Drew Dalgleish ) writes:

rocker is the amount of curve from end to end. A boat with lots of
rocker is easy to turn but will not track as well as a boat with less
rocker. More rocker is probably going to cause the boat to be slower
as well.

clarification:
that's curve in the bottom of the boat (keel), not the sides.

if you set the boat down on a level surface and measure the height of the
stem and transom above the ground, that's the total rocker. its usually
divided in half for the published rocker.

on a dory built boat it works like this:

if you set the two side panels on edge straight up and down and pull the
ends together at bow and stern there is no rocker. when you angle the side
panels out (flare) and bend them together at the bow and stern the ends
come up and you get rocker. the rocker depends only on the angle of flare
and the width of the boat and can be calculated with the sum of squares
rule for right angled triangles (Pythagorous). if you want more or less
rocker for a given angle of flare you have to shave some wood off the
bottom edge of the side panels. that's why dory side panels have a convex
curve cut in the bottom edge, to reduce the amount of rocker for the large
angle of flare on those boats. to adjust the rocker on a simple flat
bottom ("flat iorn") skiff the side panels have an elongated "S" curve cut
in the bottom edge.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned