How to Add a Draft Stripe to a Sail

A draft stripe is a horizontal, contrasting line applied to a sail, enabling sailors to visualize the sail’s shape and monitor its performance in real-time. By observing the curvature and position of these stripes, sailors can make informed adjustments to optimise sail trim and overall vessel efficiency.

Why Add One?

• Visualise Sail Shape: Draft stripes make it easier to assess the sail’s curvature and identify any distortions or inefficiencies.
• Optimise Performance: By monitoring the draft’s position and depth, sailors can adjust halyard tension, sheet trim, and other controls to enhance performance.
• Training Tool: For novice sailors, draft stripes provide a tangible reference to understand sail dynamics and trimming techniques.

Where to Place the Stripe

The placement of draft stripes varies based on the sail type and desired level of detail:

• Mainsail: Common practice involves placing stripes at 25%, 50%, and 75% of the sail’s height. Some sailors opt for two stripes at 33% and 66% for simplicity. These placements help in assessing the sail’s shape at different vertical sections.
• Headsail (Genoa/Jib): A single stripe at approximately 50% of the luff length is standard. For non-overlapping headsails, multiple stripes at even intervals can be beneficial.

Materials You’ll Need

• Self-adhesive insignia cloth (20–25 mm wide), available in contrasting colours such as black, red, or blue.
• Measuring tape
• Straight edge or long batten
• Soft pencil or tailor’s chalk
• Scissors or sharp knife
• Roller or squeegee
• Clean, flat workspace

Step-by-Step Guide

1. Prepare the Sail: Lay the sail flat on a clean surface. Ensure the area where the stripe will be applied is free from dirt and moisture to promote adhesion.
2. Determine Stripe Placement: Measure and mark the desired height(s) on both the luff and leech. Use a straight edge to draw a light guideline connecting these points, ensuring the line is parallel to the foot of the sail.
3. Cut the Tape: Measure the distance between the luff and leech along your guideline and cut the insignia tape accordingly, allowing a slight excess to trim for a neat finish.
4. Apply the Tape: Peel back a small section of the tape’s backing and align it with your guideline. Gradually adhere the tape along the line, smoothing it with a roller or squeegee to eliminate air bubbles and ensure firm contact.
5. Secure the Edges: Trim any excess tape at the edges and press firmly to secure. For added durability, especially on older sails, consider lightly heating the tape with a hairdryer to enhance adhesion.
6. Repeat on Opposite Side: For optimal visibility and balance, apply a corresponding stripe on the opposite side of the sail, ensuring alignment with the first.

Practical Tips

• Avoid Seams: When possible, position stripes away from sail seams to prevent adhesion issues and potential peeling.
• Use High-Contrast Colours: Select a stripe colour that contrasts sharply with your sail to enhance visibility in various lighting conditions.
• Regular Inspection: Periodically check the condition of your draft stripes, especially before races or long voyages, to ensure they remain securely attached and visible.