.....out it, but, if initial flights show outboard wing up in both directions, what do I do?....

Maybe I don't understand, but why would  vertical cg offset result in "wing up in both directions"?

Bill

Maybe I don't understand, but why would  vertical cg offset result in "wing up in both directions"?

  It doesn't.    I am not sure where the strange obsession over vertical CG has come from, unless you do something way off the track, it's very hard to get it far enough off that other trim problems won't completely swamp it.

   If that is the issue, it needs more tip weight.   

     Brett

I sincerely doubt that your vertical CG is off far enough to notice, even if it was 2" low or high, which it isn't, it would have a very minimal effect on the performance...it certainly would not result in a constant inboard roll in both directions, it causes inboard one way and outboard the other way.

It is still unflown, but I have to agree that it would be up level and down inverted, not both the same way...that was a brain fart, it comes with age.  As for the rest, that (I sincerely doubt that your vertical CG is off far enough to notice, even if it was 2" low or high, which it isn't, it would have a very minimal effect on the performance) is EXACTLY what I wanted to hear.  THANKS!

Ken

FWIW, the MaxBee has the CG quite high. Wing is low-ish. Motor and battery (per the plans ) are up high.
I had to tweak the flaps to get it to fly wings flat, but once done it flies fine.

What I am sensing is that Vertical CG within normal building practices causes a part of that wing up/down that we correct on day one of flight trimming and we never even asked ourselves why that warp free and perfectly alligned masterpiece didn't fly perfectly level on the first flight.  We just tweaked it and moved on to lap times.

QED - Ken   

    Just think of the angles involved. Suppose you get the vertical CG off by 1/2" and your inner wing panel is 28".  That will cause a static yaw angle of atan(.5/28) or about 1 degree. Based on everything I have seen for the last 50 or so years, if you get your trim within 5 degrees most of the time, you will be doing really well. Tweaking out 1 degree with the flaps will take maybe 0.020" of flap differential. I doubt I am getting foam wings that close, there's no hope of a built-up wing and flaps staying that straight or twisting that symmetrically over load or heat/humidity.

    There are cases were vertical CG can get far enough off to matter, like low-wing planes without dihedral (like the Firecat), and I have seen several people with 2-d leadout guides to adjust it. But in most cases tweaking it out will almost always get it close enough that there are other things will swamp the effect.

     Brett

What I am sensing is that Vertical CG within normal building practices causes a part of that wing up/down that we correct on day one of flight trimming and we never even asked ourselves why that warp free and perfectly alligned masterpiece didn't fly perfectly level on the first flight.  We just tweaked it and moved on to lap times.

QED - Ken   

No, we are not trimming out vertical CG issues. With the relatively smallish fuses we use they are non existent. We are trimming out natural roll and yaw flap position.

BB already explained the difference in VCG spread over the length of the wing. This is what I was referencing the other day in our text convo. Your twin is close to ready will be very interesting to see the performance.   

Wotcher dois , hang it - from the leadouts . And look at a door jamb , in the distance . Can the battery go up & down . But a diagonal voiticle C G might ensure . . . . 

That's interesting.  How does your lower-than-usual vertical stabilizer contribute?

Yes, you got it  Low rudder seems to work the opposite way compared to the trick with vertical CG (a high vertical stabilizer in a side wind tilts the model outward, so over the head in zero side wind, the same effect should occur). Therefore, a low vertical stabilizer is counterproductive in this sense, but centrifugal force works differently than crosswind, even we feel it similarly on the handle.

I learned to make low vertical stabilizers as a boy when I was flying with Jozef Gabris and his Supermaster with an extremely high vertical stabilizer. I often had trouble in the wind when entering the wingover because the model slowed down against the wind, and thanks to the high vertical stabilizer, it tilted inward into the circle, making the entry into the wingover problematic because of loss of line tension. I realized this when I noticed that entering from normal flight was difficult, but entering from inverted flight was safe(r).

The Maxbee has the entire surface of the vertical stabilizer aproximately symmetric around the thrust line and the stabilizer axis. The CG is vertically somewhere between the wing and the thrust line, but the moment in side wind come from distance to wing (LO exit) so it still creates some small moment in a side wind. However, compared to the MAXII which had higher vertical stabilizer, which I had at the World Championships in 2008 (placed second between David and Han), I don't feel too much difference in normal flight (except in extreme wind when entering the wingover). But iw was orriginally piped model (first time used in Sebnitz 2002 powered by OS.46 and pipe) so the wing was placed little up.

In any case Maxbees fly in wind much better than MAXII and MAX (MAXII and MAX are identical, differing only in logarithmic controls).