It's wood.
Even if you get it dead on it will change over the next couple years or so as it finishes curing, weathers, shifts in the mount, etc.
While I'd try to get the blades as close to the right position as possible, I wouldn't worry too much about it. Being off a bit does several things:
- Angle-between-blades errors moves the center of gravity a tad off center. (You can counter this with static balancing - which you have to do anyhow because the blades won't come out dead-even in weight and weight distribution.)
- Angle-between-blades errors moves the center of effort a tad off center. (But it's a tad off-center anyhow because the profiles of the airfoils won't be a perfect match, either.) This will cause a slight circulation of the force on the mill as it rotates. But if the error isn't enormous it will be small compared to other things, like turbulence and other non-ideal conditions in the incoming airflow.
- Along-axis errors (i.e. tip of blades passing a point at different distances up/down wind) will cause dynamic imbalance. Like the center-of-effort error this can also can produce a once/rotation cyclic force on the axle - this time with strength proportional strictly to rotational speed rather than being proportional to wind drag. But again you also get this from uneven weight distribution. Most of the mass of the blades is in a very thin disk and the rotation rate is pretty slow, so it takes a lot of misalignment to make dynamic imbalance a problem.
So in you're position I'd:
- try to get the blade tips within an inch or so of evenly spaced around a circle,
- also try to get them within an inch or so of equally fore-aft,
- statically balance the blades, then
- check for non-trivial wig-wagging around the yaw axis as it runs.
That will probably take care of it entirely.
If it wig-wags nontrivially I might then tweak the for-aft position of the tips or add dynamic balancing weights to the hub (equal amounts of weight on the front and back, 180 degrees apart) to kill the wig-wag. Since drag goes up with rotation speed for the steady state, the wig-wag from dynamic balance and center-of-effort errors track well enough that you probably don't have to try to fix them separately, but can get it down to something that won't put excessive wear on your yaw bearing or twist on the power cable if you tune it out at a steady wind speed in the upper-middle of your typical wind speed range.
If it wig-wags a LOT I'd look for a defective blade, unbalanced alternator, bent shaft, or defective hub. B-)
