thread6-175834: twisting rotorblades
In Ray W. Prouty', VOL 1 Aeordynamics book Pg 248, he talks about blade twist. He says that there is a nonlinear "ideal twist" which in theory will even up induced velocity distribution. This type of twist to a blade is to difficult to produce. So it is common to have a linear twist. You can get the most efficiency from a negative 20 degree twist. But the first 10 to 12 degrees is the greatest gain in efficiency. Blade twist can give you a five percent increase in figure of merit. This is an increase of about 20 percent payload capability. On the UH-60, we have a negative 18 degree twist. You can also gain another 2 to 4 percent inrease in figure of merit by adding anhedral tips.

With composites, non-linear twist can be achieved a bit easier than twisting an aluminum extrusion (which would require clamping and re-clamping along the length to literally apply a series of twists on the section).  But, since a linear twist can closely approximate the capability of an ideal rotor for say the outer two-thirds of the blade (where it really counts), one would question the value.

See Leishman Principles of... 1st Ed. Figure 3.8.

You might find it easy enough to do the "back-of-the-envelope" calculations yourself if you consider that you're looking for a relatively constant inflow velocity across the span of the blade, an ideal angle of attack of the airfoil for certain conditions, and a constant RPM.  This does zero you in on a vector diagram that gets you in the ballpark.  Make a new vector diagram for each station along the blade, say, divided in 10 pieces or so, and you get a progression of twist angles to ensure the angle of attack is constant.
Some heli manufacturers do pretty crude things to adjust the twist and/or airfoil profile of the blades from root to tip.  Perfect is sometimes not as good as "good enough".

- from another SAIT AET grad.  (are there too many or not enough of us in the world?)

Steven Fahey, CET