Adding weight to Nose Heavy Tower
 

I was just wondering if it matters where you add weight to the plane. Thanks

RE: Adding weight to Nose Heavy Tower
 

If you add it as far from the CG as possible it takes less total weight than if you add it close to the CG.

RE: Adding weight to Nose Heavy Tower
 

Yes. It matters.

First, you want the weight to be on the other side of the plane's CG from the "heaviness" if you will. So, since your thread title says "nose heavy", you'd want the weight to be aft (rearward) of the CG.

Second, the FARTHER away from the CG, the LESS weight you'll need. Simplified, you can do some basic multiplication and arrive at some numbers. Multiply weight x arm (arm being length from CG), and you'll get a "moment".

For example:

Put a 2 oz weight 12" aft of the CG, and you'll have a 24 oz-in moment.
Put a 1 oz weight 24" aft of the CG, and you'll get the same 24 oz-in moment...and thus, the same change to the CG.

So...yes. To balance a nose heavy plane, put the weight rear-ward of the CG, and the farther to the rear, the less weight.

Also worth noting...sometimes simply MOVING some weight a bit will help. The math works the same:

If you have a 6oz battery 6" forward of the CG, that's a 36oz-in moment. Move it back 3", and you cut the moment in half...which would have the same effect as adding an 18 oz-in moment rearward. So, even if you don't move stuff to the other side of the CG, moving something CLOSER to the CG can have the same effect as ADDING something to the other side.

RE: Adding weight to Nose Heavy Tower
 

Here, btw, is a fairly good "primer" for understanding balancing of forces:

http://www.grc.nasa.gov/WWW/K-12/Win...of_forces.html

And here is a pretty decent lesson on how Weight and Balance are calculated in scale aircraft....for they have the same CG considerations our models do:

http://www.pilotfriend.com/training/...ing/wt_bal.htm

RE: Adding weight to Nose Heavy Tower
 

gboulton, very nice lesson - thanks!

One more thing to add, make sure you check the lateral (left/right) balance after you add weight.

RE: Adding weight to Nose Heavy Tower
 

It's all about torque (weights, arms, and moments). Think about a teeter-totter at a playground. Put a 50 pound kid on the end and a 200 pound guy 1/4 of the way from the datum on the opposite side. The teeter-totter balances, but would you want to add four times the weight to do the same job? In other words, keep the arm long and the weight low to get the balance you want.

RE: Adding weight to Nose Heavy Tower
 

Thanks, rwright. :)

Weight and balance has, for some reason, been one of those things I just sorta "clicked" with from the first moment I encountered it. Dunno why. http://www.smileyhut.com/confused/dunno.gif

Glad the knowledge proved useful to someone. :)

RE: Adding weight to Nose Heavy Tower
 

Best weight and balance tutorial for beginners on RCU to date.

Rob Stewart

RE: Adding weight to Nose Heavy Tower
 

Aw shucks. [sm=red_smile.gif]

I respectfully disagree, but thanks. :)

RE: Adding weight to Nose Heavy Tower
 

Thank you!

RE: Adding weight to Nose Heavy Tower
 

My plane's manual also talks about adding the weights to the side opposite the muffler. I don't know how much the lateral distribution of the weight matters, but I imagine it does.

RE: Adding weight to Nose Heavy Tower
 

You're much - much better off moving stuff than adding weight that doesn't contribute to strength or anything else. You would be increasing the wingloading by adding weight. One other suggestion....if you move your battery....be sure and secure it or it will become a projectile inside your model on a rough landing. NOT A GOOD THING MARTHA !

Flash

RE: Adding weight to Nose Heavy Tower
 

Did you balance it right side up or inverted

Balance it INVERTED...becuase you don't wanna be tail heavy.lol

Move the battery pack back behind the servo or wing mount former...before you add lead.:D

lateral balance matters alot...becuase it won't track straight when you pull into a vertical

tape some cions to the wing tip if your at the field.

