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