Cruising Cat Sail Trim

[monte]

Gday, Im curious on others thoughts on sail trim in a cat. We have a Lagoon 400 and I find the headsail trim effects speed quite a bit, but not so much the main trim. Interested to hear how much others adjust and tweak the sails for maximum speeds. Here is a good starting point for discussion
Twixter -Â* Sail Trim & Reefing
Ive found adjusting the traveller as shown on that page does very little and I rarely move it from the centre, perhaps when running downwind to hold the boom more still and prevent gybes I would move it all the way to leeward.
Also an interesting polar if anyone wants to comment/compare to their experience is here
Twixter -Â* Performance
(thanks Twixter)

[Factor]

Traveller on my boat is critical, absolutely imperative in getting performance and in dumping drive'

[monte]

Do you use it similar to Twixters diagrams? Pull it to windward when beating to add twist and loosen the mainsheet?

[DRS]

Generally have the traveler 12 to 18 inches to windward and use the main sheets to adjust from there. I like the info in the twixter link. Thanks for posting it

[monte]

Thanks DRS, why do you have it to windward? To allow the boom to lift and the sail to twist at the top? Do you have the boom around the centre of the boat?
Do you notice any performance improvement doing that instead of leaving the traveller central and sheeting the main in tight?
As I said I don't see any difference, perhaps our square top main behaves differently, twisting more than a standard cut sail.
Something I've also noticed is the jib likes to breathe more than I am used to. Normally on a homie 18 or racing mono I would sheet in a lot more, but best speeds seem to be when the upper leech is very soft and fluttering at most points of sail (close hauled to broad reach..

[belizesailor]

Originally Posted by monte

.....

Something I've also noticed is the jib likes to breathe more than I am used to. Normally on a homie 18 or racing mono I would sheet in a lot more, but best speeds seem to be when the upper leech is very soft and fluttering at most points of sail (close hauled to broad reach..

Yes, makes a big difference on most crusing cats, but most are not set up well to adjust jib clew position. A simple barberhauler helps a lot.

Most cruising cats have jib car tracks that are only well located for a limited range of points-of-sail (usually close haul to close reach). With such wide beam its not practical to have a fixed track ideal for every angle...you would need several on the deck. But a barberhauler can come in very handy for positioning the jib clew so that the slot can "breathe".

You can use a barberhauler, in combination with the jib sheet, to adjust clew position inboard/outboad. This allows you to open the slot, but still maintain good trim/shape, without losing proper tension/shape in the leech.

[Factor]

Only time traveller is to windward is in really light stuff. And even then only just enough to bring the boom to centre line. At almost all other times its out a bit/a lot. Short rule of thumb on most multis, Is traveller out and sheet on.

Its going to depend on the boat and the sails, But 2/3 to windward in close reaching - nope. Get out and try it and change trim and watch boat speed.

I t appears Mr Twixter has his traveller to windward more often than not, as I said, I suppose it depends on the boat, but that wont work for my boat or any that I have sailed/raced. And I have sailed Lagoon 440 and whilst the weight and hull beam issues mean the response is often slow and delayed, I still found traveller out sheet on to work reasonably well.

[Hoofsmit]

Belizesailor is spot on with the barber hauler , on the 380 we chartered the 7+ year old genoa was hopeless until we set up a dock line to the mid ships cleat, it did mean the tacks took a bit more manual input !

We found the main, hard sheeted , but with the traveller to leeward by a few inches created the best slot but with a bit of backing on the luff created the best slot and performance, but , as with the 400 it was never built as a racer!!!


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[Hoofsmit]

Ha sorry Factor
We were obviously typing at the same time


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[thinwater]

My advice is to ignor Twixter's postings. He is over trimmed much of the time and it really shows on the speed polar. My PDQ 32/34 is faster, even though he has 10 feet of water line on me. The polar also has some very odd shapes; not too poor to windward, but much slower on a reach and deep reaching than he should be, with some odd dead spots.

a. Cruising cats suffer from windage and poor foils, but we have beam for smart sheeting; use it.

b. Because the foils are low aspect, it seldom makes sence to sheet as hard as a mono. Specifically, this means the traveler goes down bit by bit with reefs, and certainly goes down reefing, when you want the force FORWARD.

c. The trim of BOTH sails matters very much. You will only fully understand that after you tweak them both.

There are better information sorces. The best learning method is to get next to another boat of similar potencial and try to keep-up or pass. The most certain thing about rules-of-thumb is that they are boat-specific and rig-specific; without more information they can lead you down wrong paths. I have sailed many cats for many years, and the variation is considerable. But only the vary fastest cats keep the beam centered on a beam-reach; they can do this because the apparent wind hasn't shifted much (they are sailing over wind speed). That is NOT the case on a cruising cat, which by his own SP is going at best 50% of wind speed when it blows.

