Mainsail halyard tension

[Colin Brown]

Hi, having been use to high performance dinghies where the main halyard is either locked at mast head or held up via a top quality rope/ wire- then a high purchase Cunningham is used to tension the luff etc. On smaller dayboats / racing cruisers this seems to be carried out via retensioning the main halyard. Is there a reason why a Cunningham downhaul is not commonly used?

 

[dunedin]

Hi, having been use to high performance dinghies where the main halyard is either locked at mast head or held up via a top quality rope/ wire- then a high purchase Cunningham is used to tension the luff etc. On smaller dayboats / racing cruisers this seems to be carried out via retensioning the main halyard. Is there a reason why a Cunningham downhaul is not commonly used?

We have a Cunningham downhaul on our 38 footer. Gets used a lot. Even with dyneema halyards and halyard winches, much easier to adjust the Cunningham.
Cunningham eye was fitted as standard on North mainsail.

 

[flaming]

Hi, having been use to high performance dinghies where the main halyard is either locked at mast head or held up via a top quality rope/ wire- then a high purchase Cunningham is used to tension the luff etc. On smaller dayboats / racing cruisers this seems to be carried out via retensioning the main halyard. Is there a reason why a Cunningham downhaul is not commonly used?

On actual racing boats a Cunningham is definitely used.

On high end race boats, Cape 31 etc, they use halyard locks and powerful downhauls. Trickier, but not impossible, to do with a mainsail that needs reefing.

Which boats have you sailed that are not using cunninghams?

 

[Daydream believer]

I have Hyde Fibrecon
I find that by the time I need cunningham I need a reef so cunningham is not used much. I do tend to adjust the halyard on the winch a lot as it avoids another set of tackle when cruising. Although I do have one I feel that it is stretching the sail where I do not need it stretched. But that is down to the cut of the sail, the rig tension & backstay.

 

[PeteCooper]

Tensioning the halyard or cunningham have slightly different affects on sail shape. The halyard tends to close the leech, the cunningham tends to open the leech.

 

[Chiara’s slave]

Tensioning the halyard or cunningham have slightly different affects on sail shape. The halyard tends to close the leech, the cunningham tends to open the leech.

Which is partly why cunninghams are for depowering in stronger winds. We don’t have one, we open the leech by freeing the mainsheet a couple of inches, it being a square top. Our main halyard is 2:1, and likes to be quite tight. As tight as allows the battens to flip when we tack, without resorting to heaving on the end of the boom. It would be perfectly possible to pull the main up to the top then use a multi purchase downhaul, beach cat style, but what would be the point. The blocks would be a few hundred quid, and it’s yet another control line. Simplicity is often a good thing. We can adjust the main halyard quite easily.

 

[Bobc]

Main halyard is much more difficult to adjust when the main is under load, than a cunno.

On the Formula One we don't have a cunno, so we use main halyard to adjust the draft and use the backstay to de-power (which is a very effective tool on the F1 with the fractional rig, as it flattens the main and opens the leech, and also tensions the forestay and opens the jib leech. I use it as my primary tool for gust response.

 

[TiggerToo]

I have always seen it written that tensioning the halyard and tensioning the Cunningham has a different effect on sail shape.

Can anyone actually explain to me how this works? I sort of seems like contradicting the laws of physics.
(but we are talking about sailing here, so I would not be entirely surprised)

 

[oldbloke]

I don't know if there is any appreciable difference to the rig, but I would suggest 2 advantages in hoisting to a fixed position and then tensioning with a downhaul/cunningham. The first would be repeatable accuracy . Hoist to the mark/lock/loop and then tension to an easily visible scale on the lower end of the mast. The other is that it is easier to adjust the downhaul as you are only adjusting the tension in the cloth, not heaving the whole tensioned sail up the mast. One of the otherwise idle crew with a 4:1 v getting into the cockpit, untangling a winch and winding on. It probably depends whether it is adjusted once a day , or every 5 minutes

 

[Bobc]

I have always seen it written that tensioning the halyard and tensioning the Cunningham has a different effect on sail shape.

Can anyone actually explain to me how this works? I sort of seems like contradicting the laws of physics.
(but we are talking about sailing here, so I would not be entirely surprised)

Think of it like this:-

When you tension the halyard, you are pulling the sail up, both on the luff and on the leech, so you are effectively tensioning them both at the same time.

When you pull on the cunno, you are only tensioning the luff.

 

[dunedin]

Think of it like this:-

When you tension the halyard, you are pulling the sail up, both on the luff and on the leech, so you are effectively tensioning them both at the same time.

When you pull on the cunno, you are only tensioning the luff.

Only if you don’t ease the mainsheet kicker whilst winching up the halyard - and few can tighten the halyard much without easing the sheet.
But a Cunningham is more efficient anyway, as pulling down. Plus you want the maximum sail area in light winds so better to have halyard at the top at all times, and pull down to tension in stronger winds. With race boats this is generally necessary if have black bands set to maximum sail size.