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From: CozyGirrrl@aol.com
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Date: Mon, 9 Jul 2012 12:48:00 -0400 (EDT)
Subject: Re: [FlyRotary] First lift off with single rotor
To: flyrotary@lancaironline.net
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Congratulations Richard, it's a great start.
 
Big "general rule of thumb" is give your exit (in a low pressure area) 150% 
 of air inlet area. Think of the impact heat has on air in a hot air 
balloon plus  the under cowl turbulence and slowing the air way down in there it 
is easy to  see back pressure building up. 
It is a good starting point and you can always begin blocking off bits  of 
both inlet and outlet once it all looks like it is cooling then you can 
begin  working on lessening the cooling drag.
 
Chrissi &  Randi

_www.CozyGirrrl.com_ (http://www.cozygirrrl.com/) 
ClickBonds  10/$7.50
CG Products, Custom Aircraft Hardware
Chairwomen, Sun-N-Fun  Engine Workshop


In a message dated 7/9/2012 10:50:15 A.M. Central Daylight Time,  
res12@fairpoint.net writes:

 
Cleared the ground for a brief period today. As far as the airplane is  
concerned, everything is good. CG seems to be right on the spot. Much better  
as it was 12 years ago at the first flight with the SOOB. 
Here is the reason why it was not a flight. A few days ago when I started  
high speed taxi, as soon as it picked up air speed, the engine started to  
sputter and almost cut out totally. This was at the same RPM as at a run up,  
where it does not do that. With a wiggly tail dragger as the Avid is, there 
 was no way reading enough instrument for making a preliminary analysis. I  
recorded the instrument panel with a GoPro at 2sec intervals.
Looking at the first pictures, the answer came up right away, increasing  
pressure under the cowl where the intake for the engine is located. Like the  
EGT shot up over 1600 just before the sputtering started. Since my radiator 
 air is going to the outside of the cowling, there was no impact on 
cooling.  Btw cooling is really good. At an OAT of 95F, oil and water stayed at 
around  170F no matter what I did. 
 
For todays runs, I taped the inlet around the prop hub shut. Sure enough,  
the sputtering occurred at higher airspeed, and was not as total, however, 
EGT  was still going to around 1600. 
 
The conclusion is, I have to open the cowling exits a lot.
 
Richard  Sohn
N2071U

http://www.fairpoint.net/~res12/home.html


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<DIV>Congratulations Richard, it's a great start.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Big "general rule of thumb" is give your exit (in a low pressure area)=
 150%=20
of air inlet area. Think of the impact heat has on air in a hot air balloon=
 plus=20
the under cowl turbulence and slowing the air way down in there it is easy =
to=20
see back pressure building up. </DIV>
<DIV>It is a good starting point and you can always&nbsp;begin blocking off=
 bits=20
of both inlet and outlet once it all looks like it is cooling then you can =
begin=20
working on lessening the cooling drag.</DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT lang=3D0 face=3DArial size=3D2 FAMILY=3D"SANSSERIF" PTSIZE=3D"10=
">Chrissi &amp;=20
Randi<BR><BR><A=20
href=3D"http://www.cozygirrrl.com/">www.CozyGirrrl.com</A><U><BR></U>ClickB=
onds=20
10/$7.50<BR>CG Products, Custom Aircraft Hardware<BR>Chairwomen, Sun-N-Fun=
=20
Engine Workshop<BR>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>In a message dated 7/9/2012 10:50:15 A.M. Central Daylight Time,=20
res12@fairpoint.net writes:</DIV>
<BLOCKQUOTE=20
style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid">=
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=3D3>
  <DIV style=3D"FONT-SIZE: 12pt; COLOR: #000000; FONT-FAMILY: 'Calibri'">
  <DIV>Cleared the ground for a brief period today. As far as the airplane =
is=20
  concerned, everything is good. CG seems to be right on the spot. Much bet=
ter=20
  as it was 12 years ago at the first flight with the SOOB. </DIV>
  <DIV>Here is the reason why it was not a flight. A few days ago when I st=
arted=20
  high speed taxi, as soon as it picked up air speed, the engine started to=
=20
  sputter and almost cut out totally. This was at the same RPM as at a run =
up,=20
  where it does not do that. With a wiggly tail dragger as the Avid is, the=
re=20
  was no way reading enough instrument for making a preliminary analysis. I=
=20
  recorded the instrument panel with a GoPro at 2sec intervals.</DIV>
  <DIV>Looking at the first pictures, the answer came up right away, increa=
sing=20
  pressure under the cowl where the intake for the engine is located. Like =
the=20
  EGT shot up over 1600 just before the sputtering started. Since my radiat=
or=20
  air is going to the outside of the cowling, there was no impact on coolin=
g.=20
  Btw cooling is really good. At an OAT of 95F, oil and water stayed at aro=
und=20
  170F no matter what I did. </DIV>
  <DIV>&nbsp;</DIV>
  <DIV>For todays runs, I taped the inlet around the prop hub shut. Sure en=
ough,=20
  the sputtering occurred at higher airspeed, and was not as total, however=
, EGT=20
  was still going to around 1600. </DIV>
  <DIV>&nbsp;</DIV>
  <DIV>The conclusion is, I have to open the cowling exits a lot.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV style=3D"FONT-SIZE: 12pt; COLOR: #000000; FONT-FAMILY: 'Calibri'">Ri=
chard=20
  Sohn<BR>N2071U<BR><BR>http://www.fairpoint.net/~res12/home.html</DIV></DI=
V></FONT></BLOCKQUOTE></DIV></FONT></DIV></FONT></BODY></HTML>
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