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So, to kick things off (I guess)...

Does anyone know of any plans of a good helicopter available online right now? I need a starting point for design. Thanks in advance!

daydreamer0023 wrote:So, to kick things off (I guess)...

Does anyone know of any plans of a good helicopter available online right now? I need a starting point for design. Thanks in advance!

First pull up a picture of a helicopter from the image gallery, wiki, etc. and examine it. Making a helicopter is kind of like making a plane for Wright Stuff--except instead of a rotor that provides thrust, it provides lift; and for helicopters you'll have to make the blades to your rotor yourself. Helical pitch blades complicate the build process, so skip them for now (I don't have evidence that helical pitch blades are much better; if someone has a paper on it I'd like to see it). So making your blades is kind of like making a wing, though your blades don't need to be rectangular (like wings). For thrust bearings, you can use the same ones from the Freedom Flight kit, buy them from Ray Harlan's site, or hand make your own pigtail bearings (search Youtube for this). Pitch your blades like shown in pictures. One rotor is typically fixed/stationary and the other is mobile (attached through a thrust bearing and free to rotate). Mount the thrust bearing to a large cross section stick of balsa, make and attach a hook for the rubber motor, attach the stationary rotor to the helicopter, etc. And unless you've made helicopters before, don't start out going for the bonus.

I don't have any data on helical vs not, but I KNOW helical isn't that hard to build and I strongly suspect that propellers are helical for very good reasons.
Specific suggestions.
There's a perfectly good design from the past on this site, look up the River City Rocket. You might have to adjust the dimensions to this year of course.
http://gallery.scioly.org/displayimage. ... 2&pid=2885

Don't forget the helicopter wiki on this site.

A couple of years back the North Carolina SO site had a VERY beginners plan, hints and tips. Didn't load up for me today, but keep an eye out, they'll probably reload.

General comment. For free flight, a dual counter rotating design with a simple motor stick is very competitive. You'll need to play with rotor pitch, blade width and rubber dimensions to get things optimized, but if you start with something like the river city rocket you'll get there pretty quick.

Jeff Anderson
Livonia, MI

NC Science Olympiad: Helicopters
https://www.youtube.com/watch?v=xsGwOCiREBU

NC Science Olympiad: How to Make a Motor Hook
https://www.youtube.com/watch?v=prUuqjsqFRE

NC Science Olympiad: How to Attach a Motor Hook
https://www.youtube.com/watch?v=mJPFSg1uLAQ

NC Science Olympiad: Stationary Motor Hook
https://www.youtube.com/watch?v=JbA3pSYUfc0

NC Science Olympiad: How to Attach Wing Covering
https://www.youtube.com/watch?v=CkADhiyD2z4

NC Science Olympiad: Rubber Band Motors
https://www.youtube.com/watch?v=AAhEmGVXSvo

NC Science Olympiad: How to Wind and Fly your Helicopter
https://www.youtube.com/watch?v=H7HqkcE1oO4

NC Science Olympiad: Helicopters how to wind and fly
https://www.youtube.com/watch?v=uDhcxS_OTv8

NC Science Olympiad: Helicopters Demo
https://www.youtube.com/watch?v=2UDSRa7gB_I

what are the specs for the rotors this year?

20 cm diameter is the max for the rotors.

Thanks!

A single blade rotor can have a radius of 12.5 cm. Note that single rotors can not be rigidly connected. 25% bonus for single blade rotors.
3 rotors max, but no limit on the chord or the number of blades.

retired1 wrote:A single blade rotor can have a radius of 12.5 cm. Note that single rotors can not be rigidly connected. 25% bonus for single blade rotors.
3 rotors max, but no limit on the chord or the number of blades.

No, blades that are rigidly connected cannot count as multiple single rotors.