Seriously now, can it take off or not? What do you think?  
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All Forums >> RC Airplanes >> Aerodynamics >> Seriously now, can it take off or not? What do you think?
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[Poll]

Seriously now, can it take off or not? What do you think?
Yes, it will take off.
  69% (61)
No, it won't take off.
  30% (27)


Total Votes : 88
(last vote on : 8/21/2007 11:55:01 PM)
(Poll will run till: -- )
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Seriously now, can it take off or not? What do you think? - 12/5/2005 11:53:47 AM   
Phlip



Posts: 548
Joined: 11/17/2002
From: Auburn, MA, USA
Status: offline 		Regarding the plane on the belt question, do you really think the plane will take off or not?


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Cicero (106 - 43 BC)
       Post #: 1

RE: Seriously now, can it take off or not? What do you... - 12/5/2005 1:49:10 PM   
juanes1969


 

Posts: 375
Joined: 5/10/2005
From: Comayaguela, , HONDURAS
Status: offline 		Well, if we are talking about a "normal" airplane, with normal power to weight ratio, meaning no 3D power to weight or to put it simple, just an ugly stick with a .40 engine... no, I would not think so. But if you have at least 2:1 power to weight and the plane is capable of taking of fron your hand without throwing it... yes it problably will take off.

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(in reply to Phlip)
       Post #: 2

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 7:34:56 PM   
Time Pilot



Posts: 1468
Joined: 10/25/2003
From: Vancouver, BC, CANADA
Status: online 		It's airspeed that determines take off, so while the treadmill speed may be impressive, the airspeed over most of the wing would be pretty close to zero.

< Message edited by Time Pilot -- 12/5/2005 11:07:57 PM >

(in reply to juanes1969)
       Post #: 3

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 7:41:02 PM   
Liberator


 

Posts: 794
Joined: 3/2/2005
From: Sandy, UT, USA
Status: offline 		What?!!!!!!!

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(in reply to Time Pilot)
       Post #: 4

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 9:41:18 PM   
Flyfalcons



Posts: 6100
Joined: 7/27/2002
From: Bonney Lake, WA, USA
Status: offline 		IT IS ALWAYS BETTER TO POST IN AN EXISTING THREAD THAN START YOUR OWN

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Cub flying - the new EXTREME SPORT!!! (evarrr)

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       Post #: 5

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 9:53:10 PM   
Phlip



Posts: 548
Joined: 11/17/2002
From: Auburn, MA, USA
Status: offline
quote:

IT IS ALWAYS BETTER TO POST IN AN EXISTING THREAD THAN START YOUR OWN


This I know. However, I could not figure out how to add a poll to the existing thread. If this is possible, please enlighten me.

The reason I wanted the poll is because I could not, for the life of me, believe that anyone could seriously be on the "no" side of this question, and therefore the one or two still arguing for it (and arguing pretty vaguely, I might add) must be trolls. I thought, perhaps wrongly, that a poll would help us identify if there really any members worth trying to convince.

By the way, my eyesight is fine, thank you.

Phil


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If the truth were self-evident, eloquence would be unnecessary.
Cicero (106 - 43 BC)

(in reply to Flyfalcons)
       Post #: 6

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 11:07:04 PM   
Time Pilot



Posts: 1468
Joined: 10/25/2003
From: Vancouver, BC, CANADA
Status: online 		How could the plane take off if it were on a treadmill that kept pace with the movement of the plane so that the plane wasn't moving relative to the ground?

Any thrust generated by an engine is used to get it moving so that there is enough airflow over the wings to get it to lift off (unless there is enough thrust for a vertical take off, but I didn't think that's what we were talking about). If the forward movement is 'erased', then you can't get to a lift off speed.

It's like the opposite of a catapult launch, instead of the forward speed added to the movement of the plane which helps take off in a shorter distance, the treadmill launch removes the chance for a take off.

That's why we need the runway. If planes could take off from a treadmill, we could save valuable real estate, put those 747's on a big treadmill, let them spool up and get a good go on the belt and watch them take off from zero ground speed.

I didn't follow the other thread--I guess I still need convincing.

(in reply to Phlip)
       Post #: 7

RE: Seriously now, can it take off or not? What do yo... - 12/5/2005 11:22:13 PM   
LarryC


 

Posts: 405
Joined: 10/9/2002
From: Brookland, AR, USA
Status: offline 		Time Pilot,

If the catapult were connected through rotating wheels the plane would just sit there. But it has a hook. Likewise, if you hook the back of the plane to the runway with a hook, it won't move. But the plane is sitting on wheels with bearings, movement of the tires doesn't matter. It's movement of air that makes the plane move. That comes from propeller thrust.

Rutan just made a flight in a rocket powered plane that took off from a runway. Do you think it would sit still on a treadmill? Nope, don't think so. It doesn't care what the wheels are doing either.

The wheels aren't propelling the plane down the runway. It doesn't matter what they are doing.

