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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>7600-7800rpm passes 94db<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If your model is not “loud” meaning composite drummy
type fuse then some foam in the cowl helps…Hollow fuse and hollow wings
and such will act like a megaphone. Seal any belly pan connections so they are
not banging together, rubbing, and such. Any holes on the right side of the
model stuff with foam. Totally enclosed header and pipe is quieter.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The 18” dia makes noise above these rpms. Take the 18.1-11
and remove about 3/16” from each tip and reshape. Clean up the L.E. of
the prop and make sure it doesn’t have nicks in it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Use a velocity stack it will also help the noise. The last
little carb opening creates very little power for the amount noise gained. SO
set it all up and detune the top end with ATV until the noise meter is happy.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>A good solid wood model will yield about 76-7800 and make noise.
A composite model will be less RPM because the noise drum affect inside the
fuse. This is where dampen it with foam from the Engine box.
Exhaust deflectors will also have an effect.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If you are trying to make AMA noise limits its 96Db….and
the microphone set is 30mm off the surface. Mic is off the right hand side of
the model 3meters away and downwind. Point the mic directly inline at the prop,
then turn it 70degs toward the right…meaning the microphone is 70degs away
from the nose of the model. This is where readings are taken in AMA classes.
The limit is 96db(A) use slow response and “A” weighting on the
meter.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>F3A measurements are totally different. First off the model
points into the wind. The meter is set off the right side directly inline and
pointing at the prop meaning pointed at the prop right inline with it….but
the meter is 90degs to the wind. Readings are taken here and the limit is
94db(A)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Penalty for AMA class is a raw score % deduction for 96-98db(A),
in F3A it is ZERO for the flight over 94db(A)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I have done extensive testing on the 170’s and the noise
meter….tons and tons of props and played with all kinds of ideas to make
things quiet. There are lots of things that help. Nothing is a secret
bullet that gives 1-2db other than the RPM and the vel stack. The type of fuse
is so huge its not even funny. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Troy Newman<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b>On Behalf Of </b>colin
chariandy<br>
<b>Sent:</b> Tuesday, August 04, 2009 6:58 PM<br>
<b>To:</b> NSRCA Mailing List<br>
<b>Subject:</b> [NSRCA-discussion] YS170 at 96dB<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<div>
<p class=MsoNormal>Does anybody know what rpm will pass a noise test for a
YS170 turning 18.1X11? <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Colin.<o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
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