How to Trim Your Mainsail on a Catamaran

[Catsoon]

OK Folks- I need some help. I was a monomaraner, and two years ago bought a 1995 FP Athena and brought her here to the SF Bay. I am struggling with how to properly and effectively trim the mainsail. Given the width of the boat, the fact it doesn't heel, doesn't have a boom vang, and has a 20 foot traveller (that's not easily moveable)- I don't think I am optimizing the trim. A few questions:

what visual things should I have installed on the mainsail to assist in trim? Stripes, TellTales, anything else?

what are your main trim mechanisms? Mainsheet vs. Traveller?
What are the right traveller settings? How much does Boom height matter?

It seems like such a basic question- but I'm not getting it yet and would love your opinions? If you want to point me to some good articles or books, I am great with that too!

Thanks! CHRIS

[Adelie]

My experience is on smaller cats. On them we used leech telltales.

Close hualed I would adjust the mainsheet to get all the telltales steaming aft nicely, then bear off to the desired course and adjust the traveller.

With some practice I got to the point where I could steer the desired course, set the traveller about right and then adjust the mainsheet to get the telltales streaming.

[daddle]

It's exactly the same as a monohull (flame resistant suit on, check): Do whatever it takes for speed, safety and comfort. There are no rules about actual position.

Telltails on the upper leech are the most useful.

Make sure everything runs easily so you can easily experiment.

Multis do heel. And you can feel overpowering and weather helm. It just much more subtle.

Main trim has much to do with headsail trim.

You probably need more twist in both sails than you'd ever guess. The telltails will tell you.

Keep the boom up until you have enough power, then lower.

I learned fastest by sailing alongside other cats while racing. Trimmed and watched and felt until we pulled away ahead and to weather.

[Multitalent]

I agree that generally speaking trim is Trim, However...on the cat I believe that the main is a more important driving sail. So always work from fore to aft, i.e. first trim the genoa, then the main, YES you want leech tell tales at each batten pocket. You want those telltales streaming but also be sure you have it strapped in, not just flagging. you will want surprisingly little twist and ALWAYS USE the TRAVELER - rarely but occasionally in light winds, bringing it up above midships. Once set with appropriate twist for the conditions use the traveler when changing course - not the sheet. Of course if you have old blown-out sails there is not much you can do other than boat (break out another thousand [or three])
Have Fun

[Cheechako]

Head the direction you want to go. Crack off the mainsail until it just barely starts to luff behind the mast. For max speed: If on a reach, lower the traveler down to leeward to keep the boom from lifting in the gusts dumping the wind out. For safety: dont lower the traveler down and the boom will lift dumping some pressure off. You should find that not trying to point quite so high with the cat, and reaching for speed will work well. Attaching tell tales on the aft edge at each batten can help with finer tuning also.

[Multitalent]

[QUOTE=Cheechako;698803]. Crack off the mainsail until it just barely starts to luff behind the mast.

if you see luffing behind the mast your sail is blown out - so just enjoy it but do not expect great performance. As to feel- don't be afraid if you see the weather hull lifting just clear of the sea but if you ever see the entire rudder exposed $#!t CUT the SHEET

[cal40john]

As said before start with the jib, trim it. Then position the main traveller to get the lower telltales flying, then use the mainsheet to pull the boom down until the top leech telltale occasionally breaks. The mainsheet, when not grossly loose, sets leech twist, primarily up high. The two controls are interactive, if one needed lots of adjustment, the other is now wrong.

This is no different than a monohull, other than you run out of traveller early as you sail lower and then have to rely on a boom vang to control leech twist.

John

[imagine2frolic]

You can always get behind Adventure Cat, and watch them. If you can keep up that is........i2f

[44'cruisingcat]

Originally Posted by Catsoon

...... and has a 20 foot traveller (that's not easily moveable).......
Thanks! CHRIS

Your traveller should be easy to move. What's the issue here?

[impi]

From a sailor who still has a lot to learn, I found I was sailing with the sheet in too tight - which also made moving the traveller that much more difficult.
Keep the main sheet 'cracked off' a bit, and even more so if the traveller is moving with difficulty.
Standing at the back if the vessel and looking up at the main sail provides a good picture of what's going on.
Sail loose - but not too loose.

[Catsoon]

Thanks for the great replies so far- this forum is Great!

@44"cruisingcat - here are my traveler struggles:

Its the original equipment that came with the boat- some of the angles for how the traveler leads aren't ideal, as you haul it in

The purchase isn't great

But the biggest issue seems to be that as you lower the traveler, the slack leeward traveler line jams in the multicar traveler, or gets caught on a series of things back there - (bimini poles, etc) - I don't have a continuous line that takes up the slack.

What's the best solution- would love to have a kick ass traveler that is easy to adjust since it seems so critical on a cat

Any ideas welcome!!!

[Aussie_Sequoia]

It's posts and questions and answers like these that make me love CF. Excellent sharing of knowledge.

[makana]

The modern catamarans full batten mainsail technology has it's origins from the windsurfing industry. The full batten main and long travler track offers a wide range of options in regards to trim. Sail shape is the defining element in trim, low wind or an "under powered" sail should have a full shape which would requiring an easing out of the main sheet while adjusting the traveler depending on point of sail. The more the wind increases the more the sail should be flattened out by increasing the tension on the main sheet and adjusting the travler. The latest generation cruising mainsails even incorporate the top flat area to twist off in overpoweing wind just like windsurfing sails have been doing for over 10 years. There is an artical in this months Cruising World on catamaran sail trim which suggests not to adjust the main sheet while bearing off, only the traveler??? However when the traveler is moved from any position outside of center, due to the physics of a straight travler the overall effect on sail shape without releasing the main tension would be to flatten the sail when typically you would want a fuller sail, unless your travler has the same curve in relation to the length of your boom. I've found the sails shape on my catamaran to be much more important than exactly where the travler sits. And when I'm tryting to get the most out of my sails I turn off the auto piliot and hand steer.

[Southern Star]

Multitalent, I assume your comment "don't be afraid if you see the weather hull just clear of the sea.." was intended to apply to beach cats, and not the FP Athena that Catsoon was inquiring about. You should NEVER fly a hull in a cruising cat. Indeed, Chris White, who designs very high-preformance cruising cats, has recently come out against one manufacturer who claimed that their boats were designed to fly a hull. If you get into that situation, you are massively overpowered and the problem is one of sail area and not just trim.

Brad

[Multitalent]

Hi Southern Star, my post about heeling in a cat was written with a bit of smile.
In practice you may see the weather Stern just clearing the water when sailing swiftly, this is many feet from actually "flying a hull" which probably is impossible in an Athena, as the sails would rip or the rig fail long before achieving that much power.
Your hulls are most likely only 2 or 3 inches imersion at the sterns - just as you will note "squatting" under power, you will also see some forward pitching moment when under sail, this due to the Center of effort being well up above the boom, so forward force is also pitching force, lifting the stern. about 4' from "flying"
In any case the original post was how to get more performance from his Athena (which is a pretty nice sailing cat as a type) so I suggested; fall off, sheet in, and hold on to your junk.
Sail like you Love it.