Sail Trim

As a follow on to the spin discussion I thought I would post my somewhat unusual thoughts on sail trim here to start a discussion. For me it's all about boat balance, a balanced boat is a happy, fast, easy to sail boat. The indicator of your boat balance is your rudder, as this is the counterbalance to the other forces acting on the boat. You can balance the feel of the rudder (tiller or wheel) by adjusting the sails and crew weight. The target is a very slight weather helm (2-3 degrees) and a light, positive, controlled feel. What follows is the basics of how to do that.

Sail trim for the blind, deaf and dumb, literally:

Hold the tiller in your hand, strike a steady course to windward take a couple of deep breaths, feel the movement of the boat through your seat, then close your eyes. That's right. Feel the tiller in your hand. How does it feel?

- inert, ie totally neutral. ok, you need at least some weather helm, get more sail power aft. power up the main and depower the jib/genny.

- lee helm - ok, problems here, you need to move sail power aft now! same sorts of stuff as neutral helm but more drastic

- strong weather helm, boat is fighting you - time to move sail power forward! depower main now, and maybe power up genny if appropriate.

- strong lee helm - ok, you must reef or drop that jib/jenny now! oops, you forgot to raise the main, do that now.

- light weather helm, boat feels responsive and in control - smile you are in the fast lane. Now open your eyes, you're gonna hit that DUCK!!

other points of sail have their own special subtly, but they can all be deduced with your eyes closed. start there, a balanced boat is a happy and fast boat. the balance shows at the tiller.

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Wacked notes on 'sail power'. (this is just to set down a point of departure for the conversation - kibitzers join in!) for example: increasing sailpower in the genny moves the total sail power foward. here are the effects of the control on the sail power of the sail they control.

Main (aft power)
outhaul ( tightening - | ease + )
sheet ( tightening + | ease - )
traveler ( to windward + | to leeward - )
cunningham ( tighten - | ease + )
vang ( tighten - | ease + )
reef ( in - | out + )
halyard ( tighten - | ease + | drop -- | raise ++ )

Genny (fore power)
sheet ( tighten + | ease - )
reef ( in - | out + )
halyard ( tighten - | ease + | drop -- | raise ++ )

Crew weight effect on balance
goes in direction opposite of the movement of power, ie
you need to move sail power aft, move crew weight fore.

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So, which control do you use once you figure out what you need to do to balance? Easiest way is probably to look at the sail shape, the telltales, etc. To really understand how boat balance works in relationship to sail trim you need to spend serious time sailing without using the tiller, either lash it down or let it swing free. everything starts and ends at the tiller IMHO.

Hope that is useful or at least starts a good argument!

I've been wondering about the relative effects of these trims, and have been trying to wrap my head around the use of the traveler, as in the classes I took we kept it centered and just used the mainsheet. I've been reading through the Annapolis book lately but it's a lot of information to digest -- and I find myself debating the purchase of a boat with a a fairly lame implemention -- a Catalina 25.

Catalina 25.

Get the version with the tall mast option and fixed keel for here in Puget Sound (unless you are gonna trailer it), it aint a bad boat for a cruiser. Windworks has a bunch of the Catalina 25s and they a lot of fun to knock about in, pretty big interior for that size boat.

Alas this one I was looking at was the standard rig, but definitely fixed keel.

Todd -

Great discussion! Thank you for bringing your experience to the forum like this. This is the kind of informtion that many of us come to this group to learn.

I thought I would add a book title to this thread for those who may be interested. I found this information to be very helpful in understanding how to shape sails to work with the wind at hand:

Illistrated Sail & Rig Tuning
By Ivar Dedekam

Jake

One other tip I would add would be reefing and weather helm…

My ASA instructor gave me this tip a while back during a heavy weather exercises and I thougth I would add it to this discussion since it relates to trim.

So, We have all been there: you are on a beat (close hauled) , the apparent wind is high, we got serious heal and weather helm – but the situation isn’t dangerous. You are moving along at a good clip but you spend most of the time managing the tiller (weather helm). Do you reef? ASA would say “yes.” Why? You can get better speed in situations with heavy weather helm by reducing sail an straightening your rudder. Reducing sail lowers weather helm allowing you to reduce the amount of helm you use to keep your course true. Essentially, you trade sail area for a straight rudder – which reduces the friction or “breaking force” of compensating your rudder for weather helm.

ASA has a great article about this in their Autumn 2008 issue. LMK if you would like a copy!

Found this link googling for other info. It expounds the same ideas, but better and with pictures. :D