Shaping Sails
Having a properly shaped sail is the most critial part of racing.
Having a sail with a good shape will allow you to point higher into the wind, and make better progress.
Most good sails will let you point 45 degrees into the wind.
Bad, and completely flat sails usually only allow 60 degrees into the wind.
The following are all of the methods I know of for shaping a sail.
The exact dimensions and amount of shape that is best to put into your sail has always been up for debate.
As a general rule of thumb, a maximum of 10% draft (depth of shape) at 30% aft of the luff is considered a good shape.
Curved Luff & Foot
The simplest methods to add shape to your sail is to curve the luff and foot.
When the sail is laced to the mast and spars, the curves push extra material towards the middle of the sail creating draft.
You can even use 2 straight edges on each side instead of a curve, it won't make the best shape, but it will work.
The A and B dimensions of a pdracer sail would typically be around 3".
Mother Dart
Another simple method is to fold a dart (or pleat) into the sail.
The point of the dart will form the center of the sails maximum draft.
You can use all sorts of math to calculate the proper dimension for C, or a simple way is to put a stack blocks under the sail that form the maximum draft, and then fold the dart from that.
A typical pdracer sail would use a C dimension of 4 to 6"
You can also use a series of smaller darts around the perimeter.
Other Dart Patterns
The Mother Dart shown on the left is the most common dart pattern, but there are many other dart patterns that can be used.
Shown in the middle are Vertical Darts, which are placed at the maximum draft point(s), and on the right are Baby Darts, which are placed in various places to form the draft shape.
Broad Seaming
When making sails from strips of dacron, sail makers often form the sail's shape by curving individual panels of the sail before attaching them together.
This is a very good method for creating exact sail shapes.
3D Laminates -- "3DL"
The most complicated and expensive method to create sails is to make 3D Laminates.
A full size plug is created in the exact shape the sail.
Then layers of threads and laminating material are placed on the mold by men in hang glider flying harnesses.
After all the layers are placed, a heating element is flown over the surface to fuse them together creating a perfect sail.
For more information about this method, see North Sails
Curved Luff & Foot
Mother Dart
Other Dart Patterns
Broad Seaming
3D Laminates -- "3DL"