing tacks downwind to solve the problem, and that has worked well. Thanks to that... er... "someone".

Matt
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Old 15-01-2015, 13:56   #10
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Re: dumb asym spinnaker question

Assyms sheets can be inside or outside the forestay, really depends on the projection of the bow sprit. Purpose built race boats with long projecting bow sprits will be inside gybers and most cruisers/cruiser racers will have short bow sprits so therefore the sheets will go outside the forestay. The sheets do need to be quite long to do this because the assyms clew when flying is going to be pretty much alongside the cockpit/pit. I have only used them with two sheets although I imagine you could use one single continuous sheet with the clew attached in the middle which may help the clew get around the forestay. You shouildn't need to sock it to gybe although if you are short crewed it is probably less stressful. We do have lighter weight sheets for light winds and heavier sheets for heavy winds.

When you get used to them assyms are actually easier to use than symmetric spinnaker
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Old 15-01-2015, 15:08   #11
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Re: dumb asym spinnaker question

Canibul,
Others have given you the straight scoop....and yes, I gybe my asym forward of the forestay, so I use 2 long sheets...
I have a adjustable (from cockpit) tack line, whose block is on the end of the very HD anchor roller, a few feet forward of the forestay...

In actuality, flying a big asym (assuming you have a good sock system like the ATN) is quite easy and fun....
I do it offshore on passages often....
(I actually had a owner of a sistership ask me to go thru my logs and determine how often, and it even surprised me....on my two most recent Atlantic crossings, I used the asym about 17% - 18% of the hours at sea, both eastbound from Florida to Gib and westbound from Gib to St. Thomas....)


If you care to see, I have a few minutes of flying the spinnaker in each of these videos...

A few minutes, right at the start of the first video...(westbound)



And, about 8 minutes into the second video...(eastbound)




Fair winds and have fun...

John
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Old 16-01-2015, 04:53   #12
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Re: dumb asym spinnaker question

Thanks, but the inside/outside forestay and bowsprit answers don't seem relevant to this situation. That's why I posted it in the multihull section.

The boat has a hard point on each bow to attach a spinnaker. I cannot imagine gybing with the sail tacked all the way outboard. So we'd have to pull the sock down, disconnect the tack, move it over to the other bow attachment point, and then re-run the sheet to the other hull, and finally re-deploy the sail. Plenty of time to move a 70 ft. sheet over to the other side, in a leisurely downwind tack. But I'm having trouble remembering what the previous owner said about that 70 ft. of line he told me to buy as the new spinnaker sheet.

Here's a photo of another identical hull with a spinnaker. you can see that the tack is well outboard on the port bow. These guys had the sheet run back through a block amidships. our turning block is much further aft, only about four feet forward of the transom. If this were our boat, our block would be about where the forward edge of that solar panel hanging on the life lines. Just forward of our backstay.

But looking at this photo, I can't see that gybing would be a simple thing, and I don't see the need for two jib sheets in a situation where one will never gybe and therefore will never need a lazy sheet at all.

Can you see why this boat, for example, would need two sheets in this situation?
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Old 16-01-2015, 05:34   #13
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Re: dumb asym spinnaker question

Some people use a bridle to shift the tack from one bow to the other.

Ideas on bridle for asymmetric between hulls
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Old 16-01-2015, 05:52   #14
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Re: dumb asym spinnaker question

I can see how a bridle could work, if one were going to be going directly downwind with a spinnaker. I've been studying this photo, how Angel Louise rigged it, and can see two lines to the tack and also two jib sheets. But this is different than the way ours was rigged. The previous owner made up about a four foot section of stainless steel wire to attach the tack to the bow fittings. I have never liked the steel wire as line approach. I'm going to be making changes, but I'm a bit of a limbo having never used a spinnaker in my life.

Boat also came with a standard spinnaker, and we have two spinnaker poles. But we took them off the boat and they've been lying in the garage for a year or two.
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Old 16-01-2015, 06:14   #15
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Re: dumb asym spinnaker question

Following this thread with interest as I have an asymmetric that has never been flown to a large extent because I also have a great screecher and only one halyard for the both.

Wondering about VMG running before the wind as I have often seen VMG get better as I get on a course more than 30 degrees from dead down wind, not to mention what seems to me to be less of a chance to broach in some seaways.

Some what related to reducing the chances of a broach is not going directly down wind also reduces the chances of an unintended gibe. I have to confess I have plenty of experience with unintended gibes, enough so that I also have experience with preventers.

YMMV

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