Dream_Flyer - at our field noise is an issue and we have a 93Db limit on engines below 1 Cube and 96 for 1 Cube and over. This is measured over grass at full throttle from all four quadrants from the standard distance (can't remember right now if it's 2 metres or 3 - just got up!). Meeting this limit is tough for smaller engines that spin up higher RPMs and tougher for bigger engines. .60s seem the easiest to quieten down, especially long stroke/high torque designs that can lug a bigger prop. An efficient mufflering system and reduced diameter high pitch props to minimise prop tip speed are the trick. The Wasp is shockingly quiet - when people from other clubs see/hear it for the first time they are astounded. On the other thread re my profile fun fly plane using Sig Something Extra wings and tailfeathers, you'll see I have an O.S. .61 FSR with the stock muffler modified with a Dubro Arise muffler and then have an after muffler attached. Doesn't seem to hurt performance too much and sure quiets things down. I'm transferred to Winnipeg shortly where noise isn't as much (if any!) concern at their fields. I do prefer quieter planes though - I just find it less stressful/more pleasing. I think this is part of the reason why 4 strokes have taken off the way they have, but to my way of thinking they have all those extra parts... :^) Here's how I make those after mufflers: