What are the benefits of a self tacking jib?

Technical discussion of ARC products
whalerman
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What are the benefits of a self tacking jib?

Post by whalerman »

What is the big deal of a self tacking jib? The sail looks smaller, I don't think you can use a furler with it, soooo?
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What are the benefits of a self tacking jib?

Post by fjviola »

While piloting three SC17's over the last nine years, I too had the same question: "What are the benefits of a self-tacking jib?"
Yes, the self-tacking sail area is smaller .. I really liked 'wrapping' my SC17 jib way out to the leeward hull on a beam reach. Were times I wondered if a barber-haul system might enhance the shape on this run. And yes, the self-tacker does not furl .. a really nice to have feature when we needed to quickly reduce sail area, and to stop that annoying sail-stressing whap-whap-whap on the beach between sessions. Furl her in and done!

Also, the curved self-tracking rails I saw protruding from my buddies' beach cats simply looked 'dangerous' to me. Perhaps my own 'miss-perception'? But I have been on many runs trapped-out forward of the SC17 crossbar (driving the bows down and pointing higher into the wind), and those curved metal self-tracker rails remind me of a razor sharp guillotine waiting for a rogue way to sling me into their jaws ... :shock:

However, now that I am driving an ARC21 with a 'clean' self-tacking rail that is secured straight and flush to the forward crossbar, my mind has been opened! The ARC21 is a much larger and more stable boat than the SC17, yet just as simple to rig and pilot. The self-tacking jib makes tacking (and jibbing) much smoother and efficient. Especially when my crew is not an experienced beach cat sailor.

And while I thought I would miss the ability to furl the jib, this battened forward sail actually out performs what would be a larger whap-whap-whap jib.

The difference in performance of a self-tacking jib vs traditional jib is like trying to manually out perform an automobile's cruise control with your foot. Over the course of a trip, the 'automatic' jib will always give your better fuel savings 8)

I am sure other SC/ARC sailors may provide a more nautical response, but for me (at least on the larger beach cats), a self-tacking jib is the only way to fly :D

Franklin Viola

ps - addend that closing statement to a "Bill Robert's engineered" self-tacking jib!
Mac M
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Re: What are the benefits of a self tacking jib?

Post by Mac M »

I have a self tacking jib on my SC 20 and the F16 we race, tacking is faster. It really comes into play when you run a spinnaker. Going downwind you would have to jibe the spin sail AND the jib. With the self tacking set up you don't have to worry about the jib, it takes care of itself.


I just put a self tacking jib on my 17. Ordered most of the stuff from Tom, pretty easy install.

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Kevin Keller
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Re: What are the benefits of a self tacking jib?

Post by Kevin Keller »

It was the best performance enhancer for my SC20 that I have done. It really takes care of itself. Tacks are effortless. Most of the time I have the sails in tight and a tack consists of me pushing the tiller over. That's all. Well... I usually move my butt over to the other side.

I do point much better than the old contraption (however my sails were old and stretched which didn't help). The sail area is a little smaller but self tacker comes down a lot further so it makes up makes up for some of that loss.

I highly recommend one.
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Re: What are the benefits of a self tacking jib?

Post by DanBerger »

I installed one on my 15 and I can't say enough good about it! It makes single handing a charm, I can practically roll tack the boat and fly through tacks!

The up and downside: I can point MUCH higher since it is a skinny sail. I have been gradually raking my mast forward and it doesn't seem to effect the upwind performance, any. I think I'm at like 8-10 degrees rake, I was at a lot more and could really point.

However, I feel that my downwind performance has dropped with the sail. The Hobies have that big overlapping sail that just does really well and powers them up. I lose a lot of ground down wind, but I make it up on the upwind legs.

