Available rotors discussion.

[Abid]

The drag reduction resulting from a modern airfoil wouldn’t be all that noticeable to the typical the seat of the pants pilot.

A comparison via rotor angle of attack measurement would show a rotor drag reduction of something like going from a L/D 6:1 to 7:1. That’s in the range of L/D measurements that I made a number of years ago comparing a SkyWheels rotor, an excellent example of an 8H12 to a DW rotor.

Other factors, namely misconceptions, enter into seat of the pants comparisons; Skywheels are tail heavy and as a result, pitch noseup when entering an upward gust. This is often misinterpreted as “high lift” but is nothing more than an indication of angle of attack instability. A stable gyro will pitch nosedown in an upward gust, always heading into the relative wind.

So Skywheels are divergent. How are they then a good example of 8H12 implementation? Most so called 8H12 gyro rotors have modified 8H12 profiles

 

[Kolibri]

rwdreams, what's your static thrust? If you've the power, then you could push 8"x25' Sport Rotors.
(A big advantage of the 8" (and 8.5" and 9") rotor is their Heim-jointed hub bar -- the blades find their own lead/lag and coning angles.)
Call Jim Vanek to discuss empty weight, AUW weight, thrust, altitude, etc.
Every kind of gyro imaginable has Sport Rotors on it, and he can dial in what you'd need.

 

[C. Beaty]

Skywheels rotors are an accurate rendition of the NACA 8H12 profile but being tail heavy and being less stiff in torsion than similar tail heavy extruded blades, suffer more from angle of attack instability.
People who modify the 8H12 profile don’t have the foggiest idea of what they’re doing.

 

[All_In]

As long as we are discussing rotors I have a question for Chuck. For a jump take-off gyroplane what rotors would you use?

 

[C. Beaty]

Dick DeGraw’s jumpers all used DWs with extra tip weights.

The increase of moment of inertia resulting from tip weights provides a 3:1 weight advantage compared to heavy blades. In other words, a 1 pound tip weight produces the same increase of moment of inertia and therefore stored energy as 3 pounds spread uniformly along the blade.

 

[C. Beaty]

Here’s what a skilled pilot can do with high inertia rotorblades; in this case DWs with extra tip weights.

 

[All_In]

Thank you, Chuck! U-ROCK!!!

 

[Abid]

Skywheels rotors are an accurate rendition of the NACA 8H12 profile but being tail heavy and being less stiff in torsion than similar tail heavy extruded blades, suffer more from angle of attack instability.
People who modify the 8H12 profile don’t have the foggiest idea of what they’re doing.

Right. They (Skywheels) don't suffer just "more". They are outright divergent Chuck. There is no other way to put it even nicely. There is tons of rather simple software and web based resources available to give you flow simulation of most airfoils and even suggest changes for different properties you want to achieve. SolidWorks flow, Ansys and 100's of other resources are available. I think some people may have a little idea when playing with some airfoil trying to get whatever they want

 

[C. Beaty]

The desktop airfoil programs can give accurate pitching moment coefficients based on the shape of the mean line but drag polars and maximum lift coefficients aren’t much better than educated guesses.

Wind tunnels are not obsolete.