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RC Myths, Facts, Truth, and Reality

Old 05-31-2008, 06:54 PM
  #51  
Kingcrash
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Originally Posted by FlyWheel View Post
Seriously though, if you were to try taking off from a moving treadmill...
But that's so easy to solve. The solution is actually given in the statement, but abstract thinkers overlook it every time

Greg S
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Old 05-31-2008, 07:02 PM
  #52  
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Originally Posted by FlyWheel View Post
Considering WattFlyers' general opinion regarding the validity of the information gathered on Wikipedia, I'm finding the popularity of this thread somewhat suprising.
I'm not sure I follow you Michael, but OK.

I'm wondering what my next Myth/fact should be. There are so many.

Frank
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Old 05-31-2008, 07:10 PM
  #53  
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Ummm...Frank,
Where did you hear all this stuff?

Greg S
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Old 05-31-2008, 07:32 PM
  #54  
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Does a KF airfoil really make a difference in flight
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Old 05-31-2008, 07:54 PM
  #55  
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Originally Posted by KingCrash View Post
Ummm...Frank,
Where did you hear all this stuff?

Greg S
I do a lot of reading about RC and have been involved with aircraft since I was about 10 years old. I don't watch TV except for two shows; Lost and Ghost Whisperer when they are on so I have some "extra" time on my hands. I also watch for posts like this one and try to learn what I can from them.

Frank
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Old 05-31-2008, 07:59 PM
  #56  
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Originally Posted by smokejohnson View Post
Does a KF airfoil really make a difference in flight
James,

This should help answer your question.

http://www.rcgroups.com/forums/showa...mentid=1700073


Frank

Edit: Added photo. The internet is a wonderful tool.

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Old 05-31-2008, 08:00 PM
  #57  
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I've been an "aero-nut" since I can remember, but about the only thing I heard "R/C" wise is, "shiny side up!"

Keep the myths coming.....


Myth: Helicopters fly

Fact: They don't, they beat the air into submission.

Greg S
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Old 05-31-2008, 08:37 PM
  #58  
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The vast majority of models either have constant chord or mildly tapered wing planforms.
Hence the wingtip cannot stall first.
Wash (wing twist) will change the story.
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Old 05-31-2008, 09:02 PM
  #59  
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Originally Posted by Murocflyer View Post
James,

This should help answer your question.

http://www.rcgroups.com/forums/showa...mentid=1700073


Frank

Edit: Added photo. The internet is a wonderful tool.
Thanks Frank...yes it is
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Old 05-31-2008, 09:27 PM
  #60  
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James,

Where can we learn more about your plane?

Thanks,

Frank
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Old 05-31-2008, 09:30 PM
  #61  
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Originally Posted by Murocflyer View Post
James,

Where can we learn more about your plane?

Thanks,

Frank
Right here. http://www.wattflyer.com/forums/showthread.php?t=34269
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Old 06-01-2008, 12:55 PM
  #62  
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Something a little different.

Myth: "I want great take-off and vertical speed so I need a big pitch on my prop."

Fact: For take-off thrust and good vertical climb rates a less pitched prop is preferred since lower pitch pitch propellers create very high thrust at a lower velocity.

True or false?

Frank
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Old 06-01-2008, 08:41 PM
  #63  
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Originally Posted by Murocflyer View Post
Something a little different.

Myth: "I want great take-off and vertical speed so I need a big pitch on my prop."

Fact: For take-off thrust and good vertical climb rates a less pitched prop is preferred since lower pitch pitch propellers create very high thrust at a lower velocity.

True or false?

Frank
That's a good one Frank. Maybe that's why 3d pilots usually like low pitch props as they do well at slow forward speed. -Steve
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Old 06-01-2008, 08:59 PM
  #64  
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Myths: It's best to learn RC with an instructor. Beginners should start with an ARF or RTF trainer. It's a good idea to gain skills using a computer simulator.

Fact: For most people, all 3 of those statements are true. BUT, for some people, some or all of them can be dead wrong.

RC beginners, like people in general, have many different personalities, talents and attention spans. Blanket advice given to beginners often overlooks this.

For myself, building my trainer (mini-telemaster) and learning to fly alone was the single best way to enter the hobby. It was like a mini space program-- I made small steps forward and big steps backward, but eventually learned to fly. The challenge
and adrenaline produced while trying to learn was just what I needed to get interested in the hobby.

And no stinkin' video games for me either--this hobby is about building and being outdoors, not staring blurry eyed at some computer. (well, spending hundreds of hours reading and chatting on the forums doesn't count--that's good stuff!! )

-Steve
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Old 06-01-2008, 09:11 PM
  #65  
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I'll agree totally with that last one Griffin. I taught myself to fly in a field behind my house with a Great Planes Slinger flying wing. Not exactly a trainer, but I figured it out in about 5 attempts.

When I finally flew out an entire battery, well, it was AWESOME! Now look, less than 4 years later and I get a little silly with planes... over 30 of them from 8" span up to 13 feet.

