flatening reef

[30boat]

I remember those from earlier times and was thinking that fitting one to my very baggy main might be a temporary solution until I order a new one.The sail is relatively new and came with the boat but the cut is appaling and a recut is probably not even viable.
Any views?
Thanks

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[boatless]

Very handy, quick to put in and out. Would always have one on a new sail. Take it that you have cunningham already?

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[gandy]

30boat, could you explain?

I don't know what a "flattening reef", but it sounds like our Wayfarer could do with one (baggy mainsail). I already have good outhaul, cunningham, kicker, and "conventional" slab reefing. We get a lot of weather helm in windy conditions.

Tony S

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[snowleopard]

sounds like a good argument for starting off with a loose-footed main.

one thing i can be sure of, if the top of the main has lost its camber it's fit only for the dustbin!

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[sailorman]

"leach cunningham" tightens the leach & foot thereby flattening the sail.
the "luff" cunningham only tightens the luff when the head of the sail is hoisted to max hoist (the black band) then the only way is down to comply with racing rules

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[gandy]

Sailorman, so are you saying that a flattening reef is effectively a downhaul for the leech?.

(Another reason for using the Cunningham on a small boat without winches is that it is normally a multiple purchase tackle, 4:1 on mine. The halyard is normally just a single pull)

Tony S



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[boatless]

Not exactly, it's just a normal leach reef, but only about 9-12" up. Just gets rid of the foot and flattens as a normal reef would, without the loss of area.

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[geoffatstanpit]

My main (Parker 21) has the requisite cringles for a flattening reef but only 3 lines through the boom so I have to choose whether to lead for outhaul, flattener and reef 1; outhaul, reef 1 and reef 2 (usual config); or reef 1, reef 2 and reef 3 (when windy). Halyard tension makes some difference to sail flatness and I have an adjustable backstay that can put a frightening bend in the mast but I can't say I can see any difference in heeling moment however that is set. Does help the jib though.

Do people really find that all these things make much difference?

Geoff

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[sailorman]

on racing sails the leach cunningham is the normal "clew cringle" position & a "droopy boom" was formed by adding another cringle say 150 > 300m/m lower, to gain extra sail area f.o.c. under racing rules.
a line is permantly rove from aft end of boom to the leach cunningham to enable the sail to be flattened to windward & full when "off the wind"

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[Robin]

To an extent the flatener is a rule cheater. You make the sail full height and full foot to the dimensions measured and where the black bands are placed, you do this with the sail tensioned lightly as for light to moderate winds. When the wind increases from light to a good full sail breeze, you can retension the luff using the cunningham (ie the top of the sail doesn't go above the black band) and you can tension the foot using the flatener (and the foot stays within the black bands), The flatener also lifts the end of the boom a little higher for more clearance and the net affect is a sail that is now tensioned correctly overall AND the bottom 1/3rd has been flatened. The middle and upper parts of the sail are not really affected especially if the sail is fully battened.

Of course the range of windspeed where the flatener is effective is fairly limited, much more and the first reef goes in, it is most useful going upwind.

We have 3 reefs and a clew outhaul in the boom so we can tie the normal clew off and use the adjustable outhaul on the flatener, it goes back to the reef winch/jammer on the back of the mast, whereas the 3 full reefs go back to cockpit winches.

Can you use it to correct a bad sail - no I doubt it very much.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[BrendanS]

OK, explain this in plain english to a mobo who is interested?

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[Robin]

It was in plain English if you are a raggie!/forums/images/icons/smile.gif

OK I will try again.

You tension sails to suit the wind strength. As the wind increases the draft of the sail moves backwards towards the leech, bad news for speed and the boat will be overpowered and need too much rudder to correct weather helm. More tension in the luff will pull the draft forward again, more tension on the foot will reduce the amount of draft (curvature). Too much draft too far back gives forces which resolve into more sideways and heeling force and less forward force.

Ideally you will want a sail that especially for racing is as big as will fit on the mast and boom, within the measured (black band) points. But if you have the luff and foot sized for maximum tension when stretched out in use, in light winds and normal tension the sail will be maybe 8" or more shorter on both lengths.

So you cut the sail to be full height/foot for normal F2/F3 tension say, then when you need more tension you cannot pull the halyard up more or the clew out more.

So what can you do now? Well you could reef, pulling in the first reef shortens both luff and foot so you room to pull harder on the halyard or outhaul. But the wind strength doesnt justify the 1st reef so what else can you do. Well ages ago Dr Cunningham invented a hole and put it (eye cringle) about 12" up the luff from the boom, threaded a line through it and pulled DOWN on the luff to re-establish tension and pull the draft forward again. Later on a Mr Flatener came along and did the same up the leech /forums/images/icons/smile.gif the line through this pulls both down and back, so lifts the boom end and pulls out the sail foot, flatening or reducing the draft of the sail, at least in the bottom bit of it.

Do we use a flatener whilst cruising? Yes we do. On our boat it is the only 'reef' that requires me to go on deck, the Cunningham is tensioned with a spare mast winch, the flatener uses the mast reef winch. Otherwise our 3 main clew reef lines and the 3 tack reef lines now go back to the cockpit and coachroof mounted winches. The flatener goes in when going upwind mostly, probably at about 12/15kts apparent wind speed. There are other factors like moving the traveller down it's track as well that help keep the boat powered up yet on it's feet and in the groove (baby). Lots of options, depends on sea state wind steady or gusty but you are now (upwind) on the limit of needing a reef. One thing though is certain, weatherhelm and excess heeling (the 2 are complimentary) is not fast, it might look it but it isn't.

Does that help or have I confused you more?

Robin




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[boatless]

I thought Flattener was a German?

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[Robin]

Might have been, so Herr Flatener then. I believe he was a Celine Dion fan too.

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[Gunfleet]

Come on then, who the hell was Cunningham?

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[Robin]

I think he was a Doctor of what I know not, holes maybe? I believe he might have been an Internationl 14 dinghy sailor? He would be very rich if he had patented the idea, I wonder if you could actually patent a hole. Mind you a few around her have holes named after them too! /forums/images/icons/smile.gif

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[chippie]

A gyneacologist?

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[William_H]

Some mainsails are really made for Flatteners because they have a really baggy foot in some cases made of lighter material which is really only made for ghosting conditions. In that case the flattener makes the mainsail more normal.
For the respondent who has too much camber too much heel and weather helm he could try a flattener but of much the same effect only more is to put in the first reef. Providing you can get enough outhaul effect by an additional outhaul or positioning of the outer reefing point on the boom then the sail should flatten out. If there is too much camber in the top of course only halyard tension and mast bend can help then maybe not enough. Yes all these things do make a difference even fo a cruising boat.
regards will

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[tsmyth]

An excellent discussion for a dummy like me.

I take it that if one doe not design for racing the Cunningham is probably not needed, because one can tension the luff using the halyard?

To reveal my ignorance further, please clarify what keeping the boat "on its feet means". I presume you mean upright?

Ray

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[boatless]

No, cunningham is so simple it's ridiculous. Instead of grinding away on a winch, with a bar-taut halyard, you have at leasy a 2:1 advantage, but can add more if you want.

On it's feet, is, upright and in control.

Don't agree that sails with flattening reefs are designed with any more fullness.

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