f308gtsi

My Feedback: (1)

We need help. Gas engines were just banned at the Cleveland Radio Control Field. Most of the gas flyers are flying ZDZ 50,60, and 80s. There are a few DA engines as well.

What is the best (quietest) system available ?

Can we add a J'Tec Snuffler to the end of some of the silencer cannisters and achieve any better results ?


At this point, reconstruction of firewalls and fuselages is not an issue. We will even hang something under the airplane if we have to. We are dying out here.

Thank you for your efforts on our issue.

exeter_acres

My Feedback: (2)

why were they banned??

if it is noise, find a DB meter and take it to the field

I have been to 2 IMAC meets this year where they did the dB test and the loudest planes there were the GLOW planes NOT the gas ones.......

torqmeister

If they have been banned, it doesn't make any difference what you do to silence them; the engines or the opponents. Go find a new field & enjoy your gassers.

Banks

We have temporarily banned the gassers due to the noise issue and constant complaints from the surrounding community. In order to lift the ban, we are looking to the RCU community for advise on additional components, adaptation...whatever that will effectively reduce the noise level to something closer to the level of noise a 4-stroke engine will produce. A db test will only prove we are within an acceptable noise level per city ordinances. It will not change community perception nor stymie the residents desire to shut us down.

However, there is a willingness to compromise hence, the search for ideas on noise reduction. What we have determined is it is, in fact, the gassers and 2-stroke engines are the major violators. It would be simple to ban them both completely however, that is not the answer; middle ground must be sought and we believe it to be with silencing the engines we've already invested in. It also appears we could gain increased community support if we can accomplish this. I wish it were that simple to find another field but at 200+ members strong, I would like to try anything possible to keep our club intact and maintain our current field; as selfish as it may sound.

Banks
CRCC

bubbagates

My Feedback: (32)

The most common methods are using canister exhaust systems and 3 blade props or larger 2 blade props (the key being to slow down the engine some) and good throttle mangement.

My Da50 on a 3 blade 21x11.5 on a KS rear exhaust canister is 89Db at 9 feet at full throttle and when the glow planes on stock mufflers fly while I'm up I cannot hear my plane at all

Now take the same setup with a 2 blade prop of the same brand as the 3 blade and up it went to 92db.

The addition of a good canister system on the plane and throttle mangment will give good results. As far as pitts mufflers, J&A, Supersonice (for the ZDZ engines) and beleive it or not I have seen a Bison inverted muffler (non-pitts style) be quieter on a Brison3.2 that the Bison pitts muffler but only by a couple of Db

I have found on my Da engines, KS rear exhaust canisters seem to be the quietest without loosing any power. I'm about to find out (n the next couple of weeks) how well the 3W canister systems work. They claim 89db at 20feet with a 2 blade CF prop on the 3W55i

We do not have noise issues were I fly now, but we still aks that you keep the plane as quiet as possible. Up until this week, Pete Castine flew his 40% Da150 powered Comp-arf Extra where we fly and it made more noise because of the prop than anything else. He was using MTW canisters. I do not know what his Db reading are but I can tell you at full thorttle it was not loud at all and way quieter than a 2 stroke glow

rmh

here in good old Utah --we still have a lot of the cowboys who jes gotta hear the fu-in things scream.
noise is a huge part of the fun for many
ever wonder what would happen if they sold only silent firecrackers?
making the two strokes truly quiet is not a mystery - it is simply avoided here in the Hew Ess Hay..
My 160 is very quiet - two huge JMB mufflers (cans) and a 30x14 ZM prop. (cowl primer is where th old "mufflers" poked thru) pulls ove 40 lbs of fuel n plane instantly straight up as far as u want to go.
So - what to do with the other stuff not designed for big cans and the engines and little pipes -laughingly called mufflers ?
let's face it -- these things are going the way of 39 cent a gallon gasoline.
All of the two strokes can be made quiet -
all of em

presenting DB meters and facts about noise is a joke.
The non users of two strokers don't want the noise and thats that. period
If you are really serious - you are going to have to spend money and learn to fit up exhaust system
Go to a German site on line and look at what they do -
that is what we all will eventually need to do.

onewasp

Banks,

I will be interested to learn of the complaining communities reaction. Seriously interested!

My (our) club's) experience in the past has been that once the public at large gets to the point of formal complaints it is TOO late for anything!
We were flying from a private full scale field with the owner completely on our side ------ best flying site I've personally seen ------. Once the complaints started reaching the "City Fathers" it was closed down in less than a year.

