Originally Posted by
Eric86343
Robinson is now working on a multi-blade model
The only downside to having more blades is cost.
More blades means you can make the blades with reduced chord and shorter and at reduced RPM.
Noise is generally lower with more blades.
The Osprey for example really could use more blades as increasing the blade chord would make the already bad vibration worse! Engineers have compensated by increasing the tip speed.. on the Osprey it's 559 mph!
In forward flight every time the blade passes in front of the wing the whole aircraft jumps!
That is interesting insight, In aerodynamics, induced drag is the overwhelming factor that drive efficiency, Induced drag is generated by the blade tip vortices. As the result a long aspect ratio blade will always be more efficient (akin a high performance glider). Robinson blades are one of the highest aspect ratio blades around, and I contend that it is one the design choice that has driven the success of the R44 especially. Think about it, 4 passenger with 225hp (Astro and Raven I) could only be the result of a higher efficiency rotor. roughly computed:
R44 1089Kg 225hp 4.8Kg/hp
EC120 1715Kg 504hp 3.4Kg/hp
H500 1610Kg 425hp 3.8kg/hp
So even with the benefit of the lightweight turbine engine and a heavier airframe nobody come close to the weight carrying capability of the R44 per hp.
You bring a good subject, the drivers have changed, look at Archer aviation and Joby, their creative design make you think about blades differently, aiming for different drivers (noise)