Roy's rocker formula for all purpose gun surfboards.

When designing a rocker for a new board, I use numbers and previous experience. The planshapes which I use are forgiving of rocker variations, so I use a wide range of rockers rather than small refinements.

Old Faithful 16-021 Gun surfboard

Extrapolation and interpolation of curves means that the rocker radii are controlled, this gives a different result when changing the length of the board, than is often the case when eyeballing the shape. Eyeballing tends to result in rockers which are much flatter as board length increases and more curved when length decreases.

Faceted tumblehome and displacement tail

For example a 7 inch rocker ( assuming a circular arc rocker for the moment) on a 12 foot board gives only 4 inches at 10'6". Looking at the two boards it looks like the 10-6 is flat and the 12 footer is highly rockered. Of course I do sometimes use lower radius or flatter curves on longer boards but using extrapolation as a baseline means that I know what I'm doing to the radius.

Distal taper on single fin gun surfboard

The displacement tailed pintail which I often use allows a flatter nose rocker as the tail can be sunk (this happens automatically) and the associated planshape curve means that the nose is raised whenever the board rolls on to the rail. having said that I often dose up the nose rocker anyway.
What I'm using on the current board is middle of the road I think. It's interesting that 7 inches of nose rocker is standard or even on the low side for guns. I've often been criticised for using too much nose rocker but I think that it's because people are used to longboard rockers which are limited by nose riding.

Displacement tailed pintail gun surfboard

My boards are almost always of the gun type in terms of general shape philosophy even when made as all rounders or small wave boards. I see 'gun' as a board type which can be for waves of any size (big game and small game).

16-021 plan shape

Re a 'formula' I tend to use circular arc tail rockers i.e. no tail flip and circular arc ( i.e. constant) or decelerating (typically elliptical) nose rockers, which isn't really unusual in the general sense. Rocker apex, if there is one, is always at the wide point which again isn't unusual.

Spitfire fin option

Recently a surfermag forum member superimposed the rocker of my 13'9" Dragon board on to a flat old school Phil Edwards longboard blank rocker and they were almost identical... the Dragon has 7 inches nose and tail and has been called a banana but in reality it's a large radius curve i.e. flattish... My parallel profile ( not used on the current board) also makes rocker look greater than it is as the deck curve is the same as the bottom curve.

Stainless steel leash plug security