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