Greenough Power Blade

The V-Slot Fin That Started Everything

In 1960, John "Ike" Eickhart — George Greenough's grade-school friend in Santa Barbara — took a standard longboard D-fin and cut a large V-shaped slot into the base. The modification was simple but the effect was radical: it let the head of the fin twist independently, breaking loose from the rigid plank that every other fin was. Greenough saw it immediately. The two had already been experimenting with fins shaped after tuna, shaping prototypes on Ike's shop floor at 24 East Cota Street. That floor, covered in tar paper, is where Greenough drew the template for his first kneeboard.

The idea of a fin that could twist — not just flex at the tip like a 4A, but actually rotate its angle of attack mid-turn — stayed with Greenough for decades. Through the '60s and '70s he kept refining the concept on his kneeboards, then carried it into windsurfing fin design in the '80s and '90s. The Power Blade is where it all finally came together for stand-up surfboards.

Five Years in the Water

The Power Blade as we know it emerged from a five-year collaboration between George Greenough, Santa Barbara shaper Marc Andreini, True Ames founder Chuck Ames, and two dedicated test surfers: Ellis Ericson and Andrew Kidman. Greenough hand-built the original prototypes — two identical sets from the first panel he laid up, one for Andreini and one for Ericson. Chuck Ames then measured the twist patterns, sourced materials, and set up production at True Ames in Goleta.

The hardest part wasn't the template. It was finding a fiberglass/epoxy combination that could handle the punishment. The fin needs to be stiff in the leg, flexible in the head, and able to twist under load without stress fatigue. Chuck tried dozens of layup combinations before landing on a proprietary blend of high-grade tooling epoxy and unidirectional cloth that met all three demands.

We identified some very unique fiberglass/epoxy material that could withstand prolonged flex and twist demands under high loads, and most importantly, this material has not shown signs of stress fatigue.

After a full year of testing in every condition, neither Andreini nor Ericson could spin the fin out. The project was announced publicly in February 2019 and documented in the film On the Edge of a Dream — directed by Kidman and Ericson, with artwork by Barry McGee.

How Variable Tow Actually Works

Every other single fin flexes tip-to-tail. Push a 4A through a hard bottom turn and the tip bends, storing energy and releasing it as drive. It works. The Power Blade does something different: the head twists side-to-side, like a fish tail. Greenough calls this "variable tow."

When you initiate a turn, the paddle head rotates, briefly allowing the tail to step out — then it snaps back, generating forward thrust. It's the same mechanism a thruster's side fins use to create directional changes, but accomplished with a single fin. You get the flow and trim speed of a single fin with the ability to redirect power like a multi-fin setup.

You can run in flat out trim or pull the board straight up the face with thruster drive during a hard turn if you wish, or simply hold your line and draw a long bottom turn with plenty of drive.

The Specs

The narrow base is the key. It creates almost zero water pressure where the fin meets the board, which means less drag and more speed. All the surface area is concentrated in the paddle head, where it can reach into the cleaner, less-turbulent water deeper on the wave face.

What It Rides Like

The Power Blade is not a plug-and-play upgrade for every board. It's directional, it wants to be driven from the tail, and it rewards commitment. Riders on Jamboards describe a night-and-day transformation — one put it on a 7' Mandala Super Stubby and said it "completely changed the maneuverability and feel." Another noted the tiny base loosened the board while the big paddle head kept things oddly stable and sprung them around turns.

• +Speed: The narrow base yields minimal drag. Expect more speed than any traditional single fin.
• +Turns: Deep bottom turns and vertical redirections that feel impossible on a standard single fin.
• +Trim: It still trims. The flow and glide of a single fin are fully intact.
• +Hold: Ericson and Andreini couldn't spin it out in a year of testing.

One thing everyone agrees on: size up. These ride smaller than the measurement suggests. If you'd normally ride a 9" fin, try the 8.8" Power Blade — or even consider the 9.75" if it's available. The narrow base means less effective area than a full-base fin at the same height.

What Boards It Works On (And Doesn't)

The Power Blade was designed for Greenough's Edge Board — a tri-plane hull with a full displacement bottom on the outside rails and a narrow, high-speed concave channel running down the center. Marc Andreini and Scott Anderson shape Edge Boards today, and they're the ideal pairing.

Beyond that, it works on flat-rocker mid-lengths and straight-bottomed single-fin boards. It pairs well in 2+1 setups where sidebites add stability. But it does not belong on hulls, traditional logs, or anything you surf from a forward stance. This is a back-foot, pivot-oriented fin.

Power Blade vs. 4A

People ask this constantly, and the answer is simple: they're built for completely different boards. The 4A has a full base for drive, a flexible tip for release, and it works on almost everything — longboards, mid-lengths, eggs, vee-bottoms. It's the most popular single fin ever made for a reason.

The Power Blade is the specialist. Narrow base, torsional twist, designed for edge boards and flat-rocker shapes. If you're surfing a traditional longboard, get the 4A. If you're on an edge board or you want to push the performance envelope of a mid-length single fin, the Power Blade is the one.