Not only was the field owner, (flew his own museum quality restored Stearman and Jet Ranger from the field) on our side, he was also a MAJOR employer in the area.

The complaining public won out regardless of the actual noise levels attained after the complaints.

Not good news for you but "them are the facts!".
Certainly hope you do better.

We ended up with the club fragmenting and going to other established R/C fields in the area.
I now belong to three different clubs-------simply to cover the eventualities of the future.

pe reivers

Dick is right concerning the european perspective, because we are smothered in noise limits. No big deal though. We have a limit of 80 dB(a) at 7 meters. (89 at 9 feet IIRC)
At your close quarters a small meter postion error will result in way off readings.
Measuring over a hard surface easily adds 3dB. so don't.
We measure over short cut grass, with possibly the plane set up at 1.1 meter height (stand that can be rotated)
Hard facts.
Tackle the loudest noise source first. That is what counts. If it is the prop, do that first.
Plane resonance easily adds 3dB. Very light airframes tend to resonate badly, so it helps to avoid drumming surfaces.
It also helps to reduce engine vibration, so the prop should be balaneced well. A snippet of paper about the size of the thumb tip should set the balanced prop in motion for every clock possition.
Large engines mostly are not vibration isolated to the airframe. points can be gained here to avoid large surface "drumming".
Power is used to drive the prop. That can be done in two ways. With a large, low pitch prop, or with a smaller high pitch prop. The latter wins noisewise. The prop tip speed should not exceed 0.7 mach. Better still, stay below 0.6 mach. This is harder for a large prop. RPM reduction gear will allow larger props if thrust is needed above all.
Going three-blade even further reduces the noise, but increases the prop disk load, which results in less thrust per unit of power.
The design of the prop is very important. A thinner blade is better.

Finally, the muffler of the engine. I put this last, because understanding noise in airframes is more important.
A good muffler has plenty of room inside to take up the expanding gasses, before they leave through the stinger pipes. The more constant the pressure at the stinger inlet, the better the silencing of the prop is. In cowl mufflers are hardly suitable.
I did some test with KS, 3W and MTW canisters.
KS has very thin walls, which produce noise by themselves. 3W has thicker walls, but the design is not as good as the MTW, which is very popular in Germany at the moment. In my test engine, the MTW gained 200 rpm over the 3W muffler. At the same time the noise was down, and more mellow, Even better than JMB, which is heavy. An after-muffler to further quiet the engine helps, if other noise sources are also reduced (see above)

Bass1

I have been involved in sound reinforcement for a number of years, setting up and operating P.A systems for casinos, night clubs, showrooms and live bands. Frequencys in the 2300 to 3500 cycle range are the most obnoxious and can/does travel far and irritate most human eardrums. With the help of a realtime analyzer (audio frequency analyzer) the muffler manufacturers could in fact experiment with different configurations to cut these ear splitting frequencys. If you're old enough to remember the older graphic EQ units we use to use on our stereo systems, generally a warmer less obtrusive sound was obtained by the "smiley face" configuration which was leaving the high and low frequencys in tact and "cutting" the upper midrange (2500 to 3500 cycles). This was/is much more pleasing to the ear and doesn't seem to carry as far. Now if we could turn our mufflers/exhaust systems into mini- tuned "speaker cabinets" while maintaining/enhancing engine efficiency, everyone would be happy.

al

f308gtsi,


Give us a call or email, We have had a lot of success with our new designed mufflers (not the incowl). Some of the areas that need to be considered in addition to exhaust noise have been touched on here but we may be able to help with your problem.. We have several new designs and can do custom work if need.

Al Young
JTEC/RADIOWAVE
704-799-1658
www.jtecrc.com

tailskid

My Feedback: (34)

Nice web site Al....you sure do have a lot of products....

NM2K

My Feedback: (14)

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If the neighborhood folks have already implied that your flying club is a menace, do yourself a favor - find a new field now. I've been down this road many times and there is no pleasing people that do not want you in their area.

The money that will be spent upon trying to find a good noise level compromise would be better spent in the acquisition of your own field, either by purchase or by lease. I prefer leasing, because sooner or later, your new field will face the same encroachment of spreading residential areas as your present field. It is time to "get real" about this and not squander your members' resources by not facing reality.