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Mufflers, or not

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  • Mufflers, or not

    Any thoughts on mufflers vs no mufflers? Is it normal to run an exhaust with mufflers? Obviously it will be quieter at TO. Is there a general consensus, or a regulatory one?
    Sorry for my ignorance. The engines I have been flying make a very loud, high pitched whine.

  • #2
    Mufflers do reduce sound levels and provide much more cabin heat than heat muffs on the exhausts. But they cost and weigh more. That is the trade off. Mark

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    • #3
      Three Sigma has mufflers. Yes, there is additional expense and weight and there may be a slight performance penalty. I don't know how much quieter they are because I have nothing to compare to. I do know that sitting in areas of high noise is fatiguing, even if your ears are well protected. You won't make any points with the neighbors with a loud airplane.
      Russ Erb
      Bearhawk #164 "Three Sigma" (flying), Rosamond CA
      Bearhawk Reference CD
      http://bhcd.erbman.org

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      • #4
        I was around an early 4-plane BH with straight pipes on a 4-cylinder. On takeoff it was obnoxious. I don’t wanna be that guy that my neighbors complain about!
        Christopher Owens
        Bearhawk 4-Place Scratch Built, Plans 991
        Bearhawk Patrol Scratch Built, Plans P313
        Germantown, Wisconsin, USA

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        • #5
          Interesting discussion here. My impression is that the prop makes as much or more noise. Russ is correct about sitting in all the noise increasing fatigue. You feel the noise even as a passenger in a high noise environment.

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          • #6
            Originally posted by tailwind View Post
            Interesting discussion here. My impression is that the prop makes as much or more noise. Russ is correct about sitting in all the noise increasing fatigue. You feel the noise even as a passenger in a high noise environment.
            Thats been my impression, too. That one time I experienced it, though, it was pretty crazy loud. Seaplane props are definitely another matter aren’t they?

            Greetings from frozen Chetek!
            Christopher Owens
            Bearhawk 4-Place Scratch Built, Plans 991
            Bearhawk Patrol Scratch Built, Plans P313
            Germantown, Wisconsin, USA

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            • #7
              The BH I flew had straight pipes and it was crazy loud. My first mod would have been a new exhaust. The BH I'm building is getting a muffler.

              I think you can tell in this video that the exhaust was louder than the prop:
              Last edited by whee; 01-06-2018, 08:23 PM.
              Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

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              • #8
                I'll definitely be using mufflers, even on a little C-85. Something like these silencer/deflectors would probably help cut the noise down quite a bit and deflect it away from the cabin if a person already had straight pipes. I flew in a Tailwind that had 4 straight pipes exiting directly under your feet, facing nearly strait back, and it was incredibly loud.





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                • #9
                  Thanks for the feedback. That is exactly what I was looking for.

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                  • #10
                    I do a 16 hour duty day, 12 hours of flight time from Guam to Honolulu. 6 legs each way. I used to be wiped out for 2 days on each end. Then somebody told me about noise being fatiguing. A pair of Bose in ear NC headphones did the trick. Amazing how less tired I was.

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                    • #11
                      The Vetterman exhausts without mufflers are not very loud for persons on the ground / outside the plane looking on. At cruise it's quite when you fly over, even at full power it's no louder than a Cessna 182. Lots of people comment on how quiet our plane is, unless it's at full power. We have no exhaust mufflers.

                      Personally, I don't know any Bearhawk who've used an exhaust, yet. Headsets are much lighter, by the numbers my impression is most don't use a muffler??

                      But inside the cabin is really noisy. Noise cancelling headsets are almost a must-have in my view. I can't say how much a muffler would help, but a Cessna is a lot quieter.

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                      • #12
                        At first I wasn't going to use mufflers but changed my mind. I will be doing cold weather flying and with two mufflers I have two good cabin heat sources since my engine is injected. Vetterman says their mufflers actually improve engine performance a little.

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                        • #13
                          Any idea how much dual mufflers weigh? I wonder if extending the exhaust and/or bending it at the end to point down wouldn't send some of the exhaust noise away from the cabin?

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                          • #14
                            I've had vetterman exhaust with mufflers on my bearhawk for 750 hours. After flying proto 2 without mufflers I really appreciate having mufflers.

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                            • #15
                              The weight of my dual muffler crossover system was the same as the 4 into 1 system, though a straight pipe system would be a little lighter. I saw a CHT increase of around 10 degrees when switching. The noise of the plane at idle is much less. I haven't ever been on the ground when it flies, so I can't speak to the volume level there. The muffled system at first came with pipes that directed the exhaust straight back, and I heard a sharper exhaust note in the cabin. Clint B provided some bolt-on turn-downs that deflected the air down just a little, and the cabin noise dropped. So far I've been running both muffs into a single heat box, but I am collecting parts to plumb a second box to the back of the cabin.

                              Noise on the ground is a top priority for me, and it should be for everyone else too. All flying sites are noise sensitive to some degree, and pretending this isn't the case is what makes them more noise sensitive.

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