Battens tapered and CE

Tapering too far forward and it will move the draft forward.
Rick

....... and move also the CE forward ?
..... and it reduces the weather helm ?

Thanks

Not sure what boat you are doing this to. If a sloop, you do not want the draft forward where the jib overlaps.
With boat with semi wing masts (large major axis, low minor axis) the mast becomes part of the sail. So, you can move the draft forward enough so the overall draft is still in the low to mid 30% range.
On a fixed stick or roundish type mast like the Wave, you do not want to move the draft forward.
Rick

I have a 20 ft. cat with wingmast ....and with more weather helm;

The issue is if moving the draft forward then reduces also the weather helm for the fact that moves also the CE forward.

Excused my very bad English .....

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can't you just reduce the mast rake?

The mast is already now perpendicular. I have tried in the forum but I have not found arguments that they put in relation the tapering of the battens with the position of the CE.

Check the rudders; can you move the tip of the blade forward; this might help.

The short answer is

yes

the CE will move forward, but by a shorter distance than that of the draft movement.

The difference is due to the jib, obviously, and due to more complex aerodynamic reasons that I will leave for someone more qualified to explain.

I would only move the draft to move the CE if the sail would also perform better after the change. Otherwise, just change the mast and/or rudder trim, as already suggested.

.

The draft now is at 40% and i not consider the wingmast ..... i think that if the draft move to 30% the sail perform better ..... or not ?

Tilting the rudder forward solves the problem and reduces the possibility of ventilation.
If the mast is vertical, I would tilt the rudder forward as much as possible and then rake the mast back until the rudder feels right.
A totally neutral helm is not ideal, so don't try to completely eliminate weather helm.

How new is your sail? An old baggy sail will give the same result.

The wingmast is part of the airofoil and must be considered. If it is a 10% wingmast, the airfoil draft is at 50% and moving it forward should be beneficial.

Still, it depends on other factors. Best thing to do is check the draft position of the regatta winners in your class.

A few relevant questions:
What boat is it?
Does the jib overlap?
Do you use a downhaul? Is it powerfull enough?
How old are your sails and of what sailcloth?
Are the battens not tappered at all or you just plan to increase the tapper?

Thanks Luiz, but i don't understand the rule for which if I move the rudder forward i reduces the weather helm. please explains me. The sail is not old but it could be cut badly

in short: no for both questions.
the centre of effort is nearly not affected by the position of the draft, but by the amount of draft. Tapering the battens will increase the draft and you get more weather helm.

Too much weather helm is in most cases a too full main and/or a too flat jib.

Cheers,

Klaus

the boat is a prototype to which it has been adapted a sail...probably F18, the jib don't overlap ( i have self tacking ), i use the downhaul that is 8:1, the battens are tapered at 40%.......

It does not look natural, but tilting the rudder forward may improve its balance, depending on how it is now. Check the drawings:

They are from this website, which is recommended reading.

instinctively I think tilting the rudder forward move the CLR forward and inreases the weather helm ..... and don't understand ......

Take a look at my last post now that I edited to add pictures and a link.

seems much easier to try to adjust the mast/rudders than to sand battens (you can't unsand)

Thanks Luiz

I have read the link indicated and i have understand that in order tu reduce the wearher helm and tiller tug i must accept that the rudders work with extra drag from turnig, and to achieve a straight course slows the boat.
I have understand that for the hobie the advantages to increase the mast rake are greater of the disadvantages to make to work badly the rudders.

This is not my case .... I want to reduce weather helm in order to make to work the rudders with the smallest drag.

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if you have weather helm and you need to pull the tiller, you create lift - something you need to go upwind. If your boat is neutral, this lift comes from the daggerboards and it will produce drag as well.

Cheers,

Klaus

It really sounds like the sails dont fit the boat very well. Draft at 40% with a rotating mast dont have to be too bad, depending on the geometry. How full the sail is and what the profile looks like on the other hand makes a world of difference.

These sails that have been adapted to your boat.. Is the mainsail designed for the mast? If not, was the luff of the main re-cut to fit the mast? It just sounds like you have a mainsail that dont fit the rig or boat too well.

Any hope of pictures?

The sail is designed for the mast .....

Yikes!

Look at those wrinkles!

Any way to add more batten tension?

X2

Yes, wrinkles are monstrous ..... but this is an other problem for an other day ...... <img src="<>/blush.gif" alt="blush" title="blush" height="15" width="15" />

Do you have another picture where the mast is rotated properly?

The battens are not tied in as tight as they should be. The current setup will not help on your weather helm issue.

What cloth is the sail built from? Some sort of fiber reinforced mylar with taffeta?

How tight is the downhaul on in the picture? The wrinkles between battens should go away when you tighten them, but the large wrinkle from the downhaul and between batten #1 and #2 is a different matter. I just hope it disappears when you rotate the mast.

If you are going to do another pic sometimes, it would be helpful if you could lie down under the boom when shooting.

wouldn't tightening the battens create more draft?