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Old Aug 26, 2007, 08:09 AM
Postcards From The Purple Edge
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Quote:
Originally Posted by Kurpal
The only problem with it is that it does not fly inverted well(at all?).
That certainly is true.

Quote:
Originally Posted by Kurpal
Since it is rudder/elevator, there is no need or possibility for inverted flight.
Not entirely true. You can hold an inverted attitude with full down elevator at the top of a loop. You're right that you can't really do much from there, but it is, at least, possible.
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Old Aug 26, 2007, 09:21 AM
Heli's don't fly voluntarily
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Quote:
Originally Posted by tuppertn
Not entirely true. You can hold an inverted attitude with full down elevator at the top of a loop. You're right that you can't really do much from there, but it is, at least, possible.
First, a top step KF wing requires very little down elevator to fly around inverted. If you know what you're doing, you can fly a 3 channel plane inverted using the rudder (even with the antihedral). Most beginners don't know that rudder is reversed when inverted, just like elevator.

I understood the original question to be about the flight characteristics of a KF airfoil vs. UC, and could the KF be flown without ailerons. The descriptions given are accurate about what a KF wing will do, but whether or not you, or your plane's configuration will allow the wing to do it, is a different story.

For the life of me, I can't understand why anyone would consider building a KF wing without ailerons! One servo doesn't cost that much, and aileron gives you positive control around the lateral axis. The 3 channel BB is fine for someone trying to teach themselves to get a plane off the ground and back on safely, but once that is learned, a person needs to learn to fly with ailerons. Airplanes have (4) basic functions. Consider, ALL full scale trainers have Throttle, Elevator, Rudder, and Aileron control, yet people learn to fly them fine. When you really know how to fly a plane, you understand that rudder is a very poor substitute for aileron, just as aileron is a poor substitute for rudder. Do you beginners know the control inputs for a barrel roll, or snap roll? It's up elevator and rudder! NOT, something I want to do on final just before landing, if my wings get blown around a bit. I prefer to level my wings with aileron, and you will too. Part of the 3 channel trainer design assumes that beginners fly in calm air with reduced control throws. I suggest beginners adhere to those assumptions.

If someone is learning to fly, STAY with Tony's original design (plug the rudder servo into the aileron reciever plug, channel 1)! If someone knows how to fly Tony's original design already, build a KF wing with ailerons for your plane, and really learn to fly. BTW, I recommend no dihedral for the KF wing (dihedral limits the aerobatic potential). If you must have dihedral, 1/2" each tip would be plenty.

So, I would say to the guy asking the original question, if you can't fly, stay with the 3 channel UC wing. If you can already fly, build a KF wing for the BB and for goodness sakes, put ailerons on it.
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Old Aug 26, 2007, 12:17 PM
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He was specifically asking about a RET blubaby for his son that is a beginner. If an RET is what he wants the undercamber is best suited. If an aileron trainer is what he wants, than the KFm step with little to no dihedral with ailerons is best suited, as you have stated. I was simply replying to what it was that he wanted out of the plane.

My original Blubaby was a ~47" RET for water take off and landing. I am now planning on building a new wing for it so I can do rolls and stuff like that. I really want to wow the onlookers .

