In the last post, I had started talking about straight and level flight with your radio control model airplane. The importance of straight and level flight and I was talking about how to achieve it. That post was getting too lengthy, so I stopped short of finishing it and I am now revisiting the topic and will conclude that discussion.
I received a question from someone who asked how to tell when the model aircraft is level when testing the CG. So, I thought it best to explain how you go about doing this. First, you should find the location of the center of gravity specified by the manufacturer. It is usually about 1/3 of the distance back from the wing’s leading edge. Not all models have the same point where the model balances. It depends on whether the wing is straight or tapered and if the wing is perpendicular to the fuselage or swept back or forward. At the beginners level, it is best to go by what the manufacturer tells you to use as the center of gravity.
When you know where the CG is located, have a friend help you ( one person on each side of the model) and place one finger on the under side of the wing tips and lift the airplane up and see how it balances. The person that asked the question wants to know what do you look at on the plane to tell if it is balanced properly. What I look for is whether the “line of thrust” of the model is level. This is an invisible line that runs through the fuselage from the center of the propeller and is usually shown on the plans. This a difficult thing to visualize and I strongly believe it is one of the things that is best learned from an experienced instructor who can help you learn by doing.
Another part of the question was, “What is the line of reference when determining the angle of attack of the wing and the horizontal stabilizer?” This is something that is taken care of in the design of the model by the manufacturer and probably best not changed by beginners. If you need to adjust these angles, I recommend that you seek the help of an experienced modeler that has dealt with this issue as it can get pretty complicated and can drastically affect the performance of your model. You will also need to use an incidence meter to make sure you are correctly adjusting the angle of attack.. The definition of angle of attack or incidence is the angle that the wing is positive or negitive to the line of the air that is passing over the wing or horizontal stabilizer. This line is also difficult to determine and is usually the same as the line of thrust.
The purpose of this post is to help you get familiar with getting your “trainer” RC model airplane set up for proper straight and level flight so that you will be able to easily control it and therefore learn how fly more quickly and to avoid accidents. This post is not intended to be a technical approach to model airplane design. My intent is to help someone that is new to the hobby get started in the right direction and it is always my recommendation that you locate a flying club and an experienced modeler to give you some hands on advice and assistance.
As I have stated before, a good place to start when looking for assistance is your local hobby shop and local flying clubs. The AMA has a list of all sanctioned clubs including the contact person for each club so it can be a great help in finding someone locally to help you with all aspects of RC model airplane flying. We all want to spend more time flying than repairing and rebuilding.
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