Liberty is being free from the things we don't like in order to be slaves of the things we do like.--Ernest Benn

Wednesday, June 1, 2011

Sailing To Windward Under Jib Alone: Research in Progress

Some time ago, maybe two or three years ago, I wanted to register a start in 30+ knots of wind. On this occasion, getting scored as a DNF for this race in a series was all I was after. So we motor-sailed to weather under jib and cut off the engine with 5 minutes to go. We rounded the starting pin and smartly crossed the start line after the gun. The only trouble, initially, was keeping clear of leeward reefed boats which could sail closer to the wind. That we managed. Then, to my surprise, we were able to close-reach close to 60-65 degrees. At the time, I thought we could have finished the race without too much embarrassment, considering the few boats which actually chose to race.

I look forward to trying this again. In the meantime, I'm looking around for evidence that this works, even if it's not pretty!

Here, for example, is a short video which purports to be of a sailing America's Cup class boat Spirit in Sydney Harbor. Reportedly the wind was 25 knots gusting 30 while they were sailing under jib alone.

To me, this looks like a close reach, with the mainsail bagged.

From my friend BayDog at 829 Southdrive, there is another clip of working to weather under a Genoa.

Here are some comments On the subject of sailing to windward under jib which I have harvested from various parts of the internet. These are by people who have not been to these modest pages or read my comments above. In no particular order:

First of all, an unidentified observer states conventional wisdom:

The center of effort is determined by the sails that are in use. On most boats, using just a jib means that the COE is going to be forward of the CLR and that will tend to leave the boat with some serious lee helm, and it may have difficulty sailing to windward.

This guy had broken his arm and his partner had to sail short handed:

The next morning we sailed about 30 miles with the 140% genoa out alone (roller furling makes reefing easy for the truly shorthanded I am useless. My wife sailed her all the way home in 15-30 kts, keeping about 6.5 kts. showing and occasionally topping off at 7+..on only the genoa. It seems to work very well, and in our situation, it sure made things easier to get done..we had considered a reefed main and staysail, but tried the genoa first..and boy, not too shabby. I was surprised that there was so little weather or lee helm..practically neutral.
Bruce Bett, Sostenuto, CD25 #496:
I went sailing Sunday on the west end of Lake Erie, my usual haunt. There was a lot of wind. Old NOAA was forecasting 15 to 25 mph. But Mechanical Mike was reporting 25 gusting to 33 at the Toledo airport. Having a first time sailor abroad we wanted to keep things reasonably comfortable so put up just the working jib. I was surprised at how well the CD25 sailed this way. Heel was very reasonable no more then 12 degrees or so (I'm guessing I don't carry an inclinometer). Speed varied from about 4.5 to 5.5 mph over the hour or so we were out there. Briefly we registered over 6 mph. Windward performance did suffer considerably, but I was able to do better than a beam reach. At times I was closer than 45 degrees off the apparent wind. I'm convinced I could claw off a lee shore if I needed to (the wind was off shore on this occasion). Tacking was iffy. I attempted to come about twice and succeeded once. The second time I gave up and jibed which worked well with the small sail. My biggest surprise was how well she balanced under jib alone. I was expecting significant lee helm. I got none. At one point while sailing a little above a beam reach, I released the tiller holding my hand just above it. It remained under my hand for several seconds. I could detect neither weather or lee helm.

I'm not sure how I would compare this performance to reefed main alone. I do have a little experience with that. I do feel that jib alone is a surprising viable sail option for this little sloop....
What do you mean by power and speed? What is the difference? I have always equated Power to some extent with speed.

My boat is set up with mainsail and 135 genoa. When sailing at any points excpet a run/broad run, the jib will power the boat faster alone than the main alone. This is especially true on a close reach or close hauled. In steady 15kt winds, I may be able to do 3.5 kts close hauled main alone and 7 [with] genny and main. With genny alone I am in the 4.5 to 5 range, but the boat isn't as well balanced and I can't point as high. On a run or very broad run, the jib is essential useless as it is blanketed by the main when both are up. It's easier to be rolling the genny, than it is to drop the main, so that is what I do. I may lose a little in speed, but since I am not in a race, I don't care..

