cuningham or boom downhaul
- Thread starter seaker236
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They do much the same thing. Along with the main halyard, it's a way to keep or add tension to the luff of the mainsail. The difference is that a boom downhaul is attached to the boom so also pulls the boom down, Its kind of a dinghy thing. Bigger boats can use a cunningham that just pulls the sail via an eye or cringle a few inches up the mainsail's luff. The difference can come under racing rules, where cunninghams are used because a boom can often be only so low due to measurement rules, and so it often fixed and attached with a gooseneck.
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A cunningham and boom downhaul do not give the exact same sail shape adjustment.
1. A boom downhaul is used on a boom that connects/attaches to a track mounted gooseneck, track is mounted to the mast.
2. A cunningham is used on a gooseneck that is direct attached to a mast (no track to slide up and down on)... favored by racers because the luff dimension of the sail cannot be stretched beyond the 'black bands' and therefore the luff will always be within or less then the luff's 'admeasured' length.
They arent the same in function for (boltroped) sail *shape* adjustment !!!!!
1. the downhaul changes tension on both the luff boltrope (that 'rope' inside the sleeve at the luff) and the sailcloth .... causing the position of maximum draft to move forward AND flattening the draft of the lower panels of the sail.
2. the cunningham will allow the boltrope inside its sleeve to move more independently, sail cloth (& sleeve) will change position relative to the boltrope; thus, the fabric is stressed more than the boltrope and thus with increase cunningham tension you get a flatter sail (mostly in the lower panels) shape, and a more 'rounded' shape at the luff, but not as much change of max. draft position as does the downhaul.
So the technical difference - a cunningham causes more luff shape change (flatter or more rounded 'entry' shape at the luff) than a downhaul which affects more position of max. draft change.
On sails that have 'boltropes, .. the most common arrangement of woven dacron sails .. for a cunningham to do the same 'work' as a boom downhaul, you also need to also change halyard tension.
So in summary of function: boom downhaul = cunningham + halyard tension adjustment
1. A boom downhaul is used on a boom that connects/attaches to a track mounted gooseneck, track is mounted to the mast.
2. A cunningham is used on a gooseneck that is direct attached to a mast (no track to slide up and down on)... favored by racers because the luff dimension of the sail cannot be stretched beyond the 'black bands' and therefore the luff will always be within or less then the luff's 'admeasured' length.
They arent the same in function for (boltroped) sail *shape* adjustment !!!!!
1. the downhaul changes tension on both the luff boltrope (that 'rope' inside the sleeve at the luff) and the sailcloth .... causing the position of maximum draft to move forward AND flattening the draft of the lower panels of the sail.
2. the cunningham will allow the boltrope inside its sleeve to move more independently, sail cloth (& sleeve) will change position relative to the boltrope; thus, the fabric is stressed more than the boltrope and thus with increase cunningham tension you get a flatter sail (mostly in the lower panels) shape, and a more 'rounded' shape at the luff, but not as much change of max. draft position as does the downhaul.
So the technical difference - a cunningham causes more luff shape change (flatter or more rounded 'entry' shape at the luff) than a downhaul which affects more position of max. draft change.
On sails that have 'boltropes, .. the most common arrangement of woven dacron sails .. for a cunningham to do the same 'work' as a boom downhaul, you also need to also change halyard tension.
So in summary of function: boom downhaul = cunningham + halyard tension adjustment
On your name plate it mentions a C22 and if the question is in relation to that boat then you probably want a cunningham. I had a C22 that we sailed alot and the cunningham was a needed item. If your sail is a bit on the worn side then the cunningham is even more needed.
It is easy to rig as it simply pulls straight down and most C22 mainsails have a cunningham hole. If not, you can very easily put one in yourself. Put it about 12" above the tack hole.
Ray
It is easy to rig as it simply pulls straight down and most C22 mainsails have a cunningham hole. If not, you can very easily put one in yourself. Put it about 12" above the tack hole.
Ray
I enjoy reading all of these tecnical explanations for this and that from the experts.
I simply use the unused halyard for the jib(I have a pvc furler) tied to the first reef point on the main and when it is time to reef I turn into the wind, ease off on the main halyard, pull down on the jib halyard, tie off the rope ties located at the first reef points on the main, and adjust the main halyard.
I am sure that the sail shape is suffering but I can get this done and still hit 6 plus knots.
I adjust the furler/jib as needed.
That being said, I will at least know how to do things "correctly".
Thanks guys!
I simply use the unused halyard for the jib(I have a pvc furler) tied to the first reef point on the main and when it is time to reef I turn into the wind, ease off on the main halyard, pull down on the jib halyard, tie off the rope ties located at the first reef points on the main, and adjust the main halyard.
I am sure that the sail shape is suffering but I can get this done and still hit 6 plus knots.
I adjust the furler/jib as needed.
That being said, I will at least know how to do things "correctly".
Thanks guys!
95% of sailing is having fun and being safe. Sounds like you are doing that!
To clarify a bit for you, although they are in the same 'area', a cunningham cringle and reefing cringle are two different things. You got the reefing one sorted out. A cunningham cringle would be below it, and used (as everyone points out) the tighten the luff or forward edge of the mainsail. This helps flatten it and more importantly moves the draft (the widest part of the sail's curve) forward. Both help the sails balance with the wind picks up.
The way the Cunningham works (as explained in some book that I have, don't recall which one) is by causing the luff to curl sooner than by normal boom or halyard tension. SO, it begins to shape the sail when you decide. Yank on the C, and you'll see that very thing happen. Now, I'm sure there's a dozen sailors who'll say I'm all wet. Could be . . . but so is the guy that wrote the book.
I don't have one. At this point of I'm not as excited about getting there as fast as possible. The longer we stay out a few miles, the longer my lovely bride improves the scenery, quite dramatically. I'm a guy.
I don't have one. At this point of I'm not as excited about getting there as fast as possible. The longer we stay out a few miles, the longer my lovely bride improves the scenery, quite dramatically. I'm a guy.
One other difference is that a boom downhaul will interact with the boom vang, if you have one. In other words, if you tension the downhaul the vang tension will ease, because the whole boom moves downwards. Likewise, if you ease the downhaul with the vang on, it (the vang) will get really tight. A cunningham does not have this interaction, so you have independent adjustments.
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