Mufflers, or not

[Glenn Patterson]

We have Continental IO-360 that we modified a rear bed mount off a Cessna 337. The exhaust that came with the engine could not be used so we were looking at building a set. One partner is certified welder & we bought a Loncoln 225 Precision TIG. We weighed the plus and minus of order the bends and parts to fabricate a set. Would take a lot of time and would likely end uo with a lot of expensive 321 SS surplus tubing. I picked up some part time contract work and agreed to cover the cost. I was absent for a good part of a couple years of during construction so this was one way to make up for my absence that would advance the project. construction. I first started to work with an aircraft exhaust co but lost confidence that has since been taken over by a great owners.. I went with aircraft side of the Stainless Steel Headers in North Dakota. The owner of the North Dakota businesses took over the Experimental; Aircraft Exhaust in Minnesota.They manufacture a lot of exhausts for aircraft and then under a subsidiary for performance cars. The exhaust flanges and mock up parts are supplied for a deposit that is applied to the exhaust invoice when the mock up is returned to be manufactured. They have jig blocks that replicate the engine exhaust mounts to fabricate an exact fit. The owner Cliff was excellent to work with and would recommend him if a person needs an an excellent exhaust that is custom. We live in a cold climate and elected to go with the mufflers and 2 heat cuffs. We managed to get quite a wide open lane under the engine to shed cooling air. The fuel system is on top of the engine so that leaves more room underneath. Each side is 3 into one and we tried to equalize the length and flow resistance in each leg like a car race header. The header system will help the engine breathe better. The cowl cooling arrangement seems to be keeping the engine cool. The airplane noise level is decent and with headsets will be very comfortable noise wise. My understanding of extreme noise and vibration is that it will get to you through the body and ears. Even with hearing protection there exposure limits. I know from working in extremely noisy industrial environments that it takes ear plugs under the muffs to increase the ear protection. The company did noise levels in the extreme noisy areas, required double protection plus there were established daily exposure limits. The companies tested our ears annually to make sure we were not losing our hearing. I think if some one is running an over length prop to have a tip speed over mach1 and straight pipe exhausts that they should learn what precautions they need to take. A good safety supply or an competent industrial safety person may give good insight. As the decibel level goes over 85db is where my industries to extra precautions as noise & db levels are not a linear relationship. It is expands I believe in a cubic exponential so if 85db is loud then 90db is multiples of the 85db noise to be more extreme.

It is a free world to do as one pleases but it is best done with education . Study noise to make an informed decision or any other aspect of construction to stay safe. Hearing is lost permanently and may be returned to some degree with hearing aids.I know of no hearing aid wearers that enjoy the hearing aids. I worked in extremely noisy areas during my 40 years on the job. I followed the safety training & paid attention to the posted noise levels & exposure rates. I have some minor loss in my left ear that does not require aids. Wife says I don't hear her but that has been ongoing since we got married 40yrs ago.