Jib Power

[HAL]

How far can you roll the jib and still expect some reasonable amount of power for the square footage left? To be specific, this would be a 110, not something bigger that would make a big luff when mostly rolled?
So what is reasonable, is much below 50% adding more heel and drag than power or 33% or 25% or is anything that's out there adding some power no matter how small.

 

[Rich (P303)]

How far can you roll the jib and still expect some reasonable amount of power for the square footage left? To be specific, this would be a 110, not something bigger that would make a big luff when mostly rolled?
So what is reasonable, is much below 50% adding more heel and drag than power or 33% or 25% or is anything that's out there adding some power no matter how small.

Looks like a question for the sail trim department on this site.

Depends on the sail... some are made for furlers... some are just regular headsails that people "think" can go on furlers.

I would imagine you could go down 35%... then on to a storm sail. This is just a rough guess.

 

[sailaway78]

Furling

Agree that this might be better placed on the sail trim board. I think it depends on several things. There would be a difference between a fractional and a mast head rig. Many sail makers also now are offering a foam luff strip, that helps keep sail shape when furled. Point of sail would also be a factor. Personally I have never tried anything below 60% or so, on a masthead rid. At that point there is still some decent power.

 

[sailingdog]

HAL-

It really depends on how the sail was cut, the type of roller furling unit, and whether the sail has foam or rope luff padding added to it, how much sag the forestay has, etc...

Generally, most will reef down about 30-35% without losing shape horribly... but with a rope/foam luff pad added, you can probably go down a bit more, say 50% or so. Some furlers, like the Harken Mk IV do a better job of it than others.

 

[RichH]

Most roller furling sails can only be reduced by 30% and still have 'decent' shape.

There are supposedly 'new' roller-furlers (Harken) that can do better; but, Ive been there before too many times (aero luff, 'special luff shape', slit luff support tapes) and have yet to see anyone reduce more than an honest 30% and still get decent sail shape.

If you are starting fresh and having a new jib made, then there are 'special shapes' that can be cut into the luff and without foam luffs, etc. that can do better than 30% reduction on a standard furler, etc.

 

[newly anonymous]

five turns

although you'll often see the figure that a sail will only hold it's shape at 80% of its build, I'm skeptical of this claim, especially because sail A is going to be cut with a flatter luff than sail B. I've found that most headsails I've owned will hold their shape to some degree up till about 5 wraps around the headfoil. After that, even the flattest of sails will significantly lose their ability to point.

Clearly, the more you shorten a sail, the more you compromise its shape. Take a number 1 (150% of J) down to a number 3 (100% of J), and you might as well just roll the sail all the way up.

Downwind, of course, is a totally different story.

 

[gmeyerga]

jib furl

How far can you roll the jib and still expect some reasonable amount of power for the square footage left? To be specific, this would be a 110, not something bigger that would make a big luff when mostly rolled?
So what is reasonable, is much below 50% adding more heel and drag than power or 33% or 25% or is anything that's out there adding some power no matter how small.

my 110 jib has a foam luff. but with snap shackle jib sheet blocks on the toe rail i usually don't go to the trouble of resetting them when i roll in the jib. so the more i roll in the jib the less i can point. if the jib sets, no matter what size, i get power, i just may not be on my preferred course. stretching the jib is another matter. i think it suffers damage when frequently rolled in over 20 (?) %.
i have been surprised at how well the boat (h27) goes upwind in a breeze under full jib alone which is a convenient alternative to reefing the main.. {let me add, i have forward and backward mast stays and therefore don't worry about the mast coming down.)

 

[Capt. Ed]

Re: jib furl

All good points .But as the sail gets reefed you also have to move the blocks leading the sheets aft. If you don't you defeat the reef by imparting a belly in the sail .My experience is ,if you need a sail that will reef,let the sail maker know . Then I find about 80% is good then you look at reefing the main .

 

[ITMaster]

I Have a 155% Genoa

for my head sail. In very high winds, I can reduce my head sail usually down to what would be about 80 to 90% or even less. By then, I have usually reefed the main by three reefs and have put the head sail away. Like was said, the fairleads go as far forward as they can.

I have three luff cords in lieu of the foam. In addition, I have multiple tell tales on the sail, so that when I furl up the sail, I can still watch the flow of the air. The cords do an excellent job of helping the sail get rolled up nice and tight without the bulge similar to the way a football looks.

 

[sailingdog]

Why would you move the blocks aft??? They're already effectively being moved aft relative to the sail's clew as the sail is reefed. If anything, you'd probably have to move them FORWARD, since you're effectively dealing with a much smaller sail.

All good points .But as the sail gets reefed you also have to move the blocks leading the sheets aft. If you don't you defeat the reef by imparting a belly in the sail .My experience is ,if you need a sail that will reef,let the sail maker know . Then I find about 80% is good then you look at reefing the main .

 

[HAL]

Thanks

Thanks for your ideas.
Lots of variables to this, cut of sail, sag, type of furler, types of luff, fairlead position and of course point of sail. Apparently I can’t expect to take a whole lot off and still have it work well up wind. I was looking at it wrong, it’s really more of a furler than a continuously variable reefer. Forgot about sail trim forum at the time.

 

[Capt. Ed]

Re: jib furl

Mis stated mis read of course the blocks go forward

 

[Don Guillette]

Jib Furling.

With a 110 you really don't have a lot of sail to play with from a power standpoint. Experiment with it and see what you come up with and be sure to mark your setting so the next time your in a furling situation you don't have to guess about the point of no return.