cunningham?

[EGregerson]

Hi; i recently bot a (used) main with 2 rings I'm not familiar with; maybe the forward is a cunningham; the aft one is a mystery to me. How do these work? and when? It seems to me that all they would do is reduce sail area. the sail is shelf footed; I don't know if that has anything to do with it.

 

[Loren Beach]

flattening reef...

The aft one was for the "flattening reef" and the forward one could be the cunningham.

Covered better in this prior thread:
http://www.ericsonyachts.org/infoexchange/showthread.php?t=7149&highlight=flattening

LB

 

[Blue Chip]

Another possibility is the basic design of a sail that had single line reefing somewhere in it''s history?

 

[Seth]

Nope-

It is a flattening reef. You can use the first reef for this, and when you crank this down you will flatten the sail a lot and make breezy sailing easier...

Having said that, they are not common these days-sails are designed with flatter foot sections now.

If your sail cannot be flattened with max outhaul, then go ahead and try it-although you may want to just use the first real reef at this point. More of a racing tool than cruising..

Seeya,

S

 

[bayhoss]

The answer is that they are both cunninghams. The rear is far out of date and seldom used. The front is one of the single best inventions ever put on a boat. Here's where it came from. In the days of 6 meter racing a man named Briggs Cunningham devised a means of adjusting the tension of the luff while under way. Here's how she works. As the wind increases, the point of camber in your sail wants to move aft causing the sail to reduce effective shape and thus cause the boat to heel and give even less sail area to the wind. The primary culprit is the luff. It becomes slack. Bringing the cunningham tight will tighten the luff and pull the dynamic center of the sail forward and grealty benifit the shape of the sail and have a profound reduction in heeling. Do this, pick a day with good wind 12 knts or so. run a line thru the forward cunningham and with a line and block (a boom vang works fine) pull it snug and watch the luff tighten. As you tighten you can see the camber in the sail move forward and the healing decrease. Also, look at your knot meter - you'll like what you see. Briggs Cunningham was to sail shape what Eric Clapton is to the gutair. Try it, you'll like it.

Frank
E28+ Valinor

 

[Seth]

Love the Clapton comparison

But, the aft ring is for a flattening reef, not a cunningham.

As you say, the purpose of the cunningham is to increase (or decrease) luff tension in the lower part of the sail, which in turn moves the deepest part of the camber (point of max depth) forward (with tension), or aft (by easing tension if any).

It does the same thing as increasing or decreasing halyard tension, but whereas you get more effect from halyard adjustments in the upper section of a sail, the cunningham affects the lower portion.

The flattening reef is like a turbocharged outhaul; as you add tension here on the mainsail leech, you REMOVE draft (rather than MOVE it as with a cunningham), thus flattening the sail, or making it fuler when you ease tension on it. It will have the effect of reducing heeling as Frank says and in the right conditions be faster, since less heel is almost always much faster.

They are not used much anymore since mainsail shapes have evolved to be flatter to begin with, and you can achieve what you need simply by adjusting the outhaul, but this is what that ring was for..

Cheers,

S

 

[bayhoss]

Corrected

After looking in Sail Power I stand corrected. The aft hole is a flattening reef. My mistake.

Frank
E28+ Valinor

 

[tenders]

I'm confused. Is the flattening reef designed to be used by itself (does the line run down to the boom or through the outhaul?) or are you supposed to attach it to the outhaul and bring the luff of the sail down to the first reef point?

 

[Seth]

Flattening reef

I would not even bother with it. It designed to use the reef line (but just the clew reef line), which is run from the end of the boom through the cringle and then either around the boom (like a normal reef), or back, or if you have enough purchase on your reef line, just grind it down. By pulling back and down on this ring, the foot of the sail is made flatter.

My suggestion is that just use your outhaul, and once it is maxed and you are still overpowered, go ahead and do a normal reef. The benefit a cruiser will get from a flattening reef is not really worth the effort-especially with such an old sail.

Just ignore it..



S

 

[Loren Beach]

Seth is Right

I would not even bother with it. It designed to use the reef line (but just the clew reef line), which is run from the end of the boom through the cringle and then either around the boom (like a normal reef), or back, or if you have enough purchase on your reef line, just grind it down. By pulling back and down on this ring, the foot of the sail is made flatter.

My suggestion is that just use your outhaul, and once it is maxed and you are still overpowered, go ahead and do a normal reef. The benefit a cruiser will get from a flattening reef is not really worth the effort-especially with such an old sail.
Just ignore it..


S

Agree Completely. I remember when this mini-reef idea came into vogue and so we all thought that whatever those "racing boats" in magazines had, we had to have one too! So I put one on the main of my 20 foot one design boat. It might have been helpful on some big ol' SORC ton class boat in a magazine but did nothing that I or my crew could figure out for our racing.

If, and it's a stretch, it actually would make the boat go faster, I would catalog it with other devices that an old sailmaker once told me were meant to gain "micro knots" or "nano knots"...

i.e. Any advantage was so immeasurably slight as to be negated by your smallest error in boat prep or driving or sail handling -- anywhere on the race course!

LB

 

[bayhoss]

I agree with Seth

As for the flattening reef, ignoring it is a great idea. The cunningham (I feel) is a very useful tool in sail shape. I use mine when conditions are just short of the point where I would start to consider reefing. Pulling the luff tight works wonders in strong air.

Best Regards,
Frank
E28+ Valinor