silent flight

Last year at a funfly I ran into a modeler flying a Extra or an Edge w/ a old Tartan Twin turning about 8000 RPM. On a high speed pass the model exibited a distinct prop noise that I think is caused by the prop cavitating in the air. I just liked the sound and asked what it takes to duplicate it and his answer was only you may have to modify the prop. I even offered to buy the model.
Does anyone know how it is done? We have no noise restrictions at our rural flying site. I have a Midwest Extra 300 Zen g-45 with a Bolly 18-10 composite hoping to incresae the RPM needed. Can I come close?

If any one watched any of the videos of the Tucsan Shootout. Mark Lesbergs model had the sound I am looking for just before the crash.

BaldEagel

I thought I was comming onto a responsable thread about reducing noise, polution is polution noise is polution not only that but a cavitating prop is inefficient.

Mike

rc bugman

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Hi,

Bolly props are some of the loudest props. Try dropping to an 18 x 8 to increase the rpms on your g-45. The other possibility is to increase to a 20 x 8. I think that you need to decrease pitch and increase rpms to look for the noise you want.

Elson

bubbagates

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Certain prop designs are just noisy to start with.

Bolly, Zinger (not the pro version) Master Airscrew, MSC, NX and I think a couple more.

Another way to get prop noise is high rpm just as Bugman suggested. So now take a noisy prop, go down in size and pitch to get more rpm and you will get loads of noise.

You need to be careful, too much rpm and you will toast the G45 in pretty short order as well as sending the prop tips supersonic and possibly throwing a blade which will ruin your day

The best prop noise I've ever heard is a very powerful engine, turning the prop it supposed to have at the right rpm and the prop singing because it's doing it's job on the transition from level flight to a vertical upline because the pilot added power just a tad bit too soon. The prop is not cavitating at all, it's just "digging in". PT models, Mezjlik, 3W, Xoar and a few others are good for this.

I'd have to admit, I was expecting to answer questions on how to make it quieter

pe reivers

to all:
Props do not cavitate in air. That only happens when submerged in fluid.
What you hear is the sonic pressure waves off the airfoil wher the airflow speed approaches Mach-1. The danger zone starts above a tip speed of Mach 0.7 , so it is quite easy to calculate the rpm limit.

Danger alert!
Sonic slap will set up severe vibrations in the prop, and there is no telling what will be destroyed. If the prop falls apart in a low pass, that is not the place I would like to be.

Tired Old Man

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More than once an entire plane disintegrated in the air after losing a prop. The amount of vibration that takes place once a prop sheds a blade is unbelievable. Full scale planes have lost the entire engine from the nose when a blade separated. It's not pretty. Props with high tip speeds do sound neat, though.

silent flight

OK guys, sorry for being misleading. I should have titled the post More Prop Noise!
I understand and appreciate your comments, Safety, Noise etc.
FWIW I live in a very rural area, private field, nothing within a mile most directions. 29 out of 30 tiimes I am the only one flying. I carry a cell phone & a two way radio to contact my wife one mile away.
I have flowm r/c for nearly 40 yrs. I try to be VERY safe.
Heres the rest, Ever been to Nascar race and the sound (NOISE) comes from the back streach when 43 cars get the green, and the hair stands up on the back of your neck, Same scenario.
Thanks

Tired Old Man

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Know what you mean. Same feeling as a pair of F-18's ripping over the top of your head at 100 feet with the throttles shoved to the burners. Or the buzzing roar in your ears when a AAFD top fuel dragster does it's burn out 50 feet away. The absolute sounds of power and freedom that can't be rationally understood.

silent flight

Silversurfer, Yooou got it. So I smoke the G-45 or crash the model, at least I tried.

Thanks

bubbagates

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Guys, please don't take my previous post as me being negative. I too love the nice deep sound of raw power, be it 43 race cars screaming down the straight away, a top fuel car doing it's burnout, a hydroplane screaming over the water, etc...

The very first time I was ever in Va Beach, I had arrived at my sisters house about 3am and went to bed. About 6:00am I woke to the sound of some very loud jet engines. Since I really did not know what was around me I ignored it but it kept going on so I finally went outside. I was greeted by the site of 2 f-14's taking off in full afterburner.

About that time my sister came out and said she was right on the border of Oceana Naval Air station and said a aircraft carrier had just left port and they were probably flying out to meet it. I grabbed a cup of coffee and my smokes and a lawn chair and was in heaven for about 45 minutes watch f-14's taking off in pairs. There were others tossed in for good measure but all I seem to remember is the F-14's

KC36330

anyone wanting more noise needs to increase prop diameter (not decrease it) and decrease prop pitch, larger props have faster tip speed and that is where the noise comes from as the tip speeds approach Mach (as pe reivers stated). the sound is small sonic booms.

kc

RTK

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silent flight-- I reeeaaallly like that sound too, just ask Silversurfer I have a couple of engines that can rip a prop like no ones business.
One of the fields we fly at is a private crop dusting strip. When the piston plane takes off 30 feet from you just breaking ground, now that is some noise. Yee haa

Tired Old Man

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silent flight

RTK

Been ther many times with the crop duster!

GreaTOne_65

Hi guys, just can't resist replying to this post. What your hearing and has been explained before is the tips of the props breaking the sound barrier, so I've been told. I have an Edge 540, 3.2 Brison, Paint stick Zinger, 22x6-10, straight and level at WOT really rips! I too fly at a field that has no noise resrsrictions (I own the field)LOL!! I am not bragging, but it is one neat sound. Just for comparisons sake, I have TF Mustang, with a Fox 3.2, and it makes the Paint Stick Zinger howl as well. I boke the Zinger and replaced it with a Top Flight 22x6-10, with the Power Points, and the Mustang is much quieter, still rips but softer.

