Adding a cunningham?

[hoppy]

Does the main need to be cut specifically for a cunningham or is it just a case of having the eyelet in the sail and the line.

Just can't picture how the main would be flattened if the halyard is eased off and the cunningham pulled on to tighten the luff.

[MartyB]

I use the cunningham to tighten the luff when the head of the sail is hoisted as high as it will got. You then pull down the cunningham to tighten the luff, giving you more power, yet do not remove all the sail in higher winds as you would a reef.
Its just another sail tweak that works well in some conditions. NOT ALL conditions, but some higher wind conditions.

Marty

[Deleted]

The cunningham eyelet is also a little bit behind the luff. So it also pulls the sail a little forward which moves the curve forward. With closed haul it's a good thing to use.

[so36idavid]

Hoppy,

Adjusting the cunningham is something that racers do all the time but it's rare for cruisers to do it, or even have a cunningham rigged. I know you're getting into racing so I'll talk you through how I think about the cunningham when racing. I race a lot (not my boat) and I can pretty much work every position on the boat. My favorite is mainsail trim in heavy air. The mainsail on a race boat has more control lines than the rest of the boat combined! It's a very complicated sail and everything affects everything else, lots to think about. Here's a very basic introduction.

Firstly, you don't really want to ease off on the halyard when beating because that reduces the size of the sail particularly up there where the wind is strongest and blowing from the best apparent angle. So playing the halyard (upwind) is not advantageous for racing. We'll save downwind trim for a separate chapter . 

Your sail should have two or three horizontal dark stripes at different heights. They're there to allow you to visualize the draft, i.e. the curve of the sail. You generally want the curve to be at its deepest about 45% of the way back from the leading edge. A little further forward in heavy air, a little further aft in light. Typically your mainsail should go to full hoist (black line) without the luff of the sail being so tight that there are vertical wrinkles. However, when beating into a good breeze this results in the draft of the sail being blown aft. Go out and try it, you'll see what I mean. When the draft blows aft the sail will have increased drag and reduced lift giving you more leeway and costing you point angle. So what you want to do is lock that draft forward. The cunningham allows you to do this for the bottom 1/3 of the sail. The draft in the top 2/3 of the sail is controlled by the backstay. When beating, as the windspeed increases you want to increase the tension on the cunningham and backstay. Your mainsail trimmer should be looking up the sail and monitoring the draft at all times, at all heights. Every wonder how your competitors are pointing so much higher than you in a breeze? Mostly it's mainsail trim. Or at least a dance between the main trimmer and the helm. 

In summary when beating in light air you want backstay off, cunningham loose, outhaul loose, traveler up, sheet off to get maximum twist. As the wind comes up you want more of everything on to flatten the sail and lock in the draft and then traveler down to keep the boat on its feet. In heavy air the main trimmer should be adjusting the traveler about as rapidly as you're adjusting the helm. As the gusts roll through adjustments on the traveler should be keeping you from feeling weather helm. Finally, in heavy air some boats like more twist (sheet off) and traveler up, giving away power at the top of the sail. Go out and practice, look at the numbers on your instruments, they don't lie. 

Sorry for the wall of text, I hope this has been useful. Feel free to follow up if you have any questions.

David

[so36idavid]

One more thing, you want a quality main halyard. Something with vectran or dyneema would be best but not 100% necessary. Inexpensive halyards (like the one that came with my boat) will stretch and creep and make all of this adjusting kinda pointless. No point in cranking on the cunningham if the halyard stretches the same amount with each gust!

[hoppy]

David,

Mainsail trim feels like a black art sometimes. One moment I think I understand it and the next I'm confused as hell. One big challenge when racing is not having a crew who knows how to trim the sails, so I have to do it remotely or hand over helming duties. The main is definitely more challenging because of the many control lines.

I got thinking about the cunningham when someone commented on SA about the fact that they don't touch the halyard. Even without your explantation of the benefits, I think using a cunningham is probably easier to use and to get an inexperienced crew to adjust than to get them to do the halyard.

Can't do anything about trying it until I can be bothered taking the sail to a sailmaker.

[seattle519]

Hoppy,

David's explanation is concise and accurate. Learn the ramifications of all his adjustment suggestions. It's a complicated dance.

I would add a little more emphasis to the out haul. Be grinding it in as the wind builds. In a blow it should be real tight, with the full sail or if reefed. Our old boat (30') had a set of blocks in the boom to give a 2:1 advantage that we will be adding to the new boat.

Dean

[hoppy]

I'm well versed at using the outhaul. After the mainsheet, the out haul is probably the 2nd most used control line for the main on my boat.

Why add the 2:1 block on your 519? I have no problem using the winch to get the sail out the max.

[so36idavid]

Jul 30, 2017 11:10:23 GMT hoppy said:

I got thinking about the cunningham when someone commented on SA about the fact that they don't touch the halyard. 

That's not quite how I do it. Often times you'll want to ease the outhaul, completely slack the cunningham and ease the halyard an inch or two when running or reaching off the wind. You're looking for more power in the lower apparent wind. Just remember to tighten it all up again before the leeward mark.

Building a good racing program is like building a house of cards. You painstakingly add one good crew member at a time and then one gust blows it all apart and you start again. But it's fun so we do it anyway . 

[Deleted]

No I'm a bit confused; is the outhaul the same as the main traveller?
I have a question about the traveller. When going closed haul does it make sense to move the traveller all the way to luff or will it be enough to put it in center? Because what about the gap action between main and genoa? I tried it yesterday crossing the North Sea and I noticed that when I decreased the gap the boat accelerated. So then I put the traveller to center instead of all the way to luff. On the other hand, when I had to point higher I put it full to luff again never minding the speed. So is that a good practise?