Kaos, how is the yaw on this plane as a aileron trainer w/ KFm wing and no dihedral?
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Old Aug 26, 2007, 12:35 PM
John 3:16
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I appreciate both answers guys. Now for the decision.........I think I will build.....................................both! I'll build the 33" as a RET with an undercamber wing. When he wants something new, we will build either the 42" or the 52" with a flat KFm wing with ailerons to use as an aileron trainer for him. I may build the larger model to play around with myself, and just pass it down to him when he wants it. Sounds like a plan. Thanks guys!
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Old Aug 26, 2007, 01:56 PM
Heli's don't fly voluntarily
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Quote:
Originally Posted by Kurpal
Kaos, how is the yaw on this plane as a aileron trainer w/ KFm wing and no dihedral?
I haven't flown a BB with a KF, no dihedral wing, but my Regal has huge ailerons and the wing has no dihedral, so i have a idea how a flat KF wing flies. My BB had 1" dihedral on each wing tip, and 2" ailerons. There was a bit of yaw, but nothing that would prevent a person from flying with aileron & elevator only. It's very similar to a Clark-Y flat bottom airfoil as far as aileron yaw is concerned. For an aileron trainer, there's plenty of stability in a high wing cabin plane design such as the BB. Dihedral should be unnecessary. For those who don't know, it's the wing's dihedral that makes the rudder act like an aileron in 3 channel planes, producing bank for turns. Since you have ailerons to "act" as ailerons with an aileron trainer, it's preferred that the rudder only do the rudder function. Also, any dihedral will have to be fought against when flying inverted, therefore, I recommend none. I'm not implying that ailerons are for aerobatics either. Ailerons are necessary to have proper control of an aircraft. If they weren't, you see small full size airplanes without ailerons used as trainers.

Also, I'm not recommending flying with just the 2 controls, since I've always advocated the use of rudder and aileron in coordination. On a 4 channel plane, flying elevator/aileron or elevator/rudder only is a bad habit! All 4 channels exist for a reason and need to be used in a coordinated fashion. I taught 30V2 to fly and if you've seen his video flying the Regal , you'll see that my training approach produces a very good pilot.

Anyone who has seen my Blu-Baby Flies Again video can see that all control surfaces have to work together to not have a skidding, yawing plane in the sky. Also, if you look closely at the (2) stall turns I perform near the beginning of the video, you'll see that when I punch the rudder to rotate down, the plane wants to roll around the lateral axis also. THAT's THE DIHEDRAL in action. Not a desireable trait in aerobatics.
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Old Aug 26, 2007, 02:10 PM
John 3:16
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Kaos2, What is your setup on that Blu-Baby Flies Again vid? What did you mean when you said that you had '1" dihedral on each wing tip, and 2" ailerons'? I understand that you had 1" dihedral on each wing tip (which gives a total of 2" if one wing tip is flat on the table), but is that what you meant? I don't think 2" ailerons would turn that plane like it did. I loved you video, by the way.
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Old Aug 26, 2007, 02:29 PM
John 3:16
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I have a question about the landing gear. Are you guys just gluing the wire gear into the foam (slot), or are you guys putting some balsa or lite ply on either side of the wire? It looks like it should have some reinforcing on it.
Daddy-O
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Old Aug 26, 2007, 03:07 PM
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Daddy-O

If you are planning to start with RET and move to a full on 4ch plane, I would recommend building the 42" version with a KFm airfoil wing with dihedral. When you are ready to upgrade to the aileron trainer, you already have the plane built! All you will need to do is build a new wing, or simply slice the wing you have in half and glue it back together straight. That is what I am planning on doing with "The Plane that currently has no name" The KFm airfoil w/ an RET plane does not produce quite as much raw lift as the undercamber, but has great stall characteristics, and will allow you to upgrade later.

Kaos,

I guess my question would be, is the Yaw due to having a high wing? I completely understand that 3D planes(such as the one you mentioned) do not have yaw, but their main wing and tail wing are also usually directly lined up. Can yaw also be due to having an undercamber wing/aileron set up? The Dihedral also serves a purpose that I am after, self correcting!! I am a newb still as I have spent a lot of time on simple RET planes.
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Old Aug 26, 2007, 03:15 PM
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Kaos -

I'm a 3 channel flyer with a 4 channel heart. As a beginner, I'd like to see the way you set up the 3 servos - especially the aileron servo. I'm building a 42 inch with under camber to continue my learning process. I plan to convert the 33 inch at some point to an aileron trainer. Then convert the 42 inch. Lots of converting.

