Hello,
I'm new to the forum and fairly new to the hobby.I am putting together a Hobbico Avistar ARF with a Thunder Tiger Pro .46 engine.It is very nose heavy,and to get it to balance by moving the battery,I'd have to put the battery 6 inches or so behind the trailing edge of the wing.That would require cutting up the fuselage to be able to put it inside the plane that far back.I'm looking for advice from others who have put this plane together,on how best to balance it.I can get it to balance by adding about 2 oz of lead back by the tail,but don't really like the idea of that much weight being stuck to the outside of the plane.Maybe I could slap some epoxy on some lead and fish it back in there with a dowel rod somehow.Any advice?
thanks,
Jeff

Have you considered a bigger, heavier battery? I have this plane with an OS46FX and have really enjoyed it. To balance it I added a second battery and put both to the rear as far as I could get them. I used two balsa pieces glued across and above them to hold them in place. Now I have 1200 mah of battery and can fly the heck out of this plane without worry. I used a Y to connect both batteries to the switch, but have to charge them separately.

i don't have this plane but on some planes i have made a hatch that can be removed easily to get access to the battery.

There's no room to move the battery back,unless I put it behind the servo tray,wich would be aft of the trailing edge,and I'm not sure I can get my fingers back in there to work with it.The servo tray was pre-glued in by the factory,so I had no choice in where it was located.Seems really cramped in there.Kinda hard to picture what you are suggesting.Are your batteries located behind the trailing edge of the wing,in the back side of the fuse?

I may be able to use both your ideas.....2 batteries right behind the servo tray is just about the right amount of weight.But I'll have to cut a hole in the fuse to get them back there and make some sort of brace to keep them from sliding around.So perhaps cutting a hatch in the bottom of the fuse is the way to go).

When you use a Y harness with 2 batteries,aren't you doubling the voltage in the process?I saw another idea where you simply put one battery into the battery slot,and another into an empty servo slot.

Be careful working in the rear of the Avi*. Behind the wing, it's very weak.

I swapped my 40LA out in favor of a 46FX at the field one day and didn't have any weights to rebalance. The plane didn't seem to care. Even inverted didn't seem to be effected. It did kinda hover 'till I couldn't keep up with it though. Gotta love more power!

To get my two batteries behind the servo tray and under the push rods I did this:

First, I wrapped them in thin foam making sure the leads came out on the same corner. Then I wiggled them through the former behind the servo tray, and yes it is a tight fit but mine went in fairly easily. I put them through on edge with the connecting wires up, then using my fingers, big - chunky -clumsy ones at that, I rotated the batteries to horizontal under the push rods. I also had pre-placed some foam to the rear of the batteries, or in front of the second former to prevent the battery from sliding to the rear. Finished by gluing in a piece of balsa across the top. I've had many flights with this plane and no problem that I can blame on the battery arrangement.

No, connecting the batteries with a Y does not increase the voltage - I'll let one of the battery experts expain that or you can look in the Battery Forum and get additional information.

If I had it to do over again I would try using just one bigger battery, I have since used 1400 mah and think one of these would be a good solution.

I would be VERY RELUCTANT to cut into the rear of the plane, with luck you shouldn't have to.

Good Luck

While your are at it have you considered changing the wheels that came with your plane? I fly of a grass field and when first learning had a tough time landing and not snapping props. I switched to 3 inch light weight wheels and found that I could not only land and reuse the props, but the landings came easier, the plane also rolled out better on take offs.

Make sure the engine is mounted as far back as possible.

It is a little more work/money, but a Macs one-piece muffler or a mousse can muffler will save 1-2 ounces up front.

Just a few thoughts.

Leonard

Barland,
Are you using flat packs or square ones?Mine are square.Also,can you get your batteries back out of there?I don't have any spares right now,will have to share with another plane.

I am using flat packs.. I can see where square would be a problem with what I suggest. Consider those 1400 mah's in flat pack... mine were under $25.00 at a local hobby store, on the Internet you could likely beat that price. Sharing would be tough with my idea. I did fly this plane nose heavy and as one of the other responders noted it flew OK. When doing that I only filled it 3/4 full of fuel to "sort of" off set the noise heavy status.

I discovered it balances with one battery pack in the rear,and one up front.I cut loose the rectangular piece of ply that is only there to hold the pushrods in place,and I glued some balsa on the back of it making a battery hold down,then used some spare screws to re attach the plywood.That way I can remove it if I need to.Took alot of frustration getting it in there,but hopefully it will hold up ok.I like your idea of just using a higher mah battery,but I also like the idea of having the spare battery in there for safety.I hooked mine up with 2 switches,and fed the extra battery into an empty servo slot.Had to borrow the switch and battery from another plane.This will get me started.I can always experiment later....after I forget about how much of a royal pain it was the first time lol.
Now i have to figure out how to balance it laterally.Never really done this before.
anyhow,thanks for the help

Good for you, another solution in our hobby. I like the Avistar, and am new enough, that I will likely have another and will try your approach when building that one. As to lateral balance you will find this far easier than your battery struggle. Some will glue a washer into the wing tip, or on the wing. I was able to get enough clear silicone into the plastic wingtip from the small open slot next to the aileron to balance out. Nothing cut, nothing shows, and since it is also an adhesive nothing moves.

I've built 2 of these and the way I finally got it to balance was by using the minimal amount of weight as far back as possible. There is a former located just forward of the stab. I cut a small hole in the covering, then cut a small hole in the fuse. I bought a package of the stick weights with the foam tape and epoxied it to the inside of the fuse straddling the hole. I used a piece of string to pull it tight against the hole. When the glue dried I patched ofer the hole with lightweight spackle and put a white monokote patch over the hole. The fix is nearly invisible and the weight is protected inside so I don't have to worry about it falling off.