Ask three pilots at the field which prop brand is best and you will get four answers and a story about a prop that "sounded wrong." The truth is less dramatic. A propeller is a rotating wing, and the right one is the one that matches your motor, your plane and the way you fly. The brand matters less than the line, the size and whether it is balanced and centered on the shaft.
This guide explains what the numbers on a prop mean, how APC's prop lines and RPM limits differ, where Xoar's beechwood PJN props and Master Airscrew fit, and how to balance and mount whatever you choose. It is written for electric airplanes, which is what most of our customers fly.
The Short Answer
Choose the size first, from your motor maker's recommended range and a watt meter check, then pick the brand and line for the job: APC Thin Electric for most powered sport planes, APC Slow Flyer only for low-power park flyers, Xoar beechwood for scale looks and larger electrics, and Master Airscrew for durable nylon sport and pusher props.
- Size: 10x7 means 10-inch diameter and 7-inch pitch. More of either means more current draw.
- RPM limits: APC rates Thin Electric props at 150,000 / diameter and Slow Flyers at 65,000 / diameter.
- Balance: check every new prop. Remove material from the heavy blade; on electric props, clear tape on the light blade is acceptable.
- Centering: let the adapter ring or a carefully reamed hole center the prop, never a sloppy shaft fit.
1. Reading a Prop: Diameter, Pitch and Line
Every prop is labeled diameter x pitch in inches. Diameter is the tip-to-tip span. Pitch is how far the prop would move forward in one turn if it were a screw in wood. Both change how hard the motor works.
Diameter vs pitch
A bigger diameter moves more air at low speed, which gives strong thrust for takeoffs, climbs and hovering. A higher pitch moves the plane farther per turn, which helps top speed but asks more of the motor at low airspeed. A quick check is pitch speed in mph: pitch x RPM / 1,056. A 7-inch pitch at 9,000 RPM works out to about 60 mph. Trainers and bush planes like more diameter and modest pitch; fast sport and pylon models like more pitch.
Bigger props draw more current
Going up an inch in diameter or pitch can raise current a lot. That is why the first step is the motor maker's range. E-flite, for example, lists 12x8 to 14x10 for its Power 46 outrunner, and its own Ultra Stick 40 data uses an APC 13x8E. APC says it does not make specific recommendations for propeller sizes, so the motor instructions are your starting point. Pick from the range, then confirm with a watt meter that amps stay under the motor and ESC ratings.
APC's lines, decoded
The letters after an APC size tell you the line. E is Thin Electric, the general-purpose powered electric prop. SF is Slow Flyer, very light for low-power park flyers. EP is Electric Pusher, reverse rotation for pusher motors and some twins. APC also makes Folding (F) and Multi-Rotor (MR) props, plus glow sport props. Never mount a tractor prop backward to make a pusher; buy the pusher version.
RPM limits matter
APC's suggested limits by line, with D as diameter in inches:
| APC line | Suggested max RPM | Example: 10-inch prop |
|---|---|---|
| Thin Electric (E) | 150,000 / D | 15,000 RPM |
| Folding Electric (F) | 120,000 / D | 12,000 RPM |
| Multi-Rotor (MR) | 105,000 / D | 10,500 RPM |
| Slow Flyer (SF) | 65,000 / D | 6,500 RPM |
A 10-inch Slow Flyer on a hot 4S motor can exceed its limit. If your setup spins faster than the SF limit, use an E prop.
2. APC vs Xoar vs Master Airscrew
All three brands make good props. They differ in material, line-up and what they are best at.
| APC | Xoar (PJN Electric) | Master Airscrew | |
|---|---|---|---|
| Material | Molded props in separate lines built for specific jobs | German beechwood, heat-treated, hand-finished | Glass-fiber nylon (the company introduced it in 1980), plus wood |
| Electric lines | Thin Electric (E), Slow Flyer (SF), Electric Pusher (EP), Folding (F), Multi-Rotor (MR) | PJN Electric, 10 to 28 inch in the spec table | Electric Only series, tractor and pusher, roughly 6 to 14 inch |
| Hub | Through-hole sized so the supplied adapter ring (electric props) centers it | 6 mm (10-14 in), 8 mm (15-26 in), 10 mm (28 in) | Varies by series |
| Published RPM limit | Yes, formula per line | Not stated on the PJN page | Check the series and size |
| Best for | Matching a prop to a measured power system; widest size choice | Scale looks, larger electrics, smooth running | Durable sport props and pushers |
APC: the widest menu
APC's strength is choice. Between E, SF, EP and folding lines, in many diameter and pitch steps, you can tune a power system half an inch at a time, and APC publishes RPM limits for each line. On our bench, APC E props are the default for electric sport planes and conversions because we can fine-tune current draw by size.