Thanks for all of your posts. I'm learning a lot. Of course, flying is the best teacher.

elight50
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Old Aug 26, 2007, 03:34 PM
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One More Thought About Training -

I for one would be interested in hearing from the more experienced pilots how the BB should be used for training. I'm sure there are training threads in the beginner's section but I would really like to hear from those who have built and flown the BB. I suppose the question is, now that I have a BB, what should I do with it (be nice). I can fly in circles and up and down and land near by, but how do I acquire the skills to move on to ailerons and such?

Maybe not the right forum but thought I would ask.

Elight50
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Old Aug 26, 2007, 03:49 PM
John 3:16
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The purpose of a high-wing undercambered 3 channel plane in training is to allow the new pilot to get a chance to fly. You need to first practice on steering (controlling) the plane left and right when going in any direction, land and take off until until you are comfortable. It is good to practice figure 8's, circles, rectangles, trapizoids, etc until you can make the plane go where you want it to and feel comfortable doing it.

Then you move on to an aileron plane and do the same things. In my opinion, an aileron plane with a little dihedral is not any harder than a RET plane. You can just do more with it. If you can fly a RET plane easily, take off and land without mishap, just build one with ailerons and go for it. The reason why this is a good trainer is because it is durable, cheap, easily flown (forgiving flight characteristics), and upgradable!

Not everyone needs to go through this entire process though. I started out with a Slow Stick (another great trainer!), and went to a PCW (Pocket Combat Wing). There is no doubt that it wasn't the smartest thing to do, but my PCW was durable enough for me to make the transition. It just took me a few crashes to get it to fly well. That was a great plane. I now own about 7 wings (crashed my favorite last week when it got behind some trees (out of sight) for just a moment, but let's not open up that wound right now (I just have to fix the motor mount).

Daddy-O
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Old Aug 26, 2007, 04:08 PM
Heli's don't fly voluntarily
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Quote:
Originally Posted by Daddy-O
Kaos2, What is your setup on that Blu-Baby Flies Again vid? What did you mean when you said that you had '1" dihedral on each wing tip, and 2" ailerons'? I understand that you had 1" dihedral on each wing tip (which gives a total of 2" if one wing tip is flat on the table), but is that what you meant? I don't think 2" ailerons would turn that plane like it did. I loved you video, by the way.
Daddy-O
What specifically do you mean by setup? I'd be happy to share, but are you looking for motor, battery, prop, etc., or throws for the control surfaces, dual rates, expo, etc.? Or are you looking for the KF wing setup i.e. top-step or bottom-step, step height, spar material, etc.

You got the dihedral exactly right. The wing has a total of 2" dihedral.

The ailerons are the only 2" wide. It's a 40" wing span, 10" chord w/the last 2" being ailerons.

What you're seeing in the video is how ailerons coordinated with rudder turn a plane. When you turn with rudder only, really you're skidding around a turn. If you turn with aileron only, you're actually falling into a turn. When you use both controls, you groove through a turn. Simple as that.

By the way, my original posts about my KF Blu-Baby were back around page 30 - 32 of this thread. Most of the details about my plane were provided.

I pleased that you enjoyed the video. I hoped to show that you can have some real fun with a trainer type airplane, and that you don't have to jump around the sky in a spastic manner to be intertaining. About 80% of what I did could be performed by the average flyer after about a years flying experience. That's providing that they are striving to develop skills during that year. If just getting a plan off the ground and back on in one piece is good enough for a person, that person will rarely develop much past that point.
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Old Aug 26, 2007, 04:35 PM
Heli's don't fly voluntarily
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Quote:
Originally Posted by elight50
One More Thought About Training -

I for one would be interested in hearing from the more experienced pilots how the BB should be used for training. I'm sure there are training threads in the beginner's section but I would really like to hear from those who have built and flown the BB. I suppose the question is, now that I have a BB, what should I do with it (be nice). I can fly in circles and up and down and land near by, but how do I acquire the skills to move on to ailerons and such?

Maybe not the right forum but thought I would ask.

Elight50
I can make a few suggestions for your skill development. I'm assuming an original design BB (3 channel) and that your rudder is plugged into channel #1 (aileron).

