Silent Running

LAST EDITED ON Dec-01-04 AT 04:39 PM (CST)
 
In my quest for silent flight I went flying yesterday with the LA .40 ARF Cardinal. I usually limit myself to 3 flights so I don't bug the neighbors too much. I decided to take the tongue muffler off and try the stock OS muffler for one more flight.

Wow, night and day, the full muffler was whisper quiet. I could hardly hear the engine. The engine had less power but a 1/4 turn needle adjustment fixed that. I'd been running a lean 4 stroke with the tongue muffler and had plenty of power. I had to go into the 2 stroke zone with the full muffler. That,s ok it'll run longer now.

I've seen RC airplanes that have a home made can muffler that's made from a moouse can and aluminum tubing. It attaches to the main muffler with silicon tubing. Maybe I'll make one and strap it to the landing gear strut.

The plane seemed to handle about the same but, I'll try some tail weight next time out. This is great I can fly all I want if the weather is nice.

The stock LA muffler is very nice, although it is a bit weighty(85 gr.)

I found a 3 blade prop quiets is even more. An 11/4 is a bit noisy because the tips are going pretty fast, 10,500 rpm and 11 inches approaches that "magic" 130 number for rpm x diameter where the tip speed starts to make noise. For 8 bucks and 15 minutes with a heat gun you can repitch a Master Airscrew 10/7 to 3.5-4 pitch.

The LA 40 with a 3 blade is getting down in dB to the electric motor range.

Giffyu, you can up the nitro percentage a couple and go back to your "lean four" needle setting.
Bigiron