How do you set sails correctly?

[Norman_E]

After 5 seasons with my boat I think I am getting it right more than I get it wrong, and for most of us I suspect that it is a trial and error learning curve. At LIBS I bought the RYA Sail Trim Handbook for Cruisers by Rob Gibson. It seems to be pretty good, particularly on the basics of getting the rig set up right.

 

[Little Rascal]

....thinking about the effect that halyard tension has on shape? And how many people adjust the tension when the wind builds / drops?

Get the basic aerofoil shapes right, and you can build from there....

More luff tension = moves draft forward

So
More luff tension for
Heavy winds
Rough water
Upwind
Drift conditions

Sound right?


Saying that I don't think my baggy sails notice what I do with the halyard anyway

 

[GruffT]

If in doubt let it out.

+1
In combination with my personal fave.... "a flappy sail is not a happy sail".

Or in a slightly more scientific way...(but only slightly)... oh and I talk of sloops here....
a) sails act in 1 of 2 ways, 1) an aerofoil (jib/genona/main upwind & spinnaker) or 2) an air damn (white sails downwind). Most "trim" is concerning 1). Downwind, white sail trim generally reacts well to projecting as much surface area of a "bag" of sail to the wind as possible. ease out and hold the clew down (pole out your headsail). make it nice and deep.

b) upwind - a more curved shape (often called deeper) is more "powerful" than a flatter one. Choose which suits the conditions you're experiencing, including considering sea state. Sometimes it's better to reduce canvas and go for power rather than to keep canvas up and flatten to depower (in chop for example). In flat water, you should be a little quicker and higher with flat sails and more canvas. (it's to do with drag but that's not important right now).

c) upwind - sail angle should be "roughly" aligned so that the angle of the front of the sail is aligned to the wind flow. this is what you're seeing when the tell tales flow horizontally both sides of the sail. Then they spin or hang the air flow is disturbed on that side. If the inside telltale is dancing, the forestay is interfering with the air flow on the inside so bear off a little, go too far and the outside one will dance as air can't get around (you may have to look for that thou. ;-) ). When beating, align the boom* on the centreline and steer the boat to manage this. On a reach - play the sheets.

* if using twist (see e) ), align the approx 1/3 up the sail leech to the centreline. The boom may be above it.

c) balance your sail plan. the foresails and main sail are in the same air and interact. generally their trim should follow each other. See b)!

d) generally, more tension = flatter sail. Here look across the whole sail. Is one bit very flat and one bit very deep? What am I pulling it with? Do i need to adjust the angle of the sheet (ie genoa car) to get more tension higher up and release some tension lower down? Don't forget halyards too. Get on board and play with the bits of string one at a time and see what they do. On the main you're looking to try and achieve a nice "smile" when you look up the sail. You may well have a handy coloured band or seam to help you see this. On the foresail, go for a nice round shape from the forestay to the sheet (not too much halyard tension). Make this shape too "hard" and it'll make staying in the groove tricky.

e) twist is your friend. (twist = tighter at the bottom than at the top so the shape seems to "twist" off at the top). It's like a release valve on a pressure cooker and reacts to changes in wind strength way faster than you will. for main, set with sheet tension and your traveller, for foresail, move your cars, back = more twist, forward = less (see point d) )

Gosh - I've gone on a bit. I'm sure I've missed a load of things too or plain got them wrong, but hope this is helpful to some.

For (much) more detail, I'd recommend the North U Trim book (http://www.amazon.co.uk/North-Trim-Book-Racing/dp/0972436111). Great resource on all aspects of trim and boat handling. OK it's racing biased but it's all applicable to all sailing and it's in a format that you can just read the bit you want to.

Two things to bear in mind is that quite a lot of sail trim literature is focused on racers with nice shiney new (exotic) sails. I suspect that flattening to depower the main by cranking on the outhaul, backstay, haliyard and cunningham won't do much if your sails resemble a tired old hanky. I once cranked on the mainsheet to close the leech on a charter boat only to notice the boom had twisted to an alarming 30 degrees. I let that off sharpish. Similarly a couple of rolls on a roller furler and the tell tales aren't going to tell you much.

Also don't underestimate the rig setup. Having suitable stay and shroud tensions for the conditions (and equal on both sides!) can make a huge difference. Fractional sloop rigs are particularly sensitive to backstay. But that's another thread....

Or get a coach.

 

[ianat182]

I can recommend Lawrie Smith's Book "Tuning Yachts and Small Sailboats" available from Amazon( ref.97809067754351) Liberally filled with descriptions,explanations and photographs of examples of sail trim in various sailing situations.

He was a 6metre World Champion and J24 Eurpean championship winner, and a very good Merlin Rocket sailor I recall.

ianat182

 

[Twister_Ken]

I can recommend Lawrie Smith's Book "Tuning Yachts and Small Sailboats" available from Amazon( ref.97809067754351) Liberally filled with descriptions,explanations and photographs of examples of sail trim in various sailing situations.

He was a 6metre World Champion and J24 Eurpean championship winner, and a very good Merlin Rocket sailor I recall.

ianat182

Didn't do badly in Big Boats either.

 

[Clyde_Wanderer]

Another good book on the subject is; Sails for cruising, Trim to perfection. 2nd addition, by Mark Chisnell, Fernhurst books.
ISBN 1 904475 04 3. supported by Hyde Sails.
C_W

 

[Babylon]

Or in a slightly more scientific way...
a) ...
b) ...
c) ...
d) ...
e)...

Thanks for your effort in posting that - it has added to my understanding.

I'm one of those people who need to know why one needs to do something, and not just the fact that it needs doing. So an explanation of the principles and how they need varying in different conditions and points of sail, followed by the controls available to achieve all this, is most useful.

The problem however with the 'scientific approach' is that, sometimes, say when the wind is a tad flukey, you don't know whether you've slowed right down because you've pulled on the wrong bit of string - or just because the wind is playing silly-boggers!

My own easy-to-remember rules of thumb are:
- trim the sail nearest the wind first,
- if in doubt, let it out,
- luff in a puff
- I'm not trying to win!

 

[Storyline]

There seems to be many books on the subject.
A good basic starter is "How to trim Sails" by Peter Schweer (Sheridan House)
It has a really useful set of trimming tables - for differing wind strengths and directions you can quickly see how the genoa car, mainsheet traveller, kicker etc should set up. When you know they are all correct it is easier to start to tweak other things.

 

[LouisBrowne]

I would add to what the others have said that it is a good idea to have marks or numbers e.g. on the deck for halyard tension, on the boom for outhaul tension and beside the genoa tracks. When, as the original poster says, the boat is flying along, you can record the settings and replicate them next time you have similar conditions.

As to not cleating sheets and trimming constantly, I think that is good advice for sailing off the wind since then one is sailing in a straight line, but for upwind sailing my approach would be to set up the jib as you think it should be and then steer to the telltales; leave the jib unless the conditions change and the trim has to be altered e.g. a bad set of waves. The mainsail, on the other hand, may need regular adjustment to keep the angle of heel constant.