Use(s) of Kicker

[Babylon]

I know this is terribly basic, however:

As I understand it, the kicker's primary function is to maintain twist in the sail when going downwind, when the mainsheet itself can no longer pull the boom down. So 3 questions:

(1) at what point of sail does it become necessary to tension the mainsheet?

(2) how much tension is necessary, and does this need to increase the further off the wind one sails?

(3) is the amount of tension also dependent on wind strength?

On our boat the kicker line is led back to a clutch on the coachroof by the cockpit - I've been told that it should never be necessary to winch the kicker in, that it should only ever be tensioned by hand (it has a 4:1 purchase). Is this correct?

 

[photodog]

I dont understand your question number 1.....

The use of your kicker will depend upon the particular set up on your boat... the kicker works in conjunction with the mainsheet and the traveller (and the backstay adjuster on a fractional rig) to maintain the appropriate sail shape for the conditions.... (Oh and the Main Halyard and outhaul as well....)

If like ourselves you have no traveller ( /forums/images/graemlins/frown.gif) then you will probably make more use of the kicker upwind as well as down... as it is our primary tool for keeping the sail flat and controlling twist on any point of sail (except when close hauled.... whan the mainsheet effectivley takes over..) The kicker is a important tool in our arsenal to control the power of the main, in reality it is the primary tool, as my backstay adjuster is underpowered.

So, when going upwind you can flatten the sail to depower the main by using the kicker if your point of sail is ouside of the range of your traveller or if you have no traveller....

/forums/images/graemlins/smile.gif

Now I am sure someone more qualified than I will give a better explanation and point out that I am doing it all wrong!!

/forums/images/graemlins/smile.gif

 

[flaming]

Assuming you're asking in terms of the cruising boat, and not your recent forray into the world of racing?

If so, the kicker actually gets more important upwind in a way, as very few cruising boats have propper mainsheet travellers, so have to rely at least partly on the kicker to balance angle of attack and twist even closehauled.

Does your boat have leach telltales on the main? if not, fit some. Bits of ribbon on the end of each batten is about right.

These help you see the flow of air off the back of the sail, and hence the impact that the twist is having.
This is a subject that has whole books dedicated to it, but absolute simplistic approach is that upwind you should tension the leach (using whatever method works best on your boat) until the top telltale flys 80% of the time. This is for flat water and moderate wind strengths. If either waves or strong winds exist, add more twist.

As you bear off the wind the sail should be more twisted, so kicker eased. It's kind of hard to describe how much, but it will just "look right". And from a cruising standpoint the kicker is normally just left from reach round to run.
It's important to remember that as you add twist to the mainsail you should also add it to the jib by moving the car back, otherwise the untwisted top of the jib will just force air into the back of the main, causing drag and slowing you down.

As to the winching... Really hard to say without giving it a yank and seeing if it's enough, but you're probably right, only use the winch sparingly if at all. To date I've broken the fitting where the kicking strap meets the base of the mast on two cruising boats by winching the kicker. I took this as the final piece of evidence that the sail was so stretched that I couldn't get the set I wanted without overstressing the system.

 

[photodog]

So your saying that as wind strength increases, we should increase twist? Ie back off the kicker.......

We always flatten the sail by hardening up the kicker as wind strength increases to flatten the sail and depower the main..... which seems to work for us!!

We do have a FB main...so does that make a difference??

/forums/images/graemlins/smile.gif

 

[Babylon]

Flaming, Photodog

Yes, cruising boat. Have a basic traveller with sprung pins that need to be released so the mainsheet can be hauled over by hand (rather than a sophisticated setup with blocks etc). Have just had telltales sewn into the leach of the mainsail specifically so that I can start to guage the correct twist (also now telltales on the foresails). Don't have a backstay tensioner.

So, the basic principles as I understand it:

On the wind: mainsheet (also, as I now understand it from your replies, kicker if needed) to control twist; traveller to control angle of sail to wind (and therefore helm balance).

Off the wind: kicker to control twist; mainsheet to control angle of sail to wind.

Strong winds: to flatten sail, increase halyard tension, clew outhaul tension, and use mainsheet, with kicker to help (or slacken to increase twist?!).

Light winds: to give sail more draught, slacken all three above, but monitor twist (by reading leach telltales) and increase tension on kicker if needed to reduce twist.

I'm aware that there's also cord position to consider, but I'll worry about that later once I've got the hang of the basics.

