Genoa Lead Block Systems
Why You Need Them
Revised by BoatUS editors in April 2012
Most sailboats today have adjustable genoa leads. When used correctly, these will give you optimum genoa performance in all wind conditions.
A complete system incorporates an aluminum or preferably stainless T-track installed (through bolted with substantial backup) on the toerail, deck or coaming, a pivoting wide-sheave lead block on a sliding car assembly, and a foot block to maintain the correct winch lead angle. For the lead blocks, we recommend that you use a ball bearing model. You won't have to wrestle with these under load, making your adjustments easier.
How to Use Them
By sliding your lead blocks fore and aft, you control your genoa's shape. Moving the lead forward tightens the leech, loosens the foot and gives your sail a fuller shape, making it more powerful on a reach. Moving your block aft tightens the foot, and allows the leech to twist off, which allows the sail to work more effectively in light to moderate air. This also helps you to depower the sail in heavy winds. Being able to move your lead blocks can also improve your tacking. Moving the block forward slightly before a tack will produce more power. This gives you more momentum through the tack, making it faster. On the new tack, ease the new leading block aft slightly to improve your boat's pointing ability.
Since your lead blocks will be on adjustable cars, it's worthwhile running a tackle system from these to the cockpit. This means that your trimmer can move the blocks without having to leave the cockpit. Just make sure that you use low-stretch line for these controls, otherwise you'll have an automatic depowering system!
Reefing is made easier too. As your genoa is being furled, you can adjust the lead block position. Simply mark the positions on the track that match the genoa's reefing points and furling your sails will mean no unnecessary loss of performance.
Use great care in using this equipment.