I am getting ready to order some spare props and all the descriptions I read say "less noise" "quieter operation" I must be a strange one, I want a prop I can hear! I want it to sound like a full scale when it goes flying by 3 ft off the ground! Can anybody recommend a prop that "talks" Maybe theres no such thing, thanks for any ideas[>:]

The only ones I can actually hear are the bigger props some of the sport guys use at our club. Even then only really while the prop is slowing the plane down in a dive. The clearest prop sound I have heard so far was this one http://www3.towerhobbies.com/cgi-bin...?&I=LXGAE5&P=7 and it was on a giant Big STIK. It was really noisy in a dive.

I find Master Airscrew's K series to be pretty loud, especially when the engine is really revving up. I had an 11x5 and a 12x4 on my 46AX; the 12x4 was a screamer! Everyone kept asking what I did to my engine.

You're gonna find the noise you're looking for is caused by a combonation of engine size, cowling, and prop size and pitch...I have an Edge with a 1.60 and a 18x10 APC prop it does not have the noise but the airplane performs well. Now my 60 sized Ultimate with a 75 AX and a 14x6 APC prop does have the noise....All I can tell you is keep trying different sizes and pitch and different manufactures as well

Joe, you do know that the MAS K series is designed for four strokes and lower RPMs?? I still have a bunch of the older style in my box from when the K line first came out. Just wondering??[:-]

Many of us live in areas that have fields with restricted noise issues, so we try to keep the noise down as best we can.

One thing that I keep preaching is that noise does not equate to power. Revving the engines beyond their actual power band does nothing but make more noise and can actually damage engines. The RPM range that engine manufacturers show does not reflect reality. For instance the OS 46 AX specs state 1.6ps @ 16,000 rpm. Yeah, sure.. Ok. try that some time and see how long your AX lasts.

A more practical RPM max goal is about 12,000 RPM. So, if you manage to find a prop that will give you good performance, good acceleration, and good power at 12,000 RPM and gives you the noise you want, then go for it.

But, you will find that the smaller props won't make the kind of realism noises you desire. The sound is there, however, the sound level becomes attenuated by the exhause note. A quieter muffer will give you more prop noise, to a limit. The only real way is to get a larger prop and spin it, but you won't have the power to spin a very large prop with your smaller engine.

If you want that realism, get a large four stroke with a large prop.. of couse, that means a larger plane too.

CGr.

Well, Tower's site says for 4 strokes, but doesn't say why. They don't have MAS in 12x4,5,6 without being K series. So no, didn't really know it but I don't really use them anymore. Thanks for the tip Gene.

The trick to making your prop loud is to get the tip speed up over about 0.8mach.

circumfrence the prop tip is traveling is pi * diameter, or 3.14 * diameter. Multiply by RPM to get inches/min and convert units. Look up speed of sound at your altitude, and compare.

The larger the diameter, the faster the tip speed, the more noise you make at the same RPM.

Of course, when props get going this fast, they also loose efficiency, and that noise is energy that's being "wasted", so the louder the prop, the more energy is going to sound and not into moving air.

If you just want more noise so you can hear your plane better, then the best way is to mess with the muffler, then you get more power and more noise. Depending on the engine and muffler, there is a lot you can do. Many glow engines have baffles in the muffler. OS and Evolution for example. Take the baffle out and you get free power and noise (well, not quite free. You get less backpressure to the tank as well, which may or may not matter depending on your fuel system). On some mufflers, you might be able to drill out the exhaust outlet a little as well.

Take the muffler apart and look for flashing or rough edges as well. I worked over the mufflers for my limited-class .25 combat engines and picked up 3-500rpm just by cleaning out flashing and such in the mufflers. Of course, in this case, the muffler isn't much louder, but you get the idea.

Replacing the muffler works. I have an OS .32 with a Slimline pitts muffler. The outlet area on the slimline is much higher than on the stock muffler, and that little .32 has quite a bark to it now compared to the stock noise. (I also turn it at a low RPM with a big prop, so it really confuses people. It doesn't have anything like the typical small two-stroke whine, it's more like a mini-gasser bark).

If you want a LOT of noise, see if you can find one of the old style non-muffled tuned pipes. They make a whole new category of "loud" possible.

Have fun, and I hope you don't fly near me

For what I have found is more pitch=more noise.
Not really a big difference but you can tell it when the plane fly near in front of you, that is a more scale noise, but as I said not much noticeable.
Best way to get a more scale sound is by using a four stroke engine at around middle throttle in the air.
There is also a big difference in sound when the plane is on the floor than when it is flying.

As Montague said there is also a big difference in sound when you change the shape of the tip, but the difference is more like a buzz than a scale prop. sound.

Good luck.

Ha, you know, I missed the part on the OP where he said "sound more fullscale". I was talking about just making it LOUD, not necessarily full scale sounding .

Ok, for full scale, get the RPM down, and play with the muffler. I've noticed that the Slimline mufflers seem to make even small 2-stroke glow engines sound more like larger engines, and when you match that to a bigger prop at lower RPM, you get a good result. I've done that on the .32 powered plane I mentioned, and also on my .46 powered twin engine Mossie.

I also agree that 4-strokes usually sound better in some applications. I have an old OS .61 FS that I fly with no muffler at all. It's not as powerful as more modern 4-strokes, and not as loud, but with out the muffler, it sounds nice to my ears

I’m getting ready for my first flight next month I thought using wood prop’s would protect my engine, rather have a prop break than the engine?

That's the theory, but in practice the plastic props break well before harm comes to the engine. At least that is true for glow engines up to the 1.20 size using APC, Master Airscrew and Graupner props. If you have a big gasser or some unusually strong brand of prop, things may change. I've bent crankshafts in crashes, but only by hitting so hard that what the prop was made out of had no bearing on the damage .

Oh, I forgot, I mostly fly off of grass. Grass is more forgiving of noseovers and dorked landings that result in digging a divit. But I've also broken plenty of props off on other things besides dirt with out a problem, so I don't think pavement will change things much.

Thanks for all the input guys! I did fail to mention the plane I was referring to Is my new (to me) Bel-air 60 Bipe, It has a OS FS 90 on it and it runs great, 14-6 top flite prop has suffered a few minor dings, I just wanted some ideas on brands before I ordered, I did go with the master airscrew k prop because of my engine the prop was a match, I have a 11X6 master airscrew on my cub and I really like the prop. I wanted a 14x4 but lhs did not have any so went back to 14x6. Little brother will be here tomorrow with new props and more fuel so I will be back in business, plan on burning up that gallon tomorrow between the two planes.......................Still havent maidened that decathlon.............still scared to death of it Maybe after I get good with the bipe[>:]

Check out the thread on my bipe aquisition if you get a chance, pics there too
http://www.rcuniverse.com/forum/m_8682837/tm.htm

...I still think those screaming MAS props sound pretty cool [8D]

I'll admit i like the sound of props ripping in the air.... on my 50cc with a 22x8 3W breakin prop it ripped nicely but went up to a 22x10 Vess for a little more performance less rip i have noticed Vess props perform well but are very quiet props 3w props are noisy which isnt bad either