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Old 11-11-2016, 16:26   #1
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asymmetrical spinn v. twin foresails

I am wondering about the pros and cons of using an asymmetrical spinnaker rather than a twin foresail for the pacific puddle jump.

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Old 11-11-2016, 16:56   #2
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Re: asymmetrical spinn v. twin foresails

Twin foresails let you sail dead downwind. Assymmetricals dont. Also, a twin foresail arrangement will be better for reducing roll than anything else you can do. You will sleep way better!!
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Old 11-11-2016, 17:04   #3
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Re: asymmetrical spinn v. twin foresails

Are there any problems with steering while using twin headsails? I have a windvane.

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Old 11-11-2016, 17:46   #4
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Re: asymmetrical spinn v. twin foresails

DDW bites majorly!!! I wish I knew who started the idea that it’s a good way to sail, so that I could go wring their neck… over, & over, & over again. DDW is SLOW! As well as being a terrible point of sail from a safety perspective, & in terms of controlling the boat. Not to mention that it cause the boat to have a horribly, uncomfortable motion as compared to when sailing one’s gybing angles downwind.

Put simply, sailing to your gybing angles, commonly found on your Polars, will get you to your destination faster, in more comfort, with less accidental gybes (& comparatively little rolling).
Along with much less wear & tear on your; sails, boat, & gear. Ditto on her crew. Particularly as it’ll be easier to sleep, cook, & bathe, etc. due to consistently higher wind pressure on the sails & foils making her ride smoother. Coupled with less rolling, & few to no worries about accidental gybes… the standard sort, & ones in the wrong direction (Chinese gybes).

Throw up the kite & sail to your Polars!
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Old 11-11-2016, 17:54   #5
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Re: asymmetrical spinn v. twin foresails

It depends on what sails you have and what boat you have. Or the other way round, if you do not have any sails.

Twin jibs ask for two extremely long poles. Few boats have such poles.

Unless you have special purpose jibs, it may be a challenge to get enough SA. This is often easier with a big kite.

IMHO boats under twin jibs and extra long poles are very easy on AP or windvane. Boats under kites can be more difficult to control, unless you have a cat.

In a typical (not ultra modern) mono, all other things equal, I would go for two custom jibs and two telescopic poles (1.5J).

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Old 11-11-2016, 20:45   #6
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Re: asymmetrical spinn v. twin foresails

Quote:
Originally Posted by UNCIVILIZED View Post
DDW bites majorly!!! I wish I knew who started the idea that it’s a good way to sail, so that I could go wring their neck… over, & over, & over again. DDW is SLOW! As well as being a terrible point of sail from a safety perspective, & in terms of controlling the boat. Not to mention that it cause the boat to have a horribly, uncomfortable motion as compared to when sailing one’s gybing angles downwind.

Put simply, sailing to your gybing angles, commonly found on your Polars, will get you to your destination faster, in more comfort, with less accidental gybes (& comparatively little rolling).
Along with much less wear & tear on your; sails, boat, & gear. Ditto on her crew. Particularly as it’ll be easier to sleep, cook, & bathe, etc. due to consistently higher wind pressure on the sails & foils making her ride smoother. Coupled with less rolling, & few to no worries about accidental gybes… the standard sort, & ones in the wrong direction (Chinese gybes).

Throw up the kite & sail to your Polars!
Don't knock DDW with twin headsails unless you have tried it.
It is safer
No gybes to worry about at all, because the mainsail is down.
Reefing for squalls is an easy one man job
The boat is pulled through the water instead of being pushed, making it
much easier on the autopilot/windvane. In fact you can self-steer by
using the sheets (crossed) on a tiller.

You roll less
You can line up with the major wave train
The physics are complex (see CA Marchaj), but most sails augment
oscillations downwind.
In my personal experience running with twin jibs rolls less
than either jib or main alone, and is much more stable than main and
spinnaker.

Having crossed the Atlantic twice in the tradewinds, once wing and wing and once with twin headsails, I'd go for the twin headsail rig again. You only need one pole, and 100% of J worked fine for me with 125% headsails.
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Old 12-11-2016, 01:17   #7
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Re: asymmetrical spinn v. twin foresails

I was hoping to avoid getting into explaining all of this, but apparently that ain't going to work. So here it goes.

Quote:
Originally Posted by donradcliffe View Post
Don't knock DDW with twin headsails unless you have tried it.
It is safer - How?
No gybes to worry about at all, because the mainsail is down. - Please define gybe here.
And why reduce sail when you can power up, & stabilize the boat via using a main & a spinnaker?
Reefing for squalls is an easy one man job - As is using a spinnaker with a snuffer or furler.
The boat is pulled through the water instead of being pushed, making it
much easier on the autopilot/windvane. - Read the below explanations.
In fact you can self-steer by using the sheets (crossed) on a tiller.