[tedp]

The outhaul tensions the foot of the mainsail - it pulls out the slide that runs in the track of the boom, flattening the lower half of the sail.

Regarding the traveller, when sailing close-hauled in a light wind, you add twist to the main by slacking the mainsheet and hauling the traveller to luff on the rail. It takes some experimenting, but it may add a few 10ths of a knot to your speed. Check on the tell-tales flying from the leech of the main.

In a strong wind, the mainsail should be flat with little twist, and the traveller may be eased to lee to reduce pressure on the rudder. At any rate, that is how I get best results.

[hoppy]

Aug 1, 2017 20:21:47 GMT tedp said:

Regarding the traveller, when sailing close-hauled in a light wind, you add twist to the main by slacking the mainsheet and hauling the traveller to luff on the rail. It takes some experimenting, but it may add a few 10ths of a knot to your speed. Check on the tell-tales flying from the leech of the main.

In a strong wind, the mainsail should be flat with little twist, and the traveller may be eased to lee to reduce pressure on the rudder. At any rate, that is how I get best results.

That's roughly my traveller technique. In heavy winds at the max for the mainsail, I may sheet in fully and then move the traveller to leeward to get the tell tails flying right. If I am overpowered I will move the traveller further to leeward to ease the pressure and then decide whether to ride it out or reduce sail.

[Deleted]

But what about the gap between genoa and main. Is that something to take into account as well?

[tedp]

I fail to see how you can adjust the gap between the genoa and the main, unless you use a barber hauler to pull in the sheet angle on the genoa. I'm sure there is a delicate balance between main trim and genoa trim, but I'm not qualified to explain the finer points. Perhaps David can tell us more?

The genoa itself needs to be trimmed as well by moving the sheet block on the rail. Some people fit trim tackles on the sheet blocks so they can easily be adjusted from the cockpit.

If the mainsail is set too loose compared to the genoa when sailing close-hauled, there may be some back wind on the luff of the main, which means it loses power. This may not be harmful in a gust.

[so36idavid]

Aug 3, 2017 8:27:09 GMT tedp said:

I fail to see how you can adjust the gap between the genoa and the main, unless you use a barber hauler to pull in the sheet angle on the genoa. I'm sure there is a delicate balance between main trim and genoa trim, but I'm not qualified to explain the finer points. Perhaps David can tell us more?

The gap between the sails is usually referred to as "the slot". We're definitely getting into second order effects here. I wouldn't spend too much time worrying about it. It depends strongly on how hard the wind is blowing, how big the headsail you're flying and the point of sail. You really have to look at what the air coming off of the jib is doing to the main. As a rule of thumb you trim the luff of the jib and the leech of the main. They work together as a single unit. But since you asked, a few things to think about...

If you're beating in heavy air (something most people here won't do anyway) the backwash off of the jib is going to put a bubble into the luff of the main. If you have plenty of power then you don't want to trim this out. Trim the jib to the course and use the traveler to fly the main battens while keeping the boat on her feet. You've got plenty of power so who cares what's going on in the slot?

In medium air you can adjust the twist of the jib (moving the car fwd/aft) to change how the backwash coming off of the jib affects the main at different heights. In a perfect world the main and jib will have about the same twist in them. 

In medium-light air you might want to close the slot a little bit to get the acceleration off of the jib. I think this is what Marien was referring to. Don't go crazy with this though. If you close that slot too much you'll stall the flow over the main and stop the boat.

In light air I get depressed and go and lie in the shade on the leeward side. Don't ask me about trimming in light air . 

We haven't even started talking about the effect of sea state, that's a whole other conversation. 

I doubt that any of this has helped. As I said these are minor adjustments that may win/lose you boatlengths in a race but they're not going to change the quality of your life if you're cruising. If you want to really get into the art of this you need to go race with a good quality crew and watch what they do for many hours in all kinds of conditions. 

David

[tedp]

Thanks, David, you have answered a few questions I had as well. I usually don't bother too much with the backwash bubble in the main - I read the speed from the GPS and if it's OK I'll stick with it.

I wonder how you'd close the slot between the genoa and the main. Use a barber hauler? Not that I'm very keen on going to such lengths.

Regarding sailing in light wind, I found that controlling the twist of the main by slacking the sheet and hauling up the traveller will help in my boat. Otherwise I agree with you - I find little fun in light weather sailing.

[Deleted]

I understand you cannot close the gap by trimming the main but I mend that pulling the traveller all they way to luff will create another airflow from the head sail over de leeward side of the main. It resulted in a lower speed then when I moved the traveller back to mide ship. I assume it has something to do with the wing (lift) effect and air pressure.

[tedp]

Aug 14, 2017 19:02:02 GMT @marien said:

I understand you cannot close the gap by trimming the main but I mend that pulling the traveller all they way to luff will create another airflow from the head sail over de leeward side of the main. It resulted in a lower speed then when I moved the traveller back to mide ship. I assume it has something to do with the wing (lift) effect and air pressure.

It depends on how you do it. If you slacken the sheet so the boom is still midships or even a bit to lee, but with the traveller to luff, the angle of the sheet is quite flat so the boom tends to lift up. This adds twist to the sail. I found this often helps in a light wind.

If you on the other hand keep the sheet tight and move the traveller to luff, the sail will 'overdraw' like an aircraft wing tilted too steeply and lose the laminar air flow.