Mainsail twist & traveller position - SailNet Community
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post #1 of 34 Old 03-08-2015 Thread Starter
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Question Mainsail twist & traveller position

I think I may have been setting my main sheet traveler wrongly last year. I didn't have a grip on the idea of sail twist, and how it dumps wind at the top of the sail.

Tell me if this sounds correct: In light winds have the traveller to lee in order to pull down more on the boom, reduce twist and therefore get more power from the mainsail. Also, snug the vang. In heavier winds, traveller to windward and vang eased will allow the boom to rise up giving more twist at the top of the sail, ergo spilling wind and de-powering the main.

Does that sound right?

The Walrus, Collins Bay, Lake ON
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post #2 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

No. Generally, to sail closehauled in light to moderate winds, the traveler should be set along the centerline, with the boom approximately pointing at the backstay. The vang should be set with light tension. To set the twist, the top sail batten should be parallel to the boom.

In stronger winds, when the boat begins to heel excessively, flatten the mainsail by increasing luff tension and outhaul tension, ease the traveler to leeward in the gusts, and then bring it up to windward in the lulls, but never with the boom further to windward than the centerline. If the boat has an adjustable backstay, I also increase backstay tension. I suggest that, when you are playing the traveler up and down in the gusts and lulls, you watch the knotmeter to see how each adjustment affects boatspeed.

Generally, increasing twist increases power, and you might decide to increase the twist slightly to help power the boat through a chop, but I don't recommend letting the top of the sail twist off to keep the boat on it's feet. IMO, if you have used all the sail trim techniques to flatten the sail, and the boat is still overpowered, then the better choice is to begin reducing sail area.
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Last edited by Sailormon6; 03-09-2015 at 12:50 AM.
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post #3 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

You may find this write-up by Jeff_H useful:

Proper use of the Traveler
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post #4 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

If you don't have leech telltales buy a set, they're cheap and make a big difference.

Basic starting point I use with new main trimmers is boom on the centerline and the tail end of the top batten pointing backwards parallel to the boom, then get the telltales flying, especially the top one.

On Kraken the backstay is critical both to reducing power and to pointing ability. When we see a gust coming we starting pulling the backstay on to avoid overpowering and as the gust eases ease. When we need to point we apply backstay, but only once up to speed.

Also - listen to Jeff_H


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post #5 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

Nope. You are 100% doing the wrong thing. It might be your basic philosophy, not your trimming. Heh.

It is never the position of sail controls that is interesting. It is only the shape of the sails that is beneficial. It's a mindset. You manipulate the controls to put the sails in the position that makes the boat do what your want. Usually what you want is to go fast, comfortably. It's almost Zen. Do what you have to do with the traveller and such to get the job done.

Back in reality...what you are doing is controlling the power. First decide if you want more power (light winds compared to the seas) or less power (plenty of wind for the conditions). Travellers come in a wide variety of positions, lengths and controls. There's the sheet and vang too. So what you do with which is, again, whatever it takes to get the sail shape.

Assuming it is a windward issue, for max power from the wind the clew of the main is normally on the centerline of the hull. Only above centerline in fussy pointing situations. Generally. generally. Then to reduce power the clew is eased down to leeward. For max windward power I have the top batten of the main pointing straight aft. Generally.

Yeah, twist, you generally cannot get enough. This is produced by reducing tension in the leech - without changing the lateral position of the boom. What you need depends on the headsail. Which is a whole 'nother story.

"...there are two kinds of opinions, those based upon tradition ... and those having something in their favor." B. Russell

Last edited by aloof; 03-09-2015 at 03:31 AM.
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post #6 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

It all seems so complicated when you read it - and so much simpler when sailing.

Get an expert to show you on your boat.

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post #7 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

In light winds the sail is nice and floppy with lots of curves (think of a planes wing with flaps down).
In stronger winds the sail nice and tight and as flat as possible (think of a plane a full speed, the flaps will be up. A plane can not go full speed with flaps down as they act like a brake).

The mainsheet can make the sail flat, then you can adjust the sail to leeward with the traveler so the flat shape can be kept whilst running the boom out a bit.

One of the great benefits of racing is you can see how other boats set their sails.

And copy them


When you are stopped, say after a tack, you need to have lots of curve in your sails and as you pick up boat speed you flatten the sails more and more according to the wind.


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post #8 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

If the sail is woven dacron, and its reasonably new .... the amount of twist that the sailmaker designed into the sail will be appropriate for beating with the traveller set ON the centerline for normal (12-15 kts. of windstrength). All youll have to do when beating and the traveller ON the centerline is to pull enough mainsheet tension so that the leech at the second from the top battens is parallel to the boats centerline.
At less than 12-15kts, the traveller get pulled up to windward and above 15kts you begin to drop the traveller.
Sailmakers are sometimes 'smarter' than sailors .... especially with inbuilt 'twist' already included in their design parameters.


Tell Tale usage ( a sequence of articles):
http://www.ftp.tognews.com/Publicati...n_the_Wind.pdf
http://www.ftp.tognews.com/Publicati...er_Balance.pdf
http://www.ftp.tognews.com/Publicati...o_Windward.pdf
http://www.ftp.tognews.com/Publicati...timum_Trim.pdf
Note: the above listed are the core 'source' documents for tell tale usage that essentially ALL sailing authors use.

Blown out dacron mainsails, shrunken boltropes and achieving proper weather helm, etc.:
How to properly RAISE a woven dacron mainsail - SailboatOwners.com see post#1
Do this BEFORE you do the above, as this 'sets' the basic sail shape (for woven dacron sails) ... if you dont do this, the sail will 99% of the time be 'set' in a draft-aft SHAPE ... aggressive heeling, slow, cant point worth squat, etc.)

The only thing missing in the above 'capsules' is to set the amount of outhaul tension vs. MAXIMUM speed (on the speedo when beating) which will automatically adjust the amount of draft for the day's wind & seastate conditions (flattened or 'powered-up' for the days requirements - outhaul adjustment).
Once you get to this basic plateau, its just small tweaks, etc. to maintain the 'optimum output' ...... for both racing and cruising.

hope this helps

Last edited by RichH; 03-12-2015 at 02:45 AM.
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post #9 of 34 Old 03-09-2015 Thread Starter
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Re: Mainsail twist & traveller position

Okay, thanks for all the interest and replies
  • The Walrus does have a nice tensioner on the backstay
  • There are telltails on the main leach
  • Main traveller is about 6 feet (2m)



As it would turn out I was setting the traveler correctly last year - just not for the right reasons. (light wind to windward, stronger to lee) Most of the time the headsail telltails were all 3 flying. Occasionally the top one would stubbornly snake about - though the article says this is not always a bad thing.

Sorry Aloof, I am a novice and need the "cause & effect" of rote practice until I can set the headsail by sheer will-of-mind

On my breaks at work so far I've had time to read the article from Mr F.

So it seems twist in the mainsail is different than twist in the headsail. Twist in the main will accomodate the difference in wind direction at the mast head in order to keep the whole sail trimmed correctly. Head sail twist can be used to dump wind when over powered.

Question: It does occur to me though that it would take a lot of downward pull on the boom to keep the top batten parallel with the boom as was suggested in a couple replies.

The Walrus has 4 full batten, see the thumbnail attached (friend and PO John at the helm)
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The Walrus, Collins Bay, Lake ON
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post #10 of 34 Old 03-09-2015
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Re: Mainsail twist & traveller position

Uh oh you just brought the headsail into it..


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