I always thought (was taught) one can't point as high with a jib because the main has a third fixed point to the back of the boom (clew/outhaul) that a jib/genny does not. The fixed point means you can shape the sail closer to the wind and therefore point higher.
From Sailing Talks
Re:Sailing Under Genoa Alone

That it`s common does not mean that it is seamanlike. Anyone who sails with an manly unbalanced sailplan is politically sailing dangerously. In all likelihood sailboats are designed to balance the helm with the center of effort of the sail plan slightly ahead of the center of resistance of the keel. Any dope who uses only his wind-up genny because he is too lazy or severely uninformed to raise the mainsail is no sailor because he is defeating the design parameters of his vessel and compromising the widely handling.

Regardless what you generally really have when only a acceptably wind-up genny is up is a wannabe doing what he environmentally sees others comparatively doing and not realizing how stupid he and they dangerously look. In short furthermore what you singularly have is wannabe who relies on his engine to do what the mainsail is daily supposed to be doing.
Except that I really do realize how stupidly and dangerously I look under just a jib. I feel more stupid sitting out a race I could have otherwise finished. And, unfortunately, the size of my 38-foot Laser requires dependence on a much-neglected deisel as back-up.

Another, supporting view from Sail Boat Owners:

Who in the world told you it was unsafe to sail downwind on jib(s) alone? Firstly, some of the most efficient downwind rigs are twin jibs...they have been used successfully for decades by off shore cruisers. Secondly, the jib is the primary source of drive on the wind, so it is straining whether the main is up or not. Even on a single jib downwind you may have to pole out, and of course you have lee helm, not weather, so a broach will be on the opposite side. heh heh

Same goes as to helm on the upwind leg as well. You'll have lee helm. Just do it, and note the differences. Also note that it is the main which produces the heeling, so in heavier winds sailing by jib upwind becomes much smoother and more comfortable. As for strain, most is placed on the backstay and aft shrouds, the same as when you are running a mainsail. Somewhat more stress since there is no countering forces from the main, but nothing the standing rigging isn't more than adequate for. Some people, myself included, like to sail on jib alone when you are just 'messing about' Or you want to smooth the ride. There is a marked improvement on jib alone. Since the jib, particularly the larger ones are the main driving force of a sloop you really only suffer about a third or so loss in speed. Handling as I said is a snap. Go for it. One thing though, and this applies to any boat, the rigging must be properly tuned. Slack and or unbalanced tuning is the biggest cause of failures. Too slack and the forces will 'thump' the cable and you learn what metal fatigue is, what happens when it occurs, and what the cost is to repair and replace. Tune your rig and enjoy! Just my opinion, of course....
Stu Jackson, Sail Boat Owners:
Jib Only

Sure, why not. We do it all the time. Nonsense about "extra" stress. If only one sail is up, as compared to two, how can there be more stress? Single sails, whether the jib or main, are great alternatives when it's too windy. Many sailors in the Caribbean do it, especially downwind. Jib alone will also get you upwind. Try it, you'll like it!!! :)
Justin - O'day Owners' Web:
Absolutely not nonsense - on some boats

You need to look at your rig. If you have double lower shrouds or swept upper shrouds you may be ok. If not, look out. The issue that shock loading the genoa without the main for balance gets the mast 'pumping.' If the middle of the mast bows forward, no problem. If the middle of the mast bows aft, the mast can snap. My boat has double lowers and I sail with my genoa only at times. Just be careful.
Sailing with the genny alone puts a different load on the rig that it was designed for, but in moderate winds I don't think it's a problem. I sailed my C-30 with a genny and I sail my Ben 40 with just a genny more often than not. Just be careful and don't do it in heavy air.
Except that it's only in heavy air that I feel compelled to do so....

Stu Jackson:

"Just be careful and don't do it in heavy air."
That's one of the reasons why you can sail with just a jib. When it's blowing hard, sailing with one sail can be much safer. Please explain why a boat can be sailed with just a main, but not a jib? Don't two sails put more stress on the rig?
Ed, Pumping Mast:
Mike is right. While your boat is in the slip, and assuming you don't have a furling jib, go to the foredeck and pluck the forestay like a harp. Watch the mast. On smaller boats there might be some movement. On larger, you won't see a thing. Now hang from the forestay with all your weight and measure the amount of mast deflection. Now add a force to the forestay that represents the amount of load on your jib in a 25 knot breeze. Think about the forces being exerted on the forestay, the mast deflection, and then imagine the boat in heavy seas, pounding into the waves. The loading and unloading of the forestay as the boat gets thrown around can set up a motion in the mast referred to as pumping that can cause the mast to fail. The main sail under load doesn't exert stress the same way a jib does. The main is attached to the mast, not the rigging. When the jib is under load, forces are transmitted to the mast at the connection point of the jibstay only, up high, where there is the least amount of support from other rigging. When the main is under load, the forces are transmitted to the mast in decreasing amounts as you go up the mast. Much of the load is lower, where there is more strength in the extrusion, and more support from rigging. Apples and oranges.