First, can you put the plane exactly where you want it? Close enough doesn't cut it! Force yourself to be the "master" of the plane. Second, can you trim it out to fly level at various throttle settings? Always fly a retangular pattern when landing (cross-wind, down-wind, base, and final). A person should be able to trim a plane to fly level at half throttle or less. At this lower throttle setting fly the plane around without loosing or gaining altitude. Start with shallow turns, then increase the angle of bank up to about 30 degrees and don't touch the throttle. No altitude gain or loss is acceptable. At a safe altitude begin practicing barrel rolls. You'll learn to pull the nose up slightly just before begining a roll to reduce the loss of altitude. Stall turns are simple and easy to perform. It will help you get used to seeing you plane at different attitudes. If you really want to go for extra credit, trim your plane for level flight at half throttle, then fly the plane in circuits without adding elevator. Increase or decrease throttle as necessary for level flight. Learn to shoot touch and goes. The better you are at putting you plane exactly where you want it, in a gentle manner, the better pilot you'll become. Oh, if you're not already doing it, loop. But, hey, don't fly an exclamation point type loop. Make them round! There's tons of things a person can do with a 3 channel plane and this list has just scratched the surface. The key is to do NOTHING in a sloppy "good enough" manner. Striving for perfection is what developes skill.
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Old Aug 26, 2007, 05:00 PM
Heli's don't fly voluntarily
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Quote:
Originally Posted by Kurpal
Kaos,

I guess my question would be, is the Yaw due to having a high wing? I completely understand that 3D planes(such as the one you mentioned) do not have yaw, but their main wing and tail wing are also usually directly lined up. Can yaw also be due to having an undercamber wing/aileron set up? The Dihedral also serves a purpose that I am after, self correcting!! I am a newb still as I have spent a lot of time on simple RET planes.
UC wings are notorious for not liking ailerons! In other words, they yaw like crazy. I'm not going to try to get too technical about my explanation about control surfaces, but your question really has more to do with aircraft design. The location of the control surfaces contribute to their effectiveness nearly as much as their shape and size. First, imagine a line going right through the center of the fuselage. If the wing is placed above this line, the weight of the plane hangs below the wing like a pendulum. The higher the wing from the center line, the greater this effect is. Look where the rudder is placed on the BB. Nearly the whole thing is above the center line. That means that instead of just pushing the back of the plane left or right, it's actually trying to twist the plane in that direction also. That, coupled with dihedral eliminates the need for ailerons in order to fly well. A 3D plane's rudder extends as much below the center line as it is above. All a rudder is supposed to do is push the back of the plane left or right, and that's what a 3D plane's rudder does. Yaw, when it comes to ailerons is fairly simple. The aileron moving up, is moving up in less dense air than the aileron moving down. That means that the aileron moving down is always more effective than the one moving up. It also creates much more drag which is what we see as yaw. Some airfoil shapes have a much higher differential in pressure between the air on the bottom of the wing and the top. These "high lift" airfoils consequently have a fair amount of yaw with their ailerons. If you move this effect higher above the center line of the fuselage, it has more leverage, or authority so it appears worse. All aspects of aircraft design determine how a plane flies. Not just airfoil selection.

And, of course I know the other effects dihedral produces, like self correcting (pendulum). I wasn't trying to write a book. My post was long enough as it was.
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Old Aug 26, 2007, 07:45 PM
John 3:16
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Kaos2,
I am curious why you didn't put longer ailerons on your plane. Many planes go the entire length of the wing. I have heard that they are more effective on the outside of the wings (i.e. wingtips) then on the inside. We know that it is pointless to put ailerons on a plane with a lot of dihedral. I appreciate your 'book' on that subject. No, really, one thing I love about rcgroups is all that you learn about the subject over a period of time. I have recently been looking at possibly purchasing an ultralight aircraft. I really think I am getting to the point where I understand enough about this subject to fly (I understand how it all works now). Thanks for the explanation.
Daddy-O
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