My 15 jib has 6 battens! Mac's above has three, BUT I really like that small square top style batten in his sail. We saw that for the first time at the America's cup and I'm glad to see Randy running with it.
Bill Roberts
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Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

The self tacking jib is smaller in area than the original jib sail plan. Now, think about where the area has changed. The original jib sail plan was a wider sail luff to leech and a shorter sail on the luff hoist. Think about the pressure bubble across the sail that generates force. The front third of the sail has the greatest pressure difference across it. Remember that the force vector from the sail is always perpindicular to the sail cloth. therefore the front third of a jib sail is where the majority of the forward thrust vector comes from. The self tacking jib may be smaller in area but it is longer and bigger in luff area than the original jib design and along the luff is where the good stuff happens. The aft or back half of a jib sail runs almost parallel to the boat centerline. The force vector from this sail area is therefore largely sideways. Siderways sail force makes the underwater lifting parts of the hull, CB and rudder work harder and so they make more underwater drag. The self tacking jib is an example of changing jib design where the increase in aspect ratio outweighs the loss in sail area. Sail thrust is a function of sail area and sail aspect ratio. Why do the AC boats have such tall wings. The could more easily have rigs half as tall and twice as wide for the same area. Why not??? Sail aspect ratio is the answer. The shorter wider rig would be slower than the taller one of the same area.
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Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

"Also, the curved self-tracking rails I saw protruding from my buddies' beach cats simply looked 'dangerous' to me."
Thanks for the reminder.
The curved jib tracks are a mistake! The copycats did not understand!
The first self tacking jib system on a 22 went to France. Soon after that I got an email from Holland asking what is a self tacking jib and how does it work. I started trying to explain that with a straight jib track, "the car moves along the track as the jib sheet tension changes". This got into some calculus and about three pages of words and I wasn't half finished. At this point I suggested to the Dutch sailors that they go see the boat in France. Evidently they did so and took many photos. The boat was not rigged and sails not up. This caused them to miss the most important point to the self tacking jib system. What is it? Does anybody know?
More later....

What's the amswer???
Last edited by Bill Roberts on November 11th, 2014, 6:37 pm, edited 1 time in total.
SC15Av8or
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Re: What are the benefits of a self tacking jib?

Post by SC15Av8or »

Bill I want to hear more on this as it could be some thing I attempt on one of my SC's. And are you saying a self tacking jib is a good or bad thing ??!?!
Lifes 2 short for cheap GROG
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Re: What are the benefits of a self tacking jib?

Post by Bruiser »

SC15Av8or wrote:Bill I want to hear more on this as it could be some thing I attempt on one of my SC's. And are you saying a self tacking jib is a good or bad thing ??!?!

The self tacking jib makes life easier and better. The key to successfully tacking a catamaran is proper sail trim going into and out of a tack. The reason is that the light boat has very little momentum (because it is very light). Therefore it is very important that you have sail power on all the time through a tack. A self tacking jib correctly trims itself all the time, and critically during a tack. The steps in a tack are to keep the main trimmed in going into the tack. (Your main turns a boat into the wind, the jib turns a boat away from the wind). As you turn the boat into the wind your self tacking jib immediately starts to slide to the other side as it simply follows the wind. As you go through head to wind you will need to ease the main (the larger the main the bigger the ease) Remember the main turns a boat into the wind, so to have the boat bare away after a tack, the main must be eased. (Failure to do this is why many find themselves in irons, especially if the jib is not trimmed in.) Now the beauty of the self tacking jib is that it is trimmed in immediately on the new tack, which is also critical to sailing out of and on to the new tack. (Remember, jib sails a boat away from the wind) If you were relying on crew to preform this function, they are usually still crossing the tramp (at least in my case) when this critical step (the jib trimmed in on the new tack) needs to happen.

In summary the self tacking jib is a tremendous help in having successful tacks. By the way, I wrote this so I can remember what is supposed to take place. I am not implying you guys don't know this, so please do not take this as I am trying to insult anyone.

Also as someone who had a straight traveler and now has a curved one, the straight one is the way to go. But, that is another story. Bill has this figured out, so go with his advise.

