what's that kicker thing for?

[johnnycomelately]

what\'s that kicker thing for?

Following a discussion in the bar at the weekend I could do with a bit of reassurance.
I was taught to sail in Enterprise dinghys and whenever we sailed to windward - beating - we werew taught to pull the kicker in tight to stop the boom riseing and so keeping the sail shape. When running or broad reaching we were taught to let the kicker off to get a fuller sail shape.
I was told at the weekend that I am doing this wrong and it should be the other way round i.e. tight in when reaching or running and let off when beating.
Now this fellow was so convincing I'm beginning to think he might be right and I have been doing it wrong for the last 20years.....Help!!
Cheers
Ian

 

[Jonny_H]

Re: what\'s that kicker thing for?

You should trim the kicker to keep the telltale which is about 1/8th of the way from the top of the leech flying 2/3rds of the time.

In practice this depends on both wind conditions and angle of sail:

Upwind: In light airs - none; In medium airs - pull mainsheet tight, tension kicker, then release mainsheet to get a nice shape to sail; In heavy airs - pull as hard as you can (you want the sail very flat to keep the power out of it).

Reach: Light winds - Very little (if any); Medium Winds - Just enough to stop the top of the sail twisting off; Heavy Winds - Enough to stop the boat being overpowered

Run: Light winds - None; Medium Winds - Enough to stop the top of the sail twisting off; Heavy Winds - Keep the twist in the top of the sail, let the kicker off to loose power, pull it on if the ride gets wobbily.

This is a general rule of thumb that I, as a former dinghy racer, would use. It is different for every boat, and sail (fully battened needs lots less kicker than semi-battened), but some tell tails up the leach will get you going in the right direction.

You can buy excellent books on sail shape (Lawrie Smith's is quite good from memory - 'The Science of Speed' or something)

Jonny

 

[Salty John]

Re: what\'s that kicker thing for?

I have very little experience with dinghys, but on big boats a principal function of the boomvang is to hold the boom down when off the wind. Upwind the very powerful mainsheet and mainsheet track arrangements on modern boats keep the boom down and provide most of the power to flatten the sail and control twist. This is particularly so with midboom sheeting, which in many ways takes over the function of the vang until the traveller is at the end of the track.
Perhaps this is an aspect of sail trim that doesn't carry on from dinghys to keelboats.

 

[William_H]

Re: what\'s that kicker thing for?

You have got some good advice there already. The boom vang or kicker is used to provide downward load especially when the main sheet is released to allow the boom to move outward.
Now in heavy weather the mainsail needs to be flat for minimum camber so min. drag to allow the wind to be dumped from the sail with min. heeling. The maibnsail is flattened by outhaul at the foot, halyard tension and mast bend.
The vang will help to flatten but by easing the vang you can allow the top of the sail to fall away so reducing sideways pressure at the top so reducing heeling. So it becomes a bit of a conflict whether easing the vang will reduce heeling or increase it.
certainly as stated a wide powerfull traveller system for the mainn will go a long way toward doing the same job as vang except when the boomm is right out. olewill

 

[Hardley]

Re: what\'s that kicker thing for?

Hi, like you I used the kicker as you describe when sailing dinghies for 30 plus years, but soon learnt that this was not the way to go on fin keeled cruisers, the advice given is now my way of using the kicker.

 

[yoty]

Re: what\'s that kicker thing for?

A problem with Enterprise dinghys is the 'death roll'. This occurs on a run when the top part of the mainsail is allowed to move forward of the mast. This can generate unexpected lift that starts a tick-tock effect that will very soon end in a windward capsize.

Keeping a tight kicker on the run can help prevent this as can restricting the boom from going out too far.

If you find yourself in the 'tick-tock' predicament a good but somewhat damp way out of it is to lean BACKWARDS into the water taking the mainsheet with you and sheet in by grabbing two or three armfuls of mainsheet.

This is contrary to normal kicker trimming but might be the source of your dinking partner's theory.

 

[wooslehunter]

Re: what\'s that kicker thing for?

Some good stuff above: the kicker controls the top of the main & mast bend. If you're beating, then generally the main will be hard in on the mainsheet. This has a similar flattening but not exactly the same effect as lots of kicker. Hence as the wind increases, it's generally a good idea to pull on more kicker to: 1 flatten the sail and 2 stop the top from twisting away too much. But, hard on the wind, the main is sheeted hard in which tends to to both of these as well. So, as the wind increases even more start to let the kicker off. Then simply relaxing the sheet will allow the boom to rise a little & the top twists away and you get less healing effect. The bottom remains sheeted in & driving. But, remember to pull the kicker on again as you free off to go down wind or the top will twist away and cause the death roll. I have to admit, I never experienced and Enterprise death roll but certainly did in a Laser where the boom can easily go beyond 90 degrees. There are lots of different types of rigs around so this is applicable to a fractional rig without a back-stay. Other rigs, like mast head & back stayed respond in different ways.

The more strings you have to control a sail the more you can stretch & pull and get right or wrong.

Explanation of interaction of sheet, kicker, cunningham, outhaul & traveller anyone? In less than 1000 words of course.