Opinion on balance please!

[Steve Fox]

Hi everyone, this is my take on the cessna 180 featured in a article here, I built it to the plans then had a few after thoughts and so there's internal mods but aerodynamically it's to the plans. One of the major things I did after building it is hack the nose back off and convert it to a battery hatch, wish I'd thought of it during building as it's a bit scruffy from being built then ripped open again!

I've got a full light set, steady white tail and white tail single blink strobe, white wing double blink strobes, the red and green steady navigation lights just forward of the wing strobes, top and bottom red anti collision beacons and landing lights when flaps are down.
Everything is controlled with an arduino nano.
Oh and the hole in the windscreen is for the telemetry antenna

I'm running an apm flight controller, GPS and video with osd, that's the reason I built this plane, I wanted something big enough to carry all the gear and plenty of battery power and was a high wing for the stability, I've built the ft racer and ripslinger too but they are not a good platform for calm "sightseeing" style fpv and have been flying all my fpv on a ft simple cub till now, it's actually pretty good for it, load it up with a 2700 3s and go for a pleasure flight!

Anyway, my highly expensive balancing rig is right on the stated cg point of the wing, what do you all think, too nose heavy?

I can shift weight around easily, there's two 3s 2700mah lipos where there power pod would have been.
the great thing is the second sits right on the cg so I'm not relying on both for balance, I can get the balance with just one if I want to fly on just one pack, removing the second has no affect other than overall take off weight.

Steve.

 

[Craftydan]

Dunno about "too nose heavy", but that doesn't look bad. Most traditional airplanes (wing + tail) can trim out a decent range of CG just fine, so assuming the plan's CG was good for flying, you're err'ing to the safe side. After all, a nose-heavy plane flies poorly; a tail-heavy plane flies once.

At a glance, she should fly fine. Get her into the air and go from there. Expect to give her a bit more up trim to get her to cruise level hands-off.


You probably won't have an issue with a balance like that, but If you find the elevator trim changes dramatically with speed (not thrust), then you can begin nudging the CG back with ballast until that behavior becomes more docile (not too far, mind you -- neutral CG does not self-correct in pitch during stalls, and tail heavy will push deeper into the stall).

Keep in mind, bad CG and Bad Up/Down Thrustline can look similar -- they both change your elevator trim as you throttle up to go faster, but thrustline will change trim with motor thrust, and CG will change trim with the airspeed. two things to look for:

- Get in level flight and punch the throttle. The speed with which the trim changes is the tell. If the plane noses up/down instantly it's probably thrustline, if it gradually pulls up/down (as the plane picks up speed) it's probably CG.

- Get SEVERAL mistakes high and into a trimmed hands-off cruise, and without adjusting throttle, put the plane into a fairly steep dive (45 degrees or so) release the stick for a second or so to see what she does (be ready to recover the dive before she hits the ground). Neutral will hold course. Nose heavy will pull up, Tail heavy will pull down deeper into the dive.


All that being said . . . "Neutral" CG isn't fun unless you're looking for a "only goes where you point it, but you always have to point it" plane. You get no help from a CG neutral plane in settling into a level cruise, so nearly everyone flies slightly nose-heavy, and the plan's marks are likely forward of neutral. The exceptions are generally competition class airframes that must be controlled by the pilot from takeoff-to-landing . . . you've got a pretty plane there, but that's not what that is designed to do. CG being a little farther forward is not a bad thing. A lot farther forward . . . well now you have the info on how to tell and tune it to your liking . . .

. . . but get her flying first

 

[Steve Fox]

Dunno about "too nose heavy"

thanks, i was reasonably confident it would be ok but had that niggling doubt and wanted anothers view on it
decided that i balance so often that i should make a proper balancing rig, its looking a lot better now its on something that lifts it clear from other objects that give illusion of angle.

the reason ive asked for opinion on this plane is that the angles on it make it hard to judge, theres not a single surface on this plane thats level when the body is level, even the elevator has an angle to it!

 

[Tench745]

I'm not familiar with this particular model, but it looks to me like it could use just a little more nose weight. I tend to trim out for the lower surface of the wing to be parallel with the ground and then back off from there if necessary.