Prop Balancing Made Easy

Feb 13, 2014 13 Comments by

I have been often asked, “Do I need to balance my prop?” and the quick answer is always “Yes!” A properly balanced prop will give you more rpm from gas, glow and electric engines. A balanced prop will reduce the wear and tear on your aircraft by greatly reducing vibration, which leads to reducing premature failure to all the components and thereby giving your aircraft a longer life. You need to do it on every prop, every single one. There are several types of balancers on the market today that will do a great job of getting different size props balanced. No matter which you use, the balancing procedure will be the same for all.

1: HOLE SIZING

The first step is to enlarge the shaft hole to a size that fits your engine. If you balance the prop first, then enlarge the hole, you will have to come back and balance the prop again, so save some time by balancing afterward. The best way to do this is by using a good prop hand reamer because this will keep the hole concentric.

2: FINDING THE HEAVY BLADE

The second step is to place the prop on the balancer in the horizontal position to find out which side has the heavy blade.

3: REMOVING MATERIAL

Two methods are commonly used to balance the propeller. The first involves lightening the heavy blade until the propeller balances close to the horizontal position. Use a razor blade or sand paper to remove small amounts of material while rechecking the balance. Don’t forget to wipe off any dust or shavings before re-checking the balance.

4: ADDING MATERIAL

The second requires adding material, generally clear spray paint or thin CA glue with a little kicker to the lighter side of the blade until it balances in the horizontal position. You want to use a fast drying paint and wait until it is dry, because it will be a little lighter when dry. To speed up this drying process I use a blow dryer. Both ways will work well; I generally will remove material from fiberglass/nylon and carbon fiber blades, while using the addition method to the wood blades.

5: PRELIMINARY BALANCE

Once the heavy blade is identified and the prop balanced level or within five to 10 degrees in the horizontal plane you can move to the next step.

6: HUB BALANCING

Place the heavy blade down so the prop is sitting in a vertical position. Check to see which way the prop wants to drop towards horizontal, whichever way it drops, you will need to add some thick CA and kicker to the opposite side so that the prop can balance in the vertical position.

7: FINAL BALANCE

Now move the prop to any position and see if it stays there, if it does then you have a balanced prop. If not keep adjust the amount of CA on the hub by adding or sanding off (in case you over did it) until it does. You may also have to adjust the blade weight to fine-tune the balance.

8: MARKING THE BALANCED PROP

After the prop is balanced, put some type of mark on it so you know it is ready for flight. I use a felt-tip marker to write a “B” on the hub for balance.

Featured News, How-tos, John Reid

About the author

West Coast senior editor About me: I’ve been involved with RC aircraft since high school and have flown just about everything. I started my RC career with scratch-building, but now like many pilots I rely on ARFs to get me in the air. My main focus is on pylon racing, aerobats, combat and scale warbirds.

13 Responses to “Prop Balancing Made Easy”

  1. John Petley says:

    Thanks for the tutorial, but it’s not clear whether you should balance the hub or prop first. If I have a prop that’s already close to horizontal to begin with, do I make it vertically heavy first, fix it, then balance the horizontal. I’ve only ever balanced horizontally, so can you tell me if I’m missing something here. Thank you, John

    • Gary Springer says:

      John, If the prop is already balanced horizontally, then you only have to balance it vertically. But you always want to begin by balancing your props horizontally first. Like the article states, once a prop is properly balances, it will remain at any position it is placed. This is what you are ultimately wanting to achieve.

    • John says:

      I always balance the prop so that it sits horizontally, sanding tips first. Then work on the hub. But I would imagine you can do it either way first.

  2. JDS says:

    I was always taught to remove/add from/to the BACK SIDE of the prop, NOT the front as that alters the airfoil. Hmmm?

    • Rabello says:

      Adding or removing material from propeller tip or the back of propeller, i.e., trailing edge, it makes sense.

      Removing from the leading edge can severely modify the profile.

    • John says:

      That all depends on how much material you are sanding off. I have never had to remove that much to make a difference in the airfoil. However it takes very little material removed from the back side to change the pitch of the prop so I would never recommend working on the backside of the prop. But that is just my opinion, I am sure there are many who will disagree.

  3. Rabello says:

    Maybe when removing mass, it would be preferable to remove material from the propeller tip. The greater the distance from the hub, less removal is necessary. Also, avoid removing from upper or lower surface, as this could modify aerodynamic profile.

    Article very good, I learned some points that I will add to my experience.

  4. James Daniel Arnold says:

    I agree JDS that by removing material from the front (convex) side of the blade you risk altering the airfoil. However I have heard that you should not remove material from the back side of the blade either. For most props (especially for electrics) I have found that a slice of heat shrink tubing applied to the light blade and secured with CA works well and is a lot faster than other methods. Adjust the weight by trial fitting wider or narrower slices of heat shrink. For props where the shrink tubing won’t work I dip the light blade in the heaviest paint I can find at the hobby shop (metalflake gold is my favorite). Dip shallow for a prop that’s close. Dip deep for more weight and sand away only the paint for fine adjustment.

  5. Murray says:

    I use clear nail polish on the back of the light blade. It dries fast, leaves a smooth surface and is fuel proof. It’s also a lot cheaper than CA or hobby paints!

  6. Rick Alba says:

    You can bypass the horizontal and balance both horiz and vertical at the hub. Dave Gierke did an article in Model Airplane News July 2002 on how to do this and 3 and 4 blade props. Doesn’t have any effect on the airfoil portion of the prop when a prop needs material removed. I have been doing it this way since with good results.

  7. Flyoz says:

    remove material only from the back of prop start at tip 1st then toward the hub if well out of balance.
    Same with glue or paint weighting.
    dip tips in say a white paint to highlight propeller arc for safety.

  8. Chris says:

    When you remove material for balancing your your blades, your picture indicates removal from the top of the aerofoil rather than the bottom where there is no change to the lift side of the foil.

  9. Tony says:

    Anyone can balance a 2 blade Prop. How about a three blade prop? That is a little tougher!

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