I just finished putting together my GP Easy Sport 40 with an OS .46 AX and a Top Flite 10x6 wood prop. It's the first ARF for me and I followed the directions exacly. I have the battery as far back as possible and the receiver just in front of the batt.

It looks as though I will need to add 4.5 oz of weight to the tail to get it to balance slightly nose heavy. Is this an insane amount of weight to add? Also, where is the best place to add this? Top or bottom of fuse? Site of horizontal stab? All suggestions and insight are greatly appreciated.

It seems like alot.
I only had a couple of airplanes that needed tail weight and both only needed a small amount.
1 was a Cessna and that makes some sense because of the short tail, the other was a Hobbico Brightstar and that took less than an ounce.
Most airplanes can either be balanced by moving the battery around or need nose weight.
Long answer to maybe its too much?
Are you sure you measured right?
The farther back you put the weight the less you will need.

i agree, try and move things around inside of your plane first, those weights should be your last choice

i agree with Missileman i would check the cg again to make sure you are measuring at the right location.that seems like an excessive amount of weight in the tale.

G'day Mate,
I agree with the above, about moving the battery, & about being sure you have measured the right point for you CG.
And just one thing, don't use the 10x6 wood prop, too small & too breakable.
Go for an 11x6, & use a plastic one, Master Airscrew or similar, we generally use 12x6 props for trainers & 46AX's, a 10x6 is a 40 size prop, if in doubt, refer to the OS manual on the engine, it sugests the smallest prop is a 10.5x6, up to a 12x7.

I have a GP CG machine. The manual says CG should be 4 1/8 inches back from the leading edge of the wing which I have checked with the CG machine and by measuring with a tape measure and marking the wing. The fuse does not allow a lot of mounting options for the battery so the only thing I can think to try is getting a battery that is 4 flat cells instead of 2x2 and placing it behind the servo's.

The only way I can get the plane to balance is to take 18 of the 1/4 oz stick on weights and set them on the horizontal stab.

Agree with the advice on prop size, I have three 46FXs and I usually use 11 X 6 for general sport flying.

Terry

is your fuel tank empty? has to be empty. are you sure you haven't left a tool in the plane cause 4.5 oz at the very tail is almost insane. something is wrong somewhere

You mentioned early on that the battery was as far back as possible. There are more possibilities.
If the servos are where they usually are, then moving the pack behind them actually puts the batteries back where they will do some good. If the pack wasn't already behind the servos then it was very probably contributing to the problem.

It's actually not hard at all to place a battery pack inside the fuselage behind where the Trailing Edge of the wing is secured. Get some scrap wood and build a box that fits the pack. Build it around the pack while it's outside the fuselage. It's lots easier to build on the bench. Don't worry about the weight of the wood. After all, you need weight. The box should be open ended, just one opening, toward the front. Fit it into the fuselage back there with something like Elmers or 30min Epoxy.

BTW, try this test.
Remove the battery and check the airplane's balance. Find out where it balances, don't worry about noseheavy or anything. Just find out how far back from the LE at the wingroot the balance point is. Where is it?
Now, tape the battery behind the servos and find out where the balance point is. Masking tape works good. Outside the airplane works too. Where is that?
Now, tape the battery farther back, say just behind the TE of the wing. Where is the balance point now?

OK - first off the 4.5 oz is way too much to add to a tail. [X(]

Next, I would suggest that you have a second opinion / inspector to have a look at the AC and confirm your point of balance. (just in case)

IF the balance is confirmed start moving things...
-Move the engine as close to the firewall as possible,
-Change the Engine mount to a lighter style,
-Get a light spinner,
-Shorten the control rods and move the servos as far aft as possible,
-Convert the AC to a tail tragger.

Do anything and EVERYTHING before you add weight to the tail.

With ARFs the quality of the wood is occasionally questionable, and it is possible that you have the nose made of a 'Heavy' type of wood - this can affect the balance...[]

Good Luck!

You said the manual says the CG should be 4 1/8 from the leading edge. Typically, there should be a range of about 1/2 inch that will work. Was the 4 1/8" supposed to be in the middle of the range?

Thanks to everyone for all your insight and "hand holding" so far.

I will swap out the prop for a 11x6 or 12x6. I thought the manual suggested a 10x6 for run-in (it’s a brand new engine), but it may have just been that’s what I had available when I started putting it together.

Jhetmech05: Fuel tank is empty. I used an epoxy mixing stick to secure the fuel tank but even that was in the instructions. I will double check to make sure I didn’t leave my cordless drill or something in there!!

broke_n_bummin: The manual says the CG is 4 1/8" back from LE, and that it can be moved forward or aft 1/8" from the 4 1/8" mark, but that initially it should be flown w/ CG @ 4 1/8" back from LE. So yes, there is 1/4" of play.

