I'm finishing my first kit, a Goldberg Eagle 2 (bought 15 years ago). It looks like I have to put 8 - 10 oz. in the nose for correct balance. This seems like a lot to me. Is this much normal? Gosh, that's half to three quarters of a pound! ...and that's laying it right against the firewall.

I have an OS .40 up front, and pretty much a stock build every where else - except I went with 4-40 push rods for elevator and rudder, instead of the balsa/wire combo.

Thanks for your help.

Doug

Doug. That seems about normal to me but if your conserned you could move around the reciver and battery forward to act as a nose weight.

I have, in the past, used 1/8" sheet lead and made a strip that would go under the engine and span the motor mounts. I used long screws for the two front mount screws and dirlled the lead to fit over these extended screws. A washer and a nut with a liberal amount of thread lock, and you have an ounce or two out front where it does the best.

On my Rupert's Dad, I found I needed about 8 oz in this mannor to balance the plane. That was with a Mag 52 four stroke. Then I found that replacing the 52 with a Mag 70 four stroke would account for 7 of those oz, and I could put the weight to work. I had to mill about 2.5 MM off the inside of the motor mounts so I could use the same bolt patern through the fire will. It has worked very nicely. I solo-ed it today. I flew it a couple times with the buddy box some months back and I thought it was very intimidating. Today it was a blast.

On my first 4*60, I needed six oz and there I used 1/2" square steel stock and cut two pices the length of back of the motor mount and then dirlled them to fit the motor mount screws pattern. It was a clean addition of weight and it also saved a bit as the motor was extended by 1/2"

If you can't take care of the weight issue by moving batterys, put weight up front that you can use if possible. Say an OS 46

Don

those 4-40 pushrods are adding weight way back in the tail where it's hard to counter it.
If possible I'd try a couple CF pushrods with 2-56 hardware.

I built mine with Sullivan blue ny-rods and an OS 40 4 stroke.. it came out right on the CG without adding any weight.

Some things you can try is moving the battery up under the fuel tank if there is room.
maybe find a heavy spinner or try a higley's heavy nut on the motor to get the weight as far forward as possible.

I will go with the other guys on moving the battery as far forward as you can. When I build I always assemble the plane in the bones and put the gear in loose to get as close to the CG as I can then hard mount it.
Sometimes you can't help it and dead lead is the only way but you can usually get close by gear instalation.

Some thoughts:

- I wanted to make sure that..
a) The plane would still fly
b) The plane would stiff take off (with an OS 40 power plant)
c) Again, this was my first kit, and I have no idea if that extra weight is normal or not

- Do you really think that the 4-40 pushrods made that big of a difference?
a) I still have the smaller gauge pushrods and balsa sticks that came with the kit,
I will probably build those and go back to them if everyone thinks it'll make that big
of a difference. I'd rather do that than add 3/4 lb. of nose weight to a 5 lb. plane.

- I have the battery as far forward in the cabin as I can get it. It would be difficult to get it
up into the fuel tank area. I wonder if it would really help that much.

- I have some steel stock I can use, or even some lead tire weights I can put up there, and just pack
in really tight with the foam for the fuel tank.

Thanks for the comments.
Doug

Doug ,

I have one of these also but haven't started the balancing yet. What is the AUW of yours?

...sorry, what is AUW?

All Up Weight

I'd move the battery up under the fuel tank AND go with the 2-56 pushrods. If the OS 40 is the non-ballbearing one your going to want to keep the Eagle as light as you can. If it's one of the hotter 40's you may be all right at 5.5 lbs AUW if your not a long way above sea level.

A friend of mine just put together this same plane with the same engine, and also had to add about 8 ounces to the nose.

Another guy at my field has an Eagle 2 with an OS 46AX, and he says it balanced out perfectly. I'm not sure what the weight difference is between the two engines.

It looks like the OS 46 is about 4 ozs. heavier, but that's not an option at this point. I told my son I would finish this plane for him, if he bought the engine and radio, so that's we he's got. We'll have to work with it. As long as the extra 8 oz. doesn't significantly hinder it's ability to fly (and in particular - take off), then I'm ok with it.

i dont like dead weight but if you have to then you have to.you can try moving the engine a little further out on the mounting rails if you havent drilled them yet.and i try to mound any lead in the engine bay on the firewall or the motor mount itself.

I will have to agree with SSCHERIN. Being that is the only thing you changed. I built mine with the stick and wire set up. Works great on this trainer and I put a OS 46 LA on mine, and put the battery and receiver as far forward as I could in the fuselage( not in the fuel tank compartment) mine balanced perfectly. In fact when I get more proficient with this plane I will move the CG back a little and see if she gets aerobatic.

Replace those pushrods (Yes, it makes that much difference) and put the battery under the tank. It may require a little work, but it will be worth it.

Then add whaever weight you need to.

I broke in the engine last night, and I'd like to take it up for a shakedown flight. I put the battery up by the tank (just barely fit), and have put about 8 or 9 oz. of weight in the fuel tank compartment. Is it safe to try to fly the model with this much extra weight? If not, how do I now - how much is too much weight?

PS: I'll probably change the push rods in the future, but not just yet.

Thanks,
Doug

Ok, more questions...

I weighed the 4-40 pushrods as bent and assembled with clevises attached. They weighed 1.7 oz. for both the rudder and elevator pushrods. Then, I weighed the 1/16" pushrods with balsa sticks and clevises, they weighed 1.1 oz. Is that roughly half an ounce really going to matter?

If I had to guess I'd say 1/2 oz off the tail should be good for removing 2-3x the weight in the nose.

I measured my eagle.. it's 9" from the cg to the firewall.. 8" behind the CG to the rods and 30" to the elevator. so figure a 3-1 advantage for the tail. but you loose some advantage since that .6 oz weight loss runs form 8"-30" behind the CG.. averaged out it's 18" behind the cg

so to be fair we'll call it 2x.. .. so you can remove 1.2oz off the nose and save .6 on the rods.. total weight loss of 1.8oz.

let me know if my math worked out in the real thing.

I made the changes today. It turns out that the two balsa stick push rods weighed 0.9 oz., lighter that the 4-40 push rods. I was able to remove about 3 oz from the nose and get the same balance as before.

- That gives me about 6 oz. of nose weight, the battery fitting tightly under the fuel tank - up against the firewall, and a total of about 4 oz. lighter than before. I don't really like the battery up in the fuel tank area, but... oh well.

Yes... it was probably worth the trouble to convert back to the original design for the push rod assemblies for rudder and elevator - balsa sticks.