Hi,

If you want a challenge, autogyros will provide that! I don't know the weight, but if you build a .25 size you should use 1-3/4 or 2" wide blades. The length will depend on the weight and the blade profile that you use. I recommend that you use the SG6043 blade profile as they seem to provide the best lift.

The blades need to flex to create a coning angle which acts like diahdral in a wing and also allows the advancing blade to flex up more than the retreating blade.

Phil