Topping Lift - Mainsail Trim - Light winds...

[mark_morwood]

Originally Posted by pbr

Lots of cruising cats come standard with a vang. Voyage, Manta, St. Francis, Yapluka, Endeavour, Tag, etc. 99% of the cruising cats I have seen without a vang would benefit from one since the travelers are not long enough to control twist on anything outside of a close reach. There is also the added benefit of eliminating the need for a topping lift. I just finished raising the boom and adding a vang to a new Helia, and I will guarantee it will be faster off the wind. The double bridle system works to a point but still allows more twist than desired at deeper angles. All cruising cats should have chafe covers on the cap shrouds so you can allow the main to touch the rig, with a vang there is even less potential for chafe since it keeps the boom from moving up and down and can eliminate twist so the main can be eased more before laying on the shrouds.

PBR, I should have said that very few of the catamarans I've seen cruising in the last 3 years of crossing the Atlantic, Med and now Pacific have vangs except some big ones with main furling. There certainly are cats with vangs. And I agree with you that many of the non-performance oriented cats I saw could have had a better mainsail shape if they had a vang and knew how to use it. I just don't see the vang as the place to focus for most cruising boats looking to add speed to downwind passages.

For all this discussion about mains, I think the first thing most cruising cats I see should do to improve performance on passage would be to add some light wind and downwind sails - Reacher/Screecher/Code0 and or spinnaker. And set them up so you are comfortable using them. Many cruising catamarans have decided that dropping the main is a good way to do that - and avoid a lot of noise and chafe challenges on passages.

And I am very cautious about letting the main touch the rig significantly for extended periods of time. Even with chafe covers, your expensive main is definitely at risk on a long passage if you do that.

[pbr]

Originally Posted by mark_morwood

PBR, I should have said that very few of the catamarans I've seen cruising in the last 3 years of crossing the Atlantic, Med and now Pacific have vangs except some big ones with main furling. There certainly are cats with vangs. And I agree with you that many of the non-performance oriented cats I saw could have had a better mainsail shape if they had a vang and knew how to use it. I just don't see the vang as the place to focus for most cruising boats looking to add speed to downwind passages.

For all this discussion about mains, I think the first thing most cruising cats I see should do to improve performance on passage would be to add some light wind and downwind sails - Reacher/Screecher/Code0 and or spinnaker. And set them up so you are comfortable using them. Many cruising catamarans have decided that dropping the main is a good way to do that - and avoid a lot of noise and chafe challenges on passages.

And I am very cautious about letting the main touch the rig significantly for extended periods of time. Even with chafe covers, your expensive main is definitely at risk on a long passage if you do that.

Frankly as a manufacturer I can tell you that installing a rigid vang with mechanical advantage led to the cockpit, with the necessary stronger boom, is more expensive than a traveler and that is probably the main reason you don't see more. All the cats I have been involved with in developing and building (over 150) have had a vang and no traveler. For me it gives you far better control over twist with a simpler more hassle free method than having to move the traveler around and eliminates the topping lift and it's associated chafe and windage. I brought the idea with me from my dinghy days where I raced many boats with "vang sheeting" where I found it faster and easier. I never did like the idea of a traveler in the cockpit on cruising cats where the mainsheet on a sliding traveler can grab things including crew necks, fingers, and toes. Having controls gets even more problematic with travelers on the hardtop or arch. Also most all of my product has utilized a bridle system between the bows for moving the tack of the spinnaker or Code 0 to windward for sailing deeper angles adjustable from the cockpit. I have found this to be far more effective than the token and rather useless fixed bow sprit we see on so many designs today. Certainly an articulating bowsprit has merit though.

[pbr]

P.S. forgot to mention all of those boats had chafe covers on the shrouds and I never had a problem with sail chafe with the sail all over the shrouds, I do believe however that the vang helped in that it does not allow the boom to move in the up and down reducing the chance of chafe.

[2Hulls]

What's a traveler?

[arsenelupiga]

Originally Posted by pbr

Please don't misunderstand me though, I advocate for most cruisers sailing the rumbline is the way to go, just a lot easier and safer and less potential to make a windshift mistake. That is why I advocate whisker poles or a device like a Hoyt boom or Camber Spar. The question was " Is sailing polars faster"? And the answer is YES.

Is it ? For example on L400

1. Having spinnaker/ps or similar of 125 m2 in one piece to pull down.

2. Vs main @56 m2 and gennaker @ 75 m2 to pull down.

To me option 2 seem easier to depower. 75 m2 first and can use main to assist. Similar sail area, and you guys claim that opt 1 will be faster DDW than opt 2. Polars say differently although may be inflated but optimum seem to be around 145 deg, which means one has to sail 22% faster at that angle vs DDW. Also, drift is a bonus.



I will test this, once i get my new gennaker, do not believe anyone anymore .

[django37]

In light winds, on my L380, it pays to tack downwind, keeping the telltales on the main blowing aft, about 160 dgr. Yes, I have larger than standard sails, incl a 125 m2 asy. spinnaker set on a long pole. As boatspeed gets closer to hullspeed and you cant raise boatspeed by pointing higher, I go DDW. As the waves start to build, catching waves to surf, is more important than winddirection. With the boat "unloaded" for racing (8t without crew), the works polar diagram fits nicely, I even can do a bit better to windward in 25 knots ;-)

[arsenelupiga]

Originally Posted by django37

In light winds, on my L380, it pays to tack downwind, keeping the telltales on the main blowing aft, about 160 dgr. Yes, I have larger than standard sails, incl a 125 m2 asy. spinnaker set on a long pole. As boatspeed gets closer to hullspeed and you cant raise boatspeed by pointing higher, I go DDW. As the waves start to build, catching waves to surf, is more important than winddirection. With the boat "unloaded" for racing (8t without crew), the works polar diagram fits nicely, I even can do a bit better to windward in 25 knots ;-)

wow, that is some serious sail trim !

what is the role of unfurled jib in this setup ?

[django37]

With the long pole and flat main it pays in some conditions to use (a part of) the genoa as spinnaker staysail, to lead the wind correctly to the lee side of the main.

[arsenelupiga]

Originally Posted by django37

With the long pole and flat main it pays in some conditions to use (a part of) the genoa as spinnaker staysail, to lead the wind correctly to the lee side of the main.

cool. what wind angle is this setup for ?

[django37]

Spi pole always at 90 deg to AWA, from 80 to 160 deg AWA

[arsenelupiga]

what is mystery to me is that you mention hull speed barrier, where one cant increase speed without major increase in forces, yet polars for lagoon do not show any congestion around 8-9 kn.

These polars are product of fantasy that is one explanation, but this was produced by lagoon in flat water without reefing and one would hope it is more to it than fantasy....

[pbr]

Polars initially are calculated on design data and with established racing boats based off of real data and refined over time sailing. I would say the polars for most cruising cats are not accurate because they do not have enough data for real results, average pay load, and sea conditions. Polars are a good baseline though to start with and use as a reference when sailing destinations are upwind and downwind and with experience can be refined. When racing of course reacting to windshifts and sailing polars can make for huge gains over someone sailing dead downwind and rumbline.

[monte]

I like the idea of a vang pbr, but I find it hard to believe it can replace a traveller. Off the beach cats have both because the traveller doesn't have enough leverage on the boom at only 20% of the distance from the mast to the end of the boom, combined with the bending force on the boom. You've designed and built these systems so I guess you take into account the additional forces and boom section strength required. Can the vang really handle the upward force applied to the clew without too much deflection?
Looking at my cat and some others in the anchorage, I think the maximum would be a 20% setback from the mast. Some, like the catana it just wouldn't fit.
Also a question regarding sailing on a beam or broad reach. I find leaving the traveller centred (it pretty much always is) and easing the mainsheet till the batten just touches the side stay gives ok sail for the top half of the sail and leech tell tails flow nicely, but the lower half is over sheeted a bit and the telltales fall away. There's quite a bit of twist this way and also the leech can move up and down quite a bit. Setting the traveller out wide and sheeting in the main would allow the bottom to work better, but the top worse when still touching the stay. How do others generally have the main and traveller set in those conditions, at around 20K TWS...

[pbr]

For a conventional rigid vang, ideally the boom would be at a height where you could have a 30- 45 degree angle at the boom with the attachment point on the boom at about 30%. Less than 30% and 45 degrees increases loads on the gooseneck compression to the mast and vang attachment point, and demands more on the return spring to support the boom. If the gooseneck is too low it is hard to get the geometry to work, so in some cases moving the gooseneck up is advised. Another modern solution is the reverse vang which you are starting to see on racing boats and boats with low gooseneck attachments. I am surprised we aren't seeing more of these. Also the boom section needs to be stiff enough to handle the load. Vangs load are greater on catamarans than monohulls so that needs to be taken into consideration when sizing. Most mega yachts are vang sheeting with hydraulic vangs so it can be engineered for any size boat. At 20 knts. true I would be using enough vang to keep the top tell tales streaming aft. With a vang and mechanical advantage led to the helm adjustments can be made easily.

[pbr]

Originally Posted by monte

I like the idea of a vang pbr, but I find it hard to believe it can replace a traveller. Off the beach cats have both because the traveller doesn't have enough leverage on the boom at only 20% of the distance from the mast to the end of the boom, combined with the bending force on the boom. You've designed and built these systems so I guess you take into account the additional forces and boom section strength required. Can the vang really handle the upward force applied to the clew without too much deflection?
Looking at my cat and some others in the anchorage, I think the maximum would be a 20% setback from the mast. Some, like the catana it just wouldn't fit.
Also a question regarding sailing on a beam or broad reach. I find leaving the traveller centred (it pretty much always is) and easing the mainsheet till the batten just touches the side stay gives ok sail for the top half of the sail and leech tell tails flow nicely, but the lower half is over sheeted a bit and the telltales fall away. There's quite a bit of twist this way and also the leech can move up and down quite a bit. Setting the traveller out wide and sheeting in the main would allow the bottom to work better, but the top worse when still touching the stay. How do others generally have the main and traveller set in those conditions, at around 20K TWS...

To answer your question about the loads without traveler. I would say if the boom and mast wasn't specifically engineered to take the extra load, you would want to continue to use traveler and mainsheet upwind where the loads are greatest. Once the boom is no longer over the traveler the vang has got it. Most cruising cats I see are sailing with way more twist than they should because the travelers are not long enough for anything more than close hauled or close reach.