Also,always try to trim heads'ls first (cutter rigged, so yankee first, then stays'l) both with telltales now to help monitor twist, before trimming main.

Will experiment with kicker tension - judging by the last owner(s) damage to the kicker blocks and fitting at the mast-base, I'll stick to tensioning by hand only for the time being.

Hope I understand this more clearly now - will just have to try put theory into practice until I get it right!

Thanks

Babylon

 

[mlthomas]

What a cracking post for us novices.

 

[rwoofer]

Really depends on the boat. If you have a fairly flexible mast, the flattening effect of the kicker can be more beneficial that the twist at the top of the main. I had a 707 without a backstay and we would use the kicker to flatten and the mainsheet to tension the forestay (in lieu of backstay). Meant the head of the sail was stalled a bit, but was much faster than letting it twist off.

That's all a bit technical for the racing boats. For cruising boats it is probably best to stick to the telltale rule of thumb (the top leech line flying 50-80% of the time).

 

[bbg]

That effect is unlikely to appear on a cruising boat. On a much smaller boat a tight vang can push the boom forward, inducing bend in the mast (and flattening the main) but you're just not going to see that on a cruising boat.

To Babylon - if your traveller is on a system that makes it difficult to move, (and if you don't want to invest in a system that will move), your vang will become more important upwind.

In general, in light to moderate winds, you will want the top batten parallel to the boom. That is not the end of trimming the main, but it is a good rule of thumb and starting point. From there play with the vang and mainsheet to get all telltales flying.

As the wind increases and the boat begins to get overpowered, you should begin depowering it by flattening the sail - using luff tension (halyard or even better - cunningham) and outhaul. If you need to depower further, easing the mainsheet a bit (but just a bit) to change the angle of attack would probably by my next step (similar to easing the traveller down the track), followed by easing the vang a bit and allowing the top of the main to twist off. Then you're into reefing.

 

[michael_w]

4:1 is pretty weedy. I had 32:1 on my Merlin-Rocket!

If you are worried about things breaking, try replacing one of the shackles with a lashing. The lashing will act as a fuse so you won't break the boom.

 

[gandy]

Just looking at our own cruising boat, I very much doubt that the kicker would be strong enough to properly flatten the sail, and if it was then I'd worry about the boom especially with a loose-footed main.

I'm comparing it to our Wayfarer where we had a 12:1 kicker led back and that was the only way to control twist upwind. The setup on our Griffon just wouldn't be strong enough to do the same.

 

[flaming]

[ QUOTE ]
So your saying that as wind strength increases, we should increase twist? Ie back off the kicker.......

We always flatten the sail by hardening up the kicker as wind strength increases to flatten the sail and depower the main..... which seems to work for us!!

We do have a FB main...so does that make a difference??

/forums/images/graemlins/smile.gif

[/ QUOTE ]

Well, like I said really thick books have been written on this subject! FB main does actually change things slightly, mainly because they are much harder to depower, and because they are much more stable it can be harder to tell when you've got it wrong.

It's worth remembering what the kicker/mainsheet does that is different from the other flattening controls, namely they harden the leach. Hardening the leach in essence gives you pointing, at the expense of straight line grunt, extra heeling moment and a narrow (hence difficult to drive to) groove.
So sometimes a very flat sail (halyard, outhaul, cunningham all maxed) and a hard leach (kicker/mainsheet on hard) is exacty the right setup. In general this would be in freshening breeze in flat water.
Other times you would find that the extra point of the hard leach is effectively screwing you into the wind, or the narrow groove is too difficult to drive to, or the boat is overpowered, or waves are stopping you. In this case you should add twist to help you power through the waves.

Classic example in solent racing, beating with the tide = flat water = hard leach for pointing.
Beating against the tide = choppy water = soft leach for the grunt to get through the waves, even when the wind strength doesn't necessarily call for it.

 

[flaming]

[ QUOTE ]
Just looking at our own cruising boat, I very much doubt that the kicker would be strong enough to properly flatten the sail, and if it was then I'd worry about the boom especially with a loose-footed main.

I'm comparing it to our Wayfarer where we had a 12:1 kicker led back and that was the only way to control twist upwind. The setup on our Griffon just wouldn't be strong enough to do the same.

[/ QUOTE ]

No it wouldn't. It was on a Griffon that I first discovered that kickers can be over tensioned!

