Build poll Summer 2022

which one?


  • Total voters
    11
  • Poll closed .

Bill Stuntz

Well-known member
I suppose it could be considered a structural failure, but that's probably be a stretch. That seems to be talking about simulated failures, not detected ones. And it doesn't specify what structural failures are simulated - probably things falling off. You could easily be correct that RF wouldn't detect the collision. But if it doesn't, why does that thing start grinding as soon as it lands in the video? It was a pretty hard landiing. I didn't hear anything similar while it was actually flying. I suppose they could be colliding with the ground, but it looks more like there's something going on between the rotors. Neither one looks like it's spinning smoothly.
 
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uncle twist

Well-known member
Hey @asj5547 ... what happens if you make the rotors turn the same direction? could you please try just to see if they actually hit each other?

It would be strange, but I wouldn't be surprised if they don't actually hit each other.
If they turned in the same direction, torque would be generated in one direction only, thereby making it necessary for a tail rotor, Counter rotating blades blank out the torque that each other generates, THUS, NO tail rotor, thereby eliminating crashes due to tail rotor failures. But you knew that already... ;) :p
 

legoman

Well-known member
If they turned in the same direction, torque would be generated in one direction only, thereby making it necessary for a tail rotor, Counter rotating blades blank out the torque that each other generates, THUS, NO tail rotor, thereby eliminating crashes due to tail rotor failures. But you knew that already... ;) :p
i think he meant was what happened when they crashed into each other. but in rf they won't as rf cannot detect one part of the vehicle "crashing" into another part of the same plane.
 

uncle twist

Well-known member
i think he meant was what happened when they crashed into each other. but in rf they won't as rf cannot detect one part of the vehicle "crashing" into another part of the same plane.
Yeah, you`re right about that, I read into it slightly different, my first thought was about the rotors rotating in the same direction...
 

Bill Stuntz

Well-known member
also there is not path for the airflow from the cooling fan to reach the rudder
How does RF work with a 🦆 ducted fan? How does it calculate thrust & airflow? It must do something. Isn't the Fletttner a "sort-of ducted fan" with an oddly shaped duct? 🦆 Does a quick bip on the throttle kick the tail over in RF like it seems to do for Trident? Or is that tail wheel vs ground friction & airspeed? I have no idea how that works, but it DOES seem to work that way. Or maybe it's just my imagination. Do you know what caused the odd sounds during/after landing in that test flight video? It sounded to me like rotors hitting something to me. Or is that my imagination, too?
P.S. My ODD sense of humor... "ducted fan" makes me think of "Duck Tape" - which I was actually amazed to find that I used for it's REAL purpose when I installed a whole-house fan a few years ago. I almost fell off the ladder when I realized that was actually using it to do the job it was designed to do - instead of "if it moves - Duck Tape it... if it doesn't - WD-40" for the ONLY 2 tools a handyman needs to fix ANYTHING.
 
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space boy

Well-known member
the 🦆ted fans are simply propellers in a shroud that doesn't move. maybe the best analogy to how the Flettner works is thrust vectoring like on the F-35:

2a74a723b0d7af1bde173f92159b402e.gif
 

Bill Stuntz

Well-known member
I'm not sure about that. F-35 does move the shroud, rather than using airflow over a control surface to generate the deflection force. Couldn't DF's be used the same way? Does a DF NEED to be "undeflectable"? Think of "jet boats" which I don't think even have rudders vs "air boats" that use an air rudder to deflect the fluid flow. That's a BUNCH of different interacting factors that I've never really thought about before. It's a case that exemplifies my learning method... knowing WHY makes me think much deeper about things than memorizing the details would. I guess that's what makes me think of myself as a "Jack of all trades & master of none" - I think I know nearly enough about everything to be dangerous. And conventional "That's just the way it is" explanations don't work with me.
 
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asj5547

Well-known member
When I force the rotors to collide, they do not break apart, they just pass through each other without any actual damage. Unlike if the rotors hit the ground or a building, then they break apart and stop the motor.
If the blades rotate in the same direction (both clockwise) they collide every time because the two inner blades (inclined up) are approaching each other on the inner part of the circle.
To stagger the blades I set the "Initial Azimuth degrees" to 60 for the 3 blade setup. (see pics)
 

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Bill Stuntz

Well-known member
When I force the rotors to collide, they do not break apart, they just pass through each other without any actual damage.
Now that I REALLY think about it, I THINK I've noticed that in the back of my mind & never really analyzed it. Thanks! Do they make noise when they pass through each other? This makes me really appreciate how complex the calculations in simulations really are.
 

space boy

Well-known member
When I force the rotors to collide, they do not break apart, they just pass through each other without any actual damage. Unlike if the rotors hit the ground or a building, then they break apart and stop the motor.
If the blades rotate in the same direction (both clockwise) they collide every time because the two inner blades (inclined up) are approaching each other on the inner part of the circle.
To stagger the blades I set the "Initial Azimuth degrees" to 60 for the 3 blade setup. (see pics)
that confirms what I suspected and what legoman said: RealFlight doesn't do calculations for collisions between parts on the same vehicle; it simply allows the parts to pass through each other visually. this is no doubt so that the simulation runs more smoothly, since fewer calculations need to be made, as you alluded, Bill.
 
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