ORIGINAL: Straight Up
Firstly, the wing and stab should be at the same angle of incidence if you intend for the plane to fly upright and inverted in a similar manner. You will then have to experiment with the CG to achieve that neutral and balanced feeling with minimal trim change. If you need up-trim to fly upright and down-trim (forward stick) to fly inverted, then your CG is too far forward. Apologies if I'm preaching to the converted, but there seems to be some confusion about this.
> Mine is nose heavy due to the 140L, that's why I relocated the tank to the cg point. Unfortunately, you do not have much room to play with the battery location.
Secondly, if this plane is turning out nose-heavy, why not mount exposed servos in the tail? I know many scoff that this looks ugly and adds drag, but the aileron servos are exposed, so why the fear? I hate adding weight to planes, so why not let the servos be the tail ballast?
> If you check one of the pix that I have posted with my friend's crashed Spot-On, you can tell the tail section is pretty hollow, making it tough to mount two servos on the tail. Besides, adding two servos is like adding "dead Weight" as you mentioned. If you used the correct power plant, you should be ale to balance the plane correctly.
Finally, I don't understand the concern about various engines being "overkill". I've never flown an aerobatic plane that was overpowered. Some correctly mentioned THROTTLE MANAGEMENT. When you drive you car to the flying field, you rarely floor-it, so why the "firewall the throttle" mentality when flying? If you only need 75% throttle to maintain speed in the up-lines, why go to 100%? I fly with throttle management all the time, and I really love that no matter how much trouble I get into in the vertical, I've always got the power to pull out, especially after a mult-snap. The 3D flyers understand this need for pull-out power VERY well.
> Again, the plane is designed for a 120 sized engine. Since I do not own any more 120s, I decided to use a 140L and pay the price of being nose heavy and have to keep playing with the cg, it is not a matter of having too much or too little power. Don't forget, bigger engine not only generates more power, but also more torque thus generates more vibration, especially with a 4 stroke. End results, more punishment to the airframe and your airborne packs.
Anyhow, this has been a great thread and I will be submitting my order for a Spot On as soon as time permits. If anyone finds a good CG point please advise the thread. Power to all of you, and happy patterning. Any lead on how to order the Naruke canopy? The stock canopy looks a little weird.
> Good luck to yours, I'm sure you will enjoy building and flying it. Now the WC is over, I will start flying the Spot-On again and may be able to shed more light on the cg. The Naruke canopy came with my Astral XX, I just happened to have two spare ones. You may be able to obtain one from BVM, X-treme's US distributor.
"The power to go unlimited vertical!"