Can someone describe the performance characterstics between wood and fiber props?

I'm done with my Four Star 60 which has a Magnum 91 four stroke.

I bought a couple wood props and one Master Airscrew, all 14x6. But, I'm not sure which to use.

I noticed the blade on the Master Airscrew is much wider (thicker?) than the wood props.

Please educate me.

Thanks,

JPF

Stick with the glass/nylon (master airscrew) props untill you're really comfortable with the plane. One 'ding' on landing, and wood props shatter.

The black props are 'glass filled nylon' and are quite strong. It is also highly reccomended to paint teh tips white (pink, yellow, red...) so you can see them the prop circle, as these props virtually dissapear when spinning. Just be sure to balance them.

Master airscrew also make a 'Scimitar' shaped blade that a lot of people like.

As for them being wider. Dunno. Figure it's in the manufacturing process, or the airfoil of the design. Someone else?

The more flexible the material, the more the prop will "self-adjust" its pitch as load increases. The old white nylon Top Flite brand props could flex enough after being boiled that they essentially functioned like constant speed props. The automatic variable pitch effect was an unintentional bennefit for some purposes.

Since some plastic/composite props are more flexible than wood, and some are MUCH stiffer than wood... you can't simply say composit will always do one thing and wood another. The blade shape and airfoil has more effect than the material, as long as you aren't significantly flexing the material.

Composite/plastic props tend to be heavier than the wood props. The added weight can help with breaking in some engines. The increased weight gives a better flywheel effect, helping with starting a cold engine and giving a smoother idle. (the weight differences can be useful for minor CG adjustments too. [img]i/expressions/face-icon-small-wink.gif[/img] ) After the engine is broken in... the flywheel effect of the heavier props usually isn't significant enough to be the reason for choosng composite over wood.

Bolly Clubman props are more flexible than most wood props. Master Airscrew's black nylon is more flexible than the wood, but the thicker material tends to compensate. APC's grey props are stiffer and lighter than the Master Airscrew and Bolly Clubman props (generally...). The carbon fiber composite props are the stiffest (and most expesive...) And then there's the CF stiffened wood props....

Wood props tend to have a better scale appearance on some models. (especially planes like the Piper Cub.) The Master Airscrew "Classic" series is intended for scale appearance on planes that had metal props.

You'll find through experimentation that there IS a performance difference with the wood prop vs the Master Airscrew or the APC.... Fly with each type to make the determination of which you like better. (My O.S. .91 4-stroke seems to work better with the APC 14X6 than with the Zinger wood or the Master Airscrew black nylon. Your Magnum may do better with the wood... or the black nylon.) I'd start out with the black nyln if the engine has low operatng time.

I use the Master Airscrew 14X6 on my Sato .91 and I like it better than the APC prop with this engine. A nice by-product of the wide prop blades is thay add more drag at idle making it easer to blead off airspeed on down lines and landings.

Jerry

In very general terms, wider chord propeller blades were intended to be better suited to four strokes with their higher torque and also were intended to work well with longer stroke 2 stroke engines that also tend to have a little more torque than the average short stroke two stroke engine.

As an aside, two bladed props tend to offer better cruise/top speed performance due to their improved aspect ratio while three blade propellers tend to offer better low speed performance due to better disc loading at lower speeds.

In general, R/C propeller efficiency has been pretty low - maybe 50% - compared to a full scale aircraft expectation of 80% prop efficiency. However the newer generation propellers and APC's new props in particular are reported to have an 80-85% efficiency. This means a lot more performance. So you really need to just experiment with several types as well as with pitch and diameter until you find a prop that works best for your particular aircraft, engine and type of flying.

A key to getting good prop efficiency is matching the prop to the aircraft. There's no point in putting a prop with a "theoretical" pull speed of 150 to 200 mph on a trainer. (calculate "theoretical" by multiplying pitch by rpm, convert inches to miles, min to hours.. you'll be there, as the pitch is inches per revolution.) If the calculated pull speed is more tha 50% higher than the expected maximum flyig speed (trainers... about 70 mph) You've got too much pitch. (at .40 size, trade 1 inch pitch for in inch dia... 11X4 or 11X5 is usually a better match for a .40 size trainer than a 10X6)

We don't have practical in-flight variable pitch props available for our models... or you'd be using another channel and getting a wider performance range out of almost everything you fly.