Arthur....we will have to agree to disagree about the 35 yard thing. I can shoot well out past 90m in my yard and during the summer months do it quite often. That being said, keeping everything the same except for the helical vs. offset, I start to notice the difference in POI right around 35 yards. By the time I am out to about 70 yards, I can't even hit my rinehard 18-1 with my normal sight marks and helical feathers.
Disagree with me on this topic at your peril, 98Redline. [8D]
If you'll reread my post, you'll findyour results are very much in line with what I mentioned about using too much helical.
Think of it this way....
If you put too much wrap around the shaft, so much that the leading end of each feather is overlapping the direct line to the trailing ends of the adjacent feathers, you don't have good air flow. Instead of steerage, you've got a parachute. A mini-fluflu, if you will. But rather than blame themselves for a poor fletching job, many people prefer to blame helical fletched feathers for poor long range trajectory.
If you keep the helical down to a moderate level, so that there is clearance between the direct line between the leading end of each feather and the trailing end of the adjacent feather, then you've got good air flow around the fletching, andgood steerage with no, or at least minimal,parachute effect, and downrange trajectory just as good as any other fletching configuration will give.