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Physics of the Funnel?

Old 05-08-2010, 01:26 PM
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helicub81
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Default Physics of the Funnel?

I'm kinda new at these helicopters and i have kinda mastered the basic things, like hovering nose out/nose in etc.... and from the sides too. Now i was wondering why when you do a funnel (upright, with the nose facing the center of the circle) the pilot has to push the cyclic in the opposite direction of the helicopter. For Instance, if the helicopter is flying to the left, why does the pilot push the right stick (mode 2 transmitter) to the right... I know this isn't exactly too important, but its been puzzling me for a while now.
Old 05-08-2010, 04:06 PM
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BarracudaHockey
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Default RE: Physics of the Funnel?

http://www.littlerotors.com has some great articles on doing funnels.

I'm stuck on answering your question........lol........I just give the control input it needs
Old 05-10-2010, 11:55 PM
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Default RE: Physics of the Funnel?

I'm not sure if I understand your exact question, but the best explanation Ican come up with is.When flying an RC model, as faras the model being flown is concerned it's Right is always Right and Left is always Left. On the ground looking at our model we need to remember this. I have heard people term it as reversing.

Ihope Ianswered your question, and if Idid I'm glad Icould help. If Ididn't and Ijust added more confusion, please forgive me.

Aloha,
Les
Old 05-10-2010, 11:56 PM
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helicub81
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Default RE: Physics of the Funnel?

i kno, but like when you press right on teh transmitter, the heli goes left in funnel, but if it were just hovering, it would go right.
Old 05-12-2010, 08:29 PM
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Default RE: Physics of the Funnel?

Next best answe Ihave in the physics of a funnel.

Think of it as drifting a car, as in Fast and Furious Tokyo Drift.As the front of the car startsto move left,you quicklysteerright causing the rear ofthe car to slide rightthus basically pivotting on the front of the car. With proper counter-steering the car goes around 360 degrees in a movement that would be similar to a heli doing a funnelwith the nose facing inwards.

If you were to give only left input on the TX the heli would keep going left till it eventually would just be doing a left aileron roll. Iam having difficulty wording my answer.

Just fly have fun and leave the physics up to the scientists hehehe LOLjust kidding

Aloha,
Les
Old 05-12-2010, 08:37 PM
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helicub81
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Default RE: Physics of the Funnel?

haha, that explanation works for me
Old 05-12-2010, 11:03 PM
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Default RE: Physics of the Funnel?

Sorry - not for me.

I'm from the northwest and drive in ice and snow and the same countersteering action applies. Something has to make the car start to go in one direction before you can countersteer. In your example you said "As the front of the car starts to move left, you quickly steer right causing the rear of the car to slide right..."
What caused the car to start to move left at the beginning? In drifting the driver intentionally starts the car left then countersteers right. Up here ice does it for you, and you countersteer.

Ignore the language barrier and just watch the heli and the stick movement. This guy gives a short back stick burst to bring the nose up, then almost full right stick at which point the heli starts to slide left into the funnel. In the countersteering example I think he would have needed to feed a short left input to make the heli start to move left and then right stick to countersteer, and I don't see that. [link]http://www.youtube.com/watch?v=ZqXJWH5JnR4[/link]

I have just learned that I can't funnel for more 1.7 seconds but I tried it in the sim. I pull the nose to vertical, feed in right stick and the heli starts to move left into a counter clockwise circle.

I'll openly admit that I have no idea of what's going on... and for all I know the drift theory may be correct. I hope you understand that it's hard for me to say your answer is wrong when I don't know the right answer I just can't see this being the result of countersteering.
Old 05-13-2010, 04:35 AM
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Default RE: Physics of the Funnel?

Something has to make the car start to go in one direction before you can countersteer. In your example you said "As the front of the car starts to move left, you quickly steer right causing the rear of the car to slide right..." What caused the car to start to move left at the beginning?
I'm not trying to start an argument about my explanation of the "Physics of a Funnel", but in my defense I'd like to elaborate on my explanation since you have pointed out the video of the funnel in slow motion on the sim. You are correct in that you need to "make the car start to go in one direction before you can countersteer." As you seein thesim the tail is used to set the nose of the heli movingleft and then the pilot counteracts that movement withtheinput from right aileron.

At any rate Icould be wrong but thats just my theory of it all. I'll go out to the field tomorrow and see if Ican figure it out. This has turned into an interesting topic hehehe, got me thinking a little too much, when Ishould just be flying and having fun.

Aloha,
Les

Old 05-13-2010, 06:46 AM
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Default RE: Physics of the Funnel?

