I have a four star .40 and Im using a OS 46AX engine on it. The way I have it set up right now is with the battery foward of the servos but as far back as possible and Im still quite nose heavy. Today was her maiden flight and I had to trim the hell out of the elevators to keep her from wanting to dive. And rolls were everything but axial. So Im trying to find out if any of you have the same engine on this plane. I was thinking about putting the battery behind the servos to balance the plane. I was just wondering if anyone else ran into the same problem with having this plane nose heavy and if you were able to balance the plane with battery placement or if you had to add weight to the tail. Also, I was going off of what the manual says for balancing.

You can indeed move the battery to the back of the servo's to obtain the proper balance. Just make sure that you do not get it tail heavy. Good Luck, Dave

Behind the servo's? How can a plane become that unbalanced, its not like he put a gasser in the front.

I've built three 4*'s and two were on the nose heavy side. The one that wasn't had a very light Norvel .40 in it. Having to play with battery location or adding weight (last resort) isn't uncommon.

Yeah, it just seems odd that his battery would end up behing the servos.

I forgot to mention that this plane is a ARF. I have used all hardware that was included. I have three standard Futaba s3004 servos in the fuselage. There aren't any modifications, just a bone stock arf. The only thing that I could think of that would make this plane nose heavy is the 46ax. I checked the O.S. website and the 46LA weighs 9.6oz compare that to the 46ax which weighs 17.2oz.

Yeah...that's why I sheeted the rear deck, extend the rudder, beef up behind the wing mount former.
I went as far as even drilling holes in the doublers for the front part of the model.
Even then it was still nose heavy.lol

I could have went and bought liter landing gears...but I like the ex300 gears on it. it's beefier and taller.
The wheels on it..didn't help much in the matter..but I like those too.
The wheel pants and all the hardware probably added more wieght.

I cure it by spray painting the canopy black, Use screws to secure it. Moved back the head rest when I sheeted the rear deck.
Mountd the battery pack inside the cokpit. Drilled 2 hole on the cokpit bottom so I can run tie wrap to secure the pack.
CA a couple piece of wood in fornt and back of the pack to prevent the battery pack from move forward or backwards.

Trimmed the canopy down a little bit...to remove wieght.lol

It came out perfect for me after that.

So I take it you had a kit. What kind of engine do you have on it?

Couple of things............

You don't mention where the CG actually is. Have you measured where it is? The building plans will give a CG range. What is that, and where is yours?

It's not strange for ARFs to come out with lousy CG's. The workers over there aren't modelers. And they have proven to know nothing about wood selection. So it's not uncommon to have nose heavy or tail heavy ARFs.

If you look at the picture, it shows a battery installation at the farthest aft the battery can be and still be inside the equipment bay in the fuselage. The blue piece is foam insulation I used to box in the battery for that airplane. You'll notice that it's directly under the aft hold-down bolts that go through the trailing edge of the wing. A couple of ARFs have required placing the battery even farther aft. I've built battery boxes back inside the aft part of the fuselage. You're limited only by how far the switch/battery wiring will reach. You do need the box structure back there because the fuselages aren't designed for that much weight back there. But it works.

After seeing how often ARFs wood selections have screwed up the balance, I now delay placing the switch harness until I can do a preliminary CG check.

So tell us where your present CG is, and don't worry if you need to move the battery back.

As indicated above you need to find out where the CG is. Below is a shot of where I had my batteries when I had a 46AX in my 4* 40-Behind the servos. I also had a Dubro Isolation engine mounts which add more weight. If you can't get the CG back far enough, move your engine back or try a APC prop and heavier spinner.

It depends..sometimes a magmun .46 or .52..or a tower .46. So they're on the heavier side to begin with.

I cliped 2" on each side of the wings to make it lighter .lol
It's still a floater to me, even after I lowered the diehedral.
My lift ratio is not as much....but ya know....that's why i slapped .46 or .52 and take out the muffuler's baffling.
It rolls better and i can kind of do a fake knife edge better.lol
I have the power to wieght ratio on my side.lol

But it still takes off and lands like a kitten because of the airfoil design and it's a stright wing cord.
It's not that much heavier...becuase i don't add lead wieght like some people do.

It's right on the main spare(empty tank) that's what it shows on the plans i have.
...give or take here and there...the fuel level will shift it anyway.

I start off nose heavy anyway....incase virgin models turn out too touchy.
And I forget to turn off high rates during take off on it maiden flight
Some old guy at my club told me to do that.lol

then i move it back a little bit at a time after i get use to the model.