RE: Adding weight to Nose Heavy Tower
 

I keep telling folks to stick with 12 ~ 13 ounce engines on the Tower Trainer, but they keep putting on ball bearing .46s and then having to compensate for the extra quarter-pound of weight by adding more to the tail. Lighter flies better.

RE: Adding weight to Nose Heavy Tower
 

It's worth noting here that lateral balance works the same way as fore/aft balance. The farther from the CG the weight, the larger the moment, and thus the greater the impact on balance. For that reason, it's usually complete overkill to try to offset the impact of a muffler being on one side or the other. Unless it's a BIG heavy muffler, chances are pretty high that the difference it will make will be negligible, especially in all but the most demanding of precision flight situations.

If lateral balance is off, as suggested above, usually a very mall weight (like a coin) taped to a wingtip (or even just tape itself) will be enough, and is a quick fix at the field.

For a more permanent (but not as elegant as some other methods) solution, you can use the commonly available stick-on weights (just be sure to keep an eye on them) or, if you can find a screw that works at a particular location, just drill a hole for it, chase the drill bit with CA, and then insert the screw under the wing.

Obviously most preferable is to balance the aircraft laterally before sheeting/covering the wings, and insert weights into the wings themselves by whatever means seems appropriate. Just make certain it's secure....the weight rattling around in there is bad. ;)

Finally, before you go adding weight to ANY plane, as mentioned above, it's ALWAYS preferable to try to find ways to solve the issue by MOVING weight...or, in the case of a kit, REmoving weight. If you find you have, say, a lateral balance issue, take some time to consider just how much weight is needed to bring things into balance. If you're looking at only an ounce or so, you can easily make that up with a little extra sanding on the heavy side's wing sheeting...or even by simply carefully weighing sheeting pieces, and distributing them such that the heavier ones end up on the "light" side.

Last but not least, you'll often hear a lot of "balance it inverted" or "upright" or whatever...depending upon the type of aircraft. I HIGHLY recommend to ANYONE the construction of [link=http://home.mindspring.com/~the-plumber/Vanessa%20CG%20Machine.htm]a Vanessa CG machine[/link]. It's incredibly simple, very inexpensive to build, and is a DEAD ON reliable method of determining the current CG of ANY aircraft. The beauty of it is it can be used for everything from a 3d slab foamy to a giant scale bipe:

http://img.photobucket.com/albums/v1...IMG_0013-1.jpg

Indeed, with a little thought and creativity, it can even be used to check the lateral balance of the aircraft. :)

RE: Adding weight to Nose Heavy Tower
 

How do they Tower RTFs with the .46s come balanced?


I balanced mine out with 6oz. I'm farily sure the .46 will be well worth it despite having added weight. :)

RE: Adding weight to Nose Heavy Tower
 

You added 6 ounces of weight to the tail, plus you added 4 or 5 ounces of nose weight you added by choosing a .46 ball bearing engine versus a .46 LA or GP-42 engine. You increased the all-up flying weight of the plane a full 12% (from approximately 80 ounces to around 90 ounces) and the wing loading about the same percentage.

The added 1,500 rpms you'll get from your ball bearing .46 will sound cool, but won't provide a significant performance gain on your trainer. Your trainer will cut through the wind better because of the additional weight.

It will glide more poorly and land faster, however, because of the additional wing loading. The .46 ball bearing engine will also likely drink fuel faster than a .46 LA or GP-42, and you'll be enjoying shorter flight times. Don't run out of fuel in the air, because your heavy trainer with it's shorter flight time won't glide quite as well as if it had balanced without all of that additional weight.

Every time you have to straighten out your bent landing gear wires, remember that it probably wouldn't have been necessary if you'd paired your airframe with the appropriate engine. Twelve percent more weight on those landing gear wires will take its toll every time you don't feather your landings in just the right way.

Good luck, and good flying!

RE: Adding weight to Nose Heavy Tower
 

This is incorrect info for this situation.

