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Pumpkin drop event

So, I too wish to look into building a Bicopter, with the rotors next to each other.

#1
Hi, I guess many try the challenge of building a Bicopter, no thanks to that one movie with them tall blue dudes. :rolleyes: Here in the Netherlands no one seems to go that far sadly... So time to change that.

Now, I consider myself creative and good with technical stuff, but I expect this to be a challenge still. To start, what are the main things to watch out for when designing/building a Bicopter? I noticed already that the CG must align with the rotors as perfectly as possible, but must it also hang below it for stability? (Noticed many of these things tend to rock back and forth.) Also, I guess the rotors must counter each other, so I was kind of surprised when I saw that the stock Bicopter settings in my KK2.0 both turn clockwise... (Maybe it is possible and done with the idea in mind that it is easier and maybe cheaper to get two identical props?)

Also, I guess the best way is just to stick with simple prototypes, just essential stuff, so I figured I'd build something like this first. Symmetrical both seen from the length and width axis which should keep it easy to have the CG dead-centre.

Eventually I hope to make a fuselage for it and there then comes the question if a functional elevator and maybe a rudder would be useful for when the craft is in motion. Of course if it works it's still the question whether or not it's worth the trouble.

Anyway, any tips you guys can share?

Edit: Actually, crazy, crazy idea maybe, if taking a bit of an Osprey-ish design, could it perhaps even glide in case of engine failure?
 
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TDM22

Junior Member
#2
So....you are essentially building a Chinook helicopter. (Boeing CH-47) Like 300px-080301-F-2207D-394.jpg

Though if you're considering a winged, why not build a quad or even bicopter and build a foam plane around it. By going forward you may be able to create lift on the fixed wings as well as the blades. It would have the benefits of a VTOL craft, but advantages of a plane.
 

Cyberdactyl

Misfit Multirotor Monkey
#4
Yep, I imagine all sorts of flying contraptions can be devised nowadays with gyros and accelerometers sampling at thousand of times per second and put on a small 2"x2" piece of G10 for the cost of a cheap bottle of scotch. :p
 

rcspaceflight

creator of virtual planes
#5
I wonder which would be more stable, having the two motors far apart, or close together. Farther apart seems like it would be more stable, but it would require more movement to get back to level. Short arms and it could snap back to center with little effort. I'm sure it's all a careful balance of the right arm length, the right weight, and the right settings on the board.
 
#7
Okay, thanks for the replies, but first, no, no Chinooks. :p I'm planning on making something that's like an Osprey, like this one:

Only the rotors won't tilt this far, they mainly stay horizontal. The reason I want it to act like a plane still is because of the simple fact that engine failure tends to automatically mean the end of a craft in case of the multirotor. Hence why I'm wanting it to have wings and some control surfaces.

Now there is only one major issue that I've noticed so far, the center of gravity. With an in-width-placed Bicopter, the CG has to be dead center of the propellers, while a plane has the CG slightly forward. I guess this may be solved by placing the engines slightly forward on the wings.

Now I hope it to work with just an elevator and rudder, and make the wings dihedral (5° enough?), else add some ailerons too. (First thought this may require extra channels, but I bet connecting the control surfaces directly to the receiver and the KK2.0 to the same ports by using Y-cables should work.)
 
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rcspaceflight

creator of virtual planes
#8
You don't want the control surfaces to be directing airflow while in bicopter mode. It might compound changes into something bad.

Also, I think such a big plane is what creates such a pendulum motion for most bicopters. It creates more weight that can be swung back and forth and makes it harder for the craft to center it's self. And you don't want the wings in the way of the propellers airflow.

Because aileron control is easy to stabilize and forward and back is so hard, maybe make a flying wing type craft with the wings coming out past the props. I'm thinking something like a versa wing with holes cut out for airflow for the props.
 
#9
You don't want the control surfaces to be directing airflow while in bicopter mode. It might compound changes into something bad. And you don't want the wings in the way of the propellers airflow.
That is a concern of me too that I hope to solve by using short duct around the props like the Avatar Gun Ship has, but connected to the tips of the main wing.

Also, I think such a big plane is what creates such a pendulum motion for most bicopters. It creates more weight that can be swung back and forth and makes it harder for the craft to center it's self.
Here I indeed wonder what exactly causes it, must the plane remain light, or should it have some centered weight to employ gravity to keep the plane steady, also, might a shorter fuselage help?

Because aileron control is easy to stabilize and forward and back is so hard, maybe make a flying wing type craft with the wings coming out past the props. I'm thinking something like a versa wing with holes cut out for airflow for the props.
Hmm, going to look up the Versa Wing in a moment, curious what you mean. :)
 

kah00na

Senior Member
#10
After watching the FliteTest video, I'm a little more interested to see if you can pull this off. The FT montage video at the end didn't show much forward flying motion. Most of it seemed to be hovering around like it had just taken off.
 

rcspaceflight

creator of virtual planes
#11
Hmm, going to look up the Versa Wing in a moment, curious what you mean. :)
I thought about doing a quick drawing to show what I mean. I guess I could do one now.

bi copter wing.jpg

Okay, bad drawing. But I meant to basically just get rid of a fuselage. I'm guessing a fuselage causes nothing but trouble.
I figure by extending the wings past the two holes for the rotors, it would make the craft glide much better.

The wings would get in the way of aileron control, but since aileron is controlled by thrust vectoring, it's the most stable and could handle the extra drag. Front/back control wouldn't be very stable because it's controlled by tilting the motors, you don't want weight to be fighting against it. Same with rudder.

I was just thinking that a flying wing with two holes cut out for the rotors would probably be the most stable.
Except for the possibly CG issue. Like you said, the CG for the "plane" needs to be towards the front where as the CG for the "bicopter" needs to be center. Not sure how having more plane in the back than front of the bicopter would affect it.