Reduce the diameter of a sheet

Reducing the diameter of a sheet (typically a mainsheet or jib sheet) is an advanced ropework technique called tapering.

The objective is twofold:

1. Performance: Reduce weight aloft and limit friction in blocks when the sheet is eased.

2. Comfort: Maintain a large diameter (comfortable for the hands) on the part that is handled, while having a thin, light part that runs through the tackle.

This tutorial focuses on a double braid sheet (Dyneema core and polyester cover).

1. Necessary Equipment

• Your sheet: A double braid with a structural core (Dyneema).

• Splicing needles (fid) suitable for the core diameter.

• Marker of a contrasting color.

• Splicing scissors (Dyneema-specific if possible).

• Adhesive tape (electrical tape).

• Whipping twine and sailmaker's needle to secure the splice.

2. Step 1: Calculation and Marking

The transition point (where the cover ends) must be chosen carefully. It should never enter the clutch or be handled by hand.

1. Mark 1: On the cover, mark where you want the diameter to be reduced.

2. Mark 2: 30 cm from Mark 1 (towards the thin end), make a second mark. This is where the core will exit the cover.

3. Step 2: Core Removal

1. Fold the rope at Mark 2.

2. Using an awl or needle, separate the cover fibers to expose the core.

3. Pull the core out with a hook. You now have the core on one side and the empty cover on the other (for the last 30 centimeters).

4. Completely remove the unused cover up to the end of the rope. Warning: Do not cut the cover at Mark 1 yet!

4. Step 3: Tapering the Cover

To avoid an abrupt "step" that would jam in the blocks, the cover needs to be tapered.

1. Go back to Mark 1.

2. Between Mark 1 and Mark 2, unlay the cover strands (pull out the threads one by one).

3. Cut these threads in a "staggered" fashion: cut two threads, leave 2 cm, cut two threads, etc., until there is almost no material left at Mark 2.

4. The goal is to obtain a very thin, tapered end of the cover, about 15 to 20 cm long.

5. Step 4: Insertion (Burying)

This is where the end of the cover is hidden inside the Dyneema core.

1. Insert your splicing needle into the core at Mark 1.

2. Advance it inside the core for about 25 cm and exit.

3. Attach the tapered end of your cover to the needle.

4. Pull to feed the cover inside the core.

5. Smoothing: Massage the Dyneema core so that the cover completely disappears inside. The transition should be perfectly smooth to the touch.

6. Step 5: Securing (Whipping)

Without tension, the cover could slip and exit the core.

1. Perform a tight whipping (stitching) exactly where the cover enters the core (Mark 1).

2. Pass the needle and whipping twine through the rope several times to permanently secure the core and cover.

7. Pro Tips

• Verification: Before cutting anything, run your sheet through the entire block system on the boat to ensure that the transition does not jam anywhere.

• Protected core: Dyneema is sensitive to UV and abrasion. If the stripped part rubs against something sharp, it will wear out quickly.

• Balance: Do not reduce the diameter over too long a length if you sail in very windy areas, as the bare core is harder to grasp in an emergency.

Technical Summary