CG
 

Can someone tell me some of the different methods used to balance a nose heavy R/C model aircraft?

Add weight to the nose. And or Make sure that the battery and receiver are as far forward as possible

Thanks Jetmech05 but I meant a nose heavy A/C. What is the best way to add weight to the tail?

Depends on the aircraft and its structure. For something like a park flier, a coin or 2 taped to the tail might suffice. For something like a giant scale Corsair you're going to want to incorporate some sort of hatch for weights inside the fuse.

What plane are we talking about specifically?

Oh sorry I mis read. Slide your battery as far aft as possible. Those sticky lead weights work well

Sometimes it's possible to lighten the front instead of adding weight to the back. Smaller, lighter engine?

As Skylark-flier indicated for those admittedly rare times it may be necessary to add lead to the tail there are an infinite variety of ways to do. Really almost case by case for each airplane.

Please allow me to tell of one such solution that I came up with some years back. I was setting up a pair of Messerschmidt 109's for my team mate and I to use for warbird pylon racing. I wanted to do some fine tuning of the CG and all the internal options were done. Weight added back at the tail would be minimal for this fine tuning but where to put it?

Well fortunately these airplanes were 109E models and had scale struts from the bottom of the fuselatge up to the bottom of the horizontal stabilizer, Hmmm? so got out my little chunk of railroad track and the the small ballpen along with some assorted fishing weights and wheel balancing weights. Hammered one of the weights totally flat and almost paper thin on the anvil (chunk of railroad track).

Next step was just to cut the thin sheet of lead with scissors to a size that would balance the airplane right where I wanted it to and then it was just wrapped around the strut or struts neatly with a small squirt of thin CA. Worked well and looked very scale.

Just one of many ways to approach the problem:cool:

John

I am working on a Right Flyer Sixty. With the aircraft on a balancing stand, the nose is heavy. I have moved all the radio equipment as far aft as I can.

Went to the instruction manual for this airframe and your CG is set at 4" back from the leading edge of the wing. This is just a starting point and they allow a + or -minus 1/2" CG range. The balance most be performed with the fuel tank empty. If all this fails to remedy the problem then purchase some stick on lead weights and attach them below the horizontal stabilizer. I find it hard to believe that you are having an issue with this basic trainer.

If you use stick on weights on the horizontal stabilizer may I suggest that you do not stick them on the under side but instead on the top side next to the vertical stabilizer. The reason is that double stick tape is more likely to let go on the underside and after an undetermined degree of oil soaking from the exhaust.

It may look not so pretty there however that's better than the possible alternative when your weights let go in flight. Have seen this often.

John

I use that trainer but didn't have a CG problem, I moved the gear around and got the CG. The plane is designed to have the engine upright so the exhaust tends to slather the top of the tail feathers even when using a deflector. Just clean the covering really good with acetone then use the sticky weights on the stab close to the fin like John mentioned. I wouldn't worry too much about top or bottom on this plane but as John mentioned, over time the oil can remove the sticky on the weights but if they are down on the covering real tight it will take a very long time. When I was first given this plane it had a Magnum .91fs engine and I changed to an OS .91fs. The only problem I have had is getting a good fuel tank location. It's a nice flying plane and I have taught several students with it. It's so old and used now parts have fallen off of it and it still flies well.

John Buckner, you posted the formula for finding CG in another thread that I can't find. Can you re-post it here?

In layman's terms please I can't make sense of that.LOL

OK, just got through with a couple of days of going back and forth up to Grey Beard's 'Hood' for medical stuff. Its early AM now and getting ready to head out to the field (two days without flying:() so let me collect my thoughts on how to answer while flying and will get back later this afternoon.

And yes there are some very simple methods while maybe not as scientific or as accurate as the graphic/computer methods it has been working for modelers/experimenters since the 'beginnings'

John

Should have stopped at the lake bed John, it's right on your way. All the Bob's and Jim's would have loved seeing you there. When I have an unknown plane I use an on line CG locator but a much simpler one. I hate typing URLs but I have posted it here several times but no one has ever made it a sticky. I will have to look for it again.

http://adamone.rchomepage.com/cg_calc.htm This is a simpler calculator to use when a plane is complete with all controls installed.It's pretty much the same thing but shows both sides of the plane and very easy to follow.

The way I've been adding lead for the last few years is to hammer it flat and CA it on to the covering. It never gets noticed, it doesn't affect the aerodynamics of the plane, and it never falls off. When you hammer it flat, you increase the gluing area dramatically.

Remove a servo from the tail (if so equipped) and add a lead shoe to the servo case and reinstall.

Bolt lead (stick-on or wheel weights) under the horizontal stab. Best method is to open an access point in the fuselage.


Add a lead shim between the tailwheel bracket and the fuselage.


Drill 1/8" holes and epoxy nails in the rudder.


Move a battery back behind everything.


Use shorter engine stand-offs.