My last 3 planes have all ended slightly tail heavy. Balance point is more aft than recomended in the manual. These planes have been wonderful 3d machines due to this aft CG...but all of them have had a tendency to climb sharply on inverted flight. Something I dont particularly enjoy as I have to input slight up elevator to correct which is non-conventional on inverted flights.

I know that a tail heavy plane would climb on inverted, but is my 3d plane TOO tail heavy if its climbing? My question is: Is my 3d setup incorrect? Are we supposed to keep CG such that inverted flights need just a touch of down even if we are flying on a 3d setup? To go one step too far, do the TOC 3d guys find their planes climbing on inverted flight...considering that they are setup for extreme performance? Or do they keep it balanced forward enough such that inverted flight is conventional and flies straight and level with a touch of down elevator and yet plane is capable of great 3d.

I guess the answer to this may boil down to persoanl preference, but is there a right or wrong to it?

I may have repeated my point...but I hope its clear.

Thanks,
Anurag

i think it mostly comes down to personal preference, and what you have gotten used to. i set everything up so it needs a touch of elevator when its right side up and inverted, basically try to get it absolutely nuetral.

theres a few trimming references online, those should help too

Dylan

wow, got yours to climb when inverted? I have all mine very tailheavy, and Ive never had that happen yet.. Do they land ok?

I flew my Cub once when all the nose weight worked itself loose and went into the tail - the thing would climb in knife edge with no rudder input! [:-] I always set mine up so I have to give a small amount of down elevator when inverted, and no elevator when upright. Works for IMAC and 3D.

really good question!
I run mine neutral inverted and they all hover, waterfall, etc. just fine. I agree, its personal preference as long as you don't go so far back the ship becomes unstable.

Hi Ragz,

I fly my Cougar 2000 with the CG such that it climbs when inverted just like you say yours does! To be honest I've just to used to the way it flys as the benefits of good parachutes and flat-spins outweigh the fact I have to correct fro the climb when inverted. It seems to to 3d nicely so I'd say roll with what you've got!

Andy

My scratch built Stealth is also tail heavy. In fact on the maiden flight I had to add 4 clicks of down elevator to maintain level flight when upright. When I go inverted the airplane climbs out quite a bit. This gets worse as the fuel tank level is reduced making landings interesting to say the least. It is just something I will need to get used to. But the flat spins are awesome!! I had to add about 80% expo on the elevator. Helps on landing.

Tom...

My OMP Edge profile (.40 size) climbs inverted when the tank is full and will do an outside loop when the tank is near empty.

It is very stable upright, even with the tank near empty, but it IS hard to fly inverted. The up elevator input to keep it level is very counter-intuitive and awkward.

The scary thing is that on the first flight it was far more tail heavy. Since then, I have moved the engine forward an inch and added a heavier spinner.

Leonard

John,

Landings are an event...not too hard, but yes, I have to maintain some speed.
I dont want to add nose weight, as the plane in question is a 24% 3d aerobat and already weighs 12lbs with a saito 180. Any more nose weight, and it will be nearly impossible to 3d with it. As it is, its hard to get it to do much except IMAC routines.

Anurag

Quique wrote a 3-D article in last months Model Airplane News magazine. He said his TOC plane will climb inverted when set up for the freestyle. This is how he verifies the CG on it. My Funtana does the same thing. The first few landings were more of a harrier than a regular approach. Since then I have been putting two clicks of down trim just before landing. Then as soon as I kill the power I change the trim back. This has been working great. I actually have to hold the nose up a touch on final.

David

My Giles is set up that way where it climbs while inverted. Elevator trim is perfect at center. Some rudder coupling makes it worse at times. I just live with it for the moment.
For landings it's not so straightforward. I have to keep in down elevator all of the way down (to keep the tail up) and control the decent with throttle application. You really have to fly the plane all the way to the ground like this, and plan the landing way back from final turn in. You cant horse the plane in like a nose heavy one.
RickP

Rick,
I know that feeling. You have to actually fly the plane down to the ground...

I've got a scratch built that get's real touchy with aft CG. It will go from almost hands off inverted to tight outside loops with very little weight change. Makes for great 3D, but inverted "normal" flying is pretty much impossible. My TopCap isn't like this at all, and is completely neutral inverted (actually flies better inverted than upright!). I think the primary difference is a combination of the amount of lift the wing generates (ie a thick wing will be easier to tune) and the ratio of tail surface to wing surface area, (ie bigger stab/elevator may help smooth things out).

on my flip i have to pull down to to fly level, great for low inv passes

Just my personal opinion. But I think if you gan get it to be "neutral" I.E. fly straight and lever upright or inverted, your setup is good. Some planes will fall out of the sky before this happens so be careful

I talked to a guy (Jim A) at the Rally of the Giants 2003 who's Edge 540 was so tail heavy he had to use DOWN elevator on a final approach.