PT20 - CG Location?
 

We have a new member in our club that inherited a PT-20 from his Dad and the instructions are long gone. Does anyone out there know how far back on the wing the CG is located. We have started by putting it at the spar, but it still had quite a bit of porposing in it. He is flying it with a OS 25 and a 4 oz tank. Not sure you need the engine and tank info, but thought I would throw it in.

RE: PT20 - CG Location?
 

Measure the wing chord (distance from the leading edge to the trailing edge)

Take 25% of this measurement.

Balance the plane at this distance back from the leading edge to start out with.

You may be able to shift the balance point back a small amount later on, but the 25% point is a good starting point.

RE: PT20 - CG Location?
 

Copied from the manual, available online at:
http://www.greatplanes.com/manuals/g...anual-v1_1.pdf

Note: This section is VERY important and must NOT be
omitted! A model that is not properly balanced will be
unstable and possibly unflyable.

Use a felt-tip pen or a narrow strip of tape to accurately mark the balance point on the bottom of the wing near both sides of the fuselage The balance point (CG) is shown on the plan and on the PT-20 the balance point is located 3-1/2" (89mm) back from the leading edge. This is the point at which your model should balance for your first flights Later, you may experiment by shifting the balance up to 1/4" forward or back to change the flying characteristics.

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The control throws are also listed.

RE: PT20 - CG Location?
 

carrellh: Thanks for the info. I didn't know the PT-20 was a Great Planes aircraft, or I would have checked their website for the plans as well.

RE: PT20 - CG Location?
 

I have a PT-60, otherwise I wouldn't have known either. If that 20 flies anything like the 60, you'll really enjoy it.

RE: PT20 - CG Location?
 

Uh, actually, it is not mine, but a member of our club that is learning to fly. He has another instructor that is helping him and I just agreed to post the question. Although I am having quite a bit of fun. I just started flying my Ultra Stick Lite with a Zenoah G-26 on it. It's a little larger than the PT-20:D:D