I'm not arguing either, and if it sounded like I was I apologize. Like I said, I can't say you're wrong since I don't know the answer... you may in fact be right. It just doesn't look or feel like the right explanation to me. Watching the video again I kind of see the tail thing you're referencing but it's really hard to watch the controls on the radio and the heli at the same time. Too bad Bill Nye doesn't hang out in the forums.
Old 05-13-2010, 09:23 PM
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Default RE: Physics of the Funnel?

All the inputs make sense in that video, nothing is essentially backwards of what its supposed to do. Collective gives it thrust, rudder keeps the nose up, and aileron controls its roll. He is rolling it to the right the whole time, as his inputs show, and combined with the other inputs the heli tries to fly towards the center (actually a little past the center) all the time. But since the heli changes its position and angle the whole time, and the point at which its trying to go changes, it just ends up in that pattern. Change the roll and thrust and the circle gets bigger or smaller.

I think it would be easier to visualize if you thought about it flying nose forward through that same circle (since for all the heli cares the orientation is all the same). You give thrust, roll on its side, then pull hard back on the elevator. So long as you get the thrust and elevator right you make circles on your side. Now rotate the tail 90 degrees clockwise and you are flying nose up with right aileron going left. Another 90 and you are flying tail in pushing the elevator forward. Another 90 and you are nose down with left aileron going right.

In some sense its the same as a car/plane/rocket on a string. The thing wants to go in a straight line (in the heli's case its straight in to the center), but the tether keeps it changing direction (the roll caused by the ailerons). Cut the tether and the straight line starts.
Old 05-13-2010, 10:24 PM
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Default RE: Physics of the Funnel?

The tether works and now it makes sense.

I taped a string to an empty toilet paper tube (first thing I found) and pulled it tight in a nose up position. If I keep the point where I taped the string always facing me and move the heli to the left the string will wrap around the tube. I have to rotate it to the right to unwrap the string... so right stick is actually making the heli roll to the right. If I understand your exlanation the movement to the left movement is caused by a combination of control inputs replacing the string?
Old 05-13-2010, 11:57 PM
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Default RE: Physics of the Funnel?

Ahhhhh Let's just fly and have fun!!! LOL No need for apologies. BTWhad a great day of flying at the field today. Just keep flying and enjoy!

Aloha,
Les
Old 05-14-2010, 12:59 AM
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helicub81
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Default RE: Physics of the Funnel?

Ooooo i get it; thanks for explanation. So basically, if we visualize the funnel as a circle, the force of the helicopter would be in the direction of the tangent line to the circle. So, based on that logic, without any input, the helicopter would deviate from the circle. So, cyclic control, which is opposite to the direction of the travel keeps the helicopter traveling in the circle. And, since the force is consistently in the direction of the tangent line, we need to keep applying cyclic!!

Again, thanks for the explanation. I think this well help greatly in learning funnel
Old 05-14-2010, 03:03 AM
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Default RE: Physics of the Funnel?


ORIGINAL: helicub81

Ooooo i get it; thanks for explanation. So basically, if we visualize the funnel as a circle, the force of the helicopter would be in the direction of the tangent line to the circle. So, based on that logic, without any input, the helicopter would deviate from the circle. So, cyclic control, which is opposite to the direction of the travel keeps the helicopter traveling in the circle. And, since the force is consistently in the direction of the tangent line, we need to keep applying cyclic!!

Again, thanks for the explanation. I think this well help greatly in learning funnel
Wait huh? Tangent? deviate? Force...tangent line? Lets see... tangent was cosine divided by... nahh ... the square root of ... nope - that's not it... oh yeah - pie are round, brownies are square... that doesn't sound right either...


Oh crap. What'd you have go and make it all complicated for?? I had it for a minute there, now it's gone again. [sm=spinnyeyes.gif]
Old 05-14-2010, 06:19 PM
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Default RE: Physics of the Funnel?

Well its also not quite that, as the force of the heli is not tangent to the circle, its straight in, pretty much perpendicular to the circle. If you stop rolling it doesn't make a slide motion, it flies 'up' relative to the skids.

You could probably draw how the heli makes a circle by drawing straight lines on a piece of paper, first imagine making a square with the heli nose up. You apply collective making a vertical line on the paper down on the left side. Roll the heli 90 degrees and again grab some collective. Now you draw a horizontal line left to right on the bottom edge of the paper. Another 90 roll, vertical line up the right side of the paper. Another 90, horizontal line right to left up at the top of the paper. Thats the rough forces its using. Split the 90s to 45s and its an octagon, closer to a circle, split those 45s and i don't know what you call it anymore =D. Split those, and again, and again, eventually its a circle. The heli is always trying to go past the center a bit, but never can since you keep rolling it, there should be a smaller circle inside the circle the heli makes where the rotors are aiming for.

Old 05-15-2010, 02:44 AM
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helicub81
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Default RE: Physics of the Funnel?

oO well thanks for the explanation.its quite complicated :/

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