Kicker to the cockpit

[Ruffles]

Had a day out on a Reflex 38 with Sailing Logic. Was struck by the ability of the kicker to spill wind in the gusts. Mine is a very simple 4:1 arrangement. I set it for upwind by sheeting in the main running forward to pull it in. Not very dynamic!

View attachment 20872

View attachment 20873

I reckon I could alter the existing arrangement by adding another 4:1 cascade to give 16:1. The new kit could be relatively light weight (i.e. cheap) as it's only seeing 1/4 of the load. Question is how light?

What options can you see in doing this? I could reverse the existing block, remove the jammer and take the new cascade to the foot of the mast.

 

[lw395]

You could also put the 4:1 in what is currently the fixed end, as a kind of fine tune.
Otherwise be sure not to restrict the travel, particularly if you want to be able to lift the boom high on the topping lift or scandalise the sail.
16:1 is what we have on dinghies. I would think it would be a good starting point on a small to medium yot, but you'd want some decent string to grip and a fairly strong cleat.

 

[Ruffles]

You could also put the 4:1 in what is currently the fixed end, as a kind of fine tune

That's the idea. The question is what size blocks! 20mm?

There's also the issue of how to run the line to the foot of the mast without the thing adjusting itself as the boom moves out. I have a free organiser on deck.

Probably easy to get it to work given a large bag of assorted blocks. But I don't want to have to buy a bag of assorted blocks! Could get expensive.

 

[bbg]

You could get it to 8:1 very easily by doing the following:

- Remove the top of the system from the boom
- Attach a block to the boom
- run a line from the base of the mast up to the new block on the boom, and down away from the block a few inches (line should be led from the forward side of the block aft, so it hangs down behind the block)
- now attach the top of the system to the line you have just led (either splice an eye in the end or use a bowline)

If you want to lead the control line aft, just take it out of the final block in your system (which leads to the cam cleat) and lead it instead to a separate turning block fixed to the base of the mast, then lead the line aft to a cam cleat fixed to the deck.

6 mm dyneema cored line will be strong enough; 8 mm will be more comfortable on the hands

 

[bbg]

There's also the issue of how to run the line to the foot of the mast without the thing adjusting itself as the boom moves out.

One way to do that would be to make the system double-ended so it leads to both sides, but that will require a lot of new blocks.

Here is a formula for calculating mainsheet load which you can plug into an excel spreadsheet

=((B10*B10)*(B11*B11)*0.02104*(B12*B12))/((SQRT((B11*B11)+(B10*B10))*(B10-B13)))


Where B10 is foot length in metres
B11 is luff length in metres
B12 is wind speed in knots
B13 is distance from outboard end of boom to attachment point

If you use B13 as the vang attachment point (and increase the distance from the end of the boom), you will see the loads shoot up. Of course it doesn't tell the whole story, because as wind speed picks up, you will reef and reduce the foot and luff length, but it might help your estimates.

 

[Salty John]

Or, on the assumption that you'll reef before 25 knots apparent, just take your mainsail area in square meters and multiply by 25, answer in kilograms. That would be your maximum mainsheet load. Eg. a 30 square meter main will have a mainsheet load of 750 kilograms.
You can get a bit more technical and add 10% if it's a multihull and 10% if you have a large roach.

 

[bbg]

That looks on first blush like a pretty good rough estimate, but only works for load at the end of the boom. It doesn't take into account the distance from the end of the boom where the mainsheet is attached.

In your example, using a main that has a 4 m foot and a 15 m luff, the load at boom end would be (with my formula, which I think came from Harken) 762 kg at 25 knots. Pretty close to your estimate. Move the attachment point in by 1.5 metres and the load jumps to 1220 kg i.e. by more than 50%.

 

[Salty John]

That's mainsheet load, by the way, you can typically halve that for a kicker.

 

[Salty John]

That looks on first blush like a pretty good rough estimate, but only works for load at the end of the boom. It doesn't take into account the distance from the end of the boom where the mainsheet is attached.

In your example, using a main that has a 4 m foot and a 15 m luff, the load at boom end would be (with my formula, which I think came from Harken) 762 kg at 25 knots. Pretty close to your estimate. Move the attachment point in by 1.5 metres and the load jumps to 1220 kg i.e. by more than 50%.

That's correct, it only works for end-boom sheeting - you have to adjust for mid-boom sheeting and that depends to some extent on whether the load is spread over several attachment points.

 

[bbg]

And the real reason I posted the formula was to help the OP in calculating loads at the kicker, which - because it is well inboard of the boom end - shoot up dramatically.

I certainly agree with your approach of using a top-end windspeed (before reefing) as a basis for calculating the maximum loads.

 

[bbg]

That's mainsheet load, by the way, you can typically halve that for a kicker.

Don't you mean DOUBLE it for a kicker?

Edit - in my example (foot 4 m, luff 15 m, wind 25 knots) the load would jump from 762 kg at boom end to just over 2,000 kg at the kicker attachment point (1.5 m from the gooseneck). Well more than doubled.

Further edit - just realised, all of these calculations assume there is only one load-bearing point, which is not true. In fact the load is shared to a greater or lesser extent between the two systems (sheet and kicker). But in some circumstances the load is effectively on one system or the other. Upwind the load can be entirely on the sheet. Reaching / downwind the load of holding the boom down can be almost entirely on the kicker.

 

[Salty John]

Don't you mean DOUBLE it for a kicker?

