I have a .25 sized engine that runsw with A 5x6 prop on it, I have just started a few weeks ago and have a new job and not much money. How big of a deal is it for me to balance my prop, I will buy a prop balancer in about 2 weeks (Pay day). does anyone have an Idea to make my own.

Thanks, Dave Trimmer

A 5x6 on a .25? Can you confirm that size?

Commercial balancers are nice, but not necessary. You can make a prop balancer with some wood, a couple razor blades, and an appropriately sized piece of drill bit stock. Even something like this is better than nothing: http://www2.towerhobbies.com/cgi-bin...?&I=LXK247&P=7

And if you have purchased a good quality prop and have not re-drilled it or modified it, I have found that they are almost always balanced well enough to run OK.

I use that fingertip balancer that Chuck posted a link to. I think it works pretty good. Don't know why you'd need anything more than that.

Having learned the hard way, it's worth the few dollars to buy a decent balancer like the Dubro or others. I double checked my props balanced with a cheap balancer and found them all needing to be rebalanced. It's a small engine, but an out of balance prop can damage the engine mount bolts, servos and receivers, and glue joints. They can also rattle out your landing gear bolts like it did mine.

edited for spelling

One "hidden value" of balancing props is that you discover the bad ones before you put them on your airplane.

Most times nowadays, props are pretty well balanced. But you WILL find some that are lousy. And the WILL beat your RX and servo's and airframe to death. Sometimes slowly, sometimes fast.

There is a dead cheap way to make your own balancer. A piece of dowel that just fits your prop with a small hole in the center with a string through it works great. Glue a washer to one side of it to keep it from slipping through the prop.

To use it, thread the string through the prop's hole. Pull the dowel into the hole, and the washer stops it there. Hold the string and let go of the prop and it'll hang down with the heavy blade hanging further down than the light one.

I made myself a couple of these puppies. One fits props. I take it with me to the LHS when I'm buying props. Why buy the bad ones? I leave them at the hobby shop for the guys who think you don't need to balance props nowadays. Another one I made is larger. It fits my lawnmower blade. I sharpen the thing every year and balance it true. Someday I'm gonna put a tuned pipe on the sucker and start running 40% nitro and have lots more time to fly. I wish APC would make lawnmower blades.

Dubro's teeter balancer is a good one. DO NOT try to modify composite props to balance one. They are usually well in balance form the factory. If you get a bad one, take it back. Wood props can be balanced easily. Lightly spray the front of the light blade with clear poly-U until it balances.

CAUTION - if you run the prop you mention on that .25, you'll risk blowing the engine. try something like a 9 x 6.

Dr.1

There are several ways to balance a composite prop like the APC. I've never bought one that was balanced right.

Sometimes, adding or subtracting will not balance a blade the is heavy spanwise. You need to do something about the hub.

There are several ways to balance a composite prop like the APC. I've never bought one that was balanced right.

And I've never bought one that was OOB. Perhaps I should have been more specific to not sand, carve, or cut a composite prop to balance it. OK, let's hear your ways.

Dr.1

Are the composite props being discussed APC props ?
I use 10x6, 12x6, 13x6, and 14x6 APC props and according to the Top Flite prop balancer every one of them has been out of balance. The props have been purchased direct from APC, Tower, and 2 different LHS. I have carefully checked the balancer and I am confident that it is not giving false indications. No matter which way the prop is turned on the rod or which way the rod is installed in the stand the heavy blade remains consistant.
For the past 3 years I have been scraping or sanding the leading and trailing edges to balance the prop, I usually dull the edge of the light blade too with 150 grit sandpaper while I am balancing the prop. I have not thought this to be a problem until DR1 said not to do this. DR1 I know you have stated that you have never needed to balance a composite prop and so far I have had to balance every one I have ever purchased if sanding the edges is the wrong way to do it what is the right way ?
I just checked the APC website and there is no mention of prop balanceing.

`I once got hold of a couple of APC 11 x 5 props which had one blade obviously thicker than the other. I sanded the thick blade down to balance them. I'd say that well over half the props I have checked, most brands, have needed balancing. I don't know any serious competitive flier who does not balance their props.

I also have not found the APC props to be balanced from the box and have used a light sanding to balance them out with no problems so far I would like to know why and how to get thiese props to level out properly for a while I thought the balancer had a problem although there isn't much to go bad on one that I can see.got some wood ones and with a little light sanding and a coat of sealer they were right on the money.I would rather use a plastic prop though as one bounce or touch on the ground and all they are good for is picking your teeth with .and that gets a little pricey for tooth picks

I too have encountered plenty of off balance composite props. Sometimes they are pretty close, but it's rare to get one that's perfect. I'm a bit compulsive about balancing. This comes from dealing with boat props where they can be spinning at more than 25,000 RPMs.

