<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><BR><DIV><DIV>On May 29, 2006, at 4:40 PM, Nat Penton wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"> <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></BLOCKQUOTE><BR></DIV><DIV>Nat - I haven't compared the formula with the one I developed more than 40 years ago, but I think yours would be better understood if you use some parentheses:</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>CG (from LE MAC) = MAC/6 + 0.25x (As/Aw) M</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Also, the wing and stab area should include the ailerons and elevators, respectively.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Ron Van Putte</DIV><DIV><BR class="khtml-block-placeholder"></DIV></BODY></HTML>