Triming your hard-to-fly model: observe the angle of attack
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The angle-of-attack is one way to fine-tune your models to fly better. Too high an angle of attack will cause the model to fail to achieve a good glide, and level flight will be extremely difficult. A high angle of attack can be seen as the model flying around with its nose high in the air, even in otherwise-level flight.
When flying the FT EZ Bug for the first time, I observed that it flew really strangely. It would not achieve level flight, and when it did, it nosed up and stalled easliy. When I could get level flight, it had a very high angle of attack, and was quite unstable.
There are a few pontential causes for this. One is the amount of "up-elevator" in the model. The FT EZ Bug has much less up-elevator than most of my paper models, but the surfaces are much larger. One way to compensate for high angles of attack is to reduce the amount of up elevator.
Probably the most common and important cause of high-angle-of-attack flight is too little weight on the nose of the craft. There is an easy solution, and increasing weight in the nose will not only allow correct flight and gliding, but will also help stabalize the model.
You can check this for yourself you gently and smoothly tossing your model (with the PowerUp) in level flight. If it glides smoothly at flight speeds, then it's properly trimmed. If not, double-check your up-elevator trim, then try adding weight to the nose. If you already have a small amount of up-elevator, It's probably better to correct high angle-of-attack by adding weight to the nose than by reducing up-elecvator.
The easiest way to add weight to the nose is to slip a coin snugly under the front clips. In the case of my FT EZ Bug, I figured I had probably put a larger amount of hot-glue than the professionals in the instruction video, making the rear-end heavier than it was designed to be. A quarter under the front clips proved the perfect solution, and it glides flawlessly now!
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Thank you for the creative feedback and observations !
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Thanks for your explanation. I'd say that a quarter is a lot of additional weight. I experience the same 'nose up' with paper air planes, while due to folding most of the weight is already in the front, combined with the 'heavy' cockpit. I will slide the cross bar forward to see if that helps.
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Hi Jakenl,
You're right! The example of the quarter was on my FT EZ Bug, which is pretty significantly heavier than any paper model. Mine has a heavy rear-end from the hot glue back there, and the quarter helps balance the model so the center of mass is not too far to the rear. Smaller, or paper models should require much less weight, such as a paper clip or dime. Also reducing any extremely high up-elevator to a more modest deflection will help.
A "test glide" by throwing smoothly with the power off into a gentle grass landing, is an excellent way to determine the effects of weight and up-elevator on your model's stability. Make small changes and observe their effect. If it can enter a stable glide at a reasonable speed, it should fly well once you apply power. It's a real joy to fly a stable, well-balanced model!
Happy flying!
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When I flew my first 'milk carton' design plan, a coin was necessary to have acceptable horizontal flight. However, the added weight required a lot of thrust to keep the plane in the air. At the end I realized the center of lift was too much forward in the plane, compared to the center of gravitiy. An adapted wing design avoided the necessity of a coin.
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