Here's what Master Airscrew says about adjusting the weight of a blade:
To Add Material: For g/f nylon props, place modeling clay or silver solder in the holes in the back of the hub of the light side until balanced. For wood props, try adding paint or nail polish to the back of the blade.

To Remove Material: For g/f nylon props, use a pocketknife to trim the edges of the heavy blade. For both wood and g/f nylon, use sanding paper and take material from the heavy blade to bring into balance.

APC does not provide a balancing suggestion.

Gee, I've used APC props for many years and not gotten a really bad one. I wonder... I use a Dubro teeter balancer that is good enough for 15K RPM on a 10" prop. Someone who runs higher RPM may want a more finely balanced prop.

Scraping the edges is good. APC props have a sharp flashing that needs to be removed. What I would be hesitant about doing is sanding the face or back of the prop. that might produce scratches that may set up stress line that could cause failure. If there's no danger of this, I wish a prop "expert" (maybe someone who works for MA or APC) would step in and set the record straight. If I did anything to the face or back of a composite prop, I'd scrape, not sand.

Dr.1

You just KNOW I had to chime in on this one.

I have been flying for longer than most of you have been walking, and to date I have balanced 2 props. Neither needed it, I was just bored.

So I recommend you save your money and spend it on something you actually need.

I've got to agree with Minnflyer on this one.

I used to spend time balancing props on all of my planes. But I found it to be a futile practice. You can balance the prop but there are too many things out in the world to throw that prop back off balance. Touching the runway with prop, having a rock or pebble kick up into the spinning prop, even kicking back against a chicken stick can change the balance. Because of all of this I quit balancing props long ago. On a new prop I take a quick swipe along the edges with some sandpaper to remove the razor edge that some have, then I put it on the plane and fly.

I have engines that have literally hundreds of flights on them and I've never had any problems that come from and "out of balance" prop. IMHO we have enough things to worry about in this hobby without making extra work for ourselves. Not spending time balancing props is time I can spend on other things.

Just my 2 cents worth

Ken

Personally I think you can't hurt a thing by properly balancing anything that is spinning at thousands of rpm's. I buy the gadgets and balance. One of the homemade balancers described should do a good job.

I balance my props, it only takes a few minutes so why not?
Do I really need to? Probably not.
Does it hurt? No
I haven't gotten one yet, but eventually I expect to come accross a prop that is way out of balance so at least checking them should be on the to do list. IMO

If a wooden prop gently swings to the heavy side, I balance it. If it drops like a stone and slams into the table, I return it.

Dr.1

Nothing wrong with balancing your own props instead of returning them....imo. I use a Dubro balancer.

I will sand a small patch on the back side of the heavy blade if an APC. If it is out of balance spanwise, I will sand a little from the hub area. I balance props with the spinner and backplate. I also smooth out the leading edge flash with sandpaper.

To each their own. No problem here.

I always check the balance on every new prop with a finger balancer because I think this is about as accurate as is needed for normal sport flying. The main reason I like them to be reasonably well balanced is to take some of the load off the engine's front bearing (it takes a little extra load off the rear bearing as well). The engine's themselves are so far out of balance that anything from the prop would be almost unnoticeable if the prop is reasonably good.

I've always sanded the top (curved) surface of any type of prop to get them to balance but I'm not an expert (that's for Dr1 ) so I checked on a guy who makes composite props, both CF and GF, for racing and sport work. His method of balancing is to sand the props and gives a finish sand with 1200 paper but that's purely for aerodynamic efficiency.

Hey Downunder,

I have a finger balancer and I used it between two identical drink glasses. When I bought my Dubro balancer, I went back and checked some props. They were all out and needed rebalancing. The finger balancer still got me close.

I once landed a plane with only one engine mount bolt left. Two were missing. One had backed all the way out and was trapped by the engine. I was using a 3 bladed prop that had never been balanced. I later found it out of balance by an unbelieveable amount. Looking back, this is probably why I lost a main gear on that same plane about a week before. I came in to land the gear left the plane cleanly. It had popped the heads off of the plastic bolts as they had both vibrated out a few turns.

Ok So here is a question...
I have a new saito 82 on a new Funtana .40 flipping a 14x4w APC and am foaming the tank because the vibe is so bad. I have been really trying to balance the prop and no matter what I do it seems to still swing down. If you have alot of vibe, and the prop is as close to balanced as possible, what options do you have to reduce vibe? Can somthing in the motor be bad that is causing the vibration?

Cheers!
~Tip

My balancer can even do prop nuts
I don't find to many props balanced as is
it take a wopping 2 mins to balance
who knows it might add to the life of my radio gear and batt or my engine bearings or maybe not only the shadow knows for sure
at least thats the main reason I have read about for balancing any way
who knows who cares if you do it or not it up to you

I have found that APC 12.25 x 3.75 props never seem to need balancing, however other APC 10X6 props often do need balancing. I wonder if some props are made using more precise tooling or molds?