balancing sails

SAWDOC

SAWDOC

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Any boat attempting self steering of any type needs to have a balanced sail plan, with the gib and main providing opposing forces forward and aft of the mast. That's the theory as far as I know.

When i examined this principle on my Offshore 8 metre, I found that the boat had a tendency to luff up no matter how loosely I sheeted the main. The previous owner purchased a larger self furling genny (110%) which seems to me to be impossible to sheet flat while fully unfurled. I have taken to leaving a portion of the genny unfurled unless we are on a run, in which case it all comes out. This enables me to sheet much flatter when close hauled but does not seem to solve the problem of a balanced rig.
Having said all that, the effort required to combat the off centre helm is fairly minimal. 9 is this lee or weather helm i am describing.
Any comments or suggestions for further experimentation greatly appreciated! /forums/images/graemlins/smile.gif
 
You are describing weather helm. There are lots of possible remedies, all of which have the aim of moving the CoE (Centre of effort) forward. A simple thing to look at is the shape and set of your mainsail. If it's very full with the draft (depth of the curve of the sail) well aft, you can improve things by moving the draft forward. Tightening the halyard will do that to some extent. If you have a Cunningham and/or a flattening reef (a very shallow reef that simply takes the fullness out of the foot), that will also help. A more radical solution if that doesn't cure it would be to have the sail recut or replace it.

You can also do things like adjusting the rake of the mast. Bringing the mast more upright will move the CoE forward, or if you have an adjustable mast step., moving the foot forward may help. Others will be along shortly with possibly contracdictory advice.
 
Ken
thanks lots of food for thought there

I take it that my introductory point is correct - one should have neither weather nor lee helm when sails are set up properly?
 
Yachts are normally designed with slight waether helm as a safety feature. Let go the helm & she will slowly luff up into the wind & stall.

So you mostly won't get & don't need perfect balance. Having said that it sould be possible to set up a well balanced vessel to beat into a steady breeze in smoothish water, let go the helm & she will sail a steady course for a good long tack.
 
I have always thought that a "little" weather helm is a good thing. In particular I have taught a few people to helm and it is reassuring to be able to say if it all goes wrong just let go and the boat will head up into wind. As said before, trimming the main with halyard, outhaul and kicker/mainsheet should help balance the rig. Playing with these is interesting and teaches you alot about how the sails work.
Allan
 
The concept of a balanced helm is really only possible in light conditions and or with small sails. As soon as the boat heels most hulls to varying degrees will show weather helm till ultimately you can't control it due to rudder gets more inefficient coming out of the water.

If you are sailing to windward then the weather helm as corrected by the rudder will tend to lift the stern and hence the boat to windward counteracting leeway to a degree. However at some point the drag of the rudder detracts from speed.

The hull shape of modern boats tend to exhibit more weather helm at heel. While you would think a long keel tends to be less effected by unbalance. So long keel traditional styles tend to self steer better than fin keel flat bottomed hulls which won't.

So I would suggest your concerns about sail balance are unimportant. If you have too much weather helm and it is heeling then reduce jib area and it should ease the weather helm.

Ken McCulloch is right about sail shape. This will help reduce heel a lot. However it seems to me you may be having difficulties getting the correct sheeting point for your jib. Possibly not enough room to get the sheeting aft enough. I thought roller jibs got worse with more turns rolled up. So yours should set best unrolled. But it should be OK with a few turns provided the sheeting is moved forward.

The few people at our club who have roller reefing have indicated they wish or have a smaller jib than you might expect to cope with good winds we get in summer. But it does leave them a little short in the winter calms. The rest of us prefer individual hanked jibs for windward performance.

It really is amazing how in UK I gather virtually every one has roller reefing of jib while at our club I can think of only 3 boats out of 50 that have roller reefing. With at least one who took off the roller and went back to hank on.

Re sheeting the main loosely that may have been time to fit a reef to the main. Certainly less is best when beating to windward in any real wind. good luck olewill
 
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I take it that my introductory point is correct - one should have neither weather nor lee helm when sails are set up properly?

[/ QUOTE ] Like others here I wouldn't say that. What you really, really don't want is lee helm! That will make your boat very difficult to control and potentially dangerous. As WilliamH explains sail balance is a dynamic process and (for example) any change in wind strength or sea state will have an effect.

My own boat has a fractional rig with a large main and needs careful trimming to reduce weather helm to a minimum but it never completely goes away.

Fair winds
K
 
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I have always thought that a "little" weather helm is a good thing.

[/ QUOTE ]

Indeed, 5 degrees of rudder is about right. Any less and you lose the lift from the rudder and any more and you are slowing the boat down.
 
Hard to say without seeing the boat in question, but the basic principal is to move the CoE aft. (Assuming you can't move the centre of resistance...)

The first step should be rig setup, bringing the mast back (increasing the rake) should bring the CoE back.
But if the setup is generally ok, but you have one off lee helm, then you can tinker with the sails.
My first point of call would be genoa halyard tension, broadly speaking increasing it would bring the curve forward and decrease the drag of the sail. If that didn't do it then I would be looking at reducing the headsail size, or if I was sailing with a deep reefed main possibly looking at shaking a reef out.
 
Hi all, i cant sse shortening foresail as suggested will stop weather helm as it will do the opposite. iether that or i am getting too old !! regards.....
 
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Hi all, i cant sse shortening foresail as suggested will stop weather helm as it will do the opposite. iether that or i am getting too old !! regards.....

[/ QUOTE ]

I was replying to the post asking for how to stop lee helm!
 
Hi Sawdoc
I think William-H pretty much has your answer , but I havent seen anybody quite put it thus: I get the impression from you that you are experiencing more weather helm than normal and almost having to fight the helm a bit. Your new jib/jenny is working too efficiently for original rig specs, and is drawing boat head around into wind all the time ?. Although it seems counterintuative, reducing jib size is the answer.
Like kittern , I go with a ketch
 
No you are not going long long....
The effect of heeling causing the boat to turn into the wind is far more powerful than the effect caused by classic balance explanation.
So reduce jib size reduces heeling so reduces the round up effect of heeling. It might be more logical to reduce main sail size but if main is small and genoa is big reducing main won't help much. olewill
 
[ QUOTE ]
Hi all, i cant sse shortening foresail as suggested will stop weather helm as it will do the opposite. iether that or i am getting too old !! regards.....

[/ QUOTE ]

He was answering ref. Lee Helm.

It is possible if genoa is LWP or significantly oversized that it can reduce weather-helm by reefing it back so CoE moves fwd and not adding to mains. Unusual but possible on those big sweeping penalty gennies. Once it gets somewhat fwd, the CoE will then as reefing conts. act as normal and weather helm increase as reefed further.
The point is the nett point of CoE - that is the total of Mainsail + Genny and where it acts in relation to hull form and mast.
But you knew that anyway !!
 
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