I could use some help on trimming my electric Banshee. My flying abilities are just past the point of not crashing every time I fly. So trimming a plane is
something I have very very little knowledge or experience with.
The plane has and Arrowind 2832/05 motor with 4s battery, seems like plenty of power. Weight - 48 ozs, a little heavy. 2 1/2" was cut of the nose. The battery box was mounted above the wing to give me a CG 1/4" forward of the CG on the plans, making it a little nose heavy. Lap speed is 5 1/2 secs at about 85% of power. Plane flies like a blimp with very erratic behavior. Loops are huge. I have redone the thrust line as that seemed a little off. 4 feet of snow prevent me from seeing if there is any difference.
Where do I start trimming this plane??? Any help appreciated.
5.5 second laps seems pretty slow for a 48 ounce Banshee.
I wouldn't worry about minutia like the vertical CG. I have managed to go about 40 years without really ever considering it.
The fore-aft CG, however, seems like a place to start. With stock Banshee parts, I would guess that the CG should be about 1 3/8" or so behind the LE of the wing to start with. Normal handle movement should give you about +- 30 degrees of control motion. I don't know what you are using for a pushrod, but if it is a conventional wire pushrod, as supplied, it *must* have a fairlead about halfway between the flap and elevator. Otherwise, it will bow out on inside corners and make the turns massive.
The center point of the leadouts should be about 1" to 1 1/4" behind the CG, and very close together.
The elevator should have the same motion as the flap, i.e. 1:1 ratio. That means that the pushrod must enter the flap and elevator horns at the same height from the hinge line. Make sure that the controls move freely throughout their travel from end to end. If you used pinned hinges, you should also seal the elevator and flap hinge lines with Scotch Crystal Clear tape.
While you are at it, double-check that the fuselage is square to the wing in all three dimensions, that the stabilizer is absolutely parallel to the wing in all dimensions. Measure from the flap hinge gap to the tail hinge gap at each stab tip and make sure that it is the same to as close as you can measure. Then site along the rear to make sure the wing and the stab are both in the same plane. Make sure the flap and elevator are both neutral at the same time and neutral from side to side with respect to each other.
Also check for any visible warps by sighting from behind. Look at the root, center the TE between the top and bottom of the wing surface, and then slide your gaze out to the tip. It should be centered there, too, if it isn't you have a warp. Correct it with a heat gun or the towels and boiling water trick.
Remove any rudder offset, or leave just enough to make sure it is not inboard. I forget what it shows on the plans but it's almost certainly too much. Install about 1 ounce of tip weight.
Start with 0.015x62 foot lines, eyelet to eyelet. Cut them down from "70'" lines, which are really supposed to be about 68 feet in the package.
That's all stuff you can do sitting in the workshop, and it's very important.
When you get a chance to fly, first fly around level upright, and inverted, and watch what happens to the Roll angle. Ideally, the wing should stay aligned with the lines all the time. What is likely is that the outboard wing will be higher than the inboard and different from upright and inverted. Also check the lap speed carefully (or get your flying buddy to do it). Adjust the speed until it is about 5.0-5.1 seconds a lap, which should give you lots of tension.
If the outboard wing is low upright and inverted, add tip weight. If it is high upright and inverted, don't do any maneuvering, and after the flight, add tip weight. If the outboard wing is higher upright than inverted, bend the outboard flap up with respect to the inboard, by twisting the flap near the flap horn to bend the flap horn. If the outboard wing is lower upright than inverted, bend the outboard flap down.
Then, try doing round loops. Two things to note - on inside loops, look and see if you see the top or bottom of the wing. If you see the top, add tip weight 1/4 ounce at a time, until it stays straight with the lines. Same with outside loops, check the same thing, if you see the bottom of the wing, add 1/4 ounce of tip weight at a time until that stops.
Also, see if it takes a lot of force to keep the loops going around, or if the loops tend to come out lower than you started. If so, add 1/4 of weight to the tail and try again.
The point of this is to experimentally determine the tip weight, and remove any residual warp or flap misalignment, and to get the fore-aft CG correct. The next step is to try some harder corners, and look for similar effects to refine the tip weight better. At some point, you will want to play the CG location against the handle spacing to get the best response, but just getting it close is where you have to start.
Brett