CG for Extras
 

I have purchased two Extra's from an estate sale and need advice on setting up the CG and contol surface throws (no manual and I cannont tell who the mfg is).
One powered with a Desert Air 100CC with 104 inch wingspan and fuselage length of 88 inchs. The other is powered with a ys 140L glow with a 76 inch wingspan.
How do I calulate the desired CG?
How do I calculate the appropriate throws on the controls surfaces?
What would be the recommended expo?
My skill level is intermediate. :confused:

Use this for the CG. Dan.
http://adamone.rchomepage.com/cg_calc.htm

For both I would suggest a CG of 30% MAC. Throws and expo are a personal taste thing but for starters you can try 30 degrees on aileron, 15 degrees on elevator and 30 degrees on rudder. Expo can be set to 30% on all surfaces to start but make sure you are going the correct direction. Some radios allow you to go both directions. To verify adjust to 80% and observe the surface has little deflection around center stick and then dial back down to 30. Depending on what you goals are depends on how much throw and expo is used. I fly mainly IMAC with my Extra so throws and expo are set for that..

Cool, nice calculator tool.
I had a maiden flight with a YAk a couple of weeks ago without dual rates or expo set up, and it was good fortune that I was able to bring it home without a scratch. A few tnese moments. I was used to flying a trainer. I just had to put a little pressure on the sticks for the Yak to stay in control. I am now a firm believer in expo! 30% sounds good. I have a futaba radio so, it will be negative 30%.

Jb, I know exactly what you are talking about with the first flight of your yak. I taught myself to fly with a nexstar trainer 5 or 6 years ago. With the recommended throws on that plane, the sticks had to be moved a lot to get any response from the plane. My second plane was a sig something extra that was set up with the recommended low rates on all control surfaces. On the maiden of that plane I was out of control the minute the wheels left the ground. I was not prepared for such a sensitive plane and like you I hadn't taken the time to learn about dual rates and expo. I know exactly what you are saying about the stick pressure. It seemed like just breathing on the sticks would cause the plane to react. Well, after about 30 second in the air, being out of control the whole time, the plane ended up nose down in a soybean field. After fixing the slight damage and reducing the low rates even more I ended up with a great flying second plane. That was my biggest bump in my learning path was going from the stick response of a trainer to the stick response of an acrobatic plane.

Since then I also learned how to set up expo and dual rates and have flown the heck out of three extras, a 20cc, a 50cc, and a 111cc. I would agree with Speeds suggestions or maybe even lowering the ailerons to 25 degrees and the elevators to 10 or 12 degrees if you are still not comfortable with the sensitive stick response of an acrobatic plane. If the plane is built square and the incidences are all close those settings will let you get your plane up and down in one piece on the maiden.

Pat