Free tools · 04
Fin placement
calculator.
Where the fins go. Pick the setup and the board length, and get the distance from the tail and the rail, the toe and the cant, the way a shaper marks them before routing the boxes.
Setup
Three fins. Sides forward and toed in, a smaller centre fin at the tail.
Tail (for the drawing)
| Fin | From tail | From rail | Toe | Cant |
|---|---|---|---|---|
| Side fins (trailing edge) Toe measured as the front of the base sitting 1/4" closer to the stringer than the back (about 3°). | 10 3/4" 273 mm | 1 1/8" 29 mm | 0 1/4" ≈ 3.2° | 6° |
| Centre fin (trailing edge) | 3 1/2" 89 mm | on the stringer | 0 | 0° |
- From tail is measured along the stringer to the fin's trailing edge at the base (for boxes: the back of the fin, not the box).
- From rail is the distance from the rail's edge to the fin base, measured square to the stringer at the trailing edge.
- Toe: how much closer to the stringer the front of the base sits than the back. Point the fin at the nose for zero toe, at a spot 12–16" either side of the nose for the usual 1/4".
- Cant: the lean of the fin outward from vertical. Fixed by the box or plug you use; FCS II and Futures boxes come in set cants.
- These are starting points that match most production boards. Wider tails take the sides a touch further out and back; small-wave boards go forward; big-wave boards go back. Ask us if you want them tuned to the board.
Questions
- Where do I measure the fin position from?
- Along the stringer, from the very tip of the tail to the trailing edge of the fin at its base. For a box, measure to where the back of the fin will sit, not to the box itself. The rail distance is from the rail edge to the fin base, square to the stringer, at the trailing edge.
- What is toe-in and how do I set it?
- Toe-in points the side fins slightly toward the nose. Shapers set it with a straight edge along the fin base aimed at a spot 12–16 inches either side of the nose tip, which gives about 1/4 inch of toe over a 4.5-inch base, or roughly 3 degrees. Less toe is faster in a straight line; more toe turns easier.
- What cant should I use?
- Cant is the outward lean of the fin. Most thruster and quad side fins run 5–7 degrees, twins 3–6 degrees, keels 0–3 degrees, centre fins 0. With FCS II or Futures boxes the cant is built into the box you buy, so choose the box to match.
- Are these positions exact?
- They are the starting points that most production boards use, scaled with length. Wider tails, small-wave boards and big-wave boards move them a little. If you tell us the board and the waves, we will give you numbers tuned to it.
In ShaperLab Pro the fins are placed on the 3D board, with the boxes routed into the CNC program.