You roll less - Not necessarily by any means.
You can line up with the major wave train
The physics are complex (see CA Marchaj), but most sails augment
oscillations downwind. - Time for all of us to re-read this.
In my personal experience running with twin jibs rolls less
than either jib or main alone, and is much more stable than main and
spinnaker. - Speed = Stability. Go ride a bike & see. And again, DDW is slow.

Having crossed the Atlantic twice in the tradewinds, once wing and wing and once with twin headsails, I'd go for the twin headsail rig again. You only need one pole, and 100% of J worked fine for me with 125% headsails.
DDW is slow, period. Such is a fact, check your Polars. As well as that it's a terrible point of sail from a perspective of controlling the boat.
And by the way, DDW = Sailing at 180 deg. apparent, right? So how does one keep a boat at this heading all of the time? Or are you actually (constantly) doing small gybes back & forth? And you're doing these "small gybes" while in truth secretly hoping that you don't have a big one, or broach. Right? That's been my experience when sailing deep angles.

Your Polars will in fact show you that the best way to make good VMG/CMG (Speed & Course Made Good), is to typically sail at apparent wind angles between 120 -160 deg. You sail more distance, but the increase in speed more than makes up for this. Period. The math don't lie.

The other thing is that when sailing at an angle to the wind & waves, the boat is more stable & less prone to accidental gybing. This is true as the angle of the wind in the sails is consistently on one side of the boat, instead of constantly shifting back & forth, as is the case when sailing "DDW".
So it's then much easier for a human (wind vane, or auto pilot) to keep the boat on course. As well as to steer so that the wind doesn’t accidentally wind up on the wrong side of the boat. AKA gybing, or over correcting & then broaching.Is this even arguable?

When sailing at an angle to the wind, the pressure in the sails is consistently higher, as is the pressure on the boat’s foils (her keel & rudder). Which makes it easier to steer properly.Since without consistent flow over the rudder (& keel) it’s easy for the boat to “trip” (aka, flow detachment with loss of steering), especially when being pushed by a wave, down it’s face. As is common when sailing DDW.

When sliding down waves when sailing DDW. The speed of the water flow over the rudder often falls to zero, or close to it. Since the speed of the waves catching the boat from behind match the boat’s speed at some point when sailing (DDW) down the wave’s face. This means that the rudder physically cannot do anything to correct the boat’s course when this is occurring, as there is no flow over it. Which is an uncomfortable feeling, (& knowledge) for anyone helming the boat when this happens (repeatedly). Especially since during that time it’s much easier to do an uncontrolled accidentally gybe or broach. Which most folks aren’t fans of.

Oh, & the slower you go, & the deeper the angles you sail, the less efficient your sails are. In terms of both boat speed, & aerodynamically. Since sails function primarily by generating lift. Something which spinnakers are better shaped to do downwind than are jibs. Which have much more drag off of the wind than do spinnakers. Something which increases rolling (oscillations).
The same is true of the keel & rudder. They perform better with water moving over them at higher speeds, period. Such are simple facts.

Also, consider this. If the rudder cannot do anything to alter the boat’s course for short periods, when you’re on a wave’s face, then what’s to stop her from oscillating (rolling) back & forth when on the wave? Ditto for that percentage of time when the water flow is reattaching to the rudder, & the wind flow is reattaching to the sails. Ergo, the primary causes of rolling. Which, these things rarely happen when sailing hotter wind angles, like 140 deg. apparent. Since the speed of the water over the keel & rudder is high enough to keep it attached.

Sail to your Polars/gybing angles, & there will be less rolling, with better speed. Which means the boat will have an easier motion for sleeping, cooking & the like. Plus you’ll get to your destination faster, with less wear & tear on the boat & her gear.
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Old 12-11-2016, 02:13   #8
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Re: asymmetrical spinn v. twin foresails

I was a skeptic like you until i tried the twin genoas. Grand Canaria to St Lucia in 14.5 days ain't bad for speed, and we had some days over 200 miles without pressing the boat. But the best part was the reduced rolling. The only downside to the rig is that you have to trim two genoa sheets when reaching and beating.

Having done 6 races to Hawaii, I can tell you that spinnakers do not reduce rolling--quite the opposite.
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Old 12-11-2016, 02:45   #9
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Re: asymmetrical spinn v. twin foresails

I have twin whisker poles rigged with outhauls through the poles and do a fair bit of downwind sailing with a 140% genoa and fairly large genaker. I sail single handed and find I can handle this arrangement by myself. I usually take the genaker down from behind the genoa. Never been interested in a spinnaker as I think it would be too hard to handle single handed. I think the rolling is much worse with a wing and wing rig and tend to avoid it unless I am sailing a route with a lot of large course changes.
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Old 12-11-2016, 03:24   #10
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Re: asymmetrical spinn v. twin foresails

The discussion reminds me that during the Americas Cup races in SFO no boat sailed DDW. In my 1923 designed Ingrid with enough wind to reach or slightly exceed hull speed the rolling is heavy DDW. It's sailing the polars for me. Particularly after seeing a smaller boat pass me and sail into my shadow, broach and get knocked down 3 times before they could literally cut the chute loose. Meanwhile I struggled to bear off enough to not run them down. Thankfully they all remained aboard though submerged in 53 degree water.
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Old 12-11-2016, 05:38   #11
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Re: asymmetrical spinn v. twin foresails

I think both camps may be right here depending on the particular combination of boat, course, crew size and capability.

