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northoceanbeach 03-27-2008 07:51 AM

sailing with jib only
 
I was cruising downwind a little today and left only the genoa up. If this fine practice? SOmeone told me not to do it upwind because it puts bad pressure on the mast. I'm not sure if he knows what he's talking about or not. But I'll not do it until I know it's okay. Was fun going downwind. Was very relaxing.
Thanks.

Zanshin 03-27-2008 07:56 AM

You will probably notice that if you only have the jib up when going upwind that there is enormous pressure on your rudder/tiller that will only go away when you balance the sails by raising the main. Also, your speed upwind will be much slower with only the jib as the venturi effect with the main gives it a lot of it's power.
Going straight downwind you being pulled by the jib so not having a main up doesn't make too much of a difference and doesn't put any undue pressure on the boat.

Sapperwhite 03-27-2008 08:24 AM

I like sailing downwind with just the genoa. It pulls the boat along and gives me a more stable feel. My main also blankets the genoa, and reduces its efficiency (unless going wing and wing). It's easy and relaxing to maintain just one sail out.

Going upwind with just the genoa or jib is a bad idea because it will "push" the bow away from the wind. That is the reason you will have the helm pressure that Zanshin is talking about. You will have to work harder to stay on course. The main will balance that "pushing the bow off the wind" effect.

Imagine a picture of your boat looking down from directly above. Find the central point of the boat (relatively). This is like the pivot point when your sails are up. Imagine just the headsail up. The wind will fill that sail and force the boat to turn on that central pivot point. You have to adjust your steering to compensate for that force on the headsail.

Try going upwind with just the jib some day and you'll feel the unbalanced effect. I wouldn't say it would damage anything, just hard to sail that way.

TrueBlue 03-27-2008 09:27 AM

If dead-downwind is feasible, wind direction is steady and not too variable, I typically raise the main to one side and fully extend the Genoa clew off the opposite side with a whisker pole - wing-and-wing. With auto-pilot, I do this even when solo-sailing.

You should find this arrangement to provide the maximum thrust without the otherwise negative effects of the main blanketing the head-sail, or solo difficulties of flying a spinnaker.

maccauley123 03-27-2008 09:41 AM

If I am going to sail with just a single sail up I choose depending on where the wind is.

If sailing upwind I will use just the main. Tacking is really easy since it is essentially self tending and I can point pretty high into the wind with my boat. I have tried upwind with just the jib and while it worked the wind pushed the bow downwind pretty bad. I also found tacking was much harder due to this effect, took longer to recover from the turn and get on the new tack.

If sailing downwind and there is enough consistent wind to keep the sail filled will just use the jib.

I have seen this discussed a few times and the consensus seems to be there is no damage that can be done to the rig. The biggest consideration is what gives the most efficient performance.

Sailormon6 03-27-2008 09:58 AM

Quote:

Originally Posted by northoceanbeach (Post 289904)
I was cruising downwind a little today and left only the genoa up. If this fine practice?

Fine practice? No, but most of us do it. A sloop is designed to perform best with a mainsail and a jib, but sometimes you're sailing downwind for a long ways, and you're tired or lazy, and don't want to raise both sails. You can use either sail alone downwind. Heck, you don't even need a sail to go downwind. A boat with no sails will drift downwind, as will a leaf on a pond.

As others have said, a boat sails best if there is a balance of sail pressure fore and aft of the mast. If you'll experiment with it, you'll find that you can hardly sail to windward at all with a small jib, but you can get by fairly well with a big overlapping jib, like a 150% genoa. The reason is because with the small jib, all the sail pressure is forward of the mast, and it pulls the boat's bow off to leeward with such force that the keel can't resist it. A big genoa overlaps the mast, so that some of it's surface is aft of the mast, and that helps balance the forces on the sail and keel just enough so that the boat can still sail fairly well to windward. The problem with a big sail is that, when you tack, it's much more difficult to tack in very light air than a smaller, non-overlapping sail, because it tends to snag on the rigging as the boat swings across the eye of the wind. So, if you want to sail with only a jib, and you want to be able to work to windward a little, you should use an overlapping jib. Everything I've said assumes that you're sailing in moderate winds. When the wind is blowing hard, if you need to work to windward at all, you want two sails up, because you need the boat to perform its best in those conditions. The only time you should sail in high winds with only a jib is when you will be sailing downwind exclusively.


Quote:

SOmeone told me not to do it upwind because it puts bad pressure on the mast. I'm not sure if he knows what he's talking about or not.
I've heard that, and think it's plain nonsense. A properly supported, well-tuned mast is held erect and in column by it's supporting stays and shrouds, and, unless you're carrying way too much sail area for the windstrength, it shouldn't begin to overstress your rig.

If your rig is not reasonably well-tuned, then the answer is not to avoid doing things that might stress it. The answer is to tune it.

sailingfool 03-27-2008 11:54 AM

Just fine
 
Quote:

Originally Posted by northoceanbeach (Post 289904)
I was cruising downwind a little today and left only the genoa up. If this fine practice? SOmeone told me not to do it upwind because it puts bad pressure on the mast. I'm not sure if he knows what he's talking about or not. But I'll not do it until I know it's okay. Was fun going downwind. Was very relaxing.
Thanks.

Sailing with just a jib is just fine. When beating you are likely to experience lee helm (a tendency to turn away from the wind) and the boat will be more exposed to stalling (losing drive)...but if you anticipate these characteristics you can have a fine day sailing with just the jib...assuming you are working with higher windspeeds where a jib alone provides adequate power. The boat will sail more effecienly with main/jib if you can reef the main, but sometimes doing what is convenient and easy is OK.

Many one-designs such as the Rhodes19 don't have reefable mains, if you find yourself out in mid-20s or higher winds, dropping the main and sailing under jiob only is SOP.

On my 36 if I am leaving the mooring in 20+ knot winds for a short sail, I'll just unroll the jib and leave the main furled and covered.

Faster 03-27-2008 01:10 PM

The ease of deployment offered by almost universal roller furling on headsails has led to an awful lot of people sailing under headsails only much of the time. If you're not racing or not a purist, for the most part it's fine as long as, as mentioned above, balance doesn't become an issue.

Where the "don't do it upwind" school of thought comes from, I believe, is an incident in the Caribbean where apparently 3 charter boats lost their rigs in largish seas on the same day, all sailing headsails only. Sailormon's comment above:

"A properly supported, well-tuned mast is held erect and in column by it's supporting stays and shrouds, and, unless you're carrying way too much sail area for the windstrength, it shouldn't begin to overstress your rig."

is right on... the three boats in question were early versions of the late '90s backstayless rigs from Hunter.

XTR 03-27-2008 03:12 PM

I spent a lot of time last week on a bareboat in BVI trying to find the best downwind combo with just a main and Genoa. The swell made it look as if we were particularly susceptible to gybing if I didn't rig a preventer to go wing and wing and going deep into the wind the main blanketed the genny and it was impossible to keep full.

In the end if I was in a hurry (ok, I never really got in a hurry) or the wind was pretty light I'd rig a preventer and go wing and wing. I did spend a couple of hours rigged that way othwise I'd just drop the main and run on the genny. Just remember to to move the fairleads around to keep the top of the sail from luffing.

JohnRPollard 03-27-2008 03:33 PM

We had a similar discussion last fall:

http://www.sailnet.com/forums/seaman...-only-jib.html


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