You know, I was thinking about that. Wouldn't that make it less wind resistant and therefor require more airspeed to function? I wonder if you could cup them to cause more drag and have a super low stall speed.
A true autogyro uses the pitch of the rotors to spin them, same as a wind turbine (but the lift action is not the same). The spinning motion translates to a fair amount of lift generated somewhere from last 1/3 to 1/2 of the rotor length from the axle. The first 1/3 of the length of blade really contributes no lift and is in perpetual stall. As you move outboard, that transitions from stall to actual lift. The length of each zone depends on the rotor pitch, twist and blade profile.
Cupping the blades is an interesting idea. I think AK means cupping them up. When you do this, a vortex is generated above the blade, along the length of the rotor. This vortex is a low pressure area and will contribute to lift. Most of your lift, however, will be from the deflection of air downward. That's Bernoulli's principal working in conjunction with Newton's 3rd law of Motion, which is how wings work, anyway.
Oh and maybe the rotors were not up to speed. I haven't build landing gear for this yet so I'm hand tossing it. I might just have to try more power and see if once it gets moving faster it will stay up
Run with it in your hand to get them spinning if you are hand launching it. You, however, must yell, "WHEEEEEEE" while doing so. Also, make sure someone videos you doing this so you can post it here. We all appreciate a good laugh!