Teenage Sex


   Reducing engine noise is just like teenage sex:

   * Everyone is talking about it
      * A few are really doing it
         * The ones doing it think it should be better
            * The ones not doing it wish they were

   The difference between teenage sex and reducing engine noise is that everyone should be doing it.

   Like IT though, reducing engine noise on a motor rig is not something you go out and do right the first time–it is a learned ‘art’. Before you start doing it, you need a level of commitment because it is not that easy. For some time now, I have been trying to figure this thing out (the noise thing, that is), and I have come up with some things that seem to help. But there is still a long way to go.

   How you reduce the noise level is not the issue here–it is the WHY . In 1996, the Park will be developing a new River Management Plan, and at the same time, will be looking at wilderness designation for the entire Park. You can bet your spare prop that the motor issue will be one of the hot spots, especially when added to what seems to be happening with aircraft noise (see Jeri’s overflight article). We can’t afford not to start doing something now. If we wait until 1996, it will be too late.

   This is not an easy thing to do, but it’s not insurmountable either. From a technological standpoint, it is far less complex than the aircraft noise problem and we can’t just float along bitching about overflight noise and not clean up our own act.

   The National Park Service has a standard of 60 decibels at 50 feet as an acceptable noise level for recreational vehicle generators, and that should be our target. Granted, it is a small target, but the rewards for everyone are tremendous when we hit it.

   There are a lot of factors involved in reducing noise levels. But they really fall into three categories: the engine, the boat, and the driver. There is not much we can do about the inherent noise level of the 2-cycle engines most commonly used in the canyon, other than beat on the manufacturers to make them quieter. And we should, because there are things they can do. There are also things we can do to absorb some of that noise before it leaves the engine. Some companies are already doing it. For example, Arizona River Runners just lined their engine covers with a lead-lined foam that results in a 4 db noise level reduction. It brings the noise level at the drivers ear down to 93 db, and 69 db at mid boat. It’s not at RV generator levels, but it is a start. Other companies are doing things as well–we have to–we can’t just sit back and wait for the manufacturers to act or the park to mandate.

   Several companies and the Park have looked at 4-cycle engines. They are quieter, but I don’t think they are the answer. Being a 4-cycle engine means more moving parts, which translates to harder to tune and less reliable. Their power curve is slower to react to the throttle and they are heavy. (A 2-cycle Johnson 30 HP is 115 lbs and the 4-cycle Honda 30 HP is 138 lbs). In some applications, this could be the answer. I hope so.

   Boat design is something we can do something about. It is no secret that an open stern boat results in more noise trailing behind than a closed stern boat, although there is probably no difference to the driver or the passengers.

   The jackass that most companies use was designed for utility, not for their noise dampening potential.

   In many cases, the boat frames act just like big amplifiers, converting the vibration from the engine into noise. They need to be examined for vibration absorbing potential as well.

   A few rowboatmen have told me that GCE’s boats are the quietest on the river. I’m not sure if or why that’s true. But, if it is, it is probably many little things adding up an overall system that works. Or maybe their boatmen are better about it than the rest of us.

   The boatman is the biggest factor and probably the hardest to fix. They have almost complete control of the noise the engine produces. We can’t just leave it off all the time, but we don’t have to run full throttle all of the time either. We (me, too) need to consider the impact we have on others as well as on our own folks. Approaching a row trip and shutting down to float with them for a few minutes may not be a bad idea for everyone involved, boatman and passengers.

   One of the things that makes this such a complex issue is that what works on one boat, may not work on the next. But we need to start exchanging ideas. This is an industry wide problem, not a company problem.

   Well, I’ll get off my soapbox for now. If you are interested in some of the things that we have found that work, give GCRG a call, and ask for a copy of “The Noise Letter”. If you have any ideas, questions, or want to talk about it, leave me a message at (602)585-6943. I’ll get back to you.

   Think stealth.

Tom Vail