Excelleron 90 CG problem! HELP!

[flyboynellor]

Hello all,
I'm new to pattern flying and decided to buy a used plane to see if I liked it. My plane is a Sportsman Aviation Excelleron 90. The engine is a Saito 125. I bought the plane used from a guy on RCU that has owned three of these planes over several years. He says he loves the plane. Seems like a real nice guy. He recently decided to go big and do IMAC stuff. My problem started on my maiden flight. I didn't check the CG on my first flight because the previous owner said it flew just fine. On my first flight right after take off the plane seemed drop the nose. I added seven clicks of up trim on my DX7 radio. No problem until I rolled inverted. Went for the ground. I went home and checked the CG and found it to be on the rear most limit of the CG with empty tank. FYI the CG range is 6 3/4-7 1/4. Thought that was odd given the up needed to fly straight and level. On advise of a experienced pilot I moved the CG back to 7 1/2" by adding 2 1/4 oz of tail weight. Flew the plane and it still needed up trim. I then suspected the stab incidence was off. I checked it and only found the leading edge of the stab to have + .7 degree. Doesn't make sense. I then made a dramatic change and moved the CG back another 1/4" to 7 3/4" by moving my receiver pack 6" rearward. Flew the plane another time. NO CHANGE in trim. Still needed seven clicks of up trim. I'm at a lost as to what to do to correct the problem. Please HELP. FYI I have been flying model planes since I was 18 years old. I'm 57 now. I have never had this much problem trimming out a plane. Where to go from here? Thanks in advance for any help on this matter.

Frustrated
Bob Nellor

[wingster]

I flew an Explorer a few years back. The Explorer was the predecessor to the Excelleron, but was essentially identical. I moved the tank back against the wing tube. It flew well but was a little nose heavy even with an ounce or two of lead in the tail. Unless you move the tank so it is above the CG, the CG will always be a compromise. If the tank is in front of the CG, once you add fuel it will be nose heavy.

You will have to add a pump to the fuel system if you want to move the tank back and get a consistent fuel draw.

There is plenty of info in the Pattern forum of RC Universe on the Explorer and Excelleron. From the posts I read, 7.25" back is about right for the CG.

Here's a thread that will help. If you do a search you will find others.

http://www.rcuniverse.com/forum/m_23..._1/key_/tm.htm

[N233W]

	Quote: Originally Posted by flyboynellor
	I then suspected the stab incidence was off. I checked it and only found the leading edge of the stab to have + .7 degree.

Pardon me as a total noob, but wouldn't 0 to negative stab incidence be more appropriate?

[Al Lewis]

We have a guy that flies one at our field and the thing flies beautifully. Can't understand it but I'll ask him next time I'm out there.

[wildnloose]

Curious, what are you referencing the stab to?? Some people have to add pos incidence to the main wing. I would suggest checking all incidences (including engine thrust) to get a better picture.

My stab is at 0, engine is close to 1 deg down, right thrust is in the 2-3 deg range, and I have a popsickle stick on the trailing edge of the main wing for positive incidence (not sure about the angle but less than 0.5 deg). I need to trim some more but it is close to being spot on...

[flyboynellor]

My stab incidence is in reference to the wing. I don't think being off .7 of a degree would make that much trim problem. I could me wrong. What do you think? When you meant you used a popsicle on the trailing edge. Did you mean you shimmed the trailing edge with the stick? I'm new to pattern but I'm very familiar with trimming planes and this plane has me scratching my head. I have been told by others that the stab should be 0 degrees to the wing.

Thanks
Bob

[wildnloose]

All I am saying is that I bet you have pos incidence in the main wing, and your stab is at 0. You will have to measure from the datum line to verify. I would still verify all incidences first.

Yes, I shimmed the trailing edge with a popsickle stick to create positive incidence for the main wing.