Xoar: beechwood for electrics
Xoar's PJN Electric props are made from German beechwood that the company says is heat-treated for strength and low weight. Each is hand-balanced and rebalanced after coating, but Xoar still advises a final balance check before flying, since shipping and temperature can shift it. The spec table lists 10 to 28-inch sizes, with 6 mm hubs up to 14 inches and 8 mm from 15 to 26 inches. Wood looks right on scale models and is stiff for its weight. It also breaks rather than bends in a nose-over, so carry spares.
Master Airscrew: nylon toughness
Master Airscrew says it has designed and made propellers in the USA since 1978 and introduced glass-fiber nylon props in 1980. Its Electric Only series covers tractor and pusher sizes from about 6 to 14 inches, alongside GF, K, Classic, Scimitar, 3-blade and wood lines. Nylon props tolerate grass strips and minor prop strikes well. Check the specific series for its intended use and RPM rating before you fit one.
3. Fitting, Balancing and Safety
A well-chosen prop that is out of balance or off-center still shakes the airframe, loosens screws and wastes power. Five minutes on the bench fixes it.
Balance every prop
APC's technical advisories say most of its props will not need correction, but you should check. Our routine:
- Mount the prop on a balancer through its precision hole. APC says to use the precision-molded hole at the back of the hub, not the drilled hole.
- Set the blades horizontal and let go. If one drops, it is heavy.
- Remove material from the tip of the heavy blade, sanding both upper and lower surfaces evenly. On electric props only, APC also allows clear tape on the light blade.
- Check the hub: turn the prop vertical and see if it rotates. If it does, remove a little material from the heavy side of the hub.
- Recheck at several positions until it stays put anywhere you leave it.
Center it on the shaft
APC says the through-hole should be slightly oversized for the motor shaft so the adapter ring supplied with its electric props does the centering. If you need to open a hole, APC recommends a tapered reamer from the front, enlarging the hole slightly while keeping the reamer away from the precision hole at the back. Never drill freehand; an off-center hole makes a prop vibrate no matter how well it is balanced.
Safety at the bench and the field
Treat an armed electric motor as live. Remove the prop when programming an ESC or binding a receiver. Tighten prop nuts and collets before every session and after the first flight on a new prop. Retire any prop that is cracked, chipped or bent; don't straighten it. And stand behind the prop arc, never beside it, during run-ups.
Conclusion
Prop choice is less about brand loyalty and more about using the right line at the right size. Start inside your motor maker's range, confirm amps with a watt meter, stay under the prop's RPM limit, and balance and center every prop. After that, choose APC for fine tuning, Xoar for scale looks on bigger electrics and Master Airscrew for a tough nylon prop.
Not sure what to spin on your motor? Bring the plane and its motor specs to our Cumming showroom and we will help you pick a starting prop and check it. Browse our airplane propellers or contact us.
Gear Mentioned in This Guide
Xoar 14x8 Beechwood Electric Propeller
German beechwood, hand-balanced, with a 6 mm hub for 40-size electric motors.
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Xoar 11x5 Beechwood Electric Propeller
A smaller beechwood prop for sport and scale models that want a wood look.
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APC 10x7E Thin Electric Propeller
APC's Thin Electric line, for typical 3S to 4S sport setups.
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APC 9x4.7 Slow Flyer Propeller
A light prop for low-power park flyers; mind the lower RPM limit.
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Du-Bro Tru-Spin Prop Balancer
Check every prop, from any brand, before it goes on the motor.
Shop nowFrequently Asked Questions
What do the two numbers on an RC propeller mean?
The first is diameter in inches and the second is pitch, the distance the prop would advance in one turn. A 10x7 is 10 inches across with a 7-inch pitch. Increasing either one makes the motor draw more current.
What is the difference between APC E and SF props?
E (Thin Electric) props are for general powered electric flight and are rated to 150,000 divided by diameter in RPM. SF (Slow Flyer) props are lighter and meant for low-power park flyers, with a much lower suggested limit of 65,000 divided by diameter.
Are wood props better than plastic or nylon?
Not better, different. Xoar's beechwood props are stiff, light and look right on scale models, but they break on hard impacts. Composite and nylon props come in more sizes and survive minor strikes better. Choose by size and job first.
Do new props need balancing?
Check every one. APC says a correction is rarely needed on its props, and Xoar hand-balances its props but still recommends a final check before flight. Balancing takes a few minutes and prevents vibration.
Can I flip a tractor prop around for a pusher motor?
No. A reversed prop runs with the wrong airfoil facing forward and is inefficient and unsafe. Use a pusher prop such as an APC EP, which is shaped for reverse rotation.
How do I know if my prop is too big?
Measure full-throttle current with a watt meter. If amps exceed the motor's or ESC's continuous rating, or the motor comes down too hot to touch, go down in diameter or pitch.
Sources and Further Reading
- APC Propellers: Suggested RPM Limits
- APC Propellers: Technical Support Advisories (balancing, centering, reaming)
- Xoar: PJN Electric Beechwood Propeller
- Master Airscrew: Model Airplane and Multi-Rotor Propellers
- Master Airscrew: Electric Only Series
- E-flite Power 46 Outrunner Instructions (prop range and setup data)
