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<DIV><FONT face=Arial size=2>When you say moment arm = ac - ac I assume that
"ac" = aerodynamic center?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>How do you determine that "ac" point on a wing
with a complex airfoil?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Larry</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=natpenton@centurytel.net href="mailto:natpenton@centurytel.net">Nat
Penton</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, May 29, 2006 2:40 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [NSRCA-discussion] CG</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>The following formula was presented by noted
British modeller Gordon Whitehead in How To Make Scale Models Fly ( 1980 ??).
I have been using it over 20 years and find it dead on for
pattern:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> CG
(from LE MAC) = MAC/6 + 0.25x As/Aw M</FONT></DIV>
<DIV><FONT face=Arial
size=2>
As - area stab Aw - area
wing</FONT></DIV>
<DIV><FONT face=Arial
size=2> M
- moment arm, ac to ac</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It is easy to use the graphic method to
find the wing MAC. You can guess at the stab MAC and be close
enough.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The formula works on anything from a tailess to a
Quickie.</FONT></DIV>
<DIV><FONT face=Arial
size=2>
Nat Penton</FONT></DIV>
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