weather helm, help !

[cal40john]

Originally Posted by malcolmcampbell

I am gramos's friend with weatherhelm problems. firstly thanks all for your replies .the boat has had helm problems since I bought it [not progressive]and in spite of much sail tweaking over 2 atlantic passages without huge improvement leading me to try something more radical. The boat is a home design and home built by the previous owner. Even though she is well built I still feel the mast position is too far aft and as I have a trip from Greece to the Virgin Islands planned for this August I feel I must take this oppotunity to tackle this problem for once and all. On previous crossings I would be continually reefing to keep my aries in control thus losing valuable boat speed. Any further comments from the readers would be most welcome.
Cheers Malcolm Campbell

Weather helm has been helped by adding a bowsprit in cases like yours, a lot less drastic than moving the mast. I agree with Pblais that a naval architect should be consulted. Another thought is to find a good racing skipper in the area, give him a beer and a ride. You'll probably get more comments than you want to hear about sail shape, rig tension/position. I can almost guaauntee that if your sails are over a year old he will tell you to get the sails replaced or recut at a minimum.

John

[Alan Wheeler]

When you say "home design", how expert was the designer/biulder???
I agree with Paul and with John. But instead of a race skipper, I would be employing the help of a sail maker. They have the experiance and eye required to see what a sail is doing and just how to fix that. I also suggest that if this problem is something that is a changing issue over time, then the sails can be the only thing changing. And perhaps the rigging getting slack and needing retensioning. But sails No1 suspect.

...could a category be added to FAQ for things like this. The question could simply be "How do I correct weather helm?" and the text is simply your response

I will paste Gords comment as a "Study Hall" article.

[Weyalan]

Sounds like you may need to replace all the gear under the windex...

[cal40john]

Yet another idea. A boat I used to sail alot, the Cal 34 mark 1 has weather helm. The marks 2 and 3 do not. The mark 1 has a 14 foot boom that goes almost to the backstay, the others have a shorter boom and taller mast. Apparently a design flaw in the original version (even good designers make mistakes). The owner of the Cal 34 mk 1 bought a used sail that probably was supposed to be a close fit for the newer 34s. I don't believe the database had the two versions of boats listed. We managed to get it to fit by permanently fixing the sliding gooseneck to the bottom of the track then adjusted luff tension with a cunningham. There's a about 2 feet of boom with no sail on it. The boat balances much better now. We probably lost a little light air boat speed as I guess the used sail might have been slightly short of a full hoist on the mark 2 and 3 boats.

John

[Sailormann]

Weather helm has been helped by adding a bowsprit in cases like yours, a lot less drastic than moving the mast

I think this is the most sensible thing to do. Moving your mast is pretty drastic - will take a lot of time and energy to do properly. You'll need to reinfoce your hull and/or deckhead to handle the trasnferred loads, and if you end up moving it too far ahead, well you're back to square one again.

If you start with a long bowsprit, you'll be able to shorten it as needed to obtain ideal trim, and if the issue turns out to be the size/shape of your skeg or rudder, it's fairly easy to remove the bowsprit.

[GordMay]

See also “weather helm, help!"
cruisersforum.com/forums/f47/weather-helm-help-11788.html
http://www.cruisersforum.com/forums/...elp-11788.html

[anotherT34C]

I have a (somewhat) related dilemma. I have a centerboard, but my primary day-sailing grounds are very shallow (LI's Great South Bay). I can almost never safely use my centerboard (it locks into place) to achieve balance.

Now, my boat came with a yawl option (VERY long cockpit, short boom) so I'm thinking about retrofitting a small mizzen to compensate for the (mostly) unusable centerboard. Is this a rational course?

[Kanani]

Originally Posted by anotherT34C

I have a (somewhat) related dilemma. I have a centerboard, but my primary day-sailing grounds are very shallow (LI's Great South Bay). I can almost never safely use my centerboard (it locks into place) to achieve balance.

Now, my boat came with a yawl option (VERY long cockpit, short boom) so I'm thinking about retrofitting a small mizzen to compensate for the (mostly) unusable centerboard. Is this a rational course?

Not worth the $ IMO.

Find some other yawl owners and ask their opinion before you go sinking $ into it. Basically, a yawl is a sloop with the main-mast mounted too far forward but not far enough to make a ketch out of. The mizzen mast on a yawl does little, if anything at all.