Larry

(in reply to Time Pilot)
       Post #: 8

RE: Seriously now, can it take off or not? What do yo... - 12/6/2005 6:39:36 AM   
Time Pilot



Posts: 1468
Joined: 10/25/2003
From: Vancouver, BC, CANADA
Status: online 		Okay. I get it now, and by tomorrow, I hope I'm feeling a little less stupid.

quote:

ORIGINAL: LarryC

Time Pilot,

If the catapult were connected through rotating wheels the plane would just sit there. But it has a hook. Likewise, if you hook the back of the plane to the runway with a hook, it won't move. But the plane is sitting on wheels with bearings, movement of the tires doesn't matter. It's movement of air that makes the plane move. That comes from propeller thrust.

Rutan just made a flight in a rocket powered plane that took off from a runway. Do you think it would sit still on a treadmill? Nope, don't think so. It doesn't care what the wheels are doing either.

The wheels aren't propelling the plane down the runway. It doesn't matter what they are doing.

Larry



< Message edited by Time Pilot -- 12/6/2005 6:41:49 AM >

(in reply to LarryC)
       Post #: 9

RE: Seriously now, can it take off or not? What do yo... - 12/6/2005 2:38:45 PM   
Edge 540


 

Posts: 319
Joined: 8/22/2004
From: -, IN, USA
Status: offline 		Wheels will me moving twice as fast, but it will take off in almost the same distance as normal. The only reason it is a little longer is because the wheels spinning faster should add just the slightest bit of drag more than normal. Other than that, they make NO difference.
Now if it was in a wind tunnel and the AIRSPEED was adjusted like the treadmill it would be a different story.

(in reply to Time Pilot)
       Post #: 10

RE: Seriously now, can it take off or not? What do yo... - 12/7/2005 12:44:02 AM   
ArmedZagi



Posts: 606
Joined: 5/18/2005
From: McAlester, OK, USA
Status: offline 		Time Pilot is right it cant fly....picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters...

As you read the next paragraphs, keep in mind, when I refer to verical and horizontal directions, Im talking about the planes X and Y axis...not the ground...

Also ( i just read LarryC's post) its not the engine that provides lift...the engine propells the planes horizontal axis...not vertical...think of it this way...if the air generated by the engine is what provided lift...when you hooked your legs behind youre planes tail and full throttled it...IF THE ENGINE PROVIDED LIFT...the plane would rise verticly although not moving foward. This is why planes require a runway also...even though the planes egine is at full throttle...the plane needs to reach a certain airspeed before it leaves the ground.

Now Im sure some one is goning to read this and talk about hovering saying somthing like "when youre hovering the engine provides lift and youre not moving foward" Thats true...but the plane is pointed strait up, therefore the engine is providing (yet again) FOWARD thrust not along the planes vertical axis.

CK

< Message edited by ArmedZagi -- 12/7/2005 1:05:26 AM >

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(in reply to Edge 540)
       Post #: 11

RE: Seriously now, can it take off or not? What do yo... - 12/7/2005 1:20:17 AM   
Scar



Posts: 2276
Joined: 10/1/2002
From: Peoria Hts, IL, USA
Status: offline
quote:

ORIGINAL: ArmedZagi

Time Pilot is right it cant fly....picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters...

As you read the next paragraphs, keep in mind, when I refer to verical and horizontal directions, Im talking about the planes X and Y axis...not the ground...

Also ( i just read LarryC's post) its not the engine that provides lift...the engine propells the planes horizontal axis...not vertical...think of it this way...if the air generated by the engine is what provided lift...when you hooked your legs behind youre planes tail and full throttled it...IF THE ENGINE PROVIDED LIFT...the plane would rise verticly although not moving foward. This is why planes require a runway also...even though the planes egine is at full throttle...the plane needs to reach a certain airspeed before it leaves the ground.

Now Im sure some one is goning to read this and talk about hovering saying somthing like "when youre hovering the engine provides lift and youre not moving foward" Thats true...but the plane is pointed strait up, therefore the engine is providing (yet again) FOWARD thrust not along the planes vertical axis.

CK

Get real. Do the force balance. The prop's pulling against the air, not the treadmill. The plane immediately moves. The treadmill's gonna be struggling to keep up with the wheels, because the prop is pulling the plane through the air. When the airspeed gets high enough to give it lift, it lifts off.

Saw ZZ Top do their "Recycler" tour, back in the Michael Jackson moonwalk days. They actually had a treadmill on the stage, they'd saunter to their right, the treadmill would carry them backwards, looked like they were moonwalking. Not that that has anything to do with it, either.
Dave Olson

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(in reply to ArmedZagi)
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RE: Seriously now, can it take off or not? What do yo... - 12/7/2005 1:36:36 AM   
starwoes



Posts: 121
Joined: 10/6/2005
From: Maple Heights, OH, USA
Status: offline
quote:

ORIGINAL: ArmedZagi

picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters...

CK


ok while you have the glider strapped to your back and doing all that running, sweating, huffing and puffing and all -- imagine also that you have a rocket strapped to your waist pointing horizontally at the same time. fire the rocket and see what happens. after the heat rash, tell me if the conveyor belt stops your forward motion and subsequent flight.

(in reply to ArmedZagi)
       Post #: 13

RE: Seriously now, can it take off or not? What do yo... - 12/7/2005 1:46:24 AM