Db Rating on nitro engines

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It will depend on which muffler and pipe used.

With that being said, a typical gas engine or nitro engine with just an internal stingered pipe will run at around 89 dbA measured 50 feet from the shore line.

I know of no charts.

If you are looking to see how the sound levels drop over a distance, db levels will drop 6 db for every doubling of the distance.
 
Also.....

Gas and nitro engines with a bolt-on muffler and a internal stingered pipe will run at around 85 dbA.

Quiet pipes will get you lower.

My Novarossi .21 JAE rigger with a Novarossi Quiet pipe runs at around 77 dbA.
 
I have never seen a chart as there are too many variables to make one. An engine in a rigger will normally be quieter than a mono. If the mono has a noise isolation engine mount it will be quieter. If it is in a mono with a hard solid mount it will extremely loud. Some hulls are inherently quieter than others. The worst I have ever seen was a Sightler mono with a solid mount. Quiet pipes make a real difference. Nitro open pipes are built for performance and not for quiet running. Gas steel pipes are exceptionally loud. There are just too many variables. I have personally run Picco's, OS, MAC's, CMB's, NovaRossi's, and K&B's of all sizes and types and have not seen any substantially quieter that the others. Only a OS 21 OB is on the quieter side.
 
You can't put an accurate dB reading on any pipe. We deal with variables like acoustics of where you run. I've got a pond where I used to run at where a nitro engine would sound like a chainsaw in the woods. What might be fine at one site may be over the dB limit at another. A race a few years ago had that problem.

A lot of sound can come from the hull itself vibrating, the Europeans found that out as their limits are lower than ours.
 
Put a muffler on it. No sense in pissing off the neighbors and losing another race site.
 
Think that is where dad is going with this...we got a line on a new public pond but sound will be the killing factor of it. Looking for tips on the trial run to not "piss the neighbors off". In other words from some new guys, will a slip on muffler be as quiet as a muffled pipe? Are there tricks that you can do to help with sound? What would be the best set up to try and make this happen? Evidently there will be a city police representative with a db gun to check if we are in legal limits. Now, we have not been told what the limit is so we will be shooting from the hip on this. Just wanting to make the best impression we can for us, and future boaters that would like to use this lake. Boats test will be a .67 scale hydro and a .21 outboard.
 
it isn't just the sound pressure level (What we measure in dB or dBA if it's A-weighted,) it's the spectral content. I can tell you right away that the screech of a B Hydro is a lot more annoying than what comes out of any LSG27 or 36 gas engine. I run quiet pipes on all my boats, but at a race I stick earplugs in after the driver's meeting and they don't come out until after the last heat.
 
When we were running at the STL waterworks we had people complain and they were all the up on the hill and at Holten we had a lady claiming we were running jet skis, and the best I have ever heard a lady made a complaint at Holten that we were traumatizing the fish by running model boats.

Point is just because you run quiet doesn't mean people will not complain. Some people complain to stop others from having fun
 
I have a spreadsheet of a series of WD-40 and Axe can mufflers added to an old style M&D muffled pipe on a modified 26 cc Zenoah. It has the tests run over two days and construction details. The stock M&D pipe was 97 dB around 50' from the boat. The can mufflers got as low as 84 dB with water injection into the can. The best muffler with water injection ADDED around 100 rpm.

Unfortunately, this forum doesn't allow Excel attachments

Lohring Miller
 
In Europe, your boat must be at 80db or less with the meter located at the water's edge. You can hear the sound of the sponson's slapping on the water. You can hear the carbs open up. And, at one race, a woman whose cabin was a few hundred yards away form the race site complained that the noisy boats were ruining her holidays.

It is not that difficult to quiet down our boats, it is difficult to quiet down the people who like to complain.

Al Hobbs
 
Al, I've seen too many examples of that.

For a while we ran at a park that was barely used by anyone. A neighbor woman walked down and complained about the noise which wasn't any worse than a lawnmower, weedeater or any outdoor gas powered tool. it made me wonder if she complained to her neighbors about that noise?

A LHS had an outdoor track behind their store. The dB level in a industrial zoned area where their business is at is only 87 dB. Before they made it a residential area, people rode ATC's, dirt bikes, dune buggies and all sorts of off-road toys there. When it went Residential, the dB level is now 78dB in there. Anyone knowing what 78 dB sounds like then you know that you'd be lucky to run anything electric powered without it going over the limit!

At a local 3/8-mile oval track outside of town in farm country, they wanted to shut the track down that has been there as long as I can remember. They wanted a dB limit so low that nobody could run any farm equipment or a table saw in their garage. It's a wonder that those people who proposed the ordinance weren't tarred and feathered! Needless to say, it got shot down.
 
A lot of times the complaints are as much about the PA System as much as the racket the boats make. One of our sites is close to a residential area and won't allow any engine starts or PA tests until 9 am
 
What is it about old people that they think they have to force everyone to be silent all of the time?
 
How do you explain all of the guys in their 60's and 70's still racing noisy toy boats?

I know what you mean though as there's always somebody that wants to ruin somebody else's good times.

The Pond Hoppers in Ohio had the cops called on them for noise. They were flying electric planes that day......
 
Funny our problem is a bird watching nut. We are so excluded from any residential area and will never have any houses built near, but it's a county park so we have canoe guy. Heck this year he was down on the Ohio River during the Madison Regatta complaining about the big boats and the impact on the birds. They are out there every where in all different forms. It's all in how you handle them and the powers to be that own the body of water. Key is to keep them so happy that they tune out the complaints.Go out of your way pick up garbage clean up stuff show your interest in the environment Go to park board meetings smooze away . Sorry to soap box you, but we have to work hard to keep our water to race anymore.

One day I will win the lottery and buy a giant lake somewhere and all the signs will read. RC BOAT POND ONLY! ALL OTHERS KEEP OUT! any complaints read the sign again. Ah Dreams.
 
Yeah, can't we? I'm waiting for my wife to hit big on the Powerball. We'll have a huge place for us to run RC boats, she'll have her huge log home with dogs and horses.
 

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