I can do a perfet outside loop with the same .46 set up..on a 4* consecutively.
verse..on my super sporter, it kind of don't wanna fly over the top

I have exactly the same plane(ARF)engine......also had the same problem.I moved the batt. behind the servo tray and problem solved.I used a piece of velcro to secure.
She flies real easy.......fast with the .46AX......a big change for me from the SuperStar......but lots more fun..........try that before butcherin your plane all up.my CG was exactly as the book showed...2 15/16 from LE.....

Thats funny because I also moved from a Superstar to the Four Star. And I just bought some velcro from walmart to put the battery behind the servos. Did you balance your plane right side up or inverted? Im having trouble balancing it right side up because once I get it off the ground it will balance for a second then it tips in either direction. It doesn't seem as bad trying to balance it inverted, but was just curious if you had the same problem.

I just got done moving the battery behind the servo's, I went to check the c.g. of the plane and if I try to check it right side up, going off of what the manual says and using the main wing spar as the c.g. point the plane is tail heavy, but if I check the c.g. with the plane inverted on the same spar, the c.g. is perfect. It sits nice and parallel with the ground. What do you guys think?

If it balances upside down, and the CG is where the manual says, then you're good to go.

The manuals usually suggest a CG range. If the model balances anywhere in that range, it'll be stable in flight. The suggested CG is really only a starting point to get you into the air with some assurance the plane will be controlable.

And it sounds like your 4* balances.

Whats even funnier.....I tried to balance mine right side up too!!!..;0).....doh!!......upside down just like the pic/manual says.I have @ 10 flights on my 4* now.The .46 is arguably too much engine for that light of a plane,take it easy until you get a few runs in to see how she handles.Responds alot quicker than the Super*.My .46 wants to idle too fast and I have had to adjust the low speed some,but after @ a gallon of fuel ran thru it is starting to settle down.Make a few runs then go back to the Super* and you will get the full effect of how much more fun flying is going to get.Good luck!!

I would go back to the Superstar to see the difference if I hadn't gutted the servos out of it for the Four Star. But anyways thanks for the help. Just wondering, how far out do you have your high speed needle valve opened? About how many turns out. Mine is turned out quite a bit to run rich for the break in, but Im curious what it will sit it to get optimal performance out of the engine.

I ran 4 tanks thru on the bench for break in adjusting high needle valve as the spec book advised.The first 3 flights/tanks I ran rich.Ambient temp will effect mix as you probably know.The last 3 tanks I have been able to run a few clicks leaner...but still to the rich side.I adjust to lean until rpms begins to sag...back thru high rpm @ 2-3 clicks to rich,with a small decrease in rpm.The "pros" I fly with have always advised to run on the rich side...especially on a new engine.I am fortunate in that I have found a club that has alot of experienced flyers and even though I am 46 they consider me a kid still and watch over us "kids" like grandfathers would.They won't let me burn my new motor up if they can help it.I have learned alot from them in the short time I have been involved in this R/C airplane stuff.(5 mos.)The motor tuning part is harder than the flying part to me.My Super Star/OS .40 LA was used and already broken in....just gas up and go with little/no adjustment.........keep us posted on your progress

Well I just made the last few touches on the four star and tomorrow will be day #2 for flying the plane. I will let you know how things go. If you don't hear back from me tomorrow on this thread look for me on the crash and burn stories thread. Knock on wood.

You'll do fine....keep us posted.

btw, one thing that can really change the CG on a model is exactly where the engine is mounted. I'm not familiar with the ARF version of the 4* and what kind of motor mount it uses, but if you had to do some drilling, or if it's a clamp mount, did you move the engine as far back on the mounts as possible? Moving the something as heavy as the engine even 1/4" or less back can be huge, CG-wise. The 4* has those cheeks around the engine, but as long as you're using a small enough spinner, and the prop isn't hitting anything, you might be able to slide the engine back a bit. For that matter, cutting back on the cheeks to move the engine back removes excess wood up front as well...

Well I just got back from flying the four star and everything actually went pretty good. I didn't have to trim the elevators as much as before, and rolls were alot better than before. When I took the wing off I realized that I avoided disaster by pure luck. The battery had come loose and wasn't secured at all. The battery wire that ran pass the elevator servo which I had taped down came loose and was right under the servo arm. I think the battery came loose after I did a less than perfect touch and go. Now I just need to find a better way of securing the battery back there.

Maybe obvious question but did you check the CG with the fuel tank empty or full?

Glue a piece of wood across the fuselage back there and use a zip-tie around the wood and battery.

Hey guys,

I recently picked up a complete 4*40 and would like to know the CG range. Don't have the plans as this is built kit and the manual doesn't show anything. Noticed a few replies earlier that the CG is 2 15/16" from LE but what's the recommended range?

Thanks in advance!