 

[lw395]

Big difference from dinghies. In dinghies, booms are now strong enough we can get all the leach tension we want from the kicker, so the sheet is just used (in many cases, not all) to move the main in and out like a door hinging. Travellers have all but gone, except where they are used to move the sheet up to weather, to further remove leach tension from the sheet.
Not so in (most) yachts, the sheet delivers most of the leach tension when close hauled. Travellers are used a lot more to let the whole sail in or out. In many cases, there is more load on the kicker offwind.
It depends what the boom and fittings will take!
A decent ball race traveller system for the sheet can make a huge difference, if it is well enough sorted to play the traveller, dumping it in gusts. Particularly on a lighter boat.

 

[gandy]

Our problem is that the Griffon doesn't have a proper traveller either, and no obvious place to put one.

 

[oilyrag]

You don't say what type of boat or rig you have but, if you have a standard cruising boat with a masthead rig and no backstay adjuster, the kicker will be neither designed to, nor capable of, doing anything other than controlling mainsail twist as you come off the wind.
It is correct to say that using a multiple purchase or hard winching on a kicker in an attempt to 'tune' such a rig will achieve no more than breaking something as Flaming attests above.
If OTOH you have a fractional, tune-able, rig then other posters' comments apply.

 

[Nico]

Babylon, I would say you have a very good idea of how it all works. On the wind you tension the leech with the main and control the angle with the traveller if you have one. Once the traveller is at the end of its travel you have to ease the mainsheet to increase the sail angle of attack and from here on out you use the kicker to adjust leech tension.

On the question of flattening the sail as the wind pipes up I would say that you use halyard tension to keep the draught forward, the outhaul to flatten the lower third of the sail, mast bend to flatten the middle (if you have that luxury), but allow the head to twist off to depower it. Racers will often hold on to a full main well above 20 knots true, maybe putting up with the main backwinding.

 

[dunedin]

There are big differences between the effect of kicker on a racy boat with 3/4 rig (ie forestay attached roughly 75% up mast, not at the top) compared to a masthead forestay.
With the 3/4 rig the kicker an backstay are used to bend the mast in strong winds to flatten and thereby reduce power in the mainsail. This also happens to some degree in masthead but much less.

We use kicker upwind and down - important in a blow upwind to avoid the boom rising if need to ease off mainsheet in a gust. We hand pull up to about F2, thenwind (on 36 footer).

Kicker is a useful control on a reach. Today we were reaching in the sunshine in 20 knots, with boatspeed ranging 7.5 to 8.5 knots. In the gusts I eased the kicker to let the top of the mainsail depower and avoid risking a broach, winch back on as wind eased. Fun !

 

[kirielad]

[ QUOTE ]

With the 3/4 rig the kicker an backstay are used to bend the mast in strong winds to flatten and thereby reduce power in the mainsail. This also happens to some degree in masthead but much less. Quote

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Sorry for the Fred Drift - but I don't understand about flattening the sail as described. - I'm surely missing something obvious, but to my mind bending the mast backwards (via the kicker or adj backstay) will give the sail more chance to 'bag' at the middle and top ?

Can someone point out what I'm not getting here pls?

 

[Nico]

[ QUOTE ]
[ QUOTE ]

With the 3/4 rig the kicker an backstay are used to bend the mast in strong winds to flatten and thereby reduce power in the mainsail. This also happens to some degree in masthead but much less. Quote

---------------------

Sorry for the Fred Drift - but I don't understand about flattening the sail as described. - I'm surely missing something obvious, but to my mind bending the mast backwards (via the kicker or adj backstay) will give the sail more chance to 'bag' at the middle and top ?

Can someone point out what I'm not getting here pls?

[/ QUOTE ]

If you bend the mast then the middle of the mast "moves forward" relative to the leech. This "stretches out" the middle of the sail. It's hard to describe but quite obvious when seen. As well as flattening out the middle of the sail it also opens out the leech. You can see the top batten opening out as you crank on the backstay. This is on a fractional rig. On a masthead rig the backstay, if present, just tensions the forestay.

 

[kirielad]

Thank you - I can picture that now. My own boat is fractional rig, adjustable backstay, but fitted with inline spreaders - so no mast bend.

During the winter refit I have modified the spreader ends so they have become swept to induce mast bend (chainplates were aft of the mast anyway). When the mast goes back up next week all the useful tips above will be put into practice.

Thanks again.