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Old Feb 15, 2013, 11:55 PM
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Mini-HowTo
How can I tell the propeller direction?

Hello, I have a very newbie question. When you put a propeller on your motor, how can you tell which way is 'forward'? Forward as in facing the flight path.
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Old Feb 16, 2013, 12:32 AM
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If there is any text on the prop (size markings etc.), the text side should face forward.

To verify: the blades have an airfoil shape - one side is essentially straight and the other has a noticable convex curve. The curved side should face forward.
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Old Feb 16, 2013, 12:33 AM
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Generally, the numbers and lettering will be on the front face of the prop. This applies to APC, GWS, Master Airscrew, Graupner, Xoar, GM, Zinger, Top Flite, and most other brands, but there are a few oddballs.

The most foolproof way is to determine which side of the prop is the convex side. The blades' convex faces always, ALWAYS face forward. Somebody here has a nice little image that shows the concept pretty well. It'll probably get posted soon.
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Old Feb 16, 2013, 12:34 AM
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...

Jkettu posted while I was typing... and, incidentally, posted almost exactly the same thing.
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Old Feb 16, 2013, 11:26 AM
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Quote:
Originally Posted by C₄H₁₀ View Post
Generally, the numbers and lettering will be on the front face of the prop. This applies to APC, GWS, Master Airscrew, Graupner, Xoar, GM, Zinger, Top Flite, and most other brands, but there are a few oddballs.

The most foolproof way is to determine which side of the prop is the convex side. The blades' convex faces always, ALWAYS face forward. Somebody here has a nice little image that shows the concept pretty well. It'll probably get posted soon.
Here ya go.
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Old Feb 16, 2013, 05:47 PM
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Yup, that one
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Old Feb 17, 2013, 11:38 PM
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After you put the prop on correctly, if the motor runs backwards, if you have a brushless motor just swap any 2 of the 3 wires.
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Old Feb 18, 2013, 10:30 AM
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What most people do not realize is that a prop mounted backward, but turning in the correct direction, will still push/pull air in the correct direction, but the quantity of air pushed/pulled will be greatly reduced. I have seen a model takeoff, with the prop unknowingly mounted backward. The plane was extremly sluggish, but it did fly.
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Old Feb 18, 2013, 11:28 AM
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Simple method.

A boat going backwards cavitates. The backside of a plane propeller is concave, the word "cave" appears in both cavitate and concave.
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Old Feb 20, 2013, 01:29 PM
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Quote:
Originally Posted by dedStik View Post
Simple method.

A boat going backwards cavitates. The backside of a plane propeller is concave, the word "cave" appears in both cavitate and concave.
I remember it by "you can always go into a cave"
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Old Feb 20, 2013, 02:26 PM
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Quote:
Originally Posted by dedStik View Post
Simple method.

A boat going backwards cavitates. The backside of a plane propeller is concave, the word "cave" appears in both cavitate and concave.
I hate to be a party pooper but 'cave' doesn't appear in 'cavitate'... At least not unless you jumble the letters around a bit
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Old Feb 21, 2013, 09:45 AM
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I hate to be a party pooper but 'cave' doesn't appear in 'cavitate'... At least not unless you jumble the letters around a bit
there you go pooping on the party again
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Old Feb 21, 2013, 10:10 AM
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/me passes the tp

The root 'cav' is close enough to work as a mnemonic device.

I'm just glad I didn't misspell it and write cavities.
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Old Feb 27, 2013, 05:30 PM
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Sorry about the late post, I've been crazy busy with a new job. Good to know and thank you all.
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Old Feb 28, 2013, 06:29 AM
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Propellers are described as left- or right-handed. Left-handed propellers rotate counterclockwise and are known as "counter-rotating propellers." When the boat with a left-handed propeller backs up, it pulls to the left. When a boat with a right-handed propeller backs up, it pulls to the right.
nstructions
1
Look at the propeller mounted on the motor. When seen from above, the leading edge of a right-handed propeller is to the right of its trailing edge. The leading edge of a left-handed propeller is to the left of its trailing edge.

2
Start the motor and watch, from astern of the motor, the direction in which the propeller turns. A left-handed propeller rotates counterclockwise; a right-handed propeller rotates clockwise.

3
Put the boat in reverse, turn the motor so that it's centered and back the boat up at idle speed. If the stern pulls to starboard, the right side of the boat, it's a left-handed propeller. If it pulls to port, it's right-handed.
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