Im currently using the 3-blade prop that comes with the RTF alpha 60 (12x4 3-blade). Now, i was told by someone to buy a couple Master Airscrew 12x5 props. Im just wondering what changes i should notice with this prop. I understand the pitch and diameter effects, but going from 3-blade to 2-blade stumps me. Thanks

Shorty,

I too have the Alpha 60 and have flown it just for kicks with the stock 3-blade (13 X 4). While it does do it's job on keeping the airspeed down at full throttle, my engine only turns over 9500 RPM and it air brakes too much at idle, so I'll be changing to a 2-blade before my next flying session with the plane. I'll be running a 12 X 6 wood Topflight which is what I happen to have on hand. The 12 X 5 MAS should work just fine for your application.

When you remove the 3-blade you will need to take the drive hub with the flywheel to your vise, and using a socket that just fits over the aluminum hub but through the flywheel, drive the hub out of the flywheel. This will allow other spinners to fit the drive hub. Also remove the limiter pins and collars as they will prevent you from setting the engine. Since your going to a lighter 2-blade prop you will have to reset your settings - high-end and idle mixture, and possibly idle speed. Then your engine should come to life and run like its supposed to.

Also don't forget to check your balance since you are removing weight off the nose and learn to use the stick on the left to control your airspeed while in flight - you don't need to fly at full throttle, 1/2 to 2/3 throttle should be all you need for general sport flying.

Hogflyer

Possibly a bit more rpm and a bit more speed in the air at a given rpm. If the 3- blade is working for you, why change?, although it's fun to experiment and see what else works. The recommendation follows the accepted theory of change in pitch and/or diameter when going from 2 to 3 blades or vice-versa.
If you stay at the same diameter and go from 3 to 2 blades, you decrease the total blade area, which decreases both total thrust and induced drag of the prop, Increasing pitch will somewhat compensate for the decreased swept area of "losing a blade" and induced drag will be a bit less, so efficiency is greater, and the increased pitch also takes larger "bites" of air per revolution, increasing forward motion per revolution. These are all theoretical norms, which vary due to prop blade shape, available torque and actual prop disc diameter.

The suitability of the individual prop is what you will see.

The details that determine prop performance happen to include the number of blades. That detail is not actually of as much importance as most of the other details.

You won't see a difference between "all 3 blades and all 2 blades" in your tests, you will only see the difference between that specific prop and it's suitability to the engine/airplane, whether it's the 2 you're testing or the 3.

I've got a model with an OS55AX on it that flies a number of 2bladers great. It flies a number of 2bladers not so great. It flies a MasterAirscrew 12x6(3) great. Matter of fact, the best two props for that engine/airplane are the winning 2blader and that MA 3blader. Why? The MA has about the same blade area in it's 3 blades combined compared to the blade area of the combined blades of the 2blader. And the diameters suit the engine's rpm range for both the 3 and the 2. And the pitch suits too. The number of blades make a difference? Yeah, if the 3blader's blade shapes etc were put into a 2blader, it would suck. For that engine/airplane. But that ain't gonna happen, so it's not really a difference that matters.
(edit..... oops, I forgot that I have reduced the diameter of the 12x6(3) by 1/4" to better suit the rpm range of the engine. now, that said, do you see how that shows the relative value of the number of blades.)

The debate over 3 versus 2 is much to simple. And doesn't actually apply to the individual props we happen to have available to test.

My P47 flies better with a MA 3blader than most 2bladers. The best 2blader MIGHT fly better than the 3, but would you fly a 2 instead of a 3 on that sucker?

My Skybolt flies as well on a 12x6(3) as it does on the 2bladers that engine/airframe prefers. So I fly what I feel like flying that day. I have noticed that the 3blader MIGHT pull better on really hot summer days. I'm not sure that theory backs that up, but theory is just words on paper. How the airplane pulls verticals is right out in front of me, and the 3 seems to beat the 2. Go figure. Or go argue theory, I'm going flying.

Don't buy a couple.

But do buy a couple of different props.
My OS60 on the Skybolt works well with a number of props. A number of them are 13x6. A couple of those are Master Airscrews. There isn't a magic prop or mfg or number of blades.

The manufacturer isn't really a deciding factor. Nor is the style or shape of the blades.

You'll find that the pitch matters but not by itself.
You'll find that the diameter matters but not by itself.
You'll find that the number of blades is actually not very significant. It'll only reduce the number of samples that suit your engine. For example, there probably aren't more than two or three 3bladers you can even buy that are going to come close to suiting your 60.

What matters is the individual stick with a hole in it that you've just bolted on your engine. And the conventional sound byte wisdom about props really doesn't help sort out or predict the gamble we take when we strap any prop on that engine.

Ma 12x6(3)
The new EFlite line looks excellent. Try the 13x6. It's working excellently on the two engines/airplanes I've tried. If the engine won't swing it, try the 12x6. (This new line isn't in every LHS.)
The TopFlite 13x6 PP works really good on my 60s.
The Zinger 12x6s seem a bit light on my 60s, so you might try them if the above are turned slowly by your 60s. It these seem too fast, try the 13x6s

If any of these seem to make your airplane too fast and especially too fast on landing, try 5" pitch props. But expect to need more diameter.

edit........... wrong name for prop mfg. Most probably EVOLUTION props.

BTW, the new EFlite line of props are reinforced composites and look very expensive. Heck, they're individually packaged so ought to be expensive, right. So turn the package over and look at the price.
Amazing. Now you can't really see them through that package, so you figure they've gotta be cheaply made. OK, open the package (it just slides open).
Amazing. Now you're confused.
They look very expensively made.
And they are almost cheap.

Now fly one.
Amazing.

Where do you find these glow eflite props? I can only find the electric ones. thanks

Thanks for the information. I bought the 12x5 blades a few months back, thinking I was gonna need them after a few bad landings on my trainer. Thankfully, there still sitting in my basement reamed and balanced. So, i was just curious of what difference i'd see, because I might like to try one out next time i go fly.

Both LHSs have them. They are not really obvious because they're hanging up in individual packages. And the package is dark. They don't look like props, just some long slim dark packages.

"Both LHSs have them." What does that mean? MAS doesn't even list them on their website. All they show is "Electric Only" props and they wouldn't be safe.

LHS is internet for Local Hobby Shops. The two shops that are my local hobby shops (LHSs) both have them. That's what that means.

edit.......... see post #14 for name of this company..............
xxxxx is a company that sells R/C stuff. Most of is electric stuff, but these are a surprise. Since there are more and more VERY LARGE electric motors being put into R/C models, it makes sense that they would make props that could be used for electric motors that would power 46size and 60size models. And they have.

EFlite's new line of props probably won't show up on Master Airscrew's website anytime soon, and for sure any prop marked "Electric Only" wouldn't be safe on any glow engine.

OK, the way you wrote post #6 I saw (wrongly) an implication that these were supposed to be MAS products. Thanks for clearing that up and that you were talking about YOUR LHS's. I would have thought that with 5 of the first 10 posts being yours da Rock, that could have been clarified better.

OK, I did screw up.

Those new props are probably Evolution's.
I really did not pay close attention to the packaging after I discovered what was in it.

They have a BIG modern looking "E" on each blade and since I don't do a lot of electric stuff, my mind picked out about the only mfg I know that starts with an E and associated EFlite with the props.

They're Evolutions.

And worth a look.

Sorry for the misinformation.

OK, now that I know what to look for I found at least one place that stocks them online and can show a picture of a 13x6 version

http://www.gravesrc.com/Evolution_Pr...p/evo13060.htm

Thanks da Rock

thanks i will have to try those out.