stunthanger.com
Speed,Combat,Scale,Racing => Combat => Topic started by: Paul Smith on October 19, 2010, 01:55:40 PM
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Every nice flying day in Michigan could be the last of the year. Anyway, we had another beauty today.
I haven't flown a combat plane since September '09, but this week I dusted off an old Viko with a Fora 2008 and made up a 2011-legal 6mm muffler.
After the usual painful ritual of starting up one of these brutes after a year of idleness I was able to collect some data:
Old 8 mm muffler; ground RPM 28,500, Airspeeds 100 and 103 MPH run time, about 3.5 minutes.
New 6 mm muffler: 26,500 RPM, Speeds, 101, 100, and 98 MPH, run time, about 5 minutes.
I only took my sleeve launcher, one stopwatch and a tachometer, sorry no dBa meter, but it seemed a bit quieter than before.
This was obviously a brief test, but it convinced me that the life of F2D will go on, with some valuable fuel saving and minimal loss of speed. Actually starting the match with 1.5 ounces less in fuel weight might result in a net gain in overall performance.
Furthermore, I can still stunt at 103 MPH on 52' lines.
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I got similar results, a bit more speed loss, about 1 sec/10 laps. the 6mm outlet is noticeably quieter, mainly because the motor is running a couple thousand rpm slower.
Henning Forbech machined a 8mm->6mm restrictor with a closed stinger going into the muffler with multiple holes in it. It was even more effective at reducing noise.
The new rules won't shouldn't have any effect on the event. There isn't much loss in performance.