<br><font size=2 face="sans-serif">Mark</font>
<br>
<br><font size=2 face="sans-serif">The idea behind a rib at the end of the tube is simply to distribute the load of the wing. Without the rib, there will be a stress riser right at the end of the tube. A violent maneuver such as a snap could easily buckle the balsa skin, since the foam has such low compression strength as does the balsa itself. I am sure there are people flying without a rib but I would advise against it. When the wing tube is bonded to the wing root and the "false" rib it will carry all the load. Only the portion of the wing past the rib will then flex creating stress at the tube termination. This stress is either concentrated at the very end of the tube OR distributed over the surface area of the rib. Because the stiffest component of the wing will always carry the load (the tube) any kind of stiffening strips inside the rib are dead weight.<br>
<br>
<br>
<br>
Gray Fowler<br>
Principal Chemical Engineer<br>
Composites Engineering</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td>
<td><font size=1 face="sans-serif"><b>"Mark Hunt" <flyintexan@houston.rr.com></b></font>
<br><font size=1 face="sans-serif">Sent by: discussion-request@nsrca.org</font>
<p><font size=1 face="sans-serif">04/15/2004 09:16 PM</font>
<br><font size=1 face="sans-serif">Please respond to discussion</font>
<br>
<td><font size=1 face="Arial"> </font>
<br><font size=1 face="sans-serif"> To: <discussion@nsrca.org></font>
<br><font size=1 face="sans-serif"> cc: </font>
<br><font size=1 face="sans-serif"> Subject: foam core question</font></table>
<br>
<br>
<br><font size=2 face="Arial">Sirs:</font>
<br><font size=3 face="Times New Roman"> </font>
<br><font size=2 face="Arial">As a newbie to cutting foam cores, I have a question regarding how to strengthen the wing panel. Does the preferred method include attaching some c.f. strips to the inside of the skins? Should they extend from the root all the way to the tip? I know some guys feel it is a must to also use a false rib near the end of the tube sleeve also? I hear that some guys (r u out there Nat?) are confident without any false rib or c.f. under the skin....?</font>
<br><font size=3 face="Times New Roman"> </font>
<br><font size=2 face="Arial">I cut the cores earlier tonight (to rebuild my 2M after a mid-air) with the help of a friend, and they turned out just beautiful. I have a nice plan to machine a drill jig for cutting the spar tube hole...so that's seems to be solved.</font>
<br><font size=3 face="Times New Roman"> </font>
<br><font size=2 face="Arial">Thanks in advance for the help...</font>
<br><font size=2 face="Arial"> </font>
<br><font size=2 face="Arial">Mark</font>
<br><a href=http://www.geocities.com/markhunt_2000/INSIGHT><font size=2 color=blue face="Arial"><u>www.geocities.com/markhunt_2000/INSIGHT</u></font></a>
<br><font size=3 face="Times New Roman"> </font>
<br><font size=2 face="Arial"> </font>
<br>
<br>