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Scorpion Power GLOBAL 3D
HelicopterOff Topics › added a video) tethered boat
11-11-2016 04:09 PM  7 months agoPost 21
airboss

Elite Veteran

OC ,california

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I couldn't imagine what those spectators would say if that thing came loose and wizzed past

Urukay HPS3 KSE 700 HPS3

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11-11-2016 04:54 PM  7 months agoPost 22
wjvail

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Meridian, Mississippi

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I feel these are not aircraft, they may fly through the air but they will not fly through the air unassisted by centrifugal force. With the asymmetrical form of the motor support it should not be considered an aircraft.
This is nothing more than an exercise on how fast a person can make a motor move though a substance (air)
The same as with the boat. It won't even float upright with out the centrifugal forces acting on it. To me that makes it a FAIL!!!
Centrifugal. "You keep using that word. I do not think it means what you think it means".

Watch at YouTube

"Well, Nothing bad can happen now."

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11-11-2016 10:23 PM  7 months agoPost 23
Jerry K

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Houston Area

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Since you are calling my bluff, I will let you lead.
What does centrifugal force mean???

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11-12-2016 01:41 AM  7 months agoPost 24
wjvail

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Meridian, Mississippi

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Since you are calling my bluff, I will let you lead.
What does centrifugal force mean???
http://www.diffen.com/difference/Ce...ntripetal_Force

I think you are looking for centripetal not centrifugal. There are a number of Google sources that may help.

But more than that....

I think you are suggesting that the planes and boats we are seeing in these videos are something akin to a rock on a string. The planes are only airborne because they are swung in a circle. Have I got that right?

You are correct in that control line speed is a contest to see who can go the fastest. I think you said "...nothing more than an exercise on how fast a person can make a motor move though a substance (air)". That much is spot on.

Control line models are a comparatively old discipline of modeling and include many different events. There is "racing" that includes a fixed number of laps and pit stops and is flown simultaneously with other models in the same circle. There is "stunt" that requires flying a defined pattern. There is "combat" where two plane compete against each other for cuts and kills. Etc etc.

Then there is control line speed -or just speed. Speed simply asks, how fast can you go? You don't have to go long -just a few laps. You don't have to restart -no pit stops. You don't have to look good -it's not a scale model contest. You just have to follow a prescribed set of parameters and go as fast as possible. Take a .15, .29. .36 or .65 engine and see how fast you can go. Simple, right? I'll give it a go and you do your best and we'll see who sets the best number.

But it is FAR more complex that it appears. The wings on these models do produce very real and considerable lift. To emphasize the point, years ago modelers started using smaller and smaller wings on their speed models. That resulted in higher and higher speeds, up to a point. Eventually they got to a point were the wings were so small they were producing lift outside their optimum angle of attack. Smaller wings were actually making the speed go down.

In looking at the asymmetric FIA speed model in the earlier video, you are looking at an infinitely delicate balance of many different forces. What you see in an FAI Control Line Speed Model is decades of development to set the fastest speed possible.

To simply write it all off as a "FAIL" greatly understates what you are looking at.

Does this help???

"Well, Nothing bad can happen now."

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11-12-2016 01:56 AM  7 months agoPost 25
dialarotor

Elite Veteran

Traverse City, Michigan

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good post on the intricacies of flying CL speed and CL racing models.

Very well said. Spent many years flying all kinds of designs, experimenting with wings, pipes, fuels, propellors, wing tips and control systems to fight the big enemy, DRAG to eeck out that thousandth of a second with minimal control inputs to fly as smooth and level. Thanks.
Lessons learned sure helped as I migrated to RC modeling and still like to go back to my roots sometimes.
Thats what is fun in modeling, so much variety, IT'S ALL GOOD.

