The data I collected last year clearly showed (consistent with theory) that making the second pitch rotor higher pitch than the first increases system lift. BTW, theory says you need to increase the lower rotor pitch to keep the same lift as the upper, not more than the upper.
BUT, that was with closely spaced rotors, further apart reduces the effect. IF. both your rotors are close together at the top, its probably worth it, and wouldn't decrease stability as eta 150 speculates.
On the other hand, if your rotors are at top and bottom, not as much benefit, and you do have more risk of the stability issue mentioned.
TreeGirl_Yesteryear3 wrote:<SNIP> you can read the note, quote only included because I'm changing topics
No, doesn't sound like bearings are the problem.
OK, need more info on your copter.
What is the vertical spacing between your spars (the long sticks along the diameter, the ones between those are actually ribs)? That changes the pitch for a given end spacing, very important to match rubber size to pitch. If you have too a large vertical spacing you WILL have slow turning props unless you get really big rubber. Vertical spacing should be VERY approximately in the 1 to 1.5 inch range
How much does your copter weigh? These things are VERY sensitive to weight.
What size rubber motor are you using? Is it thick enough to turn the rotors?
How hard are you winding your rubber band? If not near to breaking, you aren't winding hard enough, probably the most common problem with otherwise flyable designs.