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Feb 22, 2020, 09:35 AM
A man with a plan
Balsaworkbench's Avatar
Quote:
Originally Posted by Top_Gunn

Some manufacturers used to claim that their trainers were "self righting" (even without electronic stabilization), so that if you got in trouble you could just let go of the sticks and the plane would straighten itself out. That never worked in practice, except perhaps at very high altitudes.
It certainly does work in practice. I've built many planes that right themselves.

I suspect that those who are skeptical of the stability of high dihedral planes probably don't have a lot of stick time with high dihedral planes.
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Feb 27, 2020, 01:18 AM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by Balsaworkbench
It certainly does work in practice. I've built many planes that right themselves.

I suspect that those who are skeptical of the stability of high dihedral planes probably don't have a lot of stick time with high dihedral planes.
Most pilots are so spoiled nowadays. I really doubt too many of them actually flown a high dihedral plane.

All they have to do is to look at some of the free flight models. They do very well without anyone trying to control them.

Back in the days radio control was actually a free flight airplane occasionally had its flight path interrupted by a radio control.
Feb 27, 2020, 09:29 AM
Registered User
I spent some 10 years competing in 1/2A Texaco contests, using RC assisted free-flight designs with lots of dihedral. Those airplanes are very different from any of the standard RC trainers like the Eagle2. Yes, they will fly hands-off in still air quite well. But they would not be good trainers, and I've never seen anyone try to learn to fly with one. They can do steep turns well, but shallow turns at low speed are awkward; they'd be awful in a landing pattern. And they are designed to be unstable in moving air when flying slowly (the Westerner being an extreme example), because free-flight planes should turn toward rising air once the engine quits: That's not something you want a trainer to do.

This thread has degenerated, with one post claiming that those of us favoring four channels thought it was a myth that dihedral added stability, a position that none of us took, and a couple of posts suggesting that we had no experience with high-dihedral three-channel airplanes. I have had quite a few of these in addition to RC assisted free-flight models. I never used any of them to train beginners except for a Kadet Senior, and for that one I eventually built a lower-dihedral wing with ailerons: It turns better that way and makes a better-flying trainer. Stability, up to a point, is a good thing. Excessive stability just makes doing ordinary things like flying a landing pattern harder.
Feb 27, 2020, 11:44 AM
A man with a plan
Balsaworkbench's Avatar
The reason I said that is because some were claiming that added dihedral won't do any good for a trainer, which is not a correct statement. More dihedral will certainly make a plane more stable. In the case of a new pilot with no expert help, the plane is less likely to roll over into a spin while a control decision is being made, which is exactly why a beginner needs a trainer.

Dihedral isn't an all or nothing proposition. You don't have to choose between free flight and flat. There is a lot of middle ground, and it is quite useful for those who haven't developed the reflexes to keep a plane flying straight and level.

For example, the Whimpy has 8.5 degrees per side. It will take care of itself if you allow it to, and it is highly responsive to control input. Having a lot of stick time on three Whimpies, I can say for certain that this plane will fly itself. I tested the claims made in the construction article. I got the plane upside down, sideways, vertical with no airspeed, any weird place you don't want to be, and let go of the sticks. In all cases, the plane righted itself and flew straight and level, provided that there was adequate elevation. And I don't mean that it had to be out of sight. Elevation requirements seemed pretty reasonable. In spite of its inherent stability, this plane also was very responsive, with minimal delay between rudder input and roll response. It was quite easy to maneuver. Certainly it is not the same as maneuvering a 4 channel plane, but the mission is to reduce a beginner's likelihood of crashing, not to win the pattern competition or to have more fun with ailerons.

The Eagle 2 is not as durable or stable as a Whimpy, but if I knew a guy who lived in the middle of nowhere by himself and it was my job to build an Eagle 2 kit and drop it off for him to fly by himself, I know exactly how I would set it up. Three channels, as light as possible, and high dihedral. I may even make a new dihedral brace with a couple degrees more than what's included in the kit. It wouldn't be very useful to think of how I would train the new pilot, because there won't be any training going on. He's going to be alone.
Last edited by Balsaworkbench; Feb 27, 2020 at 12:03 PM.
Feb 27, 2020, 04:06 PM
Registered User
The OP said he may not have an instructor so I agree, three channels would be best. I taught myself on two channels rudder and throttle, and later flew three. Stability, light weight, and damage resistance were the keys. If no instructor, then what an instructor would use to teach with is irrelevant.

I would use a smaller plane than an Eagle, because smaller planes have less momentum and therefore more damage resistance, but that’s another story.
Feb 29, 2020, 12:17 AM
AMA 46133
SeismicCWave's Avatar
Ok let's clear the air here. There are just too many partially good information which makes it hard for someone looking for help to decipher.

The fact is that mere dihedral does not make a plane more stable or less stable by itself alone. The aerodynamics of the entire plane has to be taken into consideration.

Yes a plane with lots of dihedral will fly straight and level for a longer duration of time in calm air compare to a plane with less dihedral. That is a very general statement.

Sometimes a lower dihedral plane with the proper ailerons can make a plane "turn" "better". However there are additional considerations such as differential aileron throws due to possible adverse roll coupling.

However in considering a beginner trying to learn to fly an RC fixed wing the recommendation should be toward the simplest most robust and lightest possibly construction. Aileron and the fourth channel simply add complexity.

RC hobby is a journey and NOT a destination. You don't just build ONE trainer and expect to fly that forever. The primary trainer as a first fixed wing plane will not and should not be expected to last very long. A lot can happen. A mistake in construction, a dumb thumb move during flight can bring the plane crashing down. A high dihedral plane without aileron will always be lighter. A lighter plane flies slower. Yes it is less smooth in windy days but when training or learning to fly by oneself, one should pick and choose a calm plane to learn. A plane with more dihedral and rudder control may or may not be able to return to a straight and level flight after a disturbance. . At least it will not return have time to return to straight and level flight before crashing unless it is very high. However if not disturbed by wing a high dihedral wing plane will have a longer duration of straight and level flight enabling the pilot to think and react. An RC plane is fast enough for a human to react we need all the help we can get.

So the amount of dihedral is only a small consideration for a primary trainer. Simplicity, robustness and lightness are still the most important consideration. That's why a lot of trainers still use rubber bands to hold the wing to the fuselage. A simple wing with no ailerons, no aileron servos, no aileron servo wires connected to the receiver, held on by rubber band is still the king for a trainer in my book.
Feb 29, 2020, 07:02 PM
Registered User
I agree with the 3 channel plan if no instructor is available.

If you have a good instructor you can eventually learn to fly on just about anything, including a 4 channel Eagle or a low wing aerobatic plane. I also agree that durability and resistance to severe crash damage will allow maximum stick time and minimum repair time between incidents.

I had a hobby shop for many years, and the most successful trainers for folks without help, were a GWS Slow Stick, and the old foam Hobbyzone J3 cub RTF, all 3 channel by the way. Both were supremely crashworthy, easy to repair and electric powered. However, both required light wind or no wind conditions for initial flight attempts.

With instructor assistance, 4 channel trainers with semi symmetrical airfoils were ideal even in winds up to 15 mph.

Bottom line is without help, you are likely to have a rough time learning on a self built balsa aircraft. Too easy to make a mistake in building and setting up for flight, too easy to make a mistake on the initial flight, too easy to damage and too easy to repair improperly and crash again.

Best to get help, get a simulator, or get something pre-built, pre-configured, and durable.
Last edited by 049flyer; Feb 29, 2020 at 10:22 PM.
Mar 26, 2020, 04:20 PM
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los36's Avatar
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