Greenough Knuckle vs. Nose Flip: Smackdown

One of the essential characteristics of the Greenough Knuckle is the distinct break in the rocker curve...

Slightly over half the bottom curve is straight (green arrows), followed by a moderately sharp break (red arrow), then a slight straight spot towards the tip of the nose (blue arrow.).

The inspiration for Greenough's bottom scheme comes from the lines of traditional boat hull design...

The concentration of the bottom curve in a relatively small area creates the knuckle which, like a boat hull, allows his board to aggressively bust through whatever bump or errant water it encounters.

This approach is more sophisticated than the gradual, even-arc nose flip found on most surfboards (purple). 

Flip is pretty, but it's primarily a defensive approach to nose rocker. True, it often saves you from pearling and catching, but you can't lean on it in a turn with the same authority ... because the curve is overly blended with the rest of the bottom, and therefore less effective than knuckle...

Knuckle really isn't rocker at all, but an integral element of the bottom hull ... as opposed to flip, which simply lifts the entire nose out of the water.

Along the center line, the knuckle is pronounced (red). But along the rail line, the rocker curve is flatter and more blended (green). The knuckle along the rail is expressed in the outline (blue).

-- Paul Gross

More From "The Greenough Knuckle" Files ...

One of Greenough's basic design tenets is: "Straight rocker in the last half of the board. "

He can get away with this extreme design premise because the tails on his boards are he can have dead straight tail lift and still turn easily. This is a luxury conventional board builders don't have...and the reason he developed flexible boards in the first place.

The straight tail Greenough has utilized since the late 1950's sets up the forward knuckle perfectly, because by default, the rocker break already has to occur in the front 1/3 of the board. So, the two elements fit together without a fight.

Another aspect of this design synergy is that the straight tail wants to push the nose down in the water, and the knuckle (in both the rocker and outline) resists the tendency to either catch or pearl.

Additionally, when in trim, the constant 'power-on'  push of the straight tail results in a high overall rate of speed...

-- Paul Gross

More On 'The Greenough Knuckle' ...

This image is from Greg Huglin's Fantasea, and it clearly shows that the rocker break and the outline break are placed in the same area on George's edgeboard spoon.

The 'knuckle' allows him to bury the rail without catching.

Here's a foam plug that I shaped for an edgeboard spoon. Same knuckle in the rocker and outline...

-- Paul Gross

Ted Spencer's White Kite ...


In 1970 -- during what amounted to the second phase of the transition era -- down railed/flat bottomed boards were beginning to appear worldwide. Sticking to his faith in hulls, Ted Spencer began to tweak the radical, deep bellied stubbies of the previous few years into a more versatile hull design.

Shane Surfboards, located in the Monevale 'burb of Sydney, manufactured Ted's board as a model called 'The White Kite.'

Featuring a pulled-in nose, arc tail, mild belly, and soft rails running nose-to-tail, The White Kite handled a wider variety of wave conditions than most hulls of the day.

Not surprisingly, the subtle design concept never caught on in a big way...but with 20-20 hindsight, it's clear that these boards were a gem in the long history of Greenough-inspired hull design.