Yes, the height does increase the length. For example, w=4 n=5 h=0 gives L=63.1273, while w=4 n=5 h=8 gives L=64.0530. The formulas I used were r=w*t/(2*n*pi), x=r*cos(t), y=r*sin(t), and z=h*(1-t/(2*n*pi)), and then L is the integral of sqrt(dxdt^2+dydt^2+dzdt^2)*dt from 0 to 2*n*pi.