The plane is a Tower Hobbies Trainer 40. Always balance a high wing trainer upright, not inverted

RE: Adding weight to Nose Heavy Tower
 

Why, then, do they put their. 46 on their RTF packages?

RE: Adding weight to Nose Heavy Tower
 

I can't speak for the Tower Trainer .40 RTF package. I've never owned or flown one. I have built and flown the Tower Trainer .40 MkII ARF previously. I built and flew it with the O.S. Max .46 FX ball bearing engine and I suffered with bent landing wire and faster landing characteristics. I chose to mount my receiver battery far back into the rear fuselage rather than to add additional weight.

Frankly, after building my ARF I too was asking the same question about the RTF version: How could Tower Hobbies possibly balance out their RTF with a 16.9 ounce engine on the nose? I'd have to guess that Tower simply ships them out in a fairly nose-heavy state. If I ever get the chance to examine a new one fairly close up, I'll definitely take a look and try to answer the question.

RE: Adding weight to Nose Heavy Tower
 

I'm with Yetti on this one - the RTF version comes with a Tower .46BB engine, and maybe I am just that naive but I can't imagine the manufacturer of that plane adding 6oz. of dead weight somewhere, so how do they get that package to balance?

Well before I hit 'OK' to post this, I just looked at the Tower Trainer manual, and they say "...if the plane needs balancing...add weight," and they show a STRIP of lead weights added to the tail of the plane - 9 of them located under the left side of the stabilizer. Absurd.

Yetti, can you get an extension or a switch and mount the battery behind the servos in that plane?

RE: Adding weight to Nose Heavy Tower
 

Yes. I have an extension that will allow me to mount the batteries behind the servos. How do you suggest I go about it?


The battery is 3.3 oz.

Another note: I added 3.75 oz, not 6. So, if I mounted the battery behind the servo tray, this would leave me about balanced, but I still might require more weight since the battery would not be as far back as the weights.


I had the RTF tower several years ago. In fact, I still have it, actually, minus the wings. That's where I took the .46 from. I remember flying without worrying about the CG. I didn't know better back then. Flew fine.

RE: Adding weight to Nose Heavy Tower
 

I was looking over their listed specifications on the Tower website. They show an extra 3/4 of a lb. in weight and the 12% higher wingloading (17oz vs. 19oz per sq in) that I predicted earlier in this thread. That's before you add a strip of add-on weights to the tail to actually get it to balance.

Even with my receiver battery clear back in the rear fuselage behind the servo tray, my plane was still very nose heavy. I just went ahead and flew it that way rather than adding on additional weight. Without adding weight, my plane was better with the battery far to the rear, but still not on the CG mark.

Ironically enough, a ball-bearing .46 would probably be the ideal power plant for the Tower Hobbies Tower Trainer .60 MkII ARF

RE: Adding weight to Nose Heavy Tower
 

It's hard to say exactly without the plane in front of me. Looking at the instruction manual online though, it looks like there is room in the cavity in the tail of the plane, on the left side, opposite where the push rods are. There's kind of a wall that separates the back of the plane with a big hole cut out of the middle of it, and two small holes where the push rods pass through. I would wrap the battery in foam, and drill two small holes on the top of the dividing wall, two on the bottom, and strap the battery, standing on end, tight to that dividing wall using some string or something. Just an idea, you have to play with the layout and see what would work best. Moving the battery that far back would change/create a decent moment about the CG axis, at the very least reducing the amount of weight you have to add. I'm new at this too, but have lots of experience in mechanical things, and know that the least amount of dead weight you can add, especially to something that flies, is always better.

RE: Adding weight to Nose Heavy Tower
 

I was using a .40la for my first few flights. The thing barely wanted to get off of the ground. Once it was up, it was fine, but still seemed underpowered. I can't imagine that, depsite adding some weight, this plane would not benefit from the .46. It's a stump-puller. Sure, faster landings and stressed gear, but I can handle both at this point.