Laine.
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Old 06-02-2008, 01:42 AM
  #66  
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Originally Posted by Pig View Post
Since I'm on a roll, here's another that's sure to help some folks out. I used to see this all the time at RC car races:

Myth: Adding capacitors to a brushed motor reduces the amount of noise and interference the receiver sees. If I add bigger capacitors, it works even better.

Fact: Partially true. The size of a capacitor definitely counts, but this is a case where bigger is not better.

With brushed motors, every time the armature turns there's a spark. This spark is electricity passing from the brushes to the commutator.
I've wondered about that one. I know the cap's can smooth out surges in the circuit, but those sparks make radio noise too. Would it be possible (feasable) to "encase" the motor in a Faraday cage of sorts to blank these out too?
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Old 06-02-2008, 01:49 AM
  #67  
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Originally Posted by Murocflyer View Post
Good one Laine!

Although not to be confused with bouncing off the living room ceiling light effect. That has a whole different significance.

Frank
Especially if it's equipped with a working ceiling fan (Hey, is that where the foam gets it's name from?)
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Old 06-03-2008, 05:39 PM
  #68  
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Wheel, you could but it's generally not needed. If you match the right size caps to the motor and distance it far enough away from everything else, it becomes overkill. If you're still getting glitching and you know for certain it's from your motor, it's time to re-evaluate your motor. It might be time to cut a new com and replace the brushes.
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Old 06-07-2008, 02:16 AM
  #69  
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Myth: Props unload in flight

Fact: That is in fact true.

Reference link: http://www.ozrcflying.com/2007/07/pr...r-fiction.html

Frank
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Old 06-07-2008, 03:44 AM
  #70  
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Myth: The terms, "wind" and "wind speed" are interchangeable, meteorilogically, so saying there was no wind today means the same as calm conditions and great flying.

Fact: Wind and Wind Speed are two completely separate things.
Wind is defined as:
The horizontal motion of the air past a given point. Winds begin with differences in air pressures. Pressure that's higher at one place than another sets up a force pushing from the high toward the low pressure. The greater the difference in pressures, the stronger the force. The distance between the area of high pressure and the area of low pressure also determines how fast the moving air is accelerated. Meteorologists refer to the force that starts the wind flowing as the "pressure gradient force." High and low pressure are relative. There's no set number that divides high and low pressure. Wind is used to describe the prevailing direction from which the wind is blowing with the speed given usually in miles per hour or knots.
While Wind Speed is defined as:
The rate at which air is moving horizontally past a given point. It may be a 2-minute average speed (reported as wind speed) or an instantaneous speed (reported as a peak wind speed, wind gust, or squall).
So, since the planet's surface is heated unevenly, there is always a "relative" high pressure and low pressure, meaning There is always wind.

The wind may be moving so slowly as to be unmeasurable or insignificant, (less than 1 knot). This would be described as Calm, or no wind speed.

Long story short, if there is "no wind", there is no atmosphere and you cannot fly. Instead of waiting for that, pick a nice calm day when there is low or no wind speed

(note this is also the solution to one version of the pesky plane on a treadmill myth of recent fame)


Reference:
NOAA
NASA

Greg S
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Old 06-07-2008, 06:58 AM
  #71  
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Myth:
Props unload in flight
Fact: That is in fact true.

Reference link: http://www.ozrcflying.com/2007/07/pr...r-fiction.html

Frank


Not always true. The guys in the link is struggling with the concept and is asking the question rather than explaining the phenomenon and cannot be used as a reference of prove.

If it was always true, explain to me why a static test of my plane show 21.3A, while flying at about 75% of the time with full throttle use an average of 23A. Set-up - Motor Mega 16/15/5 on 3s spinning a 4.7"x11" prop. (Diameter : Pitch = 1 : 2.34) Do a search and you will find others to have similar experiences.

Fact is:

Some props unload - Mostly under square props.
Some prop upload - Mostly over square props.
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Old 06-07-2008, 11:22 AM
  #72  
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Originally Posted by rebell View Post

Not always true. The guys in the link is struggling with the concept and is asking the question rather than explaining the phenomenon and cannot be used as a reference of prove.

If it was always true, explain to me why a static test of my plane show 21.3A, while flying at about 75% of the time with full throttle use an average of 23A. Set-up - Motor Mega 16/15/5 on 3s spinning a 4.7"x11" prop. (Diameter : Pitch = 1 : 2.34) Do a search and you will find others to have similar experiences.

Fact is:

Some props unload - Mostly under square props.
Some prop upload - Mostly over square props.
Thanks for the feedback. Wow, 4.7" long by an 11" pitch prop? You don't see those much. I've used the opposite but nothing like that.

BTW, Do you know of another reference for prop unloading? I'll add that as a reference.

Frank
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Old 06-07-2008, 02:10 PM
  #73  
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It is a 10x10 prop cut down to 4.7".

http://www.rcgroups.com/forums/showthread.php?t=869105
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Old 06-30-2008, 01:53 AM
  #74  
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Time to dig up another myth/fact.

Frank
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Old 06-30-2008, 02:34 AM
  #75  
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Myth: I had a lockout on Spektrum and my plane crashed

Fact: You lost control of the plane and crashed (I know there is a chance of a lockout, but not to the extent people are saying)
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