WingHopper · Designer · Guide · Sections · Reef · Methods · Pricing · FAQ
The Outline tab sets the planform. Each slider rewrites the leading and trailing edge curves behind it, so the fin keeps its character as it resizes. Once you drag a control point on the Curves tab, the outline is yours and the sliders stop regenerating it.
Each table has an increase column and a decrease column, measured on the fin the designer opens with (the thruster side template). FinHopper runs no hydrodynamic or structural model on fins, so the rows are shape only: area, aspect ratio, volume, rake, sweep and as-built thickness. Changes under 0.5% are left out. Other fins move by different amounts.
| Term | Meaning |
|---|---|
| Depth | Height of the fin from the base line to the tip, measured perpendicular to the base |
| Base | Length of the fin along the board |
| Sweep | Angle from vertical of the line from the base midpoint to the tip apex. This is the FCS chart convention |
| Rake | How far aft the tip apex sits, measured from the base leading edge |
| Area | Planform area. Fin makers publish it in square inches |
| Aspect ratio | Depth squared over area. Tall and narrow is high, short and long is low |
| LE | Leading edge, the front of the fin |
| TE | Trailing edge, the back of the fin |
| Chord | Distance from LE to TE at one height |
Sweep and depth together set where the apex lands. More sweep moves the apex aft and lengthens the rake.
A round tip ends the LE and TE on one apex; the tip round slider is the half-width of that round, small for a pointed pivot tip, large for a full blunt round. A square tip holds a chord at the top and caps it flat, which fish keels and some weed fins want.
How long the leading edge stays forward before turning for the tip. Fuller keeps more area up high.
How much the trailing edge sweeps forward low down, the S-curve that narrows the neck.
Drag any control point of the LE or TE. A point cannot cross the other edge, so the fin cannot invert. Scroll on a point to change its weight, which is how hard the curve is pulled toward it. Every drag and scroll is one undo step.
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