twistless blades

[autorotate]

vortech offers a single extrution aluminum blade. im sure given its construction it is most durable and it is priced fairly. what i dont like is that its twistless , my concerns are high tip loads causing exsessive stress on head and structure. doese anyone have any opinnions on this blade or twistless blades thanks

[MikeBoyette]

The Mosquito uses Dragon Wings with no twist. The designer asked my dad to build the blades with no twist. He says they auto better with no twist.

Do your self a favor get with someone who knows a little about Alum. and have them look at the fully extruded blades. There has been some question about them while in use on a gyro I would sure be concerned if using them on a powered rotor.

[Ron Iaconis]

Mike,,,,,,,I am skeptical about the Vortec/Fleck/RotorHawk,,,,after reading some reports,,,,Some say " Super" great blades,,,,,others not too sure,,,,,I use " untwisted blades" No Pre Rotator,,,,,,Are you telling me that your Dad still makes Untwisted blades or does he only make the twisted ones?

[brett s]

Twisted will perform better on either - the only issue for a helicopter is the appropriate twist for autorotation (like the gyro ones use) is the opposite of what's needed for powered flight.

[C. Beaty]

Propellers are twisted one way; windmills are twisted the other way.

Dutch millwrights figured that out 400 years ago.

Windmill twist on a helicopter rotor reduces hover efficiency and results in earlier retreating blade stall in forward flight but gives slightly better efficiency in autorotation.

With a helicopter, top speed is limited by abrupt stalling at the tip of the retreating blade. In autorotation, the root end of the retreating blade is always stalled, the stalled area spreading outward with increases in forward speed.

[MikeBoyette]

Ron,
He only makes untwisted blades for the Mosquito. He is able to this due to the fact that the blades are only 9 ft long. He has delveoped a different way of baking them for this application that allows him to not put the twis normally in full length DW's. As Chuck has said a blades that are twisted positive at the tip and negative at the root are better than ones with no twist, twisted the wrong way like RAF blades. The twist is not what makes a set of Dragon Wings harder to start than a Bensen or Rotordyne, it's the airfoil. Chuck can better expalin this than I.

There is a procedure to be able to hand start a set of DW. It takes some patience. Most people try to brute force them up you can't do this. The key is to get a rythm going. There is a guy if I am not mistaken in Ga or one of the Carolinas that flys them on his Mac powered bensen with no PR.

[Ron Iaconis]

Mike, Yes I know of a man( Rick Abercrombie) in the Atlanta, Georgia area that flys a VW with DW,,,,as my son told me( Chris , my son and Rick both work for Delta Airlines) Chris told me that Rick says that it takes a long time and patience to hand start up the DW,,,,,I believe that I am patient as far as " nursing" the blades up,,,,But I just was under the understanding that the TWIST was why they were hard to hand start. So,,,,basically what I am getting from this,,,is that it's the " air foil" that makes them difficult to hand start.?

[MikeBoyette]

Ron,
That's it exactly. The airfoil is not flat bottomed like other blades. It has a slight curve on the bottom. This makes it stall more ubruptly. This is why someone that flys them for the first time can find them a little difficult to bring them up even with a good prerotator. Once you develop a feel and your own procedure then you can get them to come to speed pretty quick. They don't like being crowded at all. This little inconvience is worth it though. Have you ever flown a set of DW's? Maybe you should try a set!

[Ron Iaconis]

Ron,
That's it exactly. The airfoil is not flat bottomed like other blades. It has a slight curve on the bottom. This makes it stall more ubruptly. This is why someone that flys them for the first time can find them a little difficult to bring them up even with a good prerotator. Once you develop a feel and your own procedure then you can get them to come to speed pretty quick. They don't like being crowded at all. This little inconvience is worth it though. Have you ever flown a set of DW's? Maybe you try a set!

Look also at this thread
http://www.rotaryforum.com/forum/showthread.php?p=110329#post110329