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The Mount tab builds the tab or head for the box you are fitting. Every dimension carries a confidence tag in the app: official, community-verified or partly-estimated. This page says what each one means and where the numbers came from.
| Box | Confidence | Source | Cant |
|---|---|---|---|
| FCS dual tab | Community-verified | finbases fcs.scad for the tab, plug depth and tab pitch corroborated by Swaylocks and RealSurf measurements. Its values are round metric and each sits a little under the real part, so treat them as rounding, not a tested clearance | In the plug. FCS II plugs come in 0°, 3°, 5° and 9°; the fin stays straight |
| FCS II | Community-verified | FCS II manual, compat-kit path, plus the finbases tab. The native click-in profile has no published drawing, so the export is the dual-tab shape FCS supports in FCS II boxes with grub screws | In the plug; the fin stays straight |
| Futures | Partly-estimated | Slot length 4.5 in and the half-inch box depth class are sourced. Tab thickness is unconfirmed by any Futures document. The ramp angle has no published spec and stays a slider | In the fin, officially 6° on side fins. Boxes install flat |
| US / longboard box | Community-verified | finbases us.scad for the rail and pin, slot width and cavity depth from published box measurements (soarfin, cleanlinesurf) | Vertical center box, 0° |
| Tuttle / Deep Tuttle | Official | The Waterat Sailing Equipment drawing set, drawn by Larry Tuttle in 1985 with revisions to 1993 and the 1998 extended-head sheet, read from the vector PDF | Vertical center box, 0° |
| Power Box | Partly-estimated | One community 1:1 drawing posted on Seabreeze. No official Power Box drawing appears to be public | Vertical center box, 0° |
| Glass-on | Official | No mounting geometry. The base exports flat for lamination | Set when you glass it on |
FCS tabs export at 6.0 mm thick and 14 mm deep. Installed plugs usually take about 12.5 mm, so expect a light file to fit. Grub screws hold the fin in both FCS I plugs and FCS II boxes.
Futures tabs default to the shallow half-inch box class so they clear both box depths. Print a test tab before cutting anything expensive.
The US box rail exports at 9.2 mm against a slot measured near 9.1 mm, so it is meant to be sanded to fit. These numbers describe the wider windsurf-style box. Surf longboard boxes (Bahne, Fins Unlimited) run narrower: measure the slot and pull the fit offset negative. The pin bore exports at the real 4.8 mm (3/16 in) and usually prints tight, so ream it. The front screw hole clears a #10 screw.
Tuttle heads are built to the finished-size drawing: 156 mm base, 80° faces, 15.75 mm thick against a 15.9 mm slot. Boxes across brands run 15.7 to 16.0 mm and heads are sanded to fit by convention. Bolt holes export at the drawing's 7.5 mm clear by 32 mm, perpendicular to the sloped top; tap M6 or quarter-20, or fit an insert. A standard head also fits a Deep Tuttle box with longer bolts.
Power Box heads follow the 1:1 trace: 160 mm long, 28 and 48 mm ends, 5° faces, 6° side taper. Which end is deep is not stated anywhere public; the export puts the deep end aft, as product photos show. New Power Box fins commonly seat 1 to 3 mm proud and are sanded down. The deck screw hole exports as a 5.0 mm pilot.
The fit offset slider adds or removes up to 0.6 mm per face on the tab thickness. It changes the tab only, never the blade. Use it after a test print rather than guessing.
Next: Printing a fin