Is balancing really necesary? Can I just buy a prop and stick it on the plane?

Electrolight

Balancing what??? The prop?? You can get away with not balancing it. The plane?? You can get away with it if you don't mind taking the plane home in a trash bag!!!

Ken

ive never balanced a prop nor have i had any problems as a result of that but i dont fly 3d or anything which i can only imagine an unbalanced prop may cause problems..

It's not a matter of being necessary, but more the likes of being safe.
Chances are that the prop you buy will be perfectly fine. The plane you build may be fine too, but if not the following are just a few examples of the possible consequences:
- Your engine may wear out sooner
- Excessive vibration may cause your engine to come loose and possibly leave the airplane, striking some 10 year old kid in the head causing a trip to the hospital for him and a trip to court for you.
- Tail heavy plane is uncontrollably and scenario above happens

The decision is yours.

(sorry for being overly dramatic, but you get the point.)

Vibration wears servos especially. Depending on your receiver padding, it can kill the receiver, but usually only does that in flight, and you can blame the crash on something else.

And today we had a case of engine vibration pop the head off one engine bolt and the added vitration had the other three out before the guy recognized what was happening and got the airplane down. The guy showed me the airplane when I drove up. It was pretty amazing because he'd noticed the airplane acting funny and had tried to throttle back and it'd sorta done so but then gone back to WOT. Turns out the engine went very sour when it went to WOT, wasn't producing power but wouldn't shut off. And was held to the airplane by the cowl around the muffler, the throttle pushrod, and lousy power. Never seen one like that. But have seen engines fly off.

I guess I've seen about one instance a year since the 60s where the head was snapped of one or more engine bolts. Usually the ones that don't break off hold the engine to the mount for awhile. And you spot the engine shaking.

Beyond that, and the reasons already mentioned, no others come to mind.

Absolutely! Just make sure you get a few replacement motor shafts while you are there to buy the prop, because the vibration will fatigue the metal and the shafts will break shortly after that.

Okay so It seems I could fly without a balanced prop but thats not such a great idea. Got it.

Electrolight

Truth be told, so far there has only been one brand of prop that I have bought that have been consistantly well balanced out of the package.
I have had numerous Master Airscrew props (all styles) APC, Power point and Zinger.
I am now using Graupner props and so far (6 props ranging from 11x6 to 14x7) have not found an unbalanced prop and the preformance is top notch.

Oh PLEASE!!!!!!!!!

Gimme a break!

I have been flying for well over 40 years.

I have engines that are more than 20 years old

I have balanced a prop exacty twice in my life (Both times during the winter when I was totally bored) and I have never had any problems with ruining bearings or crank shafts.

Also, none of my planes have ever shaken themselves to pieces, nor has an engine broken its bolts, nor have I ruined any servos or gotten Rx interference (And I don't pad my receivers, I velcro them in place)

One of the major magazines did an article a while back on balancing props and came to the conclusion that (except in extreme cases or on very large engines) it is just not necessary.

Electrolight, I'll make you an offer - don't balance your props and if you burn out a crank shaft in the next 5 years, I'll buy the engine from you for TWICE what you paid for it.

I have to agree with Minnflyer. On the times I have checked the balance of props, I found very little difference. I even go so far as to run sand paper over those razor sharp edges to tone them down and still don't balance. Never had engine trouble or excessive vibration to airframe.
But I most deffinately do balance the airplane, front to back and side to side.

You know, I presumed he was talking about flying electric motors, which have much smaller diameter shafts than the comparably powered nitro engines. I have never flown my nitro engines without balancing the props, nor my electric motors, and never will.
To each his own.

The concensus at my club is that balancing is really only necessary for large props, especially wood props, and even then some guys don't bother. I've flown electric and nitro planes for a couple of years now, and I've only balanced props on my Super Tigre G2300 (a 1.4 size engine). If you have a balancer and don't mind taking the time to do it, go for it, it can only help. If I ever get more vibration than normal from one of my setups, that's probably the first thing I'd do (check prop balance), but I've not had that problem yet.

I should emphasis that I'm not saying "Don't" balance your props. It's a good thing to do.

I'm just saying that in 99% of the cases it's not a necessity. And in 100% of the cases for a beginner, it's not necessary.

You have a lot of responses about the prop being balanced, I want to make sure you understand that the PLANE needs to be balanced. I don't think anyone will disagree with that. As for props, you have seen where some say yes, some have never had problems. I want to make sure you understand that you should absolutely check the balance of your plane, (laterally as well as longitudinally) before every flight.

It should be slightly nose heavy (with tank empty) and should be level when checking balance from nose to tail (one wing should not be heavier than the other).

That's somewhat over the top, don't you think.

The vibration usually fatigues the metal in the mounting bolts long before the big thick hardened shaft even thinks about fatigue. And the bearings would take the grief before the shaft anyway.

I can't remember all the numerous times I've seen bolt heads snapped off. What beat them off....... you think it might have been vibration?

And what caused that vibration? The normal engine vibration? yeah, sure........

Check your props for balance, beginners. It's a sensible thing to do. It might just save you an airplane some day. Might save you popped mounting bolts or allow your RXs to grow old gracefully.

You cannot predict when or if a prop mfg has a bad run of props. Think they won't ever make an out of balance prop, or that you won't be the one to buy it?

BTW, if you are the beginner who knicks a prop on landing, you'll have a prop balancer to use to see if the prop is still usable. And the experience to use that balancer properly.

Any mechanic will tell you, If it spins , balance it.

ok Let me start off by saying I balance my props..I also paint my prop tips before I balance...anyway when we get all done with our newly balanced props we proudly install our props on an engine that has but one piston that moves all that weight closer and farther from the thrust line at 10,000 times a minute.
any thoughts?

Exactly