Dale

Tired Old Man

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GreaTone,

Just to make your Edge fly better than you've ever known it to fly, pick up a Menz 22-8 for that 3.2. Not trying in any way at all to quiet things down..If you don't have to why should you. But you'll love the difference in the way the plane flys. There's other props that would be a little better, but the Menz is a nice, stiff baseline. Save the T/F and Zinger for the paint cans. They do well in the 5 gallon buckets[8D]

GreaTOne_65

Thanks for the advice, surfer! LOL! I didn't know the 5 gal. can was a better fit!!LOL!! I have tried Zinger 22x8, and I wasn't impressed, I guess you've convinced me to try one. I have got to say though, I can't hardly believe there can be that much difference. The Edge goes straight out of sight now, and in the younger hands of someone else, it seems to do 3-D quite well. As for the Mustang, it goes like a bat out of hell now! Looks much better at 3/4 throttle.
When I get home I'll will try a Menz. Just because you suggested it.

Dale

Tired Old Man

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What you're going to find will not at first be understandable. The plane will carry a bank better without anything that seems like the occasional "hunting" it had done before. You know, those times you went into a bank and it seemed like it wanted to fall out of it? Those wierd things that you could never quite figure out? When you're coming in low and slow you'll notice that the plane is under better control than you have experienced before. Those two just for starters. All those little nuances that weren't what you wanted or needed. Many of them caused by the prop.

I learned that the hard way a few years ago. Couldn't for the life of me understand why some very capable planes were doing things that they had more than enough power to do. Then one day I took off the Zinger 22-8 and the 22-6/10's that I had been using and stepped up a little to the Menz. OH MY GAWD!! Suddenly the planes came into a life that I hadn't seen before. Just about all of the little issues that the planes had were gone. Performance increased tremendously. Speed didn't change much but the effectiveness of the controls did. At all speeds! Just by changing props a predictability was there that hadn't been before. I know it doesn't sound feasible but just try one prop and then tell me if I lied.

The 22" Zingers are long enough to stir a 5 gallon paint can without getting any on your hands. Plus they bend just enough to assist in the mixing. Been there, done that.

bubbagates

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Another good prop for ripping on the Brison 3.2 is the MSC22X8. A well tuned Brison will rip that prop after about 5 gallons through it and the plane will still fly really well. NX props are good for getting a great ripping sound from. I have a well run in 3.2 in an Ultimate bipe, turning a 22A Vess that can rip that prop as well. For the first time several weeks ago I got it to rip and the Vess seems to have a bit lower sound to it when it breaks loose, but at the same time the plane visibly lost forward speed. That's the nice thing about having a bipe, loads of drag so it's easy to get a prop to rip.

All this talk about nice sounding engines and stuff is just getting my testosterone flowing [&:] Where is the Hemi Powered Road Runner that I used to have when I need it []

KC36330

i hope that's only on the Brison.......when i got my Fuji 50 it came with MSC 22x8's and i was less then impressed with the performance on my 1/4 scale Extra 300, vertical was very lacking and it wouldn't hover even at WOT, swapped to Bolly 22x8's and performance is 10 fold. hover at 1/3 throttle and will launch out with authority. i gave one of the MSC to a guy with a ZDZ50 and he had the same lacking performance over his Mejzlik.

kc

Tired Old Man

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Most of the true 50's handle the MSC 22-8 very well. With all due respect, the Fuji just doesn't measure up to most of the 50cc/52cc engines that you usually see. It works ok, but it's definately not a Brison, DA, 3W, BME, or ZDZ, which all consistently out perform it.

bubbagates

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I had a Fuji 43cc while it flew a 14lb plane nicely it swapped it for a DA50. Now I know that's not a good comparison, but I have flown next to a Fuji 50 on a 17lb Patty against a 16.5lb Yak and out of a hover on the same prop smoked the Fuji in a big way more so than a half a pound difference of weight would create.

The Brison3.2 was well run it and is the same engine that will rip the Vess that is on it now.

KC36330

the comment wasn't in comparison between the Fuji and the DA, the Fuji is a 46cc not a true 50, the comment was about the MSC prop. they just didn't perform as well as others on a couple of different engines all be it none of those engines were Brison's.

kc

EDIT: we do have a guy building a 27% Extra 300 w/ DA50R, I'll pass along the last of the MSC props I've got to him for a comparison on it as well but i feel if the Fuji, G45 and the ZDZ had lacking performance between the MSC and other brand props (no Zingers) then the DA will equally have lacking performance with it.

Tired Old Man

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I know that there is at least three other people that watched a 22-8 MSC out perform a 23-8 Xoar on a Taurus 52. I'm not by any means saying that the MSC is the best prop for all engines or conditions. That's not possible. What I am saying is that in a very large number of instances involving 50cc engines it works extremely well for most things and is hard to beat. Not the best for IMAC where high torque performance is not needed, but where they are it generally excells. A 22-8 MSC would be pretty hard on an engine smaller than 50cc, imo. Where a slightly smaller engine could work well with, say, a 22-8 Menz or Mejzlik, it would under perform with the MSC.

OK, I'm done with the prop arguements.... Let's get back to being LOUD!!

byoung466

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I was standing off the edge of a runway at a fly in when one of the top pilots took his unlimited pylon racer 20 ft off the runway full on doing a slow roll...my neck had that cool tickle....