Da Rock: I will need a flat battery pack to put underneath or behind the TE as there isn't enough clearance for my 2x2. I will follow your suggestions of checking the CG w/o the battery before proceeding or purchasing a new battery. If I do build a battery box do I build to fit a battery wrapped in foam or a bare battery? How do I secure the battery in said box? (I think this is going to be the answer to my problem, thanks for your help)

On a side note, I have built several combat planes (gutter pipe and coroplast) and have found balancing rather straight forward. I get them flight ready before determining where to place the wings for proper balance. This is my first experience of moving the “guts” around to achieve proper CG. The other way is easier!

yeah ... that's what I like best about SPADS. The thing about most ARFs is that usually, anything lighter than the largest recommended engine will require moving everything as far forward as you can get it. That means you should have to shift almost 5 ounces toward the front. Here's another question ... When you're ballancing the plane, you're doing it upside down ... right? Also, check the total weight of the plane. With the 46AX, it should come in at about 5 3/4 pounds.

I was balancing it right side up…. the manual shows the plane on the CG machine right side up and the manual says to mark the balance point on the bottom of the wing, not the top. Should I try to balance it upside down?

Build the box to fit the battery. Make sure the box is glued to a decent bulkhead and some stringers. You want to spread out the support. And scrap sticks can bridge the box in back there. It really is easy. I did it at the field one afternoon with scrap wood from a crashed airplane and some CA. The guys all seemed amazed how simple it was and how little time it took. And the newbie who owned the airplane seemed to like the airplane more for the silly box than for how much better it flew. This is one amazing hobby.

The box I did for that one was really just a couple of support sticks. Or more like a cage. We actually used wireties to hold the battery to the framework so it wouldn't move.

The last one I did for myself was a box. And I CA'd a stick across the front to hold the battery in. There was a bit of rubber to keep the battery from moving at all, but I don't worry about vibration back that far.

Only balance low wing airplanes upside down. They will balance any orientation and show the CG just as accurately no matter what. But they are more stable during the effort when the fuselage is hanging down.

NO, with the design of that plane I would balance it right side up. Inverted balancing is what you do for low wings.

As for the battery mounting. I use self adhesive velcro that you can buy at any fabric/sewing store.
I can easily remove or move around my battery and it holds the battery really good. The velcro will also add enough cushion to absorb any vibration.

BobCat1506,

I just maidened my Easy Sport-OS46 FX. It check out so nose heavy I couldn't believe the plans. I thought it had to be a mis-print. (spent 2 hr on RCU researching ES posts)

My original guestimate was 4 oz of lead in the tail to balance.
Well, that's just nuts. So I decided to move my battery as far aft as possible-- behind the servoes against the rear bulkhead.

To fit the battery, I had to remove the linkages and the servos.(that I had just so carefully calibrated.) [].
After reinstalling sevoes, et al, it's back on the cg stand. Damn, it still needs over 2 oz of lead to balance. I added 1 oz ea(2) of tire, stick-on weights to each side of the tail up under the elevator and rudder push rods. The balance point was only back to 4" not 4 1/8th called for, but close enough for govt work. When I got to the field I noticed the throws on the rudder were not even. (Big caution here) The rudder control horn was hitting on the lead weight I had added. Had to cut down the throws to try and even them out. (after all this work, its going up). Flew like I knew what I was doing. 1 click rt and 1 click up. I think it's still a little nose heavy, but what to do?
I can only imagine the balance problem I'd have faced, if I went with the OS 70 FS that I was going to put on it.

Me wonders if this is a recent problem with the ES? Also, those flying with 70 FS engines, concrete tails?

Fair winds and blue skys to all,

B...

I swapped the prop out for an 11x6 wood (only because the hobby shop did not have any plastic props in that size). Then I balanced the plane without the battery and it balanced at 3 1/8“ back from the LE, a full inch away from the recommended balance point. I then moved the battery to roughly the TE of the wing (would not fit any further back) and secured it with velcro and foam (not enough room for anything else). Then it balanced at 3 7/16”. I added 3 oz of weight to the fuse underneath the horizontal stabilizer and secured with 30 min epoxy. After the epoxy dried it balanced at 4 3/16” (wasn’t sure how much the epoxy would weigh). I will likely fly it and use a file to reduce the weight if I feel it is tail heavy. Thanks for everyone’s help, hope this one has a better fate (or at least a longer life) than the last one!!!

yeah....

This is how I dealt with moving batteries backwards, its not the cleanest and was done after few flights when the plane is ready

the batteries are the yellow thing under the red pushrods.

I had to add more then 1 oz to the tail, and I still need more, I’m fixing a tail dragger soon.

I placed the batteries behind the servos.

Glued Velcro to the bottom of batteries, at the last former and a strap to hold it to the former.

It flew like this and nothing moved or released. [8D]