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Apr 10, 2017, 04:27 PM
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Twirl Re-Do


We were wondering what you get if you add airfoil blades to the Twirl designed by Al Foot. Now we know...PERFORMANCE!

We replaced the rotors on a Twirl with a set using airfoil blades instead of the flat blades of the original. The blades are hot-wire cut from Dollar Tree Foam pieces and covered with Tyvek, and they are self rigging as they are glued in place just like the flat blades. One could also use balsa blades sanded to airfoils with the same result. The CG moves forward to the wing leading edge from its previous position when using the new rotors. For the purposes of this thread we'll call this Twirl "Junior".

We liked the increased performance, and especially how much the model now flies like an autogyro (which it really is) for example, with the new rotors you'd best be sure they are both turning fast before attempting takeoff or you will likely roll.

We then took things a step further by building Twirl "Senior". Senior has some further modifications beyond what we did to Junior. Senior's wing is 4.5 " greater in span to accommodate different blades. The rotor support pieces are made of plywood, and the wing strengthened against twist with a laminated double sheet. A wider shock absorbing landing gear is also fitted.

The three blades are hot wire cut Dollar Tree Foam covered in Tyvek, but in this case they are simply cut down blades we took off one of our Whippits. They are set at 120 degree intervals and glued in place to make the new rotors for Senior. The same motor and prop are used as with our Whippit, a 3C 1300 mAH battery providing power. Wow! This is superb and our favorite. Real Autogyro performance with RET controls is a perfect intro for new and aspiring GyroNut pilots.
Twirl "Junior"
Twirl Junior (3 min 48 sec)

Twirl "Senior"
Twirl Senior (5 min 3 sec)
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Apr 10, 2017, 07:10 PM
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britinoz's Avatar
Nice project....... Senior looks very stable.
Chris...
Apr 10, 2017, 09:08 PM
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similar to what I'm using on my prototype except my airfoil is hand sanded and covered in packing tape. cheers
Apr 10, 2017, 09:12 PM
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Yeah Chris,

We flew her again today and commented such. You really can just feel free to whip her around the sky and play close to the ground because she feels like she is rock-solid stable and happy to be in the air. The video was shot on a very gusty day and today was just a steady 8 mph wind. Too bad the camera couldn't pick up the autorotation sounds with all the wind. She sounds really cool, and even just like a helicopter when at high alpha. This is a fun one for sure and a keeper. I hope some other guys build one. Too much fun!
Apr 11, 2017, 10:24 AM
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Hi RedBaron,

Your blades will work fine if you decide to put them on a Twirl. No flexing is needed due to the counter rotating rotors.

Cheers!

Russ


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