Rotors

[lllazar]

Well, if you know how to make a good jig, our at least are willing to do some research, it shouldn't be too hard to make those kinds of props. But if this is your first copter, maybe try something a bit less complex, as Chia said. Building experience will help you fix all the mistakes you made on the first one.

[chia]

I think I need to find a better way of attaching the rotors to the wire. Currently I'm just gluing it straight to the side of the rotor at the center spar, with another piece of wood on top to keep it straight. Obviously not the best option, balance- and strength-wise.

[lllazar]

I poke the wire through the two spars and glue the the whole shut. It's not working too well either. I think if i used wood glue for the holes instead of super glue. Titebond is apparently as strong as oak.

[thewinner]

I do the same thing. I just wish the wire was stiffer, so it wouldn't bend under the force of the rubber band and twist the whole rotor out of alignment.

[jander14indoor]

Rotor to wire joint. DON'T depend on a straight wire held with glue, too much glue, not enough strength. With the high torques needed to fly these things, say 2.0 in oz. At the surface of a 0.020 inch wire you have 400 lb of force trying to break things!!!!! Instead, bend over a short L, say 1/8 inch at the end which lies against the wood directly and reacts the torque. Force will drop to something like 16 lb needing almost NO glue. Also, run the wire through the centers of your spars, and sandwich wood on either side, don't put it on the side.

As to wire stiffness, if bending too much, go to the next wire size up and save the weight someplace else.

Jeff Anderson
Livonia, MI

[lucwilder42]

Hey Jeff, is there any merit to a three bladed rotor for this event?

[chalker7]

I'm not Jeff, but I'd like to add my two cents.
There may be some benefit to a tri-bladed design, however I can't know for sure since very few (if any) people have built one.
I saw one 4-bladed design earlier in the year that flew extremely well (in fact, it was probably the most stable SO Helicopter flight I have ever seen), but was significantly overweight so it did not have exceptional duration. So, long story short, 3 or 4 blades could or could not help but you will definitely run into difficulties with weight (particularly with 4 blades) and alignment (with 3 blades). In either case, you should try to build a few and let us know if they work well for you!

[illusionist]

I have also experienced those properties with the 4 blade design. I tried two counter-rotating rotors with 4 blades each, and it was much, much more stable, but duration was cut short. I also had to reduce the pitch of my blades to accommodate the extra drag. The helicopter weighed about 6ish grams, obviously reducing its potential flight times. So with my more experienced building skills now, I might give it another go. However three blades seems like a challenge.

[thewinner]

How exactly would you get all four (or three) rotors to spin? It sounds interesting.

[lucwilder42]

On a separate note, assuming weight is under control, has anyone had success with three rotors? We have good two blade two rotor standard copters that we're boxing up til state, now I'm goin balls to the walls with new designs