[svquest2]

The fullness of the sails contribute immensely to weather helm by increasing your angle of heel. As your angle of heel increases the "weather Couple" increases. The "Weather Couple" is the force times the horizontal distance between the center of forward resistance of the hull and the forward component of the center of effort of the sails. The more you heel the greater your "weather Couple" and the greater your weather helm

Again this can be corrected by Twisting the tops of both sails as previously described, reefing, or getting your sails recut or replaced, so they are not so full. but when sails begin to blow out you heel more and go slower both by the loss of drive and the application of the brakes (the rudder).

[Zach]

I've been doing a lot of reading about weather helm lately.

The basics: Weather helm happens because the center of effort is aft of the center of lateral resistance. Run only the jib, and the center of effort is way forward of the clr, run only the main and it is way aft. Lee helm happens when the pressure is in front of the center of lateral resistance... the bow blows down wind.

Some of the ideas I've come across:

The first is to replace the sails. CE is determined by the dimensions of the sail plan... what we are really saying is the Center of Pressures, and where they are located. The center of pressures of sails and their locations explains why head sails give less weather helm than others. A bagged out sail moves the center of pressure aft... (On the sail!) the further aft the pressure the more weather helm. This also means the driving force is located further back. Hand in hand with this, is if your head stay sags, or your jib sheets are lead poorly. Do what you can to move the center of pressure forward, a sail with the draft up forward...

You can try reefing the main earlier and leaving the genoa up.

You can rake the mast forward to move the center of effort forward.

You can put a bend in the top of the mast (if the stick is flexible) with back stay tension, to depower the main. In the same breath, you can have some roach cut out of the sail.

You can move the mast, shrouds, and chain plates forward, to move the center of effort forward. (This shrinks the for-triangle, and your jibs won't sheet in like they do now, unless you add a bow sprit.)

You can add a bow sprit to move the CE forward.

Lastly, most boats nose down when under sail. This means they move their wetted surface forward. Trimming the weight aft makes an attempt at sailing on her lines. In the same breath, if she is squatting on her lines the mast is raking aft relative to level. When I read about that my brain about blew a gasket... but imagine a rod run athwartship through her CLR and then pivot her bow up and down. Whats the mast do? Trim is incredibly important... particularly if you have a heart shaped transom that squares off down low. Drag that back end under water and its like tossing an anchor over the side...

The last one is a pondering about whether or not weather helm is because of the ce and clr. If your rudder is skeg, transom, or keel hung it is not a balanced rudder. This means that the hand on the tiller has to apply pressure just to move it off of centerline, and once off centerline the rudder wants to return to being straight... think about a flag blowing straight out. A balanced rudder uses the rudder in front of the shaft to provide that pressure and lessen the force required to move the tiller. To much in front and the rudder tries to blow sideways once off centerline and pull the tiller out of your hands.

A rudder that is heavier than the density of water has a lighter helm pressure while on a tack... and heavier when you are tacking. Why? The rudder pivots down and the weight hangs as the boat heels... in the same direction you are applying pressure.

A rudder that is lighter than the density of water floats... and to hold it down requires pressure, but it wants to float up in the direction the helm is going while you tack.

Neutral buoyancy... is neutral.

In the same breath, a foil shaped rudder requires less steering angle to provide the same pressure. A slab sided barn door makes less pressure, stalls earlier... and requires a greater steering angle, in my mind greater steering angle means higher helm pressure. If and when it reaches a stall angle, its like dragging an anchor... I'm starting to believe that this the source of added speed from reefing.

Going back to the CLR, making the rudder longer fore and aft moves it aft, while adding helm pressure. A shorter rudder provides less pressure... and less helm pressure, but requires a greater steering angle to make the same pressure.

There are also folks that add a fixed fin, dagger board, or centerboard aft of the rudder to move the center of lateral resistance aft.

Anyone have other thoughts or ideas? I have a torn rotator cuff that doesn't like being on a port tack for long...

[Brent Swain]

Try all of the above first. If at the end of it all you still have too much weather helm, moving the mast foreward definitly works. I moved a mast 18 inches foreward once and it made a huge improvement. Try the other stuff first ,tho.
I've known people who moved their mast aft when turning a sloop into a cutter. That drasticaly increased the weather helm, far too much. Bad move.

[theonecalledtom]

Perhaps Zach's posting can go alongside Gord's sticky?

So trying to imagine all these forces I'm stuck wondering whether changing my 130 genoa over to the yankee the boat was designed for is going to reduce the weather helm (which can be fairly bad, though reading these posts I can do more to reduce it). Less sail up front overall but focused to the bow.