Cunningham versus Main Halyard and other assorted wonderings

[Rob_P]

Originally Posted by Coach Shoe

It’s somewhat counter intuitive. It would seem that it you tightened up on the main halyard you would get the same result if instead you tightened up on the Cunningham.... that is pulled from the opposite end of the sail. Wrong! That’s not the way it works.
Increasing tension on the halyard CLOSES THE LEACH. Increasing tension on the Cunningham MOVES THE DRAFT FORWARD. When the main is becoming over powered, too much halyard tension hurts performance. Increased Cunningham tension helps.

Wouldn't easing the vang a bit solve this by allowing the boom to rise and open the leach again?

[EmeraldCoastSailor]

My current boat doesn't have a cunningham (in-mast furling) but a previous boat did and I used it in a way that I thought helped. I raised the main via halyard and then cleaned things up a bit with cunningham. Made sense to me.

I am a big fan of my traveler arrangement and the vang plays a role as Snore points out.

[Bill_Giles]

As a dinghy sailor I have used the Cunningham to change the shape of the top of the sail. On many boats pulling on this control flattens the top of the sail and in extreme cases allows the leach to drop away. This not only reduces sail area it is at the point where most leverage occurs. As the crew’s body weight is all that holds the boat flat this is most important.

The vang on dinghies and race boats pulls the boom into the mast and bends the mast, this takes the belly out of the sail flattening it and de powering it. The main sheet pulls down on the boom and tightens the leach and so powers up the mainsail. If you have insufficient kicker and ease the main sheet the sail becomes rounder and more powerful which is not want when you ease the sheet.

The outhaul is used to flatten the foot of the sail. So basically the Cunningham controls the top of the sail, the vang the middle and the outhaul to foot.

The aim is to get all telltales on the leach flying together flowing straight when reaching. When beating the telltales should fly straight about 80% of the time flicking around to leeward the rest of the time. They should all be much the same. EG if the bottom one is flicking to leeward 50% of the time whilst the higher one are behaving then the outhaul needs to be tightened until the telltale behaves with 80% flow.

Here endeth the lesson!

[Sofa King Fishy]

I was taught that the traveler is used as long as the boom in located directly above it, then once the boom is outboard far enough to exceed the length of the traveler, the Boom Vang is used. Is this right?

[Lambretta]

Originally Posted by johnn33

Hallo to Rob P The explanations above are good and cover different boats.
May I suggest that you sail as an additional crew for a whole day in a racing keelboat such as for example a Dragon or an Etchell? There will be others to sail her, and they will have time to show how the sails are shaped and why. You will feel and see immediately how your changes affect the boat. (I would suggest this rather than the more hectic life in a racing dinghy where small errors cause a quick capsize). The class lessons are essential, but you will remember and enjoy the practice.
John

This is excellent advice ....... especially if the crew on the racing yacht are good sailors and prepared to share their expertise!

[Rob_P]

Originally Posted by Lambretta

This is excellent advice ....... especially if the crew on the racing yacht are good sailors and prepared to share their expertise!

"The plan" includes this goal once I get my ASA 101 stickers in my log book. At that point I'm qualified to charter the school boats to gain experience but I'm going to see if I can bum a ride or 2 for wet Wednesday beer can races with someone who doesn't really care all that much if he does well or not because the sailing is more important than bragging rights.

Ideally, I'd like to find a boat that allows crew to be rotated to different positions weekly so they gain experience in all aspects of sailing. Basically, a training boat with a skipper who wants to teach. I don't know if such a boat is out there but I'm going to ask around and see if I can find one.

For the rest: This year is for learning as much as I can. Next year (or the year after) is for owning. The years after that are for living.

[Woodfall]

Sails are not flat.

[Rob_P]

Originally Posted by Woodfall

Sails are not flat.

Like tires, they're flat unless they're filled with air.

[Bill_Giles]

When sailing and hit by a gust a typical response is to ease the traveller down the track. This works well as the sail shape stays the same (although the mast bends in a different plane so there might be some alteration). When the gust piles on and further easing is needed one will ease the main sheet. If the kicker (vang) is not on hard enough to stop the boom rising then the main will start to power up initially until the leach falls away enough to allow the air to escape. On high performance dinghies they hold the mainsheet in but control power with the Cunningham.

I don’t think that on cruising boats the controls are that sensitive. Nearly everyone I have ever sailed with sets up the sails and they never adjust anything all day. It offends my pride to see a badly set sail so I am forever tweaking the sails and rig to get another tenth of a knot out of the boat.

[Bill_Giles]

In their relaxed state and with straight spars and no controls the belly built into a sail is at its greatest. When the mast is curved it takes out some of that belly and reduces that curve in effect flattening it. Of course it never makes it truly flat, it makes it flatter and less powerful. When the wind gets up the deepest part of the curve is pushed back. Pulling on the Cunningham draws the belly forward and especially reduces the curve (flattens) the top of the sail. The sail never becomes flat like a board, it become relatively flat.

But as my friend said to me gazing at a flat tyre, “it is only flat at the bottom”.

[Coach Shoe]

Originally Posted by Rob_P

Wouldn't easing the vang a bit solve this by allowing the boom to rise and open the leach again?

Yes, but.... that does not move the draft of the main forward as effectively as the Cunningham. That’s that major objective of the Cunningham. IMHO. I’m not a sailmaker but in my 45 plus years of sailing I met a few who tried to teach me about sail trim.

[Don C L]

Originally Posted by Sofa King Fishy

I was taught that the traveler is used as long as the boom in located directly above it, then once the boom is outboard far enough to exceed the length of the traveler, the Boom Vang is used. Is this right?

Yes and depending on the location of the traveler, it won't be very far before the vang is what is keeping the boom down.

[Lambretta]

Originally Posted by Rob_P

"The plan" includes this goal once I get my ASA 101 stickers in my log book. At that point I'm qualified to charter the school boats to gain experience but I'm going to see if I can bum a ride or 2 for wet Wednesday beer can races with someone who doesn't really care all that much if he does well or not because the sailing is more important than bragging rights.

Ideally, I'd like to find a boat that allows crew to be rotated to different positions weekly so they gain experience in all aspects of sailing. Basically, a training boat with a skipper who wants to teach. I don't know if such a boat is out there but I'm going to ask around and see if I can find one.

For the rest: This year is for learning as much as I can. Next year (or the year after) is for owning. The years after that are for living.

Great stuff ............. you have it all mapped out ..... well done and good luck with that.

[Don C L]

Originally Posted by Rob_P

"The plan" includes this goal once I get my ASA 101 stickers in my log book. At that point I'm qualified to charter the school boats to gain experience but I'm going to see if I can bum a ride or 2 for wet Wednesday beer can races with someone who doesn't really care all that much if he does well or not because the sailing is more important than bragging rights.

Ideally, I'd like to find a boat that allows crew to be rotated to different positions weekly so they gain experience in all aspects of sailing. Basically, a training boat with a skipper who wants to teach. I don't know if such a boat is out there but I'm going to ask around and see if I can find one.

For the rest: This year is for learning as much as I can. Next year (or the year after) is for owning. The years after that are for living.

Once I get my boat put back together you're, welcome to tag along with me out around the oil rigs or arch rock. You really have to bring your A game though, my boat has blinding speed!

[admiralpush]

There is no need for a Cunningham until the mainsail is stretched out to the point that you can't get the luff tight enough to set your draft properly. (That is mostly a problem with old Dacron sails.) That means you are hoisting above your black band in a very competitive racing situation, or your main halyard shackle is at the limit. Having said that, there are good reasons to have the hardware and Cunningham grommet in your mainsail. Knowing how to use them will make for better performance. For someone who is beating around the bay and not concerned with performance it is far from essential.