All about lawn bowls bias and trajectory
Drakes Pride Line Trajectory video
Drakes Pride Bowls bias
Henselite Bowls bias
Bowls are designed to travel a curved path because of a weight bias which was originally produced by inserting weights in one side of the bowl. This is no longer permitted by the rules and bias is now produced entirely by the shape of the bowl. A bowler determines the bias direction of the bowl in his hand by a dimple or symbol on one side. Regulations determine the minimum bias allowed, and the range of diameters (11.6 to 13.1 cm), but within these rules bowlers can and do choose bowls to suit their own preference. They were originally made from lignum vitae, a dense wood giving rise to the term "woods" for bowls, but are now more typically made of a hard plastic composite material.
Bowls were once only available coloured black or brown but they are now available in a variety of colours. They have unique symbol markings engraved on them for identification. Since many bowls look the same, coloured, adhesive stickers or labels are also used to mark the bowls of each team in bowls matches. Some local associations agree on specific colours for stickers for each of the clubs in their area. Provincial or national colours are often assigned in national and international competitions. These stickers are used by officials to distinguish teams.
Bowls have symbols unique to the set of four for identification. The side of the bowl with a larger symbol within a circle indicates the side away from the bias. That side with a smaller symbol within a smaller circle is the bias side toward which the bowl will turn. It is not uncommon for players to deliver a "wrong bias" shot from time to time and see their carefully aimed bowl crossing neighbouring rinks rather than heading towards their jack.
When bowling there are several types of delivery. "Draw" shots are those where the bowl is rolled to a specific location without causing too much disturbance of bowls already in the head. For a right-handed bowler, "forehand draw" or "finger peg" is initially aimed to the right of the jack, and curves in to the left. The same bowler can deliver a "backhand draw" or "thumb peg" by turning the bowl over in his hand and curving it the opposite way, from left to right. In both cases, the bowl is rolled as close to the jack as possible, unless tactics demand otherwise. A "drive" or "fire" or "strike" involves bowling with force with the aim of knocking either the jack or a specific bowl out of play - and with the drive's speed, there is virtually no noticeable (or, at least, much less) curve on the shot. An "upshot" or "yard on" shot involves delivering the bowl with an extra degree of weight (often referred to as "controlled" weight or "rambler"), enough to displace the jack or disturb other bowls in the head without killing the end. A "block" shot is one that is intentionally placed short to defend from a drive or to stop an oppositions draw shot. The challenge in all these shots is to be able to adjust line and length accordingly, the faster the delivery, the narrower the line or "green".
Lawn Bowling bias.
a. slight bulge or greater weight on one side of the ball or bowl.
b. the curved course made by such a ball or bowl when rolled.