Hand start dragon wings

[Paul_Zurawski]

I have read/heard that you cannot hand spin DW rotors...that you need a prerotator. I was just wondering why this is so...light weight,etc?

[scottessex]

They can be, Rick Abercrombie is the only one I know of that hand starts his,
I think it has to do with the airfoil shape.

[Rotornut]

Seen Craig Wall do it also. MJ :)

[gyropilot]

Paul,

As others have already pointed out, it's not impossible to hand start Dragon Wing blades... just very difficult. It's not a job for a beginner at least. But I've even watched an experienced gyro pilot give up in frustration.

Basically you can spin them up by hand as fast as you can (likely 60+ rpm), but unless you have a good wind blowing to help you maintain and build on that rpm, by the time you get the engine started, you get buckled in, and you start taxiing (to get more relative wind under the rotor disk), the blades will have slowed to the point where the rpm won't recover and build. In short, they don't seem to go into autorotation and stay there unless they have at least 75+ rpm and a good breeze.

On the other hand, something like Rotordyne or old Bensen / Brock blades will practically start autorotating by themselves if you untie them with any breeze at all.

If I understand this behavior correctly, it's caused by the Dragon Wing airfoil having rather abrupt stalling characteristics... compared to the Rotordyne or Bensen blade airfoils. But the Dragon Wing blade airfoil has superior lift performance.

Best regards,

John L.

[RockyMeLad]

I have an electric pre-rotator. The dragon wings are very light, and are easy to flap, especially if there is any wind. I can feel my 24' DWs trying to respond to the wind up to about 60-65 rrpm. I would be uncomfortable trying to hand start them in anything other than absolutely calm air. YMMV :p

[Paul_Zurawski]

Thanks for the replies. Just wanting to educate myself on different rotor blades. My Skywheels are really easy to hand spin, and either by taxi, or with any wind at all, spin right up.

[Doug Riley]

Paul, Skywheels are one of the more challenging rotors to hand-start. If you can reliably start your Skywheels by hand, you're on your way to hand-starting D-Ws!

Twist has something to do with the D-W starting issue. The twist is such that each section of the blade along its span is somewhat closer to the same angle of attack than is the case with an untwisted blade. That's good in general, but it does mean the whole blade stalls at once. A DW rotor can go from apparent happiness to smacking the rudder in a rev or two.

I've hand-started the 28-footers on my tandem Dominator and gone flying. However, the above reference to "smacking" is also derived from firsthand experience.

Centrifugal teeter stops would be a good idea if you planned to hand-start DWs regularly.

[Rehan K.Janjua]

Hello Paul.

I fly with 25 SkyWheels, easy to start and they seem to auto rotate at a bare minimun Rrpm.
Have never encountered flapping.
Regards.
Rehan

[gyrofly]

I have skywheels as well. I have a pre rotator that works sometimes better than others and I have had no problem with hand starting them. They seem to do really well as they are heavy and keep the inertia up...
Ron Dupont

[gyrofly]

Another thing, When I was training, and not that I am any expert whatso ever, I thought the dragon wings seemed very fragile and did not keep RPM as easily as skywheels. Skywheels seem to be very tough and forgiving.
Ron