Helicopters C

[bjt4888]

The teams that I coach have constructed five Freedom Flight helicopters so far and some testing has been completed. Performance is very good and it's handy that the jigs included in the kit allow so many rotor configurations (two, three and four blades top and bottom).

I can attest that the spinning disk ceiling bumper is very clever and works well. Testing in my finished basement (flat plaster 7 ft. ceiling) works very well with the helicopter usually landing about 3 ft from where it is launched and it is completely stationary on the ceiling spinning away till late in the flight.

Regarding the mention in the instructions about fuselage breakage, I believe that Dave was just mentioning to indicate how to handle a heli with a broken fuselage. I think that it is extremely unlikely that anybody will have this problem unless they are trying very high torque launches with very thick rubber. Dave mentions in the instructions that he tried as much as 2.3 grams of rubber.

Good luck and have fun testing.

Brian T.

[DoctaDave]

Has anyone tried a single bladed rotor assembly yet? I've had quite a difficult time getting the rotors to balance. Just wondering if anyone has had success with this.

[bjt4888]

DoctaDave,

Are you using a slight inward (towards the motor stick) offset for the counterweight? If not, this is the typical method to achieve a measure of dynamic balance or balance of the thrust created by the single rotor blade.

You can see this concept in plans for old time outdoor rubber models in the Hip Pocket Aero Plans pages.

Good job testing the single blade.

Brian T.

[daydreamer0023]

I know for Wright Stuff, dewinds is a common method used to reduce torque. Is it still applicable (or necessary to use) for Helicopters?

[bjt4888]

daydreamer0023,

In regards to your question about "dewinds", for maximum duration, you would not want to dewind at all for helicopter. However, there are a number of variables to consider. Of course, the motor stick must be capable of withstanding the force of a fully wound motor without bending significantly. Also, the rotor blades must be sufficiently stiff so as to not overflex when spinning fast during the initial power burst. The condition of the ceiling must also be a factor as your team may or may not want to launch a helicopter with a fully wound motor into a ceiling that has girders or other obstructions. Also, you will want your team members to practice handling the fully wound motor without losing control of it (ex. winding on a torque meter and transferring to the helicopter).

My teams are practicing using the usual airplane method of starting with a low number of turns (500-700) and then progressing to full winds with a few backoff winder turns and then practicing with no backoff turns.

One other consideration is that the helicopter will hit the ceiling at a higher rate of speed using full winds. This could cause breakage if flying in a very low ceiling like a living room or a classroom.

You will also want to determine how tight to wind. You may want to wind conservatively to 90% or 95% of breaking torque. Or, maybe you want to "go for it" and wind to almost 100%?

Good luck and good question.

Brian T.

[jander14indoor]

IF you need to fly with less than full winds for any of the reasons discussed above, then YES dewinds are just as necessary in helicopters as in WS. This is a basic characteristic of RUBBER, not the device. It has hysterisis and for the same torque you always have more winds if you wind past and then back off to desired torque. Remember, you fly on the unwind curve of the rubber, not the windup curve.
The big driver will be ceiling type. Can you drive up against it and spin safely or not.
- On a smooth ceiling, or VERY tall site, you probably always want to fly on max winds so no back off.
- If you have lots of obstructions, many rafters, lots of low hanging obstacles, etc. you may want to launch with less than full torque to keep below the hazards. In that case you are better off winding past and dewinding.

Jeff Anderson
Livonia, MI

[yew]

is there a reason why having minimum number of winds left after landing is important or is it not that important as long as rotor-rubber combo is optimal?

[Bazinga+]

is there a reason why having minimum number of winds left after landing is important or is it not that important as long as rotor-rubber combo is optimal?

It's not important on its own though it could be a nice statistic to use when looking for the optimal combo (I don't use it).

[_deltaV]

A question about the disc required about the rules. Nowhere in the rules does it say the disc must be perpendicular to the axis of rotation, so could the disc be attached with the flat side parallel to the rotor shaft, like the greek letter phi? Or is this something that would fall under the "spirit of the rules" category?

[Bazinga+]

A question about the disc required about the rules. Nowhere in the rules does it say the disc must be perpendicular to the axis of rotation, so could the disc be attached with the flat side parallel to the rotor shaft, like the greek letter phi? Or is this something that would fall under the "spirit of the rules" category?

I think the intention of the rule is quite clear, with it serving as not only a way of keeping teams from sticking to the ceiling (which teams did before the disc rule by having a pin that sticks into the ceiling and keeps the helicopter from moving around), but also to protect the competitors and observers. But, as usual, an official clarification would be optimal to full clear up this question so you could submit it (but I really doubt having the top discnsideways would give any sagnificant advantage).