Rotor

[Jenny]

I am building a gyrobee with a 447 Rotax. I am not concerned about speed in the air. But I would like to be able to get off the ground in a short run and be stable in flight. What are you all's comments on rotor diameter, chord, and brand. I am 5'9", 180 lbs. I would like a pre-rotator some time later.
Thanks
Roger

[Douglas Riley]

Roger: The "vital stats" for me and my 'Bee are identical to yours. I use 24.5-foot Rotordynes very successfully. They are easy to hand-start and perform quite well, even with the small 447. My 'Bee will easily exceed the Part 103 speed limit unless equipped with a shallow-pitched prop.

Dragon Wings blades are a bit more efficient than Rotordynes and significantly lighter. They're a lot more diffcult to hand-start, however. 23-foot Dragon Wings would do well on your gyro (especially if you spring for the prerotator up front).

[Jenny]

Roger: The "vital stats" for me and my 'Bee are identical to yours. I use 24.5-foot Rotordynes very successfully. They are easy to hand-start and perform quite well, even with the small 447. My 'Bee will easily exceed the Part 103 speed limit unless equipped with a shallow-pitched prop.

Dragon Wings blades are a bit more efficient than Rotordynes and significantly lighter. They're a lot more diffcult to hand-start, however. 23-foot Dragon Wings would do well on your gyro (especially if you spring for the prerotator up front).

Thanks for the reply. What is the weight difference between the blades and what size hub bar are you using.
Which blade gives a more stable flight and better landings. Heavy or light?
Thanks
Roger

[Douglas Riley]

There's not much difference in flight quality. Although Dragon Wings are light overall, they have tip weights. This allows them to store more energy than a blade of the same weight whose mass is distributed evenly along the blade. Therefore, they flare as well as heavier, non-weighted blades and are pretty forgiving in that respect.

On the Rotordynes, I have the shortest hub I could get. Other things being equal, you're a bit better off with a shorter hub and longer blades to achieve a given diameter. If nothing else, blade section is lighter per foot than hub bar stock (and often cheaper!). The only reason to use the very long hub bars you see on bigger gyros is to allow the manufacturer to create a big disk without having to build a longer blade jig.