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<DIV><FONT face=Arial size=2>The sound meter doesn't add up all the noises...it
measures the loudest one....If you want to reduce your noise level the first
place to look today in our current pattern setup is the prop. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Before the NATS and Teams this year I played with a
sound meter and lots of props....The biggest change was prop and rpm...If I
could reduce the diameter of the prop and or reduce the RPMS being turned the
noise went down....Didn't matter what exhaust system we used..other than
different exhausts were more or less restrictive and meant changes in
RPM....Regardless....IF you break 400mph tip speed you are going to break the
94db(A) FAI rules for sound.....By the way a 17-12 APC at 7800-7900 is right on
the border...a little wind or any wind and it tips the meter over the 94db(A)
limit.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Now it is very possible that you can reduce the
prop noise to the point where the airframe and or engine sounds are the loudest
thing...but my testing showed that it was the prop that was the make or break
noise factor...go to an old KF with the Prop tip speed chart. It will give you
some numbers.....</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Also there were certain prop designs that would
break noise limits below the 400mph....The props with thinner blade tips like
many of the 3 blades although more quiet in the air...really busted the sound
test on the ground. And by the way some of these noisy props had some
serious serious pull at lower RPMS compared tot he standard APC setups 16-12 to
17-13 APC on the 140DZ......We basically repeated the results on the OS 140's
and the same props.....</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>There are no points for in the air noise...only a
zero for the flight if you don't make noise on the ground. Ask Sean about his
first flight at the TEAMS.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>TN</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=service@clubmanprops.com href="mailto:service@clubmanprops.com">Wayne
Powell</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, August 08, 2003 11:57
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: F3A--Electric.</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=470554703-09082003>Just
thinking out loud here. Isn't there more to the electric drivetrain than
just the motor and prop? I'd suggest the gearbox as a significant source
of sound beyond the prop. If the tip speed between the two is
virtually identical, assuming similar design, there should be negligible
difference in prop noise (within reason). Taking it further, that
would mean the exhaust and carb noise are equivalent to the noise created by
the gearbox? It would be neat to compare a direct drive set-up running a
prop at the 395 mph tip speed vs. the geared system on a dB
meter...</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=470554703-09082003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=470554703-09082003><FONT size=2>Wayne Powell<BR>Bolly Props North
America<BR><A href="http://www.BollyProps.com"
target=_blank>http://www.BollyProps.com</A></FONT></DIV></SPAN></FONT>
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<DIV class=OutlookMessageHeader><FONT face="Times New Roman"
size=2>-----Original Message-----<BR><B>From:</B>
discussion-request@nsrca.org [mailto:discussion-request@nsrca.org]<B>On
Behalf Of</B> Troy Newman<BR><B>Sent:</B> August 8, 2003 7:09
PM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B>
Re:F3A--Electric.<BR><BR></FONT></DIV>
<DIV><FONT face=Arial size=2>Also some have claimed its silent
flight....Tony said the sound meter was tipping 93db(A)...That means prop
noise is our greatest noise issue....Who cares about in flight noise...the
Sound meter is 3M away from the model....</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Just some FYI.....YS 140DZ turning a 17-12 at
7800rpm is 92-93db(A)...OS 140RX same 17-12 at 7800rpm is the same
92-93db(A) this is roughly 394mph tip speed....</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Jason is using a 22" prop at around 6000rpm its
hit 93db(A) and if you calculate the tip speed its 392mph.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>So guess what prop noise is the kicker....its
not silent flight when you are tested at
3meters.</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>