Cheers,
Bill Roberts
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Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

Hey Grogman,
You have been drinking too much grog! Every comment on this thread says the self tacking jib is a good thing! I've tried to explain why.
Back to Europe and the introduction of the self tacking jib system there. Tom sold/sent/shipped an ARC22 to a customer in France. Shortly after that I received an email
from Dutch Tornado sailors asking all about the self tacking jib. I suggested that they
go see the boat in France and they did. They saw the boat in a boat park, no sails up. They made many pictures. This information went directly to the Marstrom Tornado Factory.
The factory tried the system as they saw it, understood it, and the system did not work. When the jib was trimmed to the correct sail shape for sailing to windward, the jib car was right in front of the mast on boat centerline. WHAT"S WRONG???" What did they overlook??? The jib sheet went from the jib clew to the jib car to the jib tack and back to a jib cleat. What's wrong with this system???

More tomorrow.
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Re: What are the benefits of a self tacking jib?

Post by J Drew »

When I put the self tacking system on mine, I followed the diagram that Tom described, with one exception, I missed one block, I made it 3:1. Foolishly I didn't think it would make a difference. I couldn't pull the clew in, at all. The traveler car ran back and forth on the track and the amount of travel could be controlled, but as far as letting the clew in or out I was helpless. It's set up as 4:1 now and it works like a charm.
Live and learn. It helps when you can learn from the ones that know!
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Re: What are the benefits of a self tacking jib?

Post by Bill Roberts »

J Drew, thank you so very much. You have it!!! You understand!!! That's great!!!

The engineer at the Marstrom Tornado Factory saw the system they had copied (no 4:1 mechanical advantage between the jib clew and car) and concluded "it doesn't work right". So, they fixed it. They put a curved jib traveller track in place of the straight one. The radius of the bend in the track was/is the shortest distance from the main beam at its center to the forestay. This results in constant distance between the jib clew and jib car and constant jib sheet tension as the car moves across/along the track.
The change in jib sheet tension with car position or sheeting angle is zero. To position the jib car and set the wind angle of attack on the jib sail, a second control line is required. This line positions the car along the track. It connects the car to the beam at the beam center, mid boat. Now to change jib car position and jib sail shape, the jib sheet must be adjusted and the jib car position line must also be adjusted. I guess the Marstrom factory guys thought they had solved the problem at this point. So, that spring when new Tornados began arriving in the US and Europe, they all had self tacking jib systems on them with curved jib tracks. Other manufacturers in the US and Europe saw the new jib system on the Tornado and began to copy it. Now all beach cats except Aquarius and Supercat with self tacking jib systems have curved tracks and two controls. The oversight was not realizing the importance of the 4:1 pulley system between the car and the jib clew. With the 4:1 blocks, the jib sheet controls the jib car position and the jib sail shape
in a coordinated fashion. What could be better than that?
With the straight jib track as the jib sheet tension changes both the jib car position changes and angle of attack of the wind on the sail changes in a perfectly coordinated way, sail shape and angle of attack. With the straight track there is a (delta sheet tension/delta angle of attack term) with a real value, real ratio, that can be both positive and negative. The 4:1 pulley system makes the jib sail shape and wind angle of attack on the jib dance together in harmony. With the curved track, Tornado style, this term is zero and a second jib system control line is required. Calculus can do nice things can't it.
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Re: What are the benefits of a self tacking jib?

Post by SC15Av8or »

Well slap me silly and pour me another beer!! Damn there are some real darn tootin smart folk on here that got it all figured out for us commoners !!! Gonna have to get me some 1x2's and pullies and see what I can rig up on my lil sailing boats !!
Lifes 2 short for cheap GROG
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Re: What are the benefits of a self tacking jib?

Post by havliii »

Bill, there are many days that I sail without the jib (per your earlier advice on this board) white capping conditions and beyond. Is there a wind speed that you would douse the self tacking jib or, rephrasing the question, is there an wind range where the self tacker becomes a moot point? I don't have any issues tacking the Supercats, with or without the jib, boards up or down. Okay, occasionally I'll stall a tack when I get slapped by a big breaker that pushes the bows back to leeward, but that's my bad for not picking a more opportune time to tack.


Love your posts, keep em coming
Mac M
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Re: What are the benefits of a self tacking jib?

Post by Mac M »

Bill,

The factory also offers a curved track for the self tacking set up, I have this on my 20. So the straight track is better than the curved Aquarius offers?

I have the straight track on my 17 (pictured above).
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