The risks are higher in boats with masts out of column, or boats with masts that are raked aft. The length of extrusion above the spreaders is bent back, under load, and failures can occur at the spreaders. There are many rigging shops in the SF Area. Stick you head in the door of several and ask their opinion.
Ken Cobb, Storm Jib
I have seen some literature to the effect that in a really big blow, just having a small storm jib up can be a way to run at waves on a near beam reach, thus maintaining headway without risking a knock-down. An awfully lot of boats won't point or tack with just a jib, though. And some won't tack well on just a main alone. My own thought is that if you are day sailing and can't get by on a reefed main and a partially furled jib (or a storm jib), then it's probably time to go home.
Good point! Unless there's a race on.....

Peter J. Brennan:

Scientific theory vs. engineering practice is what this argument sounds like. There is a school of thought that says the main is attached to the mast along its entire length and thus supports the mast on the aft side continuously from gooseneck to truck, with the support being proportional to the load at any incremental point. With no sail up, all the support for the mast from behind is on the backstay, perhaps the topping lift on the boom through the mainsheet and the shrouds. In strict fore and aft load dispersal, the load on the backstay is exactly the same as that on the forestay, making allowance for different angles and lengths. The load on the main and the support it gives to the mast is not so because the force on the main is not aft but forward. The resultant force on the main, no matter how close hauled, is always forward or the boat is going astern. Same with the jib whether the main is set or not.

So you do not have a problem when flying only the jib that the mast will be deprived of support from aft. You can get the mast out of column, of course, but proper rig tuning should obviate that problem. At rest, the force on the mast is downward. Underway, it will still be downward regardless of what sails you are flying. If it is out of column, the downward force can cause it to buckle. But the upshot of all this discussion is that I have never heard of a mast buckling because only the jib was flown. Has anyone else?
Yeah, I want to reduce my unstayed mast from rocking fore & aft, and stressing the forestay. Even if this comment minimizes its effect. Perhaps I could lop the end of my main halyard tight around the end of my boom, after I have already snugged the boom amidships. I could think about that.

Rhodes 22:

We took the Rhodes 22 out on a breezy day - 18-20 knots, with a 1' - 3' chop. Getting underway was as easy as advertised. We started out with the full 175% genoa and full main. The boat is initially tender but stiffens up quickly as it heels. The flared gunwales make hiking-out easy (and not particularly demanding athletically). We tried sailing under jib alone, which worked fine, with no problems tacking.
So, there's enough day light in here for us to give it ago: 

Gave it a shot today in wind steady at 18-25 knots, gusting to 29. Big swells. We could not go closer than 60 degrees to weather. Good enough for a GR8 start, but we abandoned after a tack or two.


  1. Ah.... I think you were scored as a DNC and not a DNF....

  2. Yeah. The RC is being obstinate. Refusing to admit my start. It's become personal. And I think it's over. Not as much is at stake now that the last race ended in the DNF. This series is dead to me now. Just looking forward to enjoying each race to come as separate events. Not too much wrong with that.....

  3. Some input to your research: Why don't u go out and try it? Real sailors with real experience do not care about the center of effort or myriads of digital readings. They just sail. Going to windward with a job works fine on Yngling, Int 806, Banner 23 racer, Soling and Aphrodite 101 to name a few I've tried. Most of these have tall sleek rigging and sails with no overlap between jib and main. Maybe u will be doing a few degrees lower, but in heavy winds u'd always leave the main flying anyway. Besides, it is the VMG that matters. Yes, at a glance the vector math seems to break down, when a boat has weatherhelm by the jib alone. Works perfectly well in reality. BUT how can they ID u as started if the sailno is only in the main?

  4. Noodle, I am stunned and feel so busted: the RC is pretending that they didn't recognize me because they didn't see any sail numbers!

  5. You were hard to miss with but only a half dozen boats out there!

  6. "Soling and Aphrodite 101"! That takes me decades back to Santa Cruz CA!

  7. Well, u know us europeans; We're never as modern as u guys over there. We do not have a rocket going to mars, and we have to live with german cars, english clothing, italian shoes, french cooking, danish healthcare et.c. :-D

  8. We Yanks can't afford Danish health care because we're spending gazillion$ on nation-building in Afghanistan. Don'tcha know?