PDQ32/34 speed polar
http://4.bp.blogspot.com/-CcGnoDr2vA...ar+(speed).jpg

[DRS]

Monte. I'll preface this by saying that I have in boom roller furling and fully battened main and a huge boom assembly with fixed vang and traveler attached about a foot from the end of the boom. I have the traveler to windward only to hold the boom mid-ship. On my boat it is easier to control the boom position this way rather than having the traveler and boom both mid-ship and controlling strictly with main sheet tension.

[monte]

Interesting input, thanks. I haven't experimented with barber hauls except when downwind at 170degrees I usually run the lazy sheet to the windward mid cleat to give some control over the genoa shape and prevent it collapsing. How do you set up a barber haul for the jib?
Do you use a block and tackle or run it back to a winch?
Does it attach to the clew or the sheet?
When hard on the wind I would usually have the jib sheet pretty tight, I can't imagine a barber haul having much effect on the sheet which is maybe 1ft between clew and turning block, maybe it would pull it leeward an inch or two?
Is it more useful slightly off the wind when the sheet is eased a bit?
I do notice that when the genoa is set well at the top, it seems to be over sheeted lower down, so I guess this is where the barber haul can really help.
Thanks again.
I used to trim as factor suggested, which is what I was used to from smaller cat racing. Set the main shape and use the traveller to adjust the angles, which is why I was curious as to why pulling the traveller to windward is recommended by some.

[2Wind]

I can only comment in reference to the 440....

1. The genoa needs much more attention than the main for correct trim.
2. It is sensitive to relatively minor changes in wind angle especially when tight to windward but rewards your effort with better performance.
3. Generally once optimized the genoa traveller only needs adjustment when reefing
4. If sailing with it on a reach or deeper, a barberhauler to the midsips cleat is a good idea as discussed above to allow the clue to move wider, generate a better sail shape and open the slot.
5. Only when close hauled 30-45 degrees apparent is there need to have the traveller to windward. In 15 kts or less, 30 cm to windward with the sheet on tight. In heavier air, 60cm to windward but loose the sheet to keep the boom near midline but allow the sail to twist. Above 20kts, its the 1st reef and back to 30cm.
6. Certainly from 50 degrees out the traveller moves to leaward and by 70 degrees, I usually have if out max, sheeting as required to fly the telltails and leach ribbons. I have become surprised how much better she sails when 60-70 degrees by having the taveller out wide. The Laggon manual doesn't mention this and in some ways, reflects what Twixter has said. Personally I think they are both wrong.
7. In balancing optimal flight of the telltails in the body of the sail and the leach ribbons, I try to have all flying, but more often I compromise in favour to the leach ribbons, so they suck to leaward only occasionally. This gives the best performance.
8. Off the wind you are limited by the impact of the shrouds on the main's battons, and i generally try to have them just off to avoid chaiffe esp if there is come beam in the sea state.

Always interested in other people's opinions too....

[monte]

Very interesting 2w. Are most of those observations and adjustments made by looking at the sails, or looking at boat speed or a combination of both? We only have leech telltales on the main, it might be worth adding some mid sail?
On our last cat (lagoon 380) we experimented with traveller positions and found very little difference to performance. Admittedly it can be hard to tell when boat speed is going from say 7-7.5 knots as you surf waves a little, but generally found nothing that warranted traveller adjustment. For me seeing a speed increase of .2 k would warrant adjustment. At times coming into a port after dropping the main and sailing under headsail alone we might just drop from 7 to 6k so I'm curious as to others experiences with actual performance.
I will try all of these suggestions tomorrow.
Generally with the main I leave the traveller centred and ease the sheet till the leech telltales are flowing. Usually the top ones will flow better than the lowest because of the sail twist.
As the sail nears the shrouds I will ease the traveller and tighten the main sheet to keep it off the shroud. I have tried leaving the main tight and easing the traveller as the wind comes more on the beam (as I would on a hobie cat) but haven't seen any performance improvement.

[2Wind]

Monte,
Generally, the observations are based upon the boat speed indicator, and on occasion when "racing" other boats. I think there is one half to one knot in it when done right depending on the AWA - more to be made in the 50-70 degree range with the genoa.

It seems to me that by keeping the traveller centred when off the wind and easing the sheet you are creating twist regardless of whether you need it or not.
I think its best to use the traveller to optimize the angle of attack of the lower two thirds of the sail and the sheet to modulate the twist for the top third as required by wind speed/shear and to optimize the luff ribbon flight. In light conditions its often best to have minimal twist. Sure, in heavy conditions twist is useful to depower the sail. It should be what is right for the conditions and circumstances. Nevertheless, I understand your scepticism when not observing any useful benefit in the past with the L380. I'd be experimenting with the new L400 before acquiescing.