Edit - in my example (foot 4 m, luff 15 m, wind 25 knots) the load would jump from 762 kg at boom end to just over 2,000 kg at the kicker attachment point (1.5 m from the gooseneck). Well more than doubled.

Yes, if you were selecting components for a mainsheet system that attached at the kicker point. What I meant was that the the load requirement for a kicker is about half that of a mainsheet.
For instance, Schaefer recommend a kicker system with a max SWL of 400kg for a 30 sq.m main, but an 800kg SWL for a mainsheet system (end boom). That seems reasonably consistent with other makers.

 

[Ruffles]

I think I'll look up the rating on the Lewmar blocks and divide by four!!

With a bit of luck it may be possible to put the turning block on the kicker attachment point as it will be bisecting the angle as it were.

Could do the whole thing for less than £60 if I use a standard rather than pivoting clamcleat.

 

[marklucas]

Had a day out on a Reflex 38 with Sailing Logic. Was struck by the ability of the kicker to spill wind in the gusts.

Indeed, many racing boats have a crew member dedicated to the kicker for this very reason. As a gust arrives and the helm doesn't think the boat can be held against it, the first call is "Kicker!"

 

[RobbieH]

If you want to lead the control line aft, just take it out of the final block in your system (which leads to the cam cleat) and lead it instead to a separate turning block fixed to the base of the mast, then lead the line aft to a cam cleat fixed to the deck.

I lead mine via organiser and jammers back to a 20st winch on the cabintop. No problem with getting enough power to use it or releasing quickly.

 

[Quandary]

Indeed, many racing boats have a crew member dedicated to the kicker for this very reason. As a gust arrives and the helm doesn't think the boat can be held against it, the first call is "Kicker!"

More sophisticated than on our boat where the equivalent cry is 'DUMP'
The first Sigma I had had been commissioned by a dinghy sailer with some unusual but very effective gear but all within the OOD rule. The vang (I think it was IYE) consisted of a rigid rod with a six wheel mainsheet car running back and forward on a track under the boom. It was operated by a double block purchase which led back to a clutch on either side of the coachroof where it was usually operated by the pitman once she was out on the weather rail. The power was increased considerably by the relatively shallow angle of the vang to the boom and adjustment was obvious and instantaneous. It also supported the boom in light weather without resorting to springs. All in all a very effective system and probably cheaper than the modern equivalent but I am baffled as to why it did not catch on.

 

[Seajet]

Chinese Gybe

" Dump The Vang ! " is a cry often heard on racing boats.

In normal sailing a quickly releasable kicking strap / boom vang is handy for depowering the mainsail, possibly most useful for allowing the boom to be lifted by the topping lift for people in the cockpit - on the mooring/ berth - or fitting a boom tent.

If slackening the kicker when running in strong winds, beware the Chinese Gybe, where the upper part of the sail gets very full then flips and gybes over before the lower part; this can result in the sail tearing along a horizontal seam.

Not just expensive, it's rather difficult getting the upper bit down !

Yes, tried this, fortunately on a 10' Caricraft dinghy.

On the other hand, sailing up to a mooring and scandalising ( depowering ) the mainsail by letting off the kicker and pulling on the topping lift is a sheer joy, and should be used more often.

 

[ProDave]

On my little boat, with an almost identical setup to the OP's boat, I just made a very simple modification.

Instead of using the cleat at the mast foot, I ditched that, and just led the line forward to a cleat on the coachroof, just forward of the hatch.

That makes it easily reachable from the cockpit.

 

[lw395]

Yes, if you were selecting components for a mainsheet system that attached at the kicker point. What I meant was that the the load requirement for a kicker is about half that of a mainsheet.
For instance, Schaefer recommend a kicker system with a max SWL of 400kg for a 30 sq.m main, but an 800kg SWL for a mainsheet system (end boom). That seems reasonably consistent with other makers.

If the kicker is taking 90% of the leech tension, dinghy style, the kicker needs to be somewhat stronger than the sheet. However, many yacht booms are not designed for this.
Most modern dinghy rigs, the sheet will be pulling mostly horizontally, leaving the kicker to do the vertical component. (at least on a breezy day) This is asking a lot of the boom, but does make playing the sheet easy.

 

[William_H]

Kicker or vang

To me the power hence value of a kicker or vang is in the distance vertically from the boom to the attachment. Usually cabin top. In a dinghy this can be down to the keel so very good but many cabin KB this distance is close. There is no way you can get real power from a kicker if this space is tight. More purchase will tend to bend the boom because the load on the sail is ultimately on the end of the boom.
To move the kicker attachment on the boom out from the mast simply makes the leverage worse because of the angle of the tackle.
So on my little boat with not a great distance boom to cabin top compared to boom length the kicker becomes just a preventer to stop the boom rising when running.
The real pull down power for the boom comes from a wide traveler system. Plenty of pull down power there.
Having said that I have sailed on 2 types of local racing boats Foundation 36 and Bakewell White 8. Both these boats have a console in the middle of the cockpit floor. from this emerges 3 ropes for main sheet man.
One is mainsheet (no traveller) another is backstay tension the other is boom vang. The theory being in a blow he first hauls on the backstay then dumps the vang then finally eases the mainsheet with severity of gust. (I think that is how it works) But yes vang/kicker has huge purchase. Both these boats are buitl as identical fleets for matchracing etc.But definitely for skilled sailors. 36ft no engine no electrics 2 jibs one main no reefing one spinnacker. or the smaller BW8 the same. olewill