Perfect C/G hard to find!!

[Butch777]

I scratch built a twin boom pusher out of a wild wing. I've build several of these types and they seem to fly very well, slow and fast.
I started with setting everything at netural, ballanced at about 28% back.
Then I went to a soft grass field and gave it a toss, Wow, perfect glide for over 30 ft.
So I flew it there several times and it flys great. But nows the time to cut the battery hole and so I moved the batt around to get it to dive or swoop up.
But the problem is, I can move the batt over a 1" back and forth and it still flys good!
So I tried a dive test, with trim set neutral, with the batt in the most aft possision, where it seems a little tail heavy. I flew it up to 150ft, choped the power, slowed it down, then put it into a 45degree dive, and it just went down where I pointed it.
Then I moved the batt to the most forward possision, where it dives a bit in netural trim, flew it up, did a 45 degree dive and it steepened the dive, like I thought it would.
It seems to fly better, aerobaticly, a little nose heavy. Inverted at this C/G is just a click or so forward. Any Ideas?? Thanks, Butch

[Sparky Paul]

What is the question?
It appears you have a fairly stable airplane, with a good c.g. range.

[Butch777]

The question is I have to cut a batt hole in the EPP fuselage. Should I cut it in the middle of the C/G range? a bit forward or rearward?
Thanks, Butch

[Ollie]

The purpose of the CG range is to trim to your flying style not for the model "perfect" CG position. If you want to cut the over size for the battery, then trim by your flying style and shim with more EPP. If you want to fix the battery position another way, then trim the CG range with weights in the tail or nose. Think with a better attitude to trim.

[Sparky Paul]

I'd place the battery so the c.g. is just a bit forward of half way in your c.g. range.

[BMatthews]

Your first try sounds like it was perfect if you're looking for dead on neutral. And the other test sounds like it's just a hair positive. When we're talking small amounts of movement like this (never mind the battery pack, check to see how far the balance point shifted) it's really down to what the pilot feels best with. Some will tolerate a lot of hiccups to obtain a certain performance in one area while others want a hair's worth of stability. Both are right but each is righter for their own needs.