Reefs

Use Panels > Reefs to edit reef positions and their optional reinforcement and tidying eyelets. New mainsails start with two calculated reefs; other new sail types start without them. You can add reefs from the dialog.

Add and position reefs

1. Choose Panels > Reefs. Select Add reef for the next available slot, up to three reefs. This calculates initial positions from the current sail. Remove deletes a reef; Enabled switches it off without deleting its settings.
2. Adjust Tack (% luff chord) and Clew (% leech chord) independently. Both percentages are measured from the original full sail toward the head, not from the previous reef; enter a number strictly between 0 and 100. Changes to the sail retain the entered percentages rather than automatically recalculating them.
3. Select Reset positions to recalculate the positions of the reefs still present from the current sail. This leaves their patch sizes and eyelet settings in place. Select Done when finished.

If the default calculation fails, check the sail measurements before trying again. A per-reef error reports endpoints or accessory geometry that cannot fit; adjust the positions or the affected accessory settings. There are no standalone tack/clew marker rings in the current 3-D view: with Show layout on, the visible reef details are the configured patches and eyelets. Previewing does not require panel generation.

Tack and clew patches

Expand Tack and clew patches for a reef. New reefs copy the current original-corner patch reaches. If patches are absent, choose Add patches from original corners; Reset patch sizes from original corners replaces the current sizes. Set separate Headward edge reach and Reef reach lengths for the tack and clew. They must be positive and fit their supporting edge and reef path. Each patch has three layers at 100%, 75%, and 50% of those lengths. Sizes remain fixed after moving the reef or editing the sail until you reset them explicitly. See Corner patches for the original corner settings.

Tidying eyelets

Expand Tidying eyelets and switch Include intermediate eyelets on or off for that reef. New reefs include three eyelets by default, with a 12 mm hole, zero headward offset, and two patch layers (75 mm and 50 mm radii). Adjust Eyelet count, Headward offset, Hole diameter, and layer radii as needed. Radii must be positive and decrease from the outermost layer; use Add inner layer or Remove inner layer to change the stack. The preview shows the holes and their patches when enabled. If an eyelet cannot be placed, the app reports a warning and directs you back to Panels > Reefs.

For a cloth-roll cutting plan, choose the enabled reefs' patch and eyelet pieces in Cloth Layout DXF; accessories are not selected by default. To generate the sail's flattened panels separately, see Generate and inspect panels.