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Ok so you made a trip down to the hobby shop and bought a few propellers.  The next step is to bolt  the props to the engines right?  I have been guilty of this in the past but there are some things you should do before bolting the prop to the engine such as balancing and removing sharp edges.  Checking the pitch is a good idea especially if you are flying the racing events. 

Props come in many varieties and there are pros and cons to each variety.  I am not an expert on propellers but will discuss what I have found over the years by making and experimenting with different props.

The wood prop is still one of the better material choices for a prop.  Wood is the lightest material, even lighter than carbon in some cases depending on the lay-up of the composite prop (resin to fiber ratio) and the type of wood used.  Wood props seem to allow the engine to accelerate at a faster rate than some heavier props.  Attention to the grain type and uniformity of the grain is important when selecting a wood prop.  Most if not all wood prop manufacturers use only the best wood (usually hard maple) but a good tight straight grain that is uniform on both blades will help when it comes to balancing.  The wood prop in my opinion is the most vulnerable to distortion.  After working with wood for the better part of my life I have come to understand that wood has a mind of it's own.  It likes to bend and twist depending on the grain and built in stresses.  A wood prop can be machined accurate and distort when material is removed from the blank in the machining process. I believe this is why the larger blades are more likely to be laminated from several layers of wood. I recently purchased two 20x6-10 props for a Zenoah G-45. I compared these props on a pitch gauge and they were off by two inches of pitch at the tips.  One blade was 10 inches at the tip while the other was 12 inches of pitch at the tip.  This pitch difference is enough to cause the plane to fly considerably faster with the 12 pitch prop than the 10 pitch.  The 20x6-10 means that it is 6 inches of pitch at the hub and progresses to 10 inches at the tip.  If you are off at the tip it will have a greater effect than if the pitch is off at the hub.  Another difference between these props were the airfoil cross sections at the tip. One blade had a thicker air foiled tip while the other was more flat. If the blade is thick enough, material can be taken from the face of the blade (the part of the blade that is facing rearward when mounted) at the trailing edge to remove some of the pitch.

Plastic/Composite props:  These props are inherently accurate due to the stability of the materials used in their construction and CNC molds they are made of.  These props usually utilize glass filled Nylon which further enhance their strength.  These props in the larger sizes (16" and above) become heavy and prone to stress at the hubs under extreme loads such as racing.  

Carbon Fiber and Fiber Glass Props:  True composite props are always hand layed and labor intensive.  The fibers in these props are usually the full length of the blade.  Some of the larger props are hollow and use carbon fiber woven cloth to form the blade shells.  The accuracy of these props are dependant on the fabricators attention to detail but when done right offer tremendous rigidity and light weight.




Zinger 20x6/10 on the large pitch gage.  This gage was designed by Dan Winship and Dave Poland.  Dave did the number crunching for the faceplate and Dan machined the remaining parts.  The gage will accommodate propellers up to 30" in diameter.




The Prather Pitch Gage works well for props up to 13" in diameter.  The slider block and prop retaining nut are held to the face plate for easy access.


K.I.S.S. Keep it simple stupid rule applies to this simple effective prop balancer.  This balancer will accommodate all model aircraft props.  I have machined other conical buttons to fit the larger size prop shaft holes, otherwise use spacers to decrease the diameter of the prop shaft hole.   I like this balancer since I can tell if the prop is balanced from tip to tip or from side to side.  When the prop is mounted on the balancer look at it from the tip and see if the prop is leaning from side to side.  It is important to level the table that you are setting this balancer on with a bubble leveler.  The table will be your reference for blade tilt and the table has to be leveled, otherwise you will be lining the blades up with a slanted table.



The large Du-Bro prop balancer is another good balancer for large props.  The balancer can set on a table with the blade resting on the top wheels or with the blade overhanging a table as shown in the configuration pictured.  The prop was omitted for clarity.  For both wheels to be on top, the front assembly can be removed from the posts and turned right- side up.