One thing not mentioned here is the question of an asymmetric at night when you are shorthanded. Our asymm is very large (has a snuffer) and we were not comfortable with the idea of a nighttime squall, say in the ITCZ. We came up with an unusual, but successful, approach going from Ascension to the Caribbean. During the day we used the kite on one tack and at night gybed and used a poled out genoa, in each case with the main up but reefed enough to make sure we got air to the headsail. It was quite easy to do since we left the pole up during the day when we furled the genoa. BTW, the pilot chart was quite wrong about the position and width of the ITCZ, much longer time to get back into the trades than we expected.
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Old 12-11-2016, 05:51   #12
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Re: asymmetrical spinn v. twin foresails

The double headsail rig works well in the trades. You can sail DDW or on a broad reach by simply easing one sheet and trimming a bit harder on the other, no worry about gybing. If you have a furler with double luff grooves you can run both sails on the same furler and reef both at the same time together, works like a charm. In really light winds this rig is faster than a chute. Most cruisers are reluctant to fly a chute all night but no problem with 2 headsails. We have done both while crossing oceans, we can easily fly a chute with just the 2 of us but before socks were used it was lots of work pulling down the chute, repacking it every time a squall was coming through and then resetting it. The double headsail rig is a very good option for crossing oceans. Currently we don't have a double headsail rig and have no choice but to fly a chute in the lighter winds and I don't rest well when it's dark and my wife is on watch by herself as we have had some exciting moments in the past years, nothing dangerous but these days I can do without the excitement, lol.
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Old 12-11-2016, 06:21   #13
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Re: asymmetrical spinn v. twin foresails

Quote:
Originally Posted by UNCIVILIZED View Post
I was hoping to avoid getting into explaining all of this, but apparently that ain't going to work. So here it goes.
Uncivilized, relative to the OP's question, your response sounds like a rash of theoretical spouting that is not based on experience.

Yes, DDW is slowER than the optimal deep reach. I race three times a week when I'm in Annapolis, on sym and asym boats, both windward/leeward races and distances races. We have the polars taped to the cabin wall, not that we really need them at this point. We would no sooner sail DDW than we would throw out an anchor.

I've also crossed the atlantic a few times, racing and not racing. Racing, yes, you sail to you polars, based on what Expedition suggests and your own best judgement. But you're hand steering, and trimming constantly, looking for every last fraction of boat speed.

Sailing deep downwind with a kite in a moderate to big swell is NOT something you want to trust to a wind vane. If you don't hand steer in all but the most benign conditions you're asking for all kinds of trouble. When you're on a long passage there are a few of principles for how you set up the boat; make it easy, make it stable (i.e. no broaching), and don't stress the rig. It really sucks to break something when you're 1000 miles from anywhere.

Doing a long delivery passage, for weeks, you don't really worry about polars, and sailing DDW or close to it if you're in the trades has many advantages, particularly with a wind vane. Set the boat up and go. One trip from the canaries to St. Lucia was on one tack, a poled out genoa, near DDW the whole way, and the Monitor steered for literally 2790 of 2800 miles.

If you're in a big ocean swell the motion DDW can be fine. The wind vane will handle it MUCH better than sailing at a higher angle. Yes the boat will roll a little bit, but you'll get used to it and the tradeoff is that boat is basically self-tending.

Another reason to not run an asym during a long passage is that if you're prudent you'll take it down every night.

I suppose all this comes down to how many crew you have and how experienced and energetic they are. If you have the manpower to sail to your polars with the kite, go for it, but it's a lot of work on a long trip.
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Old 12-11-2016, 11:28   #14
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Re: asymmetrical spinn v. twin foresails

I'd say no and if I could afford that sail it would be mine!!!
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Old 12-11-2016, 11:46   #15
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Re: asymmetrical spinn v. twin foresails

I have reviewed my speed polar. DDW with wing and wing is significantly faster than any jibe angle. Since I have a cat, it is also smoother with near zero rolling. Thus, overly broad statements add little.

As for sailing deep with a chute, sure you can. Get a chute that is cut to rotate to windward or get a pole. In my case, I pull the tack to a windward bow.

Some folks with sail DDW with only the A-sail. I've never tried that.

Thus, twin head sails would be my last choice. In a blow I would be happier with reduced sail or just the genoa.
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