RapRex Pilot

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11-12-2016 02:31 AM  7 months agoPost 26
Gearhead

rrMaster

Vt

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There is "combat" where two plane compete against each other for cuts and kills. Etc etc.
now not seeing those type of dog fights is one of the unlucky things about living in Vermont, but on the other hand, one of the better, and more luck things about living in Vermont is the fact that you are very apt not to see Hillary the Beast

yee-up

Jim
Buzz Buzz Buzz

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11-12-2016 03:47 AM  7 months agoPost 27
Jerry K

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Houston Area

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I 'imagin' there is a difference, but in 'general terms' and in conversation using 'general terms' they are interchangeable.

In your write up I found these definitions

Centripetal Force = The force that keeps an object moving with a uniform speed along a circular path.

I read this as the string the plane fly's on.

Centrifugal force = Tendency of an object following a curved path to fly away from the center of curvature. Might be described as “lack of centripetal force.”

I read that as, what happens when the string breaks! as in “lack of centripetal force.” or OH $hit, Period!

BTW You did a wonderful job on your write up!!!

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11-17-2016 07:49 PM  7 months agoPost 28
AirWolfRC

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42½ N, 83½ W

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Centripetal / centrifugal . . . two sides of the same coin.

They are always equal and opposite. One pushes and the other pulls.

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11-30-2016 05:57 PM  6 months agoPost 29
wjvail

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Meridian, Mississippi

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Centripetal / centrifugal . . . two sides of the same coin.
They are always equal and opposite. One pushes and the other pulls.
Hmm... Not really. There is a correct usage for each of these two different words.

One is a true force -you can feel and measure it. Centripetal force is truly a force and often represented by a vector defined by a magnitude and direction. Centripetal force is the pull on the lines you feel when flying a control line airplane. It is the tug in your arm when you swing a bucket of water over your head.
Calculate it here. Be sure to read the notes:
http://www.calctool.org/CALC/phys/newtonian/centrifugal

Centrifugal is a contrivance to describe a perceived motion and is only valid from the perspective of the rotating object. Centrifugal force would be the force necessary to describe your motion if you were in the airplane and the lines broke.

I don't intend to pick nits and the semantics isn't critical to the discussion. My comment was really to address Jerry's statement that the boat and airplanes presented in this thread represented a fail to his understanding of water and aircraft. His repeated use of the word "centrifugal" reminded me of the line from the movie Princes Bride -"You keep using that word. I do not think it means what you thing it means."

I probably should not have commented at all on that subject...

"Well, Nothing bad can happen now."

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11-30-2016 07:49 PM  6 months agoPost 30
AirWolfRC

rrProfessor

42½ N, 83½ W

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I'll stick with what I already posted.

If you want to get into semantics . . . well . . .

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12-01-2016 01:21 AM  6 months agoPost 31
wjvail

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Meridian, Mississippi

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I'll stick with what I already posted.
Dew what you think write...

"Well, Nothing bad can happen now."

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12-01-2016 01:50 AM  6 months agoPost 32
AirWolfRC

rrProfessor

42½ N, 83½ W

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Centrifugal is the force that tries to remove the rotor baldes from the hub. The blade bolts resist that force by exerting centripetal force.

Those forces are equal and opposite.

So long as things are steady state, those forces are opposite and equal.

If the blade bolt lets go, you have neither centrifugal nor centripetal forces. The centrifugal force will have been expended and the blade will be on it's way in (usually) a straight line.

A while back, I posted the method of calculating those forces,
https://rc.runryder.com/helicopter/...1/?p=2243030#RR

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12-01-2016 02:42 AM  6 months agoPost 33
wjvail

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Meridian, Mississippi

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Centripetal and centrifugal are different words with different uses.

Despite people often using the expression "centrifugal force", centrifugal is not a force at all. It is a mathematical construct. It only exists if you use a coordinate system referenced to the blade bolt or the Control Line airplane.

If you were sitting in a C/L airplane and X was forward through the dash, Y was out the right/left side of the airplane and Z was up, you would have to find a way to explained why you felt your right shoulder was being moved to the right side of the airplane. From your perspective in the airplane you are not moving and yet you have the sensation of being thrown outward in the Y direction. You have to construct an apparent force on your left shoulder moving you to the right. (C/L airplanes typically move anti-clockwise when viewed from above.) This force doesn't actually exist. It only has the appearance of existence from the reference of the plane.

The only real force is the force moving the plane from a straight line as referenced from outside the plane. That force could be a rocket motor on the right wing tip pointed at the fuselage, it could be lift generated from the rudder, it could be gravity if the plane is in orbit. In this discussion it is the pull of the lines.

Honestly I don't care how people use these two terms. There is a correct and an incorrect way to use them but as I said in a previous post, the semantics aren't important to the discussion.

With the benefit of time, I realize I should have not corrected Jerry's use of the word centrifugal and only commented on his assertion that the tethered speed models were not really flying. Given that I did open that can of worms, my goal is help others use the terms correctly.

https://en.wikipedia.org/wiki/Centrifugal_force

"Well, Nothing bad can happen now."

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12-01-2016 12:58 PM  6 months agoPost 34
Jerry K

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Houston Area

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I probably should not have commented at all on that subject...
Now I am sorry I ever brought it up!!!

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12-01-2016 02:52 PM  6 months agoPost 35
wjvail

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Meridian, Mississippi

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I probably should not have commented at all on that subject...
Now I am sorry I ever brought it up!!!
Sorry mate. You really did get stuck in the middel on this one. I wanted to comment on your thoughts on the tethered boat and airplane videos in this thread but instead noted your use of the word centrafugal. That was unkind and I appologize for that. I understood what you meant and could have posted without getting into semantics.

Now it has become something else and it's turned into a bit of thread hijack...

Cheers,

Bill

Watch at YouTube

"Well, Nothing bad can happen now."

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12-01-2016 03:11 PM  6 months agoPost 36
AirWolfRC

rrProfessor

42½ N, 83½ W

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There is a correct and an incorrect way to use them . . . .
An there you have it. . . . Correct according to who ?

Overall, everything is defined by how we (the collective "we" ) choose to define it. And, usually, the majority definition is deemed to be the "correct" one. However convoluted and/or complex it may be.

I just try to KIS (Keep It Simple).

Here, just get a working grasp of what is happening and you're all set without getting involved in the "correct" definitions.

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12-01-2016 11:27 PM  6 months agoPost 37
GyroFreak

rrProfessor

Orlando Florida ...28N 81W

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WOW, this has been an interesting thread.
The one thing I really liked was the link to the formula...
Calculate it here. Be sure to read the notes:
http://www.calctool.org/CALC/phys/newtonian/centrifugal
Now I can figure the force exerted on that bolt that holds the blade from becoming a lethal weapon.
No wonder I have seen bolts bent, it's scary How much force is exerted on that little bolt, don't use cheap bolts from the local hardware store.

I think about the hereafter. I go somewhere to get something, then wonder what I'm here after ?

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12-01-2016 11:42 PM  6 months agoPost 38
AirWolfRC

rrProfessor

42½ N, 83½ W

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I like my formula (as referenced in my previous post) better.

And if you missed it . . . . from 10 years ago,

https://rc.runryder.com/helicopter/...1/?p=2243030#RR
.

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12-02-2016 05:15 AM  6 months agoPost 39
GyroFreak

rrProfessor

Orlando Florida ...28N 81W

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AirWolf
Thanks for the link to your post with the formulas. But getting old and lazy I do like the calculator post, this tired brain doesn't have to think about the math details, just plug and play(compute).

I think about the hereafter. I go somewhere to get something, then wonder what I'm here after ?

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12-02-2016 03:17 PM  6 months agoPost 40
AirWolfRC

rrProfessor

42½ N, 83½ W

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Just for trivia,

An average size person weighs about 1/2 lb less at the equator than the pole because of centrifugal force.

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