Mould controls
Choose how the app joins your edge and section curves into the continuous sail surface shown in the preview and used for panels.
Use the full Sail Shape dialog
Open Design > Sail Shape when you want the exact-value controls together. The dialog groups Edges, Edge curves, Head twist, Profile algorithm, Profile points, and Mould. Valid changes update the live design immediately; Done closes the dialog rather than applying a separate batch of changes.
Use Rig and dimensions for the corner-to-corner sizes, Edge shape and twist for the edge and twist ranges, and Profiles and fullness for profile rows. The sections below cover the remaining Mould group.
Find the controls
The same three settings appear in two places:
| Shape card View section | Design > Sail Shape > Mould |
|---|---|
| Mould algorithm: Cubic / PCHIP | Loft algorithm: Cubic v-loft / PCHIP densified |
| Apply smoothing | Approximate smoothing |
| Foot stretch | Foot stretch (cubic only) |
Changing either surface updates the other. The controls remain at the top of the Shape card when you switch between Preview and Profile Edit.
Choose a valid combination
| Mould algorithm | Foot stretch | Smoothing state | Current behaviour |
|---|---|---|---|
| Cubic | Off | User-controlled | Turn smoothing on to relax the surface between sections, or off to pass through each section exactly |
| Cubic | On | Forced off and disabled | The loft continues below the visible foot before being trimmed back, changing how the surface meets the foot |
| PCHIP | Disabled | Forced on and disabled | Extra section rows are generated between your profiles and joined with approximation smoothing |
The disabled smoothing checkbox always shows the mode actually in use. When you return to plain Cubic, the saved user-controlled setting becomes available again.
Under PCHIP, Foot stretch is disabled because it is a Cubic-only option. Its checked appearance can still retain the design’s stored preference, but it has no effect until you select Cubic.
Compare smoothing on and off
Show the surface and edge guides
In the Shape card, turn on Show surface and Show edge guides. Switch to Profile Edit if you also want the interior section wireframes visible.
Select Cubic with Foot stretch off
This is the only combination where Apply smoothing is editable.
Toggle Apply smoothing
With smoothing on, the rendered surface averages between neighbouring section curves. The section wireframes continue to show the values you entered, so the surface may relax away from them between the edges.
With smoothing off, the surface passes through every section curve. Strong differences between neighbouring profiles can therefore appear as visible kinks or saddles.
Checkpoint
The live surface should change while the input wireframes stay in place. Edge guides can diverge from the smoothed surface and coincide with it when smoothing is off.
Understand the starting combinations
File > New chooses the following current mould settings:
| Sail type | Starting controls |
|---|---|
| Gennaker, Code 0, Genoa 135%, Working jib, Symmetric spinnaker | Cubic, smoothing on, Foot stretch off |
| High-aspect jib, Mainsail, Storm trisail | PCHIP, smoothing forced on, Foot stretch disabled and shown off |
| Storm jib | PCHIP, smoothing forced on, Foot stretch disabled and shown on |
The Storm jib’s checked Foot stretch is inactive under PCHIP; it becomes an active preference only after switching to Cubic.
The Defaults buttons in Preview and Profile Edit do not change any mould control. To restore the chosen sail type’s complete starting combination, begin that boat and sail type again with File > New.
Decide from the visible result
Mould controls operate after edge shape and section profiles. If changing the loft does not address the part of the sail you intended:
- change Round, Opening, or Position for an edge-outline problem;
- change Depth, Draft, Entry, or Exit for a horizontal-section problem;
- change Fullness when every interior section should become deeper or flatter together; or
- change the mould controls when the issue lies in the transition between otherwise-correct sections.
For diagnostic surface colouring, continue to Heatmaps.