The Template Is Everything
Before you cut fiberglass, before you mix resin, before you pick up a sander — you need a template. The template is the 2D outline of your fin. It determines about 80% of how the fin performs.
Think of it this way: the foil (the 3D cross-section) fine-tunes a fin. But the template defines it. A raked-out keel and a vertical upright fin don't just look different — they're designed for completely different surfing.
The Key Measurements
Every fin template comes down to four numbers:
Base Length
The bottom edge of the fin — the part that sits in or against the board. A longer base gives you more drive (forward projection down the line). A shorter base makes the fin looser and easier to pivot.
- Long base (4.5"+): Drive, hold, speed. Good for point breaks and down-the-line surfing.
- Short base (3.5" or less): Loose, pivoty. Good for beach breaks and quick turns.
Depth (Height)
How far the fin extends below the board. More depth = more hold and tracking. Less depth = more slide and release.
- Deep fins (4.5"+): Lots of hold. The board stays locked into the face. Great for bigger waves.
- Shallow fins (3.5" or less): The tail can slide and release. Fun for small waves and playful surfing.
Rake (Sweep)
How far the tip of the fin sweeps back behind the base. This is measured as the horizontal distance from the front of the base to the tip.
- High rake (lots of sweep): Long, drawn-out turns. The fin holds through arcs. Think of a keel fin.
- Low rake (upright): Tight, snappy turns. The fin pivots quickly. Think of a thruster side fin.
Tip Width
How wide the fin is at the very top. Wider tips hold more. Narrow tips release sooner.
Common Fin Shapes
The Keel
Wide base, moderate depth, lots of rake, wide tip. The classic fish fin. Keels are designed for speed and flow — they hold through long bottom turns and project you down the line. A well-shaped keel on a fish is one of the best feelings in surfing.
Best for: Fish boards, retro twins, point break setups.
The Upright / Pivot
Short base, moderate depth, low rake, narrow tip. This is your classic high-performance shape. It pivots fast, releases clean, and lets you surf tight in the pocket.
Best for: Thrusters, shortboards, punchy beach breaks.
The Raked Template
Medium base, good depth, high rake, medium tip. A versatile all-rounder. More hold than an upright but more maneuverable than a keel. Most twin fin setups use something in this family.
Best for: Twin fins, 2+1 setups, everyday waves.
The D-Fin
Huge base, huge depth, moderate rake, wide tip. The original longboard fin. Maximum hold and drive. These things track like a freight train — you point and go.
Best for: Longboards, noseriders, big-wave guns.
How Shape Affects Performance
Here's the cheat sheet:
| Want More... | Increase... | Trade-off |
|---|---|---|
| Drive | Base length | Less pivot |
| Hold | Depth, tip width | Less release |
| Turn speed | Reduce base, reduce rake | Less drive |
| Flow/arcs | Increase rake | Slower pivot |
| Release | Reduce depth, narrow tip | Less hold in big surf |
Every fin is a set of compromises. There's no "best" fin — only the best fin for how you surf, what you ride, and where you surf it.
Designing Your First Template
For your first fin, don't get creative. Start with a proven shape and build it faithfully. Here's why:
- You don't yet know what the measurements feel like in the water
- You'll learn more from building a known shape than from guessing
- A proven template lets you isolate your shaping skills from your design skills
Recommended first template: a medium keel for a fish.
Specs:
- Base: 5.5"
- Depth: 4.5"
- Rake: ~35 degrees
- Tip width: ~1.5"
This is a forgiving shape — it's got enough base for drive, enough depth for hold, and the keel profile means small foiling imperfections affect performance less than they would on a thin upright fin.
Making the Template
- Draw it on cardboard first. Use a ruler for the base line and key measurements, then connect the points with smooth curves.
- Cut it out and hold it against your board. Does the depth look right? Does the rake feel proportional?
- Smooth any bumps in the outline. The cleaner your template, the less sanding you'll do later.
- Transfer to thin plywood or acrylic if you want a template that lasts. Cardboard works fine for one-offs.
Pro tip: Take a fin you already own and like. Trace it on paper. Measure it. Now you have a baseline you know works. Your first custom template can be a variation on that — maybe a little more rake, maybe a wider tip. One change at a time.
What's Next
Now you know what shapes do and how to design a template. Next up: Materials & Tools for Fin Shaping — everything you need to buy (and what you can skip) before your first build.