Do the lines on a sail have a purpose? (Newb question)

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NotBirdseye

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I've been looking all over for an answer and if I ask three different sailors somehow I get six different answers. Unfortunately my google-fu has failed me.

I understand that some lines are basically marks where the 'rib' is slotted in to help the sail keep its shape, otherwise reefing points with a flappy thing (technical term) at the end (mainsail). On the same mainsail some have diagonal lines as well.

Likewise there's a bunch of lines on the foresail I have no idea what they mean or how I'm supposed to use them (if I'm supposed to use them). Any assistance (or heck link) much appreciated :).
 
Most cruising boats now tend to have fully-battened mains, with the battens forming around four lines the width of the sail. A while ago, black lines were introduced as an aid to judging the shape of the sail, though the battens now serve much the same purpose. How important you regard the shape of the sail depends on how you sail. Some sailors would be happy to put up their granny's old sheets but racers tend to be fussier, and always have been. If you look at old photos of prewar racing yachts with cotton sails you will see multi-panelled sails of great beauty.
 
LadyInBed said:
Do you mean marks like this. See Yachting Monthly article HERE about Sail Reefing.

View attachment 81050
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Ah nope. If you look at the image in the article you linked to you'll notice (or probably never have looked at before) two lines going to the very edge of the sail. They could quite easily be panels stitched together, though quite why in that shape I have no idea. The drafting lines fits so far.
 
Luminescent said:
two lines going to the very edge of the sail
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If we're talking about the zigzag lines of stitches then yes, these are where panels are stitched together. By making a sail out of many panels it's possible to make the individual panels slightly wider in the middle, so that when stitched together the whole sail is not flat but has a curved, wing-like shape.

In the simplest and cheapest sails the panels are all just horizontal, but this means that diagonal stresses across the sail from the corners pull diagonally across the weave of the sailcloth, in which direction it gives most, which makes the sail stretchy. For maximum stiffness you want the stress to pull along the line of the main sailcloth threads. So you see lots of sails with 'radial' cut, where the panels radiate out from the corner so that each panel's main threads are in line with the stress.

And of course the corners have more stress in less sail width so they tend to have reinforcing extra thicknesses added, and those panels are joined by multiple lines of stitches to make sure the stresses on the main panels are spread to the reinforcement panels.
 
Luminescent said:
Likewise there's a bunch of lines on the foresail I have no idea what they mean or how I'm supposed to use them (if I'm supposed to use them). Any assistance (or heck link) much appreciated :).
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If you mean short lengths of fine wool or cord; then these are tell tales that tell you how the wind is balanced over the luff of the sail.
If they are on the leech of the main they are an indication of how the wind is exiting the sail & if it is stalling etc.
Isuggest you go on youtube & look for some items on sail trim.
 
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If you're talking about lines, meaning thin ropes, which run in a pocket down the edge/s of sails and which can be tightened or loosened onto a cleat or similar, then those lines are for altering the tension in the edge of the sail and, hence, the shape of the sail. :)

As I type this there's an item on the news about County lines ..